Machine Disconnect

[Mikepait]

We have a machine (OLD) that the disconnect no longer works. The disconnect is no longer available, It is flanged mounted to the control box,the flange mount operates a lever that turns off the disconnect in the control box. Is it within OSHA standards to mount a Fusiable disconnect on the outside of the control box for control of power to the machine, If we remove the old disconnect and cover the hole where the old switch handle used to be.thanks

 

[S'mise]

The easiest thing to do is order another disconnect/handle. You should not have too much trouble retrofitting a new one. The external fusable disc idea might be ok as long as the nema ratings are observed. I would fab up a plate to cover the old hole to suit. Check with nfpa79.

 

[DAWGS]

We have a machine (OLD) that the disconnect no longer works. The disconnect is no longer available, It is flanged mounted to the control box,the flange mount operates a lever that turns off the disconnect in the control box. Is it within OSHA standards to mount a Fusiable disconnect on the outside of the control box for control of power to the machine, If we remove the old disconnect and cover the hole where the old switch handle used to be.thanks

We have had to do this many times. Their is nothing wrong with it as long as you keep your working clearance, within sight and 50', and label it.

 

[petersonra]

I don't recall any requirement that the machine disconnecting means be flange mounted, or even in or on the machine control panel. Not unusual for it to be a switch hanging off the busway, or a separate local switch as you are thinking of doing.

The main advantage to the flange mount disconnect is that it discourages casual entrance to the enclosure while it is live.

 

[Mikepait]

I don't recall any requirement that the machine disconnecting means be flange mounted, or even in or on the machine control panel. Not unusual for it to be a switch hanging off the busway, or a separate local switch as you are thinking of doing.

The main advantage to the flange mount disconnect is that it discourages casual entrance to the enclosure while it is live.

This is why I was asking about the disconnect. My supervisor says this way the machines power is disconnected before anyone can enter the control box. I said Unauthorized personnel should not be entering a electrical box. So if the Control box has a safety switch which prevents someone from entering the box unless power is shut off, say this device is defective can one put a Disconnect outside the box that does not prevent a person from entering the box with power on and cover up the old existing way of shutting down said machine. thanks

 

[dbaird]

NFPA 79 Electrical Standard for Industrial Machinery answers this.

http://download.yousendit.com/FDA5B6A1705F2852

 

[petersonra]

5.3.1.4 Supply circuit disconnecting means mounted within or adjacent to the control enclosure shall be interlocked with
the control enclosure in accordance with 6.2.3. Where the
supply circuit disconnecting means is not adjacent to the control
enclosure, or where the supply disconnecting means is an
attachment plug and receptacle, a tool shall be required to
open the control enclosure door and a label shall be attached
to that door warning of dangerous voltage inside and advising
disconnection of the power before opening.

Personally, I am a big fan of having the interlock.Some people use electrical interlocks, but that requires some means of de-energizing the interlock.