Two Disconnects to feed one Test Stand

[Davebones]

Engineer wants to power up a test stand ( 2 - 150 hp motor's ) with 2 - 400 amp bus switches . Basically one switch to feed one 150 hp motor each . I would like them to use one 600amp bus switch to feed both motor's . The engineer says he doesn't like this because if problem with one motor then he can't run the other motor . I say all we would have to do with one bus switch would be pull out the fuses that feed one motor should we have a problem . I see this as a safety issue where I want someone to only have to shutdown 1 disconnect vs having two to turn off to work on the stand .Just looking for some thoughts on this ...

 

[WorkSafe]

I don't see this as a safety issue. If someone needs to perform maintenance on the stand, you are required to have specific instructions on how to Lockout/Tagout the machine. The instructions will state to throw the knife switches into the open position and lock them out. Not a big deal in my opinion. If we are talking about you need to shut the stuff off for an emergency, maybe they should tie in a emergency shutoff.

 

[petersonra]

I do not believe that removing the fuses to one motor would meet LOTO requirements.

 

[Davebones]

Should we have a problem with one of the pumps we would remove the fuses and install a a tag at the fuse terminal so the operator couldn't run this pump . If we WORK on the pump or the stand we would then LOTO the main 480 V bus switch . I'm looking at the fact if we install 1 - 600 amp bus switch we only have switch to lockout vs having 2 and maybe 3 bus switches including heaters to LOTO in case of maintenance being done on the stand ..

 

[WorkSafe]

Well, technically you would have to deenergize that circuit before you remove the fuse since you can't work energized.....correct? That would render the single fuse a moot point in my opinion. It would be easier for an employee to throw a disconnect for a single machine and stick a lock on it to prevent accidental operation.

 

[pfalcon]

Multiple disconnects on test stands that size are fairly common in practice. The stands are often designed in such a way that the two feeds remain isolated from each other so that they can actually feed off separate supplies. This might be necessary due to buss capacity in that area such as our site. The stand won't run without both disconnects closed.

Make the drops near each other and post accordingly.