Enclosure Interlocks

[drumburg]

I have posted about this topic before but I think I kept getting off topic with the types of disconnects available. Ultimately, I am looking for a standard that states whether I must have an enclosure interlock or not.

I have been through NFPA79 quite a bit and from that I'm convinced that an interlock is required on any enclosure that has a disconnect and 50Vac, 60Vdc, or greater. My main problem is that we have other equipment here that should be covered by NFPA79 that doesn't have any interlocks and I'm trying to wrap my head around how the manufacturer is getting around the requirement.

I understand that OSHA may not require NFPA79 specifically but it does require a manufacturer to use some NRTL standards, does it not?

Machines that I don't see having interlocks also may not have an enclosure. For example, we use portable (on wheels) pad printers to decorate the widgets we make. These have a 220Vac (or 480Vac) power cord coming in with a power switch but doesn't have a traditional enclosure. It is a self contained unit with bolted on panels. Using a screwdriver you can remove a panel and access anything inside. Does the fact that a screw driver is needed to access the live parts allow for no interlock?

 

[Jraef]

NFPA 79 is the standard for industrial machinery, as defined in the standard as follows:

3.3.55 Industrial Machinery (Machine). A power-driven machine
(or a group of machines working together in a coordinated
manner), not portable by hand while working, that is
used to process material by cutting; forming; pressure; electrical,
thermal, or optical techniques; lamination; or a combination
of these processes. Machine can include associated equipment
used to transfer material or tooling, including fixtures,
to assemble/disassemble, to inspect or test, or to package.
[The associated electrical equipment, including the logic controller(
s) and associated software or logic together with the
machine actuators and sensors, are considered as part of the
industrial machine.] [70:670.2

Not everything falls under that and there are exceptions stated right in the beginning for "portable" equipment or that which is already listed by another agency. Your portable printers may fall under that exception.

1.3.2 This standard shall not apply to the following:
(1) Fixed or portable tools judged under the requirements of
a testing laboratory acceptable to the authority having jurisdiction
(2) Machines used in dwelling units

OEMs will often state (if asked why they don't meet NFPA 79) that their equipment does not qualify as "industrial machinery". Since it is not really an enforceable standard unless someone in authority says so (like a company standard), it's difficult to argue.

 

[drumburg]

In the 2018 Edition of NFPA79 that clause is 1.3.3 but still reads exactly the same.

So if I am reading that correctly, then NFPA79 does not apply to equipment that is marked by another NRTL recognized by OSHA. I don't like the fact that they used the word "tool" instead of equipment or machine but I assume that it is implied?

If their equipment is used in an industrial setting, how can it not qualify as industrial machinery? That doesn't sound like their opinions should matter. It's fact that their equipment runs in an industrial building.

To provide a simple example of what I am looking for:
I want to build a small machine that has an electrical enclosure powered by 120Vac. Inside the enclosure is a 24Vdc power supply, some 24V relays, and a PLC; all IP20 (touch safe).

Do I need to interlock that enclosure when power is turned on? If so, generally what standard is requiring me to do so? I don't need specific standards just a logical path to get there. For example, a subscribed to NRTL recognized by OSHA.