machine guards and interlocks

[james_mcquade]

Hi all,

When is an interlock required on a machine guard.
We have plenty of machines with guards without interlocks, but we have a four station machine with pick and place
cylinders and manupulators that have these interlocks on the doors, so when are they required?

Does anybody know where I can find the Regulation that spells out this requirement.

thanks in advance,
james

 

[Joethemechanic]

Hi all,

When is an interlock required on a machine guard.
We have plenty of machines with guards without interlocks, but we have a four station machine with pick and place
cylinders and manupulators that have these interlocks on the doors, so when are they required?

Does anybody know where I can find the Regulation that spells out this requirement.

thanks in advance,
james

I think you would do better looking at OSHA requirements than NEC

 

[jim dungar]

One of the best sources is NFPA 79, which is a standard for industrial machinery.

 

[james_mcquade]

thanks for the replies.

i have NFPA 79 but did not find anything. i will look again.

thanks again,
james

 

[petersonra]

Interlocks are added for two reasons - to mitigate hazards to people and to reduce the potential for machine or product damage.

There are no specific requirements for either that I am aware of. It is a design decision.

Generally, I am not in favor of adding any kind of interlock switch to a guard at all unless the guard has to be opened as part of normal operations.

Even if the guard is open, it may not introduce any additional hazards to people or to the machine or product.

 

[pfalcon]

ANSI B11

In general: A guard is movable if it does not require tools or excessive force to remove. If it's not movable then it doesn't require an interlock or other safety monitoring.

ANSI B11-1 and B11-19 are general. The rest tend to be specific types of machines.

As in all things safety related, general guidelines do not substitute for a proper risk analysis.