Paul Davis Automation

Do you have a question about Machine Guarding?
  

Ask...

  

The questions and answers displayed on this page are for informational and instructional purposes only. Paul Davis Automation does not assume liability for the contents of this page, or the use of any products described herein.

Sue Williams, Environmental and safety coordinador at Covidien asked:

What is the requirements for the location of E-Stops on machinery?

SafetyMan says:

Most of the standards writing body's only required that the e-stop controls be within reach of the operator of the machine. Generally, I use a 4 foot rule of thumb so that at any time no e-stop control is more than 4 foot away from the operator.

Robert Miller, E/I Technician at sun chemical asked:

A co working has wired up e-stops to our plc's to drop out the out put cards but then he is letting the program to keep it in e-stop. But the scan time is to high you are able to pull it back out and restart everything thing back up before the scan time can caught it I want it to be hard wired so the relay is dropped out until you hit a reset. He wants to add mechanical timers to the front of the relays to keep them out till the scan time caught it I think he is just putting a bandage on it he should fix it right the first time with it being hard wired. Who is correct?

SafetyMan says:

I do not like to see an e-stop function through a programmable device, assuming it is not a safety plc, no matter how it is wired! So my answer is, hard wire to the source that allows a complete machine stop, without going through a micro-processor. If you need a controlled stop, then make the investment and use a safety plc. They are not that expensive anymore. As far as timers in a safety circuit, even when used on a safety relay they MUST be judiciously used and wired so that there is NO POSSIBILITY of an accidental start while employees are working on the machine. I was assuming that the timers your co-worker wanted to use were not control reliable or part of a safety relay.

Larry Dare, Tooling Services Manager at Millat Industries asked:

We currently have a Mori-Seiki milling machine with a broken observation window. We are well aware that this needs to be safety glass. My question is can this be replaced with something other than a direct factory replacement. Possibilities we are hoping for are laminated safety glass or Lexan polycarbonate.

SafetyMan says:

This question raises a number of issues. Yes, there are off the shelf "bullet proof" polycarb materials that could be used for a replacement. However, if you look at it from a standpoint of liability, product recommended or sold by the manufacturer, displaces the liability of the party making the selection and installing the glass. In other words, if you decide to replace the window with something not approved by the manufacturer and an employee is injured by material which could exit the machine through a broken window made from material not strong enough to resist impact, then the manufacturer of the machine could claim YOU were using material not approved by Mori-Seiki. I have seen legal action taken on less frivolous matters!

Steve Mustain, Senior Project Engineer at Drilling Techncial Services asked:

In our business we sometimes rebuild printing presses - are we required to meet the latest safety standards for this type of equipment if we are not upgrading or modifying them in any way?

SafetyMan says:

That is a question for your customer. If they want their press upgraded to meet current safety requirements per ANSI B65.1 and B11.19, then you do it. If they wish to not have the presses brought up to these current safety standards, then you SHOULD document their refusal with a certified letter to them. This letter documenting their refusal protects you in the event of litigation.

Robert Miller, E/I Technician at sun chemical asked:

What is the correct way to hard wire e-stop to a plc

SafetyMan says:

To answer your question, I will refer you to NFPA 79-2007 Edition. Under section 9.2.5.4.1.4 this standard states that "where a Category 0 or Category 1 stop is used for the emergency stop function, it shall have a circuitry design (including sensors, logic, and actuators) according to the relevant risk as required by Section 4.1 and 9.4.1. Final removal of power to the machine actuators shall be ensured and shall be by means of electrical components. Where relays are used to accomplish a Category 0 emergency stop function, they shall be non-retentive relays." This section of the standard then goes on to make an exception, which more directly answers your question. The exception says, "drives or solid-state output devices, designed for safety related functions shall be allowed to be the final switching element, one designed according to relevant safety standards." What this basically says is that if the device meets the control reliable safety requirements, such as a safety PLC, then it could be used in the emergency stop scheme for your machine. It is important to remember that regardless of which standard you follow, any device used for emergency stop purposes, whether hard wired or through a safety device such as a safety plc or safety relay must meet the requirements for control reliability as stated by both OSHA and ANSI. Again, OSHA does not recognize Safety PLC's, however, throught their consensus standards, they might allow them if you were to site the NFPA 79 Standards as the standards you were conforming to.

Mike Wood, Maintenance Manager at Insteel asked:

Comments = I am having a conversation with our engineering department on E-stops on equipment. I say that e-stops are hard wired and not controlled by PLC or software at all and must be respond upon being intitated. Our Eng Dept gives me this following explanation: To be compliant with NFPA 70E and 79, many equipment manufacturers (including Insteel, SSD, GCR and Frigerio) use a two or three tiered stopping scheme for machines that have many coordinated elements. The paragraphs below describe the reasoning behind the stopping scheme we use and have been using for about 15 years. SSD, as an example, uses a two tiered stopping scheme. The line has a Normal Stop mode which brings the machine to a controlled stop in a reasonable time frame. This is the first tier. The second tier is what would be considered a Rapid Stop mode where the line is brought to a stop in a controlled manor, but quicker than a Normal Stop. A brief time after the machine should have reached zero speed, when Rapid Stopping, a timer activates which drops power to the motors. If the line has not reached zero speed before this time elapses, the motor power is removed and the lines coast to a stop or stop via mechanical brakes. Whether coasting to a stop or mechanically braking to a stop, these stop modes are uncontrollable. Companies like Frigerio, GCR and Insteel elect to use a three tiered stopping scheme. As in the two tiered scheme there is a Normal Stop mode and a Rapid Stop mode. The difference is that there is no automatic powering down of the system after activating the Rapid Stop mode. We incorporate a third stopping mode – a true Emergency Stop. When Emergency Stop mode is activated, all power is immediately removed from the system and mechanical brakes are applied, in an attempt to stop the machine as quickly as possible. Of course this is an uncontrolled stop. The Normal Stop and Rapid Stop modes are controlled and coordinated through the computer system. The three tiered scheme gives quicker response to a true emergency than does the two tiered scheme, without the risk of occasionally powering down the system prematurely and causing some damage to equipment and product. This seems counter intuitive, but it is true. The two tiered scheme must wait until the Rapid Stop mode has had an opportunity to bring the line to a stop before the Emergency Stop mode may be entered. In a situation where the electronic control system has failed, the Emergency Stop mode will not activate until the required time has elapsed. After the required delay, the power is removed and the brakes are applied. With a three tiered stopping scheme, the operator decides that the electronic control scheme has malfunctioned and is not bringing the line to a stop. In this case he will activate the Emergency Stop mode. The operator can make this decision long before the time delay of the two tiered scheme would elapse, saving precious seconds. Two tiered schemes rely on an electromechanical timer. In the event the timer fails, a relay contact welds closed or the timer’s delay setting is misadjusted; the machine can be left without a true Emergency Stop mode. The three tiered approach does not rely on this type of device. In the case of SRS #1 we elected to place the Emergency Stop button in a central location. The operator does not have to hesitate to consider which Emergency Stop button is the closest to him. In addition, since Emergency Stops are uncontrolled stops, it is very important that anyone who may activate the Emergency Stop be able to see as much of the production line as possible, before activating the Emergency Stop button. The strander operators and packaging station operators have no clear view of each other. Placing an Emergency Stop button at either end of the production line (i.e. at the packaging station or stranders) would invite activation of an uncontrolled stop without considering the state or condition of the rest of the production line. As you saw Sunday, uncontrolled stops are risky and always cause considerable damage. By placing the Emergency Stop button at the SRS Operator’s Panel, someone activating the Emergency Stop mode would only need to take a few st! eps to see nearly the entire production line. In addition, the Packaging Station #2 operator can reach the Emergency Stop button in a short time period and he has a very good view of most of SRS #1. These reasons are why we, and other companies like Frigerio and GCR, adopted three tiered stopping schemes with buttons for tiers one and two at each station and only one hardwired, true Emergency Stop button placed at a central location. Can you please tell me who is right.

SafetyMan says:

Mike, long question, short answer. It is NOT acceptable to run an emergency stop circuit through a programmable controller. If it needs to be a controlled stop, then a hard wired redundant circuit with safety relays with timers may be used. If you are using a safety plc, there is still some debate whether or not the e-stop circuit may go through the safety plc. In Europe, this is accepted. I have not seen any concensus organization in the U.S. approve this yet.

C.R., Electrical Designer at WTT asked:

We are in the process of designing some hand loaded machines that are used for piercing holes into tubing. These hydraulic machines are going to have individually fence guarding with a sliding part loading door. The customer has requested that there be no cycle start. They would like to load the part close the sliding door and have the system cycle start. The siding door would have a sensor indicating the door is closed. Is it acceptable to do a start cycle by closing a loading door? Is there a code requirement to have a part present sensor or sensors?

SafetyMan says:

I would view this are a form of PSDI, Presence Sensing Device Initiation, which is mentioned in CFR 1910.217 the OSHA power press standard. You are using the closing of the guard door to initiate machine cycle. I would say it would be allowed provided that the switch on the door is a safety switch, control reliable, and CANNOT REPEAT CANNOT be defeated by the operator to allow unsafe operation with the door open. A part presence sensor could be used as part of the safety control logic that allows cycle initiation. Another step toward assuring the machine only cycles when all conditions are met, door closed, part in place.

Rick Heitkamp, Electrical Engineering Manager at Wayne Trail Technologies asked:

Another version of PSDI. We sold a line to a customer in Mexico with four manually loaded stations. The stations perform piercing and endforming operations using hydraulics. The customer wants us to initiate the cycle of the station with the closing of the sliding guard. Is this acceptable? What standards are enforced in Mexico?

SafetyMan says:

I can't say whether this is acceptable in Mexico. I do know that Mexico has a government organization similiar to OSHA in the U.S. How closely the rules are enforced, I cannot say. If you were to do this is the U.S., I would say that with the proper safeties, switches, control reliable interfaces, it would probably be accepted by most compliance officers.

Brian Bernhardt, Assistant Superintendent at Silgan asked:

Is there OSHA standards or guidelines/recommendations pertaining to slide and die paint colors on Power Presses?

SafetyMan says:

Not that I am aware of. There are recommendations for colors for awareness barriers, yellow indicates caution, red, danger.

Brent C Westbrook, Master E&I Technician at 3M Co. asked:

What is the difference between a "guard" and a "door" when it comes to wiring a safety interlock? Can a door be wired with a defeat resistant switch to a non-safety PLC to stop a conveyor and carriage while the door is opened? This may sound crazy, may be just arguing semantics, but a definition would be nice.

SafetyMan says:

You say tomato......ect. Guard and door the same in my book. Wiring to a plc???? Wiring to a non safety plc? Not in my book. The cost of a safety plc versus a plc is so minimal these days, why wouldn't you go with a safety plc?

Juan Escudero, Safety Tech at NFSY asked:

As a newly hired Safety tech, I have been trying to make sure all is with in OSHA standards recently some of my colleges explained to me how OSHA has been clamping down on safety guards and shields for drill press, milling machines, pipe benders etc... These guards have been installed on just about every piece of equipment in their shops. I thought that as far as facial and eye injuries was concern, a pair of safety glasses and face shield was sufficient to operate on these machines.

SafetyMan says:

Shields are also used to prevent putting finger, hands, or other parts into the rotating work piece. However, even with shields, safety glasses should always be worn.

Jason , controls engineer at automation controls asked:

Is dual processor really necessary for mechanical presses. Is there a way around the dual processor.

SafetyMan says:

Yes. The dual processor is the way that the control meets the control reliability required by OSHA under CFR 1910.217, ANSI B11.19 and NFPA 79. There is no way around this.

Joe Love, at Ameriwood Industries asked:

Is it a recordable injury if two hours after an employee starts to work, the employees reports that he got something in his eye walking to his work area before he clocked in to work? The eye was observed and washed at work observed by a physician at Occupational Health. Nothing was viewed in the eye at either location. The employee had an abrasion.

SafetyMan says:

An accident is considered recordable if the event or exposure occurred in the work environment. You must record work related injuries that result in death, loss of consciousness, days away from work, restricted work activity or job transfer or medical treatment beyond first aid. You must record any work related injury that is diagnosed by a physician or other health professional. There are also other criteria such as cancer or other work related diseases which do not apply to your case. If the incident required using non-prescription medication or cleaning, flushing or soaking wounds or using coverings such as band aids, then it is considered a non recordable. Based on what you have said, I would consider the incident a non recordable.

Bob Proia, at VNY asked:

Just a follow up to a previous question asked by Ron Potts.... IF a pilot light IS used on an E-Stop, should it be ON when the e-stop is pushed in or pulled out

SafetyMan says:

As far as I am aware, there is no specific standard that says the light must be on or off when the e-stop is used. Common sense would be that the light would be ON when the e-stop is pushed so that the operator could quickly determine which e-stop has been used.

J.M., at Brashear asked:

I am procuring a 1st of a kind, large optics polishing machine. This gantry style, moving bed machine has over a 2 meter capacity. To ensure the safety of the operator and the very expensive optics, we need for the operator to be in close proximity to the deactivated polishing head during a "gap checking" setup operation. We would like to emply a hand pendant with feed rate override and E-stop as the primary safety process during this setup opertion. During normal operation (automated), all personnel will be kept out of the machine zone via an interlocked gate. This machine will be built and installed in the US. Are there any rules that allow for close proximity setup work in large machines and what safety precautions are required?

SafetyMan says:

Since there are no Federal Regulations or consensus standards that guide us to an answer, we need to search for possible solutions through standards which have similiar potential hazards. When you mention "gap checking" this sounds to me like a procedure similiar to setting dies in a press. If you refer to either OSHA CFR 1910.217 or ANSI B11.1, they state that safeguards must be in place to not allow the machine to run and that die blocks shall be used to keep the die from closing. If your pendant control allows only movement such as jogging the machine and does not allow the machine to run in continuous mode, then you are almost there. Is there a way to use a device similiar to a die block in a press that would not allow the gap to close on the operator? Also, the person doing the gap checking MUST have control over the machine so that another person cannot start or run the machine with the other person near or in it.

N. Andersen, at Detroit Tool asked:

Regarding press brakes and the bypassing of light curtains. We have a select few parts that cannot be pressed in the machine with the light curtains active due to too many lights being blanked or the material bowing into unblanked areas. If specific handling and oversight procedures are put in place for that specific job and the risk to the operator is determined to be absolutely minimal, can I legally (OSHA acceptable) then bypass the lights? Thank you.

SafetyMan says:

There are a couple of ways you can do this. One is to use the quarter inch rule. This means lower the ram to within one quarter of an inch and then insert the material into the die for bending. If that does not work, you must follow the "no hands in die" rule and either provide work tools to hold the part or use restraints that limit the movement of the operator's hands and will not allow him/her to reach into the die.

Ron Potts, Maintenance Supervisor at Vulcraft of New York asked:

I can not find anything in the NFPA 79 reguarding pilot lights for e-stops. Could you give me some advice of where to find this standard if there is any? I'm not sure if they should be lighted if the e-stop is pushed in or pulled out. Or is a pilot light on an e-stop even required?

SafetyMan says:

A pilot light on the emergency stop is not required in the United States.

Artur Kruszewski, Technical Specialist Utitlities at YVR asked:

With respect to hard wired e-stop you refer to NFPA 79 9.6.3, I have 2006 eddition, I could not find the 9.6.3 at all. Would you know if that rule was moved or deleted, and what was the reason for doing it? Thanks. Artur.

SafetyMan says:

Unfortunately, I do not have a 2002 copy either. However, what you are looking for is under 9.2.5.4.1.4 in NFPA 79 2007. There it states that for a Cat 0 or Cat 1 emergency stop function, final removal of power shall be by means of electromechanical (hardwired) components.

Arthure Zee, Consultant at TEST Automation & Controls asked:

Are there any general or specific consensus standards for operator controls on industrial equipment to avoid inadvertent activation during normal operation?

SafetyMan says:

I would refer you to NFPA 79-2007 section 10.6 where it states, " Actuators used to initiate a start function or the movement of machine elements (e.g., slides, spindles, carriers) shall be constructed and mounted to minimize inadvertent operation. Mushroom-type actuators for two handed control initiation shall conform to section 9.2.5.6." This would be considered a consensus standard.

Romeo Guillarte, Maintenance Electrician at Guelph Tool Inc asked:

In a power press with multiple two hand operator stations, is there a requirement for antitiedown between stations. Thanks

SafetyMan says:

I am assuming there are two operator stations because operation of the press requires two operators to assure that the press is clear of personnel before the cycle is initiated. Because of this, you want to assure that one set of operator controls has not been purposely bypassed or defeated. Thus, the anti tie down show be coordinated between both stations so that both sets of controls must be activated within the same set of time.

Jed Hampton, Controls Engineer at Industrial Design asked:

If a customers specifies they will integrate the safety into a robotic cell with multiple saws, how much liability does the OEM assume? NO SAFETY from the OEM!

SafetyMan says:

The OEM always assumes liability! However, you can protect yourself. Send a certified letter to your customer stating that they have taken over ALL responsibility for the safety devices on the machine and therefore your company assumes no liability for any accidents caused by the saws. I would recommend your attorney help you write the letter. Once they have received it and reviewed it, I'll bet they change their mind!

gregg edwards, at L3 asked:

Category 0 e-stop definition NFPA 79. If e-stop activation removes power from only the hazards being guarded within the machine (power still available to other sub-assemblies) Is this still Cat 0 e-stop? or does all power have to be removed from the instrument?

SafetyMan says:

Per NFPA 79 2007 Edition, a Category 0 stop is an uncontrolled stop by immediately removing power to the machine actuators. Category 2 is a controlled stop with power left available to the actuators. By the above definition it appears that what you have would be considered a Category 2 stop.

John Weiss, Safety-Training Coordinator at Solvay Paperboard asked:

I have a few questions: 1. We have three roll handling machines that were installed at different times. All 3 have perimeter fencing but not all of them have OEM guarding (Safety Interlocks). We are looking at expanding the perimeter fencing on the oldest unit to include adding an additional entry point. Would have to bring the guarding into compliance with the current regulations? The two newest units meet European Standards.

SafetyMan says:

Yes. The reason for this is in ANSI B11.19-2003, ANSI states that anyone making modifications or upgrades to a machine is considered the integrator and therefore must bring the machine up to proper standards, thus your new entry would require a safety interlock.

Bob Mullins, Loss Control Representative at FCS Administrators, Inc. asked:

Is is feasible to provide an interlock to a side door of a blow molding machine. During set up the operator turns off the power and reaches in to the point of operation for adjustments however I am afraid that some day he will forget to shut of the machine cycle during these adjustments and reach into the point of operation during a cycle and have his hand amputated or mangeled. Your insight is greatly appreciated.

SafetyMan says:

Yes it is feasible and I have seen it done for the reasons you mentioned. Properly applied and wired using a safety relay into the machine control system does provide an additional measure of security. However, be aware that due to the complicated nature of blowmolding machines, heater banks and all, the interface must be done by a trained electrician who can properly wire the safety switch to stop the hazardous motion, but leave other none accessible portions of the machine active, such as the heaters, to prevent improper cooling or startup.

Steve Myers, President at SPOT Engineering Inc asked:

My company has been asked to supply engineering support for a large project that involves moving several automated machines. Each of these machines has 8 rope pull emergency stop switches (good CE rated positive opening safety contacts). These safety pull cords are only wired to a PLC input that provides a soft stop (not catagory 0 or 1). I have declined to accept any kind of involvment in this project unless these e-stop circuits a corrected. The customer's argument is that since these machines are not being modified (only disconnected/moved/reconnected) then they do not have to upgrade the safety e-stop circuits. I am not willing to accept the liability of providing engineering support for this project unless it is done safely. What do you think about the customers position and mine.

SafetyMan says:

I think you are correct. ANSI B11.19-2003 states that anyone modifying (also interpret) providing engineering, on retrofits of machinery is responsible for assuring that the machines meet the current standard. Plus, the way they are currently wired as safety devices does not meet the requirements of the new NFPA 79 2007 edition requirements. I think you made a wise decision.

Jose Luis Ibarrola, Electrical Engineer at M.Torres Diseños Industriales asked:

Our company sold a machine to the USA market last july 2006 according to the NFPA79 (2002), we'll deliver the machine next june (2007). Are we obligated to meet the new NFPA79 (effective august 2006)or can we meet the NFPA79 (2002) Thanks in advance and best regards

SafetyMan says:

The 2007 of NFPA 79 has been released. Your machine must meet the current standards written in that document.

Sam Yates, Corporate Safety and Environmental at Meadowcraft, Inc. asked:

Can a light curtain be used as an machine initiator (non-power press application) if a proximity switch is used on the machine to detect the presence of metal, and the machine cycles after the metal is loaded into the point of operation and the machine automatically cycles as the operator's hands are withdrawn through the light curtain sensing field?

SafetyMan says:

About once a year, I get the same question regarding Presence Sensing Device Initiation (PSDI). And the answer is, there is no answer! OSHA discusses PSDI under CFR 1910.217 (power presses) and ANSI discusses it and allows it with the proper inspections for hydraulic presses. As far as I know, no standards writing organization in the United States addresses PSDI for non press applications. However, a lot of companies do it! Can you do it? Of course you can. Would it be allowed by an OSHA Inspector during a routine inspection? That is up to the individual inspector. If you decide to do it, be sure that the control circuits for the safety light curtain and the sensor are all control reliable to ANSI B11.19-2003 requirements. This would include the proximity sensor which probably will mean two will be required with a series wiring circuit. So if one fails, the other acts as the backup and would not allow the machine to run.

Steve Rennhack, Electrical Engineer at Autotec Inc. asked:

One of our customers has informed us that it is an OSHA requirement that we have E-Stop buttons located within 4-feet of machine access points. I have not been able to locate any such requirement. Our machine is already fully guarded and all guard doors (machine access points) have safety switches on them all tied back to a Smart Guard Safety controller. If any guard is open, the machine is E-Stopped. I am wondering if the E-stop requirement is real, or is it just our customers interpretation of some Safety Regulation. I do not wish to add additional cost to our machine, and in turn to our customer needlessly.

SafetyMan says:

OSHA requires that E-Stops be ACCESSIBLE to all operators on a machine. I am not sure where the four foot rule is coming from. NFPA 79 also discusses e-stops and basically says the same thing. I think your customer has some confusion with another standard.

Jim Klok, Electrical design and engineering at Blow Press asked:

In your response to Jim Phillips, you state "No employer shall permit an employee to work in such proximity to any part of an electric power circuit that the employee could contact the electric power circuit in the course of work, unless the employee is protected against electric shock by deenergizing the circuit and grounding it or by guarding it effectively by insulation or other means." Since this seems to be in a panel, if the main disconnect requires a tool to open the door with power on, or the power must be removed to access the fuses, do the fuses still need to be covered? It seems to me that these fuses are not exposed to workers, but accessible to personnel who may be working inside the panel? Anyways, getting back to my original problem, a customer has safety gates on his press, and would like to control them remotely. Are there any rules governing the control of safety gates? It seems to me that someone could easily be standing under the safety gates when they are lowered, causing injury. Is any type of presence sensing device required under a safety gate, since the main purpose of the safety gate is to eliminate the need for presence sensing devices to protect the operator from pinch points in the die area? Love your web site. Great information on a variety of issues, with some logical and informative responses on your part. Jim

SafetyMan says:

Quick answer to a long question. There should NEVER be remote control of any part of the safety system on any machine which presents a hazard to employees! I have seen enough times where machines have been started locally by an operator with someone in the hazard area. With that being said, if the area inside the safety gate is large enough for someone to be inside with the gate shut, then another type of safety device such as a safety floor mat, horizontally mounted safety light curtain or safety scanner should be used to detect operator presence and not allow the machine to start even if the safety gate is closed.

Mary Burch, System Engineer at AMERISTAR FENCE CO asked:

How do I go about writing a LOTO procedure for robots and lasers and automated equipment.

SafetyMan says:

You start by doing just what you did, ask the question! If this is your first time, and you have never written a lock out/tag out procedure before, it would be advisable to contract with someone who is proficient in doing this task. I will tell you from experience, it is not easy and the amount of time you will spend will amount to more money and more of your time than you probably expected. Thus the reason for hiring an expert consultant who has proper training in doing this. Since each piece of equipment MUST have its own procedure, per OSHA, depending on the number of pieces of equipment in your facility, robots, lasers, etc., your task could take plenty of time, including corrections, reviews and rewrites. Plus, standards change and unless you are reviewing them frequently, you may use old standards. Once you are finished writing the procedure, the people who will use it must be trained. This should be done by someone who is NOT a regular user of the procedure i.e. one of the maintenance personnel. To simply answer your question, read and understand CFR 1910.217, the OSHA Standard for Lock Out. I would also suggest reviewing Standards from the Robotic Industries Association. There are also some examples on the web that you can see by Googling the word Lock out/ Tag out. In my experience, you will be money ahead by hiring a professional to help you with this task, the first time.

Wally, risk assessment technician at clipsal aust asked:

Is one Standard operating procedure for seven power presses acceptable or is it law to have a SOP on each machine?

SafetyMan says:

I have never been in a facility where one operating procedure for identical machines was sufficient. OSHA requires that all machines have explicit instructions for all phases of operation whether it be production or maintenance. Even assuming that the machines are identical, based on my experience, they will still have significant enough differences that one procedure does not adequately cover all machines. Have each machine assessed, and then develop procedures for each one. This is the safest way to go!

Robert Mirrielees, at Ideal Corporation, Brownsville, TX asked:

Are you aware of any light curtains that are activated by color? I have an application that hand feeds a tube in to a crimper, so the tube would always be detected by a light curtain. I would like to sense when the operators hand enter the "danger" area, and I thought about using a glove that could be detected by some type of light curtain or sensor. In other words, I don't want to detect the tube, but any hand part, yes. Any ideas?

SafetyMan says:

Sorry, no such animal exists. It is an interesting thought! Have you considered using muting with the safety light curtain? Depending on tube sizes, distance from the hazard and speed considerations, you might be able to use muting. Muting is where you "mute out" a portion of the safety light curtain that would allow the tube into the area, but would detect anything larger than the tube, such as a hand. This would be tricky, so I suggest you get a safety professional involved in reviewing this idea.

jeff workman, equipment coordinator at First Solar U.S. manufacturing asked:

What are the regulations regarding guarding of emergency stops?

SafetyMan says:

I recommend following the NFPA 79 Standard for e-stops. In that standard, they comment that e-stops should be accessible to all operators and not blocked. They also describe the style of operator and note that the background, around the device, must be yellow.

Brian Horner, Maintenance Supervisor at Littleton Coin Co. Inc. asked:

I would like to know what is required by OSHA for the accidental restarting of electrical motors after a power outage. The example I have is a commercial table saw. Does there absolutely have to be a device installed or is a procedure to avoid accidental starting acceptable?

SafetyMan says:

OSHA requires that all electrical tools be protected from accidental startup after a power outage. NFPA 79 also states the same. Many devices, especially if they are 110VAC, do not use magnetic starters, and will start if left ON after an outage. There are companies that make devices to go in line with the power cord that must be reset after an outage, thus keeping the device from starting accidentally. These are also good for band saws, sanders, drill presses, grinders or any other device using 110VAC. One device that does this is manufactured by JDS Products, Inc.

Robert Rogers, Safety Advocate at Weyerhaeuser asked:

Is there a minimum requirement by OSHA on how many locks you provide each employee for Lock-out.

SafetyMan says:

OSHA CFR 1910-147 requires that a lock be provided for each employee working on the machine. Obviously, if there is more than one lock out point on the machine, then each employee will be required to have enough locks in their possession to attach to these other points.

Rocco F., Guarding Leader at Harry Major Machine and Tool asked:

If barrier guarding is around a conveyer is it redundant to have local (sheet metal guarding) around chain and sprockets.

SafetyMan says:

This is a good example for a risk analysis. One of the components of that is exposure. Are your employees exposed to the unguarded chains and sprockets by being INSIDE the enclosed area at any time. If so, how often? What is the severity of the exposure and potential injury? With these considerations, following ANSI TR-5, you will get your answer. By the way, OSHA 1910.219 does state that these areas need guarded.

Richard Osborne, at Naval Undersea Warfare Center asked:

I have reviewed the NFPA 79 concerning emergency stop buttons. To me it seems clear that a red mushroom head push to stop positive opening switch is the answer. However, this has become a bone of contention on the design team some of whom advocate for a pull to stop type function. I am biased against the pull to stop because of my interpretation of the 9.2.5.4.1 ". . . shall be initiated by a single human action." To me a pull to stop involves two actions e.g. 1) grasp 2) pull; and a push to stop is 1) push. Is a pull to stop emergency stop button unsafe?

SafetyMan says:

Yes it is unsafe. Your interpretation of the standard is the same as mine. Here is another way to look at the issue, what if the person trying to stop the machine is an individual with disabilities and cannot physically grasp the e-stop to pull it?

michael murphy, Safety Manager at TS Tech USA asked:

On an machine electrical panel, is it necessary to have a lockable shut off on the panel it self or is a disconnect that is not on the panel that is lockable ok?

SafetyMan says:

A disconnect for the machine that isolates all power from the machine, is lockable, and properly identified as the electrical energy source for the machine is acceptable.

Jim Phillips, Electrician in production/service areas at Delphi E&C Grand Rapids Mich asked:

My plant started a new department because of a new design product. Great for us and keep it coming. Engineering and staff ordered 12 machines manufactured out of the United States. Not so great, but the problem I have is that these machines is that there is no protection or safety barrier covering the main disconnect fuses in the main electrical panel. In coming voltage at the fuses is 480 vac @ 3 phase. My company overlooked this and still qualified the machine for hurry up production. My question, there must be an NFPA or OSHA code to cover the fuses. Also, funny the same company who built these machines put fuse shields on previous machines we bought 3 years ago. Please reply

SafetyMan says:

The following OSHA Requirement spells out the responsibility of the employer. An open or uncovered live fuse is an exposed electrical hazard. I have referenced the following interpretation for you from the OSHA CFR's 1926.416(a) Protection of employees - 1926.416(a)(1) No employer shall permit an employee to work in such proximity to any part of an electric power circuit that the employee could contact the electric power circuit in the course of work, unless the employee is protected against electric shock by deenergizing the circuit and grounding it or by guarding it effectively by insulation or other means. It sounds to me that the OEM may have inadvertently left the fuses uncovered, particularly since similar machines did come in to your facility with the fuses covered.

Tina Davis-Zurface, Environmental Health & Safety Leader at Ahresty Wilmington Corporation asked:

How often must a light curtain be tested?

SafetyMan says:

A safety light curtain should be tested at the beginning of each shift and any time a setup change is made. Testing should be noted with a date and signature of the person performing the test.

Jeffrey Marquart, Partner at Smith & Marquart asked:

What are the regulations specifically addressing the use of safety interlocks in conjunction with guarding panels in the environment of an auger/grinder in the food processing industry. Case involves injury to worker whose hand was caught in an auger blade when guard panels were misplaced (by cleaning crew) and process was running in their absence...with interlocks, machine could not have been powered up.

SafetyMan says:

OSHA wrote a memorandum on food processing machinery 9/12/1991 that basically stated that food processing machinery MUST be guarded. OSHA states, "The applicable regulations (1910.212 & 1910.219) do not exempt such facilities from compliance nor do they allow a lesser degree of protection for their employees." 1910.219 is the CFR regarding power transmission equipment, which would encompass the auger blade. Safety interlocks, meaning devices which are control reliable, should be able to prevent the machine from powering up if they are properly installed, HOWEVER and I emphasize this comment, safety interlocks should NEVER be used as a replacement for lock out devices. If work is to be done on the machine, it must be locked out. I realize this may not have been the situation as the covers "appear" to have been accidentally left off and your comment is correct that safety interlocks would have prevented the machine from starting.

Ray Baca, Senior Electrical Engineer at Johns Manville asked:

Allen Bradley Manufactures a VFD, Powerflex 700S, which come with a safe off option. According to literature I have read, safe off provides protection according to European Category 3 requirements. However, NFPA says that an E-stop must be a category 0 or category 1 stop and the final removal of power shall be accomplished by means of electromechanical components. Can this safe off option be used as an E-stop?

SafetyMan says:

NFPA 79 refer to Category 0 and Category 1 for e-stops. The device you reference is referring to Category 3 control requirements from EN 1050, a European Standard. Do not confuse the two. I would not recommend the safe off option being used as a replacement for the e-stop.

Karl Hall, EH&S Administrator at Keihin Mfg., Inc. asked:

We just conducted an assessment of about eight of our ENSHU machining centers. All of these machines have the two-finger, infrared actuation buttons. On several of the machines, the operator must hold their fingers in place until the machine door closes. But there are a few where obviously, the PLC system has been altered so that the machine will continue with it's cycle, when the fingers are merely "swiped" through the two finger controls. This of course, would decrease cycle time. I told our production folks that this needs rectified immediately. As an option to operators holding their fingers on the controls until the doors are closed, I suggested outfitting the machines with light curtains and one actuation control switch where once the part is in the machine, the operator could "swipe" his finger to start the cycle, and the light curtains would shut the machine down should the beam be broken during the cycle. What do you think? THX

SafetyMan says:

I think the safety light curtain is a great idea. But, my larger concern is your statement about "someone altering the plc." If you have the two hand control wired through the plc, and it is not a safety rated plc, you are in violation of NFPA 79 Standards regarding solid state devices and safety circuits. Before you do anything else, this needs addressed.

PK, Chemical Engineer at LSI asked:

On an extruder, would the location in the feed throat where the screw is rotation past the edge of the barrel be considered a pinch point? Or is it considered a sever point. If ones hand were placed in this location it would get severed off not pinched or crushed. Please help with this question.

SafetyMan says:

The answer is...A Sever Point! This is an irreparable injury, which by risk assessment forces you to highest level of safety OR removal of the hazard. Call it what you will, it needs properly guarded or the hazard must be removed.

Desmond DaCosta, Field Engineer at DNA Electrical technology asked:

At the end of a pipe conveyor there is an over travel paddle switch. This switch is not redundant or reliable, because it is removable and often left on the floor (or frequently falls off). Also its operation depends on a paddle switch, that if removed will fail close. My question is, Can this device be used in an E-Stop circuit in a medium risk area?

SafetyMan says:

How did you determine it was a medium risk area? Also, if the paddle switch is not control reliable, then how can you determine if it will ALWAYS fail closed? I think this needs further examination. Anything that is in the e-stop control circuit MUST be control reliable!

Vince Rivera, Repairman at PD. asked:

How much slack should be allowed for the emergency stop cord on conveyer

SafetyMan says:

None! Stop cords should be taut and have slack rope detection. If it is slack, how do you not know it has been disconnected?

Michael Littlefield, EHS Leader at SCA Personal Care asked:

I am dealing with a serious safety concern related to the by-passing of electrical interlocks in order to clear jams, thread raw materials, and perform other minor servicing. My understanding is that use of an interlock as a substitute for LOTO is not permitted under any circumstance. In addition, by-passing an interlock in order to make routine adjustments to machine settings is a unsafe practice. What standard, either OSHA or NFPA, directly addresses this information?

SafetyMan says:

I would start with OSHA's General Duty Clause Section 5A. It is very specific about employees NOT defeating safeguards!

mirel bogorin, controls technician at formet industries asked:

If one changes an existing Estop circuit which is not dual channel, does the law require the upgrade to dual channel of the old, existing system?

SafetyMan says:

Yes. In order to meet requirements for control reliability for a safety circuit as stated in NFPA 79 and ANSI B11-19 2003, the circuit must be dual channel.

Jason V., Safety Walk-Through Manager at California Safety Training Corp. asked:

What is the required distance away from the conveyor for a yellow safety line?

SafetyMan says:

I have not been able to find a specific standard addressing this question. It appears that the consensus is that the line should be the minimum safe distance from the conveyor based on stopping time, width of loads and potential for injury based on the numbers of people at any time around the conveyor,

Jack Haller, at USG Interiors asked:

Yes, what size should the expanded metal or wire mesh be which guards the intake & exhaust openings on a fan unit. Is there a formula for distance from the blades to the outer edge of the fan housing which determines the size mesh or expanded metal that is acceptable for personnel safety. The problem we have here at our plant, is that the fans are so over protected with expanded metal or wire mesh of which has such small opening size, that the fans air movement ability has been reduced to almost zero. The fans run in cavitation. I'd appreciate any info you can give me on this problem.

SafetyMan says:

I recently had a client who ran into this problem with the OSHA Area Compliance Officer. Their company was cited because the openings in the guards around the fans in the plant did not meet OSHA's Table 0-10 Requirements. This table is found under CFR 1910.217 in the OSHA Standards. It is the allowable opening in the guard around a hazard based on the distance from the hazard. In this case, the fan blades would be the hazard. I would suggest you follow this guideline. By the way, the guards would have been fine if the fans had not fallen over, bending the guards into a larger opening.

Paul Mollnow, Maintenance Superintendent at Tyco asked:

The OSHA standard covers Lockout / Tagout but it is gray when it comes to servicing and maintenance. I have a manger who is insisting that an extruder be locked out, however the technician needs the machine running in order to diagnose the problem with the tooling. I say that this is routine servicing and is covered under the standard. The manager wants the lockout or a better understanding of the standard requirements. Who's correct? Thanks.

SafetyMan says:

Sometimes it seems the OSHA Standards are not grey, they are more opaque! I understand your frustration. OSHA recognizes that some minor maintenance must be done while a machine is running. The key here is that guards cannot be defeated. So, if maintenance wants to run the machine, stop it, open a guard and make a MINOR adjustment, close the guard and look to see if the machine is running properly, then they can do that. Any type of interlocked machine guard whether it is a safety light curtain, a safety switch, etc. must never, ever, be used as a substitute for lock out. If a complete maintenance procedure is to be done on the machine, then all energy must be reduced to zero on the machine and all sources must be appropriately locked out.

Elwood Wendel, General Manager at Rupp Air asked:

Is there sufficient flexibility of light/laser curtains on hydraulic break presses to account for various sizes/shapes of the metal being formed. For example: If there are two inch tall flanges are each side of the material being bent, then how can the point of operation still be protected?

SafetyMan says:

This is a question that comes up often. If you are using a safety light curtain for the primary guard, then you have a couple of options. One would be to use blanking on the light curtain to allow the flange on the material to be in the sensing field of the light curtain without tripping the unit. However, when you increase the minimum object resolution by blanking out beams, your safe distance increases. Now you may need to use hand tools to hold the part. The other option is to bring the press down to within a quarter of an inch, mute the light curtain and insert the part being formed. However, the size of the part may not allow for this.

Chris Pemberton, Production Eng at com-pac asked:

what are the regulation for guarding nip rollers.

SafetyMan says:

I would refer to OSHA 1910.219 and the ANSI B11.19-2003 Standard for machine guarding. They should give you good direction in formulating your plans. ASME 1501-2000 might also be useful. This is the standard for hard guarding from the American Society of mechanical Engineers.

Mike Solander, Project Engineer at Innovative Controls Corp asked:

Is there a required location on a PB box for the ESTOP PB. Many people put it in the lower left, some in the lower right?

SafetyMan says:

As long as it can be accessed by all operators on the machine, it is fine.

Gian Argentati, Standards and safety Engineer at Ingersoll-Rand Company asked:

Is there a standard dictating the actual size of a mushroom-type E-stop?

SafetyMan says:

Not really. NFPA 79 is a good reference for e-stops. Other than color and mushroom style head which is easily accessible to all operators, that is the only requirement.

Logan Masterson, Safety Director at Hamilton Machine Co. Inc. asked:

I am unsure of how to guard our machines. We are a job shop, with a few CNC machines (which are guarded), and numerous old-fashioned lathes and mills (which are not). We are a job shop specializing in repair, and most of our jobs require serious operator involvement. Please advice the best method or product for protecting our men and meeting OSHA requirements.

SafetyMan says:

The ANSI B11 Standards cover most of these machines. Copies of these standards can be purchased on line at www.ANSI.ORG.

Danny Skidmore, Electrical Project Engineer at York International asked:

My division builds industrial Refrig-eration. I have a customer (Pacific Rim) that wants a cover over his E-Stop on our control panel. A-B makes a lock-able cover for they're other switches. Nobody makes a cover for an E-Stop. I have explained we can't provide that type of E-stop / cover. What I would like to find is a document that explains this common sense reason.

SafetyMan says:

NFPA 79 specifically addresses e-stops. Use this as your guide. E-stops must be accessible and NOT covered or recessed. OSHA does not directly spell this out, however, under their Articles of Incorporation they can use the NFPA 79 Standard on E-Stops to cite companies.

Fred Branham, Vehicle production welding at Toyota Motor Manufacturing asked:

Does an automated robot line installed in 1996 need to be upgraded to Category 4 to remain compliant?

SafetyMan says:

The current ANSI/RIA 1506-1999 for robots supersedes anything that has changed since 1996. I would review the standard, locate areas where you are not compliant, and make changes.

B. Gagnier, at Lunt Mfg. Co. Inc. asked:

Our company has many automated die casting cells that use ABB robots to handle parts from the die cast machine to other pieces of equipment. What is the proper way to interlock the fencing that goes around the cell? That is what effect should opening a gate have? Should an opened gate prevent manual operation of the Robot or the surrounding machines?

SafetyMan says:

Following the RIA 1506 Standard for robotics, opening the gate should cause an immediate stop condition. If an operator is inside the gate, the robot is restricted on speed, how fast it can operate. If there is more than one operator inside the gate, their must be a separate control for each. Trapped key style systems are very good for interlocking the door gates because they allow the person inside the robot cell to control the opening and closing of the gate since they are in possession of the key used for entry.

T L Walters, Toolmaker at EAC-Fkft asked:

Is there a requirement for clearance to an e-stop on a machine? My employer has installed conveyors for off loading parts from plastic injection molding machines ? badly. In several cases, there are three-foot wide conveyors about six inches tall between the operator and the e-stop. This requires a leaning reach to access any of the controls ? including the e-stop. It is uncomfortable at best. And, as for changeovers, it requires climbing onto one or two conveyors to access the mold. Again, uncomfortable at best. Is there an actual regulation that prohibits placement of conveyors between operators and e-stops, or the normal controls for that matter?

SafetyMan says:

Regardless of which regulations you review regarding e-stops, they all require one thing. E-Stops must be accessible to all employees in the area. Climbing over any obstacle, conveyors, etc., do not meet the basic requirement of unobstructed view and operation. Plus, if the conveyors are moving, there are other dangers associated with climbing on moving equipment, not such a great idea. I suggest a redesign which places the controls outside of the conveyors and other equipment where operators have instant access.

Richard Littleton, Mechanical Engineering Technician at Federal Mogul SPG asked:

At What height above ground do you have to guard a loading dock opening when there is no truck at the dock and door is open.

SafetyMan says:

If the opening is 4' or greater above ground, it must be guarded.

george nelson, safety advisor at GM asked:

how tall does the guarding around a robot cell have to be, and does that height change if the robot if far away from the fencing?

SafetyMan says:

The guarding must be no greater than 12" from the floor and must be tall enough that nearby personnel cannot reach into the robot work area.

Dr. Franklin Golden, Mfg. Consultant at World Wide Consulting asked:

Are motors mounted 10 ft or greater in an open area above an employee walkway required to be guarded

SafetyMan says:

A hazard 7 foot or above floors, walkways or other areas accessed by employees need not be guarded. However, the equipment must be mounted and contained in such a way that if it falls it will not injure workers beneath the object.

John Price, Maintenance Engineer at Eon Labs asked:

On a packaging line can a master E-Stop on the wall (Mushroom style) be utilized as a lockout for the entire line so operators can safely clean the equipment at product changeover? No equipment maintenance will be performed during this time. This would relieve us of the responsibility of locking out over a dozen pieces of equipment. The control power is only isolated during this period.

SafetyMan says:

Not enough information. On a line this size, there are probably many types of work that can be done that only necessitate a partial lockout where power to the affected areas is locked out. Generally, e-stops do not remove full power, only perform an emergency stop of the machine because of an "emergency". Emergency switches used as lock out points for machines, especially when they only remove control power, are not adequate. Standards require that lockout removes ALL energy sources, not only electric i.e. air, hydraulic, etc. Sounds from your description of the machine that a lockout survey would be required before any more decisions can be made.

J Fradsham, Vice President of Manufacturing at TVC Systems asked:

We have a customer that would like to use "Break-Glass Pushbutton Stations" for an Emergency Stop System. This appears to me not to meet the NFPA 79 requirements. These stations would be used for an orderly shutdown of a process; shutting down chillers, closing building vent dampers, turning on ventilation fans, and sounding horns and beacons. The pushbutton stations also appear to be momentary type pushbuttons. Would this require a latching relay and reset button.

SafetyMan says:

NFPA79 2002 in Section 10.7.2.2 states "pushbutton-type devices for emergency stop shall be of the self-latching type and shall have positive (direct) opening operation." Under 10.7.3, it also says that the e-stop device must be manually reset to restart the system. because of this, a safety relay and reset button is recommended. Generally, "Break Glass" style pb stations do not meet the required "mushroom style" head plus, broken glass around operator's hands in general does not sit well with me.

karl Hall, Env. health & Safety Administrator at Keihin IPT asked:

One of our engineers is putting in a new production line, and I am involved in the design of the equipment as far as safety equipment. Hard to believe engineering is getting safety involved before the machine comes into the plant, huh? I've trained them well. The question is: This is an automated line, and although the several work stations in question are enclosed with interlocking doors, the engineer in charge of the project asks if an e-stop is needed for each work station. Currently, the design calls for an e-stop at the master control panel, and at a robot station. I always believed that an e-stop was required at each work station - is there anywhere the number of e-stops is detailed other than ANSI? THX

SafetyMan says:

NFPA 79-2002 is very clear about the positioning of emergency stop buttons. 10.7.1.2 states that "Stop or emergency stop pushbuttons shall be located at each operator control station AND at other locations where emergency stop is required." So, go ahead and install buttons at each station, and, good job on training those engineers!

Marty Freeman, Safety Manager at Malt-O-Meal asked:

Oftentimes we rely on interlocks as an alternate means of protection under the minor servicing exception to the lockout tagout standard. A typical example might be unjamming packaging equipment. As such, is there an OSHA incorporated by reference that a risk assessment must be conducted to determine what level of interlock (1-4) in this situation.

SafetyMan says:

Interlocking safety devices can still fail in an unsafe mode and as stated above, should NEVER be used for servicing, unjamming or working on dangerous equipment. This is considered improper use of this device(s). Lockout procedures should be followed at all times when working on equipment.

ryan, at Weyehuauser asked:

If an operator opens a safety interlocked door to clear a jam is the act of opening the door sufficient or should an e-stop be hit, if not, what if it is a lockable e-stop. How much 'minor servicing' is allowed with an e-stop w/lock out capabilities

SafetyMan says:

Safety devices should NEVER be used as a means for stopping a machine for any type of servicing, minor or not. Lockable e-stops do not remove power. Disconnects for machines are for removing power and locking out the machine in a safe, deenergized manner. Using a lockable e-stop for any type of servicing, minor or not, is not recommended.

John Sandner, Manufacturing Engineer at Pollak asked:

Are Safety Light Curtains a requirement in OSHA Regulation and is there a article that I can present to my group for machine safety.

SafetyMan says:

Safety light curtains are merely one of the many ways to provide machine guarding solutions. OSHA has guidelines for using safety light curtains on mechanical power presses and press brakes. The correct safety solution must be decided by risk assessment and then what is practical for your operation from a design and function standpoint. A safety consultant can assist you with this decision. As far as articles, the American Society of Safety Engineers has many good articles on machine safety and guarding. I would suggest contacting them @ www. asse.org.

Chris Lanigan, Plant Engineering Manager at Camoplast Rockland Ltd asked:

I have a machine that is equipped with safety guards and e stops. There is a hazard of placing fingers in a nip point between a rubber belt and an aluminum roll. We have installed a touch sensitive bumper. My question is does this bumper need to be wired as an e-stop with a total restart of the system or as a stop, reset and resume the sequence where it left off. My second question does this bumper need to be run in a safety PLC?

SafetyMan says:

The question you are asking sounds like one question. Do I need a safety PLC? If you have the safety sequence when the bumper is hit configured in a stop, reset and resume mode, it sounds as if you need to do this through the PLC. Since this would need to be done through the input side, using a standard PLC would not be allowed per NFPA 79 Requirements. Thus, yes, you would need to use a safety PLC.

Fred Seip, at Corning Inc. asked:

Is there anything wrong with using an e-stop as a means for routine stops? Are there any Codes or Standards that support the uses and non-uses of e-stops?

SafetyMan says:

Nothing that I know of says that an e-stop cannot be used for a routine stop PROVIDING that the use of the e-stop does not cause some type of action that could injure an employee.

Jay Watters, at The Schebler Co. asked:

What is the proper labeling for an Emergency Stop, can it be E-Stop or just stop?

SafetyMan says:

The following answer is from OSHA Regulation 1910.217(b)(7)(ii) "A red color stop control shall be provided with the clutch/brake control system. Momentary operation of the stop control shall immediately deactivate the clutch and apply the brake. The stop control shall override any other control, and reactuation of the clutch shall require use of the operating (tripping) means which has been selected." Either "Stop" or "E-Stop" should be acceptable.

LSexton, at The Gerstenslager Co. asked:

OSHA 1910.212(b) requires anchoring fixed machinering when it is designed for a fixed location. Is anchoring also required if the weight of the equipment itself prevents walking or moving? Also, is it safe to say that if it is portable equipment or equipment used in a temporary place, that it does not have to be anchored to prevent walking or moving?

SafetyMan says:

I will answer your last question first, because it is the easiest. If the equipment is portable, it does not need to be fastened in place. It DOES need to be stable. If it is hard wired in place, then it is considered permanent and needs fastened. Your first part of the question was in regard to large equipment. Trust me, I have seen 500 ton presses walk! Permanently stabilizing large equipment not only makes it safe, it also improves the quality and accuracy of your parts. Since we are not prone to earthquakes in Ohio, they don't factor much into the equation, however, in areas such as California, I have had experience with equipment falling over during earthquakes. Something that you do not want to happen. And besides, the law says anchor it! So, yes, any permanently placed equipment must be secured, no matter of size.

Karl Hall, Safety Administrator at Keihin IPT asked:

Can a machine (not a press or cutting machine) be converted from a two hand start operation to a one hand start operation if there are already light curtains at the point of operation?

SafetyMan says:

In this situation, the safety light curtain becomes your point of operation safeguard. If the SLC is properly interfaced to the machine at the proper safe distance, then it should stop the machine safely if an employee reaches into the point of operation hazard. You could then use a one hand start instead of a two hand control. Assure that the SLC is properly interfaced into a control reliable safety system on your machine.

Jeremiah Scott, Safety Coordinator at Tower Automotive asked:

According to ANSI B11-2001 - What is the maximum distance allowed between the floor and the bottom of a light screen on a mechanical power press.

SafetyMan says:

The basic premise that ANSI wants you to follow is the rule of, over, under, around and through. None of which you should be able to do when installing any safeguards including safety light curtains. Depending on stopping times and the response time of the light curtain, you may need two light curtains mounted vertically and horizontally. The vertical detects objects passing through, the horizontal detects objects or persons potentially within the light curtain standing next to the press.

Shane Bloomfield, Associate Engineer at Albert A. Webb Associates asked:

The control panel and e-stop switch on our client's stand-by diesel generator is approximately 9.5' feet off the floor. Common sense says the switch needs to be accessible, but does OSHA or NFPA have a section that states such a requirement?

SafetyMan says:

NFPA 79 2002 is very straight forward about e-stops. Under 10.7.1 Location and Operation (E-Stops), 10.7.1.1 says," Stop and emergency stop pushbuttons shall be continuously operable and readily accessible." 9.5 feet off the floor is not readily accessible in my book. It reminds me of the company I was once helping who had gas operated furnaces. The shut off valve for the gas was on top of the furnaces, 20 feet off the ground. Unless you had a ladder handy, you weren't going to get there in an emergency. Plus I'm not sure you would want to be there. Thus, the average person with an average arm length, would probably not be able to reach an e-stop 9 feet off the floor. Plus it is definitely out of the line of sight and would probably be hard to find.

, at asked:

SafetyMan says:

Kathy Druckenmiller, Legal Assistant at Cooper & Walinski asked:

Are there specific Lock Out/Tag Out Policies and Procedures for Lock Out/Tag Out? If so, are they general as in company wide or specific as per machine?

SafetyMan says:

OSHA CFR 1910.147 spells out the requirements for a lock out and tag out program. It does not provide a specific program or a machine specific program as the requirements of every machine can be different. OSHA does give a general guideline under 1910.146 Appendix A as a typical minimal lock out procedure. Most companies develop their own machine specific lock out programs particular to their specific needs and requirements.

Dave Davidson, Maintenance Coordinator at Dana Corp asked:

If you move an E-stop button from the original machine manufacturers stock location, did you or your company just assume liability if someone were to get hurt while operating the machine, because he or she could not reach the button in its new location?

SafetyMan says:

OSHA CFR 1910.212 requires that the employer provide a safe working environment. So, you are responsible even if you do not move the e-stop control once the machine is in your plant. NFPA 79 requires that e-stops be readily accessible to ALL employees working on or around the machine.

Mike Friedman, Electrical Engineer at Kaufman Engineered Systems asked:

Is it necessary to design a control reliable e-stop circuit for machine control in order to comply with ANSI and NFPA 79 standards?

SafetyMan says:

Yes. The e-stop must be controls reliable. This means the controls device (button), and the interface into the control system, (relay) must be control reliable. Whether or not it is a Category ) or 1 stop is determined by the machine requirements. Again, any failure of the components in this system must be detected and not allow the machine to start until corrected.

Stephen Kaufman, Principal Mechanical Engineer at ETS-Lindgren asked:

We are a manufacturer of testing equipment for the electro-magnetic compatibility market. One product that we make are large metallic paddles up to 60" square that rotate within a test chamber up to 16 rpm. Testing personnel can come in contact with these rotating paddles and the paddles can be activated remotely. Would an emergency stop be required by OSHA in this case? The emergency stop that we have incorporated into the system now is not at the point of contact, it is actually outside the room on a control enclosure. Test personnel enter these types of shielded rooms regularly to set-up or change test equipment.

SafetyMan says:

OSHA and NFPA 79 require that emergency stop controls be within reach of all affected employees. Therefore, employees in the area you describe should have an e-stop control.

Emilia Siderov, electrical engineer at Gammerler asked:

Am I going to violate OSHA standards if I mount two e-stops on one control panel, which controls two different conveying systems?

SafetyMan says:

Not as long as each e-stop control is properly marked as to which system it controls. It would also be a good idea not to mount them next to each other.

Nick Wiant, Equipment Engineer at Midwest Express asked:

How far apart do buttons need to be that require the operator to push both before equipment will move? Is there a specific distance apart so that the operator can not push them with one hand?

SafetyMan says:

There is no specific distance required by OSHA. They state that the buttons should be far enough apart to prevent actuation by the operator using one hand and that actuation must require the use of both hands. Don't forget anti tie down and repeat must also be achieved in the two hand control design.

JOSEPH PAUNON, electrical-mechanical designer at AMFEC asked:

Is an e-stop required for an equipment (i.e. screw conveyor) with a simple start / stop control in order to be CE compliant-OSHA acceptable. Will a padlocking attachment forcing the stop PB to stay open satisfy e-stop requirements?

SafetyMan says:

All electrical equipment must be equipped with the proper e-stop. The device must comply with OSHA/NFPA Requirements. Using a padlock with a pushbutton is not correct or acceptable.

JB, at NUSA asked:

Does OSHA allow an interlock opened when an equipment guard is removed or opened to make equipment safe for someone to perform minor servicing? I understand OSHA does not allow it in lieu of Lockout/Tag out, but what about minor servicing covered by Subpart O? If so, are there prerequisites for using an interlock only?

SafetyMan says:

Guarding should NEVER be bypassed when equipment is in operation no matter how minor the servicing is.

Richard VanDeBogart, Engineer at Corning Incorp. asked:

I have a glass press operation which is hydraulic. In an effort to do a safety risk assessment, I discussed it with the safety manager. This individual feels that the B11 OSHA hydraulic press standard is not the requirement to use. Can you tell me what standard should be used?

SafetyMan says:

If it is a hydraulic press, the B11 Hydraulic Press Standard should be acceptable. Good practice regarding safety circuits and proper distances of controls should be followed per OSHA CFR 1910.217. Any areas that have hazards should be covered or guarded. If this is the standard you choose, document your risk assessment and evaluation of the hazards which led you to determining this to be the best standard.

J.B., Safety Coordinator at NUSA asked:

Can an electrical interlock on a guard be used in lieu of the operator activating an emergency stop switch and if so, are there any pre-requisites for using the interlock instead (such as shutting having it open the power circuit versus the control circuit as I read on the OSH.net site)? Also, are there any requirements for scheduled inspections or tests that the interlock is functioning properly?

SafetyMan says:

An electrical interlock should never be used as the emergency stop device. It does not meet the requirements of NFPA 79, which states that e-stops must be a red mushroom style head with a yellow background. I recommend that all safeties be inspected for proper operation at the beginning of each shift AND document the inspection.

Miles Lynch, Controls Engineer at RTI asked:

If I have automated conveyor equipment that is at 10' elevation, does it need to have EStop pull cords along it's length.

SafetyMan says:

ASSME B20.1-1996 states under 5.11.2(c) e-stops and pull cords must be furnished if the conveyor is not guarded by location (more than 8' above a walkway and not accessible to personnel).

P.C., Electrical Engineer at Met-Chem asked:

Is there a height/position requirement for pull cords on conveyors?

SafetyMan says:

According to ASME B20.1-1996, section 5.11.2(c) says that remotely and automatically controlled conveyors not guarded by location shall be furnished with emergency stop buttons, pull cords, limit switches or similar devices. It does not state location, however, good practice would suggest that they be accessible anywhere an operator is located.

Jim Heinrich, at Mittler Bros. Machine & Tool asked:

I would like to know if it is acceptable to use only a light curtain and part present switch to initiate an assembly or test machine cycle. I would like to eliminate the Cycle Start switch, to save part to part cycle time and reduce repetitive motion for the machine operator. Are there any standards that address this with OSHA or ANSI? Thank You

SafetyMan says:

What you are talking about is PSDI. Presence Sensing Device Initiation, using the make/break detection of the safety light curtain to initiate a new machine cycle. OSHA refers to this in CFR 1910.217, the standards for presses. Unfortunately, this is the only location where this is referenced. I am assuming that your machine is not a power press. In 1910.217, OSHA requires that a third party validates the application. At this point, there are no third party validators, therefore, you cannot achieve the requirements of OSHA's Standard at this time. If it is not a power press, now we need to look at the requirements of control reliability as stated in ANSI B11.19. If the components that are used meet the requirements of this standard, your personnel have been trained in the proper usage, and the system is hardwired and not controlled by a solid state device such as a plc, then we must assume that it is safe. Until OSHA or ANSI gives us further guidelines on PSDI, this is the best we can do. Meanwhile, I will mention that where this has been implemented, CTD's have been sharply reduced!

Brian Stuhlemmer, Regulatory Compliance Specialist at YOM asked:

I submit this rather challenging problem Safety Man. We have a parts conveyor carrying stamped pieces from a Stamping Press and sliding these onto a table. As you have probably guessed correctly, the table (where inspection occurs), is butted up to almost against the conveyor end. There is a small 1/2 inch gap which serves quite nicely as a nip / pinch point. We really cannot move the table - What sort of guard should we obtain and install for this??

SafetyMan says:

SafetyMan loves challenges! If you go to OSHA's table 0-10, they require a 2 1/2 to 3 1/2 inch distance from the point of operation hazard when you have a 1/2 inch opening. I realize you are in Canada, however, as I said this is just a point of reference to begin conversation. Some possible suggestions; make the opening 1/4 inch. If your part is too large and will not fit thru the opening, then fabricate a chute that is long enough to meet the 2 1/2 inch minimum distance requirement per OSHA and will not allow operators to access the hazard. If you would like further analysis, please feel free to send photos that we can review. BTW, hope the fishing was good this year. I did not get a chance to get to my favorite spot on Georgian Bay!

shorty fitzater, at akron steel fab asked:

BY BEING A OEM IS THERE A GOOD CHECK LIST OR SOME KIND OF INFO ON HOW TO DO A MACHINE INSPECTION ,BECAUSE ALL OUR MACHINES ARE DIFFERENT IT IS HARD TO COVER ALL ASPECTS OF SAFETY BY MEMORY PLUS TRYING TO GET ALL PEOPLE INVOLVED TO LOOK AT THINGS FROM THE SAFETY POINT OF VIEW

SafetyMan says:

I would use the ANSI TR-3 Risk Assessment procedure. Once you have identified the hazards, your engineers can then determine the level of risk and the appropriate control system for the level of risk.

MJ, Plant Engineer at DePuy asked:

What is the recommended guard setup for manual vertical mills (BridgePorts) that still allow some operator intervention for dressing and treating parts while milling? The conventional setup is for a swing away guard that is switch actuated when the operator brings the guard to the front. However, this only works if the operator is running parts which allow him to setup and walk away. Not very practical for parts requiring involved setups and manual adjustments during operation (such as tool rooms and job shops). Any advice would be appreciated

SafetyMan says:

The problem with machines like a vertical mill is that they can do so many types of jobs, it becomes difficult to provide one type of guard which will cover all applications. Depending on how the machine is used, it may be necessary to have swing away guards for some applications, chuck guards for other applications and perhaps a magnetic mount guard that can be positioned for other jobs. The main safety concern on milling machines is the swarf created. This must be contained so it does not strike the operator. The cutter must also be guarded to prevent the operator from getting clothing, jewelry, hair, etc. caught in it. Shields may also need to be applied around the table of the mill.

J.R., at Arts Electric asked:

Does a Hydraulic Press with a safety light curtain and guarding require a redundant PLC? I know ANSI recommends it, but I can't find where it is required by OSHA.

SafetyMan says:

The controller on the press must be control reliable which is the case with a safety plc. OSHA addresses only mechanical presses and will defer to ANSI Standards, such as the Hydraulic Press Standard. We always comply to applicable OSHA and ANSI Standards when we do any machine work.

Don Huggins, at The Timken Company asked:

What is the minimum accepted distance between two-hand safety switches? Obviously 2 inches apart is too close, and 10 feet apart is too far. What is the standard "min"? I know how to calculate how far each switch needs to be from the point of operation, but cannot find a firm # for the min distance between the switches.

SafetyMan says:

There is no rule written for this. However, the buttons should be far enough apart that the operator cannot actuate the machine with one arm, i.e. elbow on one button, hand on the other.

Paul Clements, Risk Manager at Friday Services asked:

The Power press standard states the PSDI, light curtain, will be checked at the beginning of each shift. Does this hold true for other applications of light curtains other than Power Press.

SafetyMan says:

Oddly enough, OSHA only references safety light curtains in its power press standards. They do state that safety systems on machines should be checked periodically (as does ANSI). Depending on the level of risk, once a day might not be enough. Checking the light curtain at the beginning of each shift is a good idea. be sure to document the check.

M. Gabey, Electrical Engineer at HON Co. asked:

Are there any OSHA requirements on brake presses controlled by PLC such as Dual PLC Control?

SafetyMan says:

Under OSHA CFR 1910.217, it states the following; "(b)(8)(vi) Electrical clutch/brake control circuits shall incorporate features to minimize the possibility of an unintended stroke in the event of the failure of a control component to function properly, including relays, limit switches, and static output circuits." I am assuming that when you talk about Dual PLC Control you are referring to a dual processor system running separate software such as a safety plc?

Craig Kimmel, Safety and IH Leader at Owens Corning, Kansas City Plant asked:

Is there a maximum stop time or travel distance for a piece of equipment to stop after the e-stop button is actuated? What regulations or consensus standards would apply?

SafetyMan says:

There is no specific information for allowable stop time after the e-stop is activated. NFPA 79 does discuss different categories of stops but time is not mentioned. The ANSI B11.19 Distance Formula discusses stopping times and allowable distances for devices such as safety light curtains, but does not mention e-stop controls.

Gerald H., Project manager at Carey Electric asked:

Our customer is requesting that we apply our E-stop in a "pull to stop" wiring arrangement. This does not sound as if it would meet standards. I would like your advice on where to find information on proving which way it should be wired to meet code. Thank you

SafetyMan says:

NFPA 79 is a good source for e-stop information. I am assuming he is talking about a rope pull safety switch which can be wired through the e-stop circuit.

Carl Van Tillburg, Senior Controls Engineer (BSEE) at Eskay Corporation asked:

Are there any safety requirements for remote starting of automatic equipment in material handling that is not "line-of-sight". Example : Control computer with (Start/Stop) is not "line-of-sight" of transport conveyors.

SafetyMan says:

OSHA CFR 1910.212 pretty much covers this when they state that the "employer should make it safe." If there is the potential for injury and unsupervised initiation of the machine is possible, then the hazard must be guarded.

Miriam C. Laracuente, Safety Design & Compliance MTS at HP asked:

Do you know about a regulation (ANSI, RIA,etc) that specifies a minimum clearance from floor to the bottom of perimeter guarding of robotic cells?

SafetyMan says:

The ANSI/RIA 1506 Standard for Robots Section 11.1 (F) Barrier Guards, fixed and interlocked, requires that "they be positioned so that the bottom of the barrier guard is no more than 12" above the adjacent walking surfaces." The top of the barrier can be no lower than 60" above adjacent walking surfaces.

Dawn Seguin, Environmental Health & Safety Coordinator at Alcatel High River Cable Plant asked:

Our production lines have 2-4 employees working on them ( these employees are moving around at all times). Is there an OSHA ruling stating how far apart e-stops should be?

SafetyMan says:

According to OSHA and NFPA 79, e-stops must be accessible for all employees working around a machine. The answer is, as many as are needed to accomplish this.

DAVID CARNAGEY, SAFETY SUPERVISOR at NATIONAL STEAK & POULTRY asked:

ON AN ELECTRONIC ROLLER GATE, IS THERE SUPPOSED TO BE AN EMERGENCY STOP? OUR GATE IS RAN BY REMOTE CONTROL, AND DOES NOT RE-OPEN WHEN A VEHICLE APPROACHES.

SafetyMan says:

Is there a hazard created when the gate closes? Could a person be caught and trapped or injured by the gate? If so, then there needs to be an e-stop provided whereby the gate could be stopped so as not to trap personnel. You may also want to consider safety edges or bumper strips on the edges of the gate and post that would cause the gate to reverse or stop if it comes in contact with an individual.

Henry Stepnowski, at CAMI Automotive asked:

Are there any regulations that address the use of E-stop shrouding? We need to partially shroud an E-stop button from accidental trips by a balancer cable in the area. The shrouding we found is a hard plastic that surrounds the outer perimeter of the button only.

SafetyMan says:

The National Fire Protection Association (NFPA) in their standard 79 the Industrial Standard for Electrical Machinery, states that the e-stop must be accessible and visible to all operators. If the shroud prevents the button from being easily recognized or actuated, then it should not be used.

JEFF BELL, MANAGER, AUTOMATED SYSTEMS at TAYLOR-WINFIELD asked:

Does the ANSI B11.19 pertain to Hydraulic Presses?

SafetyMan says:

I am assuming you are referring to the B11.2 Hydraulic Press Standard. B11.19 is the safeguarding standard when referenced by other B11 Machine Tool Standards. Where referenced, it is applicable.

T. J. Thorn, Safety Director at Hoover Wire Products asked:

Is it my imagination or is there really no OSHA guidelines regarding the color of machine guards?

SafetyMan says:

There is no OSHA color requirement for machine guards. No, it is not your imagination!

Bill Maness, at Norton Co asked:

In what publication is a force driven contactor listed as required to interrupt power from an electronic drive in case of a single point failure within the drive, i.e. the drive fails internally in the on condition and the estop circuit must be used to stop the motion.

SafetyMan says:

ANSI B11.19 7.7 references safety interface modules that must have monitored, multiple force guided captive contact relays. They do not reference contactors used with electronic drives. However, if the contactor is part of the safety related control system, then it must meet the requirements spelled out in B11.19.

Rob Rees-Evans, at JMP Engineering asked:

If a light curtain is used for perimeter guarding, what additional safety measures are required to protect the person in the restricted space after passing through the curtain. Area scanning devices, safety mats and other presence sensing devices would be nearly impractical to implement. Is a manual reset device outside the restricted area sufficient ?

SafetyMan says:

If the devices you mentioned, such as mats, are impractical, then you might consider a trapped key type system which would allow the operator to keep control with him when he is in the hazardous area. A trapped key system allows power removal to the machine and entry into the hazardous area with the operator having control over the only device (the key) which would allow the machine to restart. In the case of a robotic cell, under ANSI/RIA 1506-1999, under Section 8.4, preventing re-initiation of any motion or hazardous process while personnel are within the safeguarded space requires, for example, locking the gate open.

Karl-Ernst Lich, Electrical Engineer at Metcom Engineering Ltd. asked:

What is the maximum permissible mounting height above floor level,( operator standing on floor in front of a control panel) for an E-Stop Pushbutton? Is there a recommended height for a standing operator?

SafetyMan says:

The e-stop must be accessible to any and all operators. If there are multiple operators, there must be multiple e-stops. There is no set standard for height per any recognized U.S. Standard. The most common mistake is not having e-stops in all areas that the operator must access during operation of the machine or process.

Jim Farmer, Owner at Industrial performance Group, Inc. asked:

What is the regulated distance between palm buttons.

SafetyMan says:

OSHA does not have a standard for regulation distance between two hand control buttons. There was a UL Standard that addressed this from many years ago which, unfortunately, I cannot find. The common understanding is that the buttons "should" be 24" apart or roughly the distance between the shoulders of the operator. In any event, the operator should not be able to activate both buttons without using both hands simultaneously.

Bill Johnston, Electrical Engineer at Brown Machine LLC asked:

Are you aware of any standards that address the recommended distance an E-Stop Pull Cord should be from the hazardous motion? I am locating a pull cord above two in-running nip rollers. Thank you for your assistance.

SafetyMan says:

In the United States there is no standard regarding rope pull switches and safety distances. However, the European Standard IEC/ISO 13 850 does address your question. Under Section 4.4.2 it says, "emergency stop devices shall be located at each operator control station and at other locations where emergency stop is required. They shall be positioned for easy access and non-hazardous operation by the operator and others who may need to operate them." Section 4.4.1 lists the types of devices which include rope and wire actuated safety devices (switches). Under 417-IEC-5638 Section 4.5 Additional Requirements for Wires and Ropes used as actuators, it also states that, 4.5.1 "consideration shall be given to the minimum clearance between the wire or rope and the nearest object in the vicinity.

William Kincaid, P.E., at Lockton Companies asked:

OSHA 1910.212 is a general machine guarding regulation that does not define what acceptable guarding is. OSHA compliance staffers refer to the mechanical power press rules and (rarely) to the ANSI B11.19 machine guarding criteria to define acceptable guarding. This is not good enough for some dissenters, who state "if it has a guard, it complies with 1910.212" no matter how poor the guard is. Where is the specific quantifiable rule or reference that will defeat this argument? I need something in writing that specifies what size a guard opening can be and be in compliance with 1910.212.

SafetyMan says:

Welcome to the world of horizontal regulations! It is the manufacturers' responsibility to make it safe and most of the citations will reference 1910.212. However, the openings in the guard must also meet OSHA Table 0-10 which references minimum openings allowed in the guard based on how far the guard is from the hazard. In your safety plan, through 1910.6, OSHA's Articles of Incorporation. you can reference the ANSI Standards that you have met, or for that matter any other standard from any "recognized" authority that may be more specific to your machines. If you decide to follow another standard and use 1910.6, make sure you follow it to the letter. OSHA can also reference and cite under other standards through 1910.6 if they desire.

Randy Franklin, Senior Electronic Engineer at OTS asked:

What is a safety PLC? Why would you use a safety PLC?

SafetyMan says:

A safety PLC is a programmable logic controller which can be used to interface emergency stops, integrating light curtains or monitoring safety gates. Generally, the way they work is the safety portion of the control operates through separate channels in the plc. The input from the safety device, such as a safety light curtain, is passed through these channels and is processed by individual processors. If the different processors reach the same result, then the output switches. Hardware and software checks are constantly performed by the system to insure reliability.

Paul Santkuyl, Sr. Electrical Engineer at Marathon Engineers asked:

Is there an ANSI or OSHA Standard that prohibits E-Stops from being dependant upon a programmed plc?

SafetyMan says:

The only reference to this is in NFPA 79. Under 9.6.3, it states, "Where a Category O stop is used for the emergency stop function, it shall have only hardwired electromechanical components. In addition, its operation shall not depend on electronic logic (hardware or software) for the transmission of commands over a communication network or link. OSHA can reference this using their articles of incorporation.

Wendy Li, Manufacturing Engineer at Shiloh Industries asked:

What is the standard height when installing the two hand control buttons?

SafetyMan says:

According to ANSI Technical Report TR-1 on Ergonomics, two hand control should be set at approximately waist height for the operator. A copy of this Technical Report is available from ANSI.

Lowe Garner, Engineering Specialist at Konica Manufacturing USA asked:

Which regulations cover standards for emergency stop circuits and components to reenergize circuits? Example: Product Conveyor.

SafetyMan says:

OSHA addresses conveyor e-stops in CFR's 1917.48(d)(2)(f) and 1918.64(a). Unfortunately, they do not cover the requirements for circuits or control components. The National Fire Prevention Association (NFPA) address this in Standard 79, but does not call out circuit performance. The ANSI Standard B11.19, the safeguarding standard for machine tools also discusses e-stops and circuits, but doesn't directly specify that they must be control reliable, although the standard itself discusses control reliability for safety systems, which e-stops are a part of. My suggestion is to make the controls and circuits as control reliable as possible and be sure