Control system safety/liability

[allscott]

This is a question for all of you OEM, integrator, freelance programmer folks designing control systems for industrial machines.

What determines the level of safety equipment that you specify for your projects. Is it usually what the customer asks for, what you feel comfortable with, or do you go be someone's spec (OSHA, ANSI, etc...)

I'm curious because I have seen some machines that our company has purchased at both ends of the spectrum. A 200 ton press without as much as two hand operation. All the way to a packaging machine with safety mats, safety light screens all tied to safety rated relay (with a door switch on a 120V panel that killed all power if opened) banghead

I would also like to hear any stories of designers who have ended up in court over the systems they have designed because someone got hurt.

As a final question, what does liability insurance for people in this field cost? I am considering doing a bit of freelance control system work and am worried about liability and insurance cost.

thanks

 

[CaseyK]

I normally follow OSHA, NFPA, NEC, and UL as applicable. There is a lot of grey area, and a lot of different interpretations. Equipment operators are only as safe as they want to be, and even the most ignorant person can eventually figure a way around every safety device. It dates farther back then the famous locomotive "Dead Man Switch". It is scarey now to think that there are trains out there with a one man crew, and sometimes he is "downstairs" in the comode while the train "chugs" along. I had a real "eye opening" when I worked on controls in the locomotive industry for a few years.

There have been several threads on estops, safety relays, and safety in general, lately. Try a search.

I like to make sure there are an adequet number of emergency stops. I make sure that power to all outputs is killed when the MCR is tripped. I have seen some guys kill power to the inputs, but that makes it awful hard to troubleshoot. With dead outputs, you can still test and see the output led's light up. I am a fan of light curtains, but they are awful pricey.

I do not like a door kill switch, it is kind of a pain when you are trying to triubleshoot. Motorola had one on their base station radios, but there was also 3,000 vdc partially exposed on the high power base stations, evn though there were key locked doors.

I don't know of anyone who wound up in court, but really don't remember anyone that built a control system that hurt anyone.

I carry a 2 million / one million liabilty policy, only because I am considered a full time an electrical contractor. When I was considered a full time consulting engineer I did not have any insurance, but probably should have.

Insurance has been discussed on several threads previously, and I will list them if i can find them.

regards.....casey

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