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#149565 12/27/03 05:37 AM
Joined: Jul 2002
Posts: 8,407
Trumpy Offline OP
Member
I'm just wondering about something here.
What types of Safety controls and systems do you guys encounter in factories, using large manually-operated and semi-automatic machinery, in the US?.
How prevalent is the use of Light Curtains and Machine Guards, where you work?
Have you ever encountered a place where someone has over-ridden the safety controls?. [Linked Image]

Arc Flash PPE Clothing, LOTO & Insulated Tools
Joined: Sep 2003
Posts: 123
M
Member
Trumpy-
We have evertyhing you can think of for a guard here. OSHA rules require protecting operators. We also have some very clever operators who insist on defeating every know safety device in some way. Generally they get offended when they get turned in for a violation too.

Light curtains are the best, short of jumper wires (seen it) they are the hardest to defeat.

Joined: Jul 2002
Posts: 8,407
Trumpy Offline OP
Member
mvpmaintman,
Thanks for the reply, mate!. [Linked Image]
How far does PLC control over machinery in the US go?.
How would a machine controlled by a PLC be made to "fail safe" under a fault in the wiring or a supply failure?.
I've heard of instances where PLC controlled machines have just kept going with the controls all wired back to front here, is this the case in the US?. [Linked Image]

Joined: Jul 2002
Posts: 8,407
Trumpy Offline OP
Member
What I was looking for here was, how can we make Industrial Machine's safer and more "user friendly".

Joined: Dec 2000
Posts: 218
S
Member
Trumpy on the PLC equipment I deal with, the Emergency stop button is hardwired to the MCR. We are not allowed to use an Estop in the PLC. We also use light curtains, step mats (shut the machine off if the operator steps into a hazard area), safety gates & cables (both interlocked into the Estop line). I don't think we will ever get them "idiot proof", the idiots just keep getting smarter!

Joined: Jul 2002
Posts: 8,407
Trumpy Offline OP
Member
spkjpr,
This is what I mean,
You can never programme a PLC to take into account, any idiot that is going to try and defeat the system.
Normally, we would input any Estop or safety device as a Normally Closed contact, that way, if a wire breaks, or similar such thing, the system stops.
Thanks for your input, bud!. [Linked Image]

Joined: Mar 2002
Posts: 30
H
Member
Trumpy:

In our company, we use all manner of "safety" equipment, most having been listed before. These include: Safety E-stops, light curtains, photohelics, safety cables, physical barriers, emergency pendant switching (which moves all controls to the pendant, disabling all other controls during an emergency) and pressure sensitive mats.

All have their high points and lows, and each can be defeated in different ways depending on who attempts the defeating.

What exactly do you want to know???

Joined: Jul 2002
Posts: 8,407
Trumpy Offline OP
Member
Hazmat,
I was just wondering what types of Safety Controls were used in the US in Industrial sites.
I never really set out with a single goal in mind for this topic.

Joined: Sep 2001
Posts: 136
S
Member
What I was looking for here was, how can we make Industrial Machine's safer and more "user friendly"....

EDUCATE the worker that the guards are there for his/her safety and that the output of the machine is NOT the most important thing about operating that machine. Rather, they being there runing the machine day-in-and-day-out in safe and productive manner.

Until we speak this and walk this line, employees will ALWAYS attempt to defeat the very features we have spent $$$ to protect them!

Joined: Jul 2002
Posts: 8,407
Trumpy Offline OP
Member
Bryan,
Darn good point, mate!.
You really have to look behind the reason WHY the said safety systems are being defeated in the first place.
Is it because they are time consuming to operate or don't work correctly, or have they not been installed correctly.
The number of times I've seen an incorrectly installed Limit switch or Proxy switch.
Also, how often are these safety devices tested?.
One question, how prevalent is the Pull-Wire on an Industrial site in the US, where a horizontal wire is stretched from one end of the process to the other, a vertical pull on this wire will shut-down all Electrical and Pneumatics gear?.

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