Who is requireing it: Safety Cat 1, Cat 2, Cat 3, Cat 4

[Engineer4]

I am assisting another engineer with a robotic control panel design and I was starting down the path of putting in a Safety Relay with redundant wiring, cross-connection monitoring, and so forth.

The engineer said he wasn't considering anything along those lines and asked if it was a requirement.

I didn't know how to answer.

I know we all wish to make out projects as safe as possible, but is there anyone requiring it; anyone other than the owner or customer? If we built a control system with only a single N.C. contact EStop wired to a general purpose relay is there anyone to fine us or bring legal action in the event someone gets hurt/killed and the customer had no requirements specifying what type or level of safety?

I know there is the NEC and NFPA but do we have to follow it?

I'm not trying to get out of adding safety to a control project, I just didn't know how to answer the engineer. So as a result there is little safety in this project and there is no redundancy what so ever.

 

[petersonra]

If we built a control system with only a single N.C. contact EStop wired to a general purpose relay is there anyone to fine us or bring legal action in the event someone gets hurt/killed and the customer had no requirements specifying what type or level of safety?

I will suggest this.

Category levels are based on an older European standard that has since been superseded by what is called performance levels. It is actually close to impossible to calculate what the PL of your safety system is without using a software package of some type. Fortunately, they are readily available.

In any case, you must first perform a risk analysis to determine what PL or category is actually required. The same European standards that describe these terms also provide some guidance in making the determination as to what category or performance level is required.

The requirements consider both the severity of the injury and how frequent such an injury might be.

The requirements become more stringent as the severity and frequency of potential injuries increase.

Since I am never in a position to do a hazard analysis on my own, I ask the end user or OEM. They are in a far better position to know what is required.

keep in mind that the safety relays only deal with power removal. That is actually a tiny part of making a machine safe.

For the most part, one can do what amounts to a category 3 for the e-stop circuit for little more than what it would cost for a lesser solution, so I tend to default to that kind of an answer, since it requires little in the way of thought and I cannot make any determination on what is actually appropriate anyway.

Keep in mind I have made a point of saying this is for the e-stop circuit only. It does not cover anything else.

I would point out that for many situations the minimal solution suggested above is perfectly adequate.

 

[Engineer4]

Bob,


Thanks for the reply.


I am wondering though, who, if anyone, is MAKING me design in any form of safety?

I know that the automobile manufactures are TOLD by the NHTSA (National Highway Traffic Safety Administration) that they have to do this or install that for safety, but is there anyone other than the customer telling a control engineer what he has to design in as safety; is there any government agency? If the customer doesn't say a thing then do I have to do anything?

The NEC and NFPA write standards but who says I HAVE to follow them? Just like UL, they write requirements but if I don't want/care to be UL approved I don't have to do anything they say.

Again, I'm not trying to get out of it I just need to be able to justify why I am doing this or that.

 

[petersonra]

No one is making you do it at all, unless it is in a contractual sense.

There are some OSHA guidelines that would strongly suggest it is necessary to do the risk analysis, and then use appropriate safeguards but they apply to an employer and not a machine supplier.

 

[Jraef]

No one is making you do it at all, unless it is in a contractual sense.

There are some OSHA guidelines that would strongly suggest it is necessary to do the risk analysis, and then use appropriate safeguards but they apply to an employer and not a machine supplier.

Put another way, OSHA requires that an EMPLOYER provide a safe working condition for their employees, especially those operating or interacting with machines, specifically worded by OSHA as "...any machines that creates a hazard must be safeguarded in order to protect the operator and other employees." The employer must have a safety plan and educate the employees as to the specifics of the plan. How that all is implemented is up to the employer, but there are many suggestions as to how to approach it. In the Robotics industry, there are specific safety standards, published by the RIA (Robotics Industry Assoc).
http://www.robotics.org/robotic-content.cfm/Robotics/Safety-Resources/id/23

There are no "Jack Booted Thug Safety Police" that bash your doors down and demand to see your "safety papers", but the way OSHA works is that if there IS an accident, the first thing they will want to see in any investigation is the safety plan. "Oops, no plan? Lock the doors, IMMEDIATELY, while we investigate..."

Then once the lawyers for an injured employee find out that OSHA shut you down for not having a plan? In the immortal words of Warren Zevon, "Send lawyers, guns and money... get me outa this!"

 

[pfalcon]

... In the immortal words of Warren Zevon, "Send lawyers, guns and money... get me outa this!"

... The NEC and NFPA write standards but who says I HAVE to follow them? ...

Jraef states the situation pretty well. Nobody comes knocking until there's an accident and then ...

Strictly speaking (*)OSHA requires you to deal with recognized hazards. So if it's published in a national consensus standard such as NFPA70E, NFPA70, NFPA79, ANSI-B11, ANSI/RIA R15.06 or anywhere else then -- when (*)OSHA appears after an accident -- the next casualty may be you. Got a plan? Been active in trying to enforce it? What standards are you using?

If you can't answer those basic questions then (*)OSHA can legitimately use legal force to prosecute, fine, jail, lock the doors, confiscate, fold, spindle, mutilate ...

So since they can do all those things if you can't hold up a standard as a defense then I'd vote "Yes", they are required and you do have to follow them. An (*)OSHA rep once told me that I don't have to follow NFPA79 on my machine tools but I do have to tell him which standard I do follow. If I can't then they'll make it up as they go, probably really close to the NPFA79 since that's the one they're familiar with. But they absolutely, positively will be enforcing a standard on your company when they show. And they will be prosecuting their case against you according to a standard. The choice they give is that YOU can pick the standard or THEY will pick it for you.

 

[jvanthiel]

I am assisting another engineer with a robotic control panel design and I was starting down the path of putting in a Safety Relay with redundant wiring, cross-connection monitoring, and so forth.

The engineer said he wasn't considering anything along those lines and asked if it was a requirement.

I didn't know how to answer.

I know we all wish to make out projects as safe as possible, but is there anyone requiring it; anyone other than the owner or customer? If we built a control system with only a single N.C. contact EStop wired to a general purpose relay is there anyone to fine us or bring legal action in the event someone gets hurt/killed and the customer had no requirements specifying what type or level of safety?

I know there is the NEC and NFPA but do we have to follow it?

I'm not trying to get out of adding safety to a control project, I just didn't know how to answer the engineer. So as a result there is little safety in this project and there is no redundancy what so ever.

I'll start by saying I am not a lawyer, just a safety guy.

We write these specifications into our contracts when we order new equipment (as a customer), but most equipment has the desired specs in place out of the gate.

OSHA sets expectations for the employer, so as an employer we have the responsibility to recognize hazards and make sure they are addressed. Sometimes we receive new machines that are not guarded to Table O, it is our responsibility to add guarding before starting the machine. Since you are not the employer, I don't think you are at risk for an OSHA fine.

As a manufacturer, you are held to a looser, but potentially more problematic standard, a lawsuit for negligence by the employee or the customer, or subrogation from the customers' workers comp provider. Employees are typically limited to a state specified amount of money from their employer if they are injured at work through workers comp, but they certainly have the right to sue the manufacturer if the injury was due to negligence in the design of the equipment. I can tell you that our workers comp provider has tried to recoup money from the manufacturer after machine injuries if the machine was found to be below code. Following specifications outlined in applicable consensus standards would certainly help your company defend themselves should that occur.

This may be a good discussion to have with your company attorney to make sure you are covered through design practices or customer contract.

 

[wtucker]

I am wondering though, who, if anyone, is MAKING me design in any form of safety?

Your conscience.

And the likelihood of killing or seriously injuring someone--not to mention a lawsuit that will end your career and take your house because you knew, or should have known (based on, among other things, consensus standards and industry norms) that the hazard existed.

 

[pfalcon]

Your conscience. ...

... The engineer said he wasn't considering anything along those lines and asked if it was a requirement.
I didn't know how to answer. ...

I think Engineer4 knows why HE wants to put it in. But like many project people that don't understand safety - they DO understand money. The real question the project lead is asking is: Why are you adding cost to my project? Justify it or go away! Since they don't understand the safety they're pretty comfortable looking in that mirror when they manage to feed the family. They will often actively seek to not understand the safety behind it.

You start here:

SEC. 5. Duties
(a) Each employer --
(1) shall furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees;
(2) shall comply with occupational safety and health standards promulgated under this Act. 29 USC 654
(b) Each employee shall comply with occupational safety and health standards and all rules, regulations, and orders issued pursuant to this Act which are applicable to his own actions and conduct.

emphasis mine

5a2 says you'll read and follow OSHA
5a1 says that National Consensus Standards have published recognized hazards and you WILL protect your employees from them.
5b say that 5a1 and 5a2 apply to ALL employees and not just those given company responsibility for such.

(1) So tell him your safeties are required by law by 5a1 through the RIA. (2) If he argues then tell him you WILL put them in. Tell him if he decides to take them out later then you will happily use 5b to throw him under the bus. : Of course I'd expect you to use more diplomatic wording but I'm trying to be brief :fail:

I've had less than 1 in 20 people push me past (1). I've never had anyone keep arguing after (2).