re-torquing m.c.c's

[jamieb]

how often should you re-torque m.c.c.'s if at all, there seems to be mixed opinions on this subject.....help!!!

 

[zog]

how often should you re-torque m.c.c.'s if at all, there seems to be mixed opinions on this subject.....help!!!

IMO, You shouldnt unless you have a high resistance connection show up in a IR scan or from maintenence testing.

 

[nakulak]

as often as the manufacturer's maintainance instructions say that you should (or a problem occurs )

 

[weressl]

how often should you re-torque m.c.c.'s if at all, there seems to be mixed opinions on this subject.....help!!!

Never, never, never ever.

 

[infinity]

Many people say never if the original installation was torqued properly. My old company did maintenance for an American Express computer center. An entire building filled with computer equipment. They would periodically shut down all of the PDU's and we would re-torque every CB as part of their routine maintenance. They thought it was a good idea.

 

[brian john]

ZOG nailed it:

Terminations are historically OVER TORQUED by electricians seldom to ever under torqued. Connections are missed and not tightened but once the man with the wrench tightens he bears down with all he has.

In cases where re-torquing is recommended the value is usually less that the original torque setting.

IR and repair as necessary, torquing a bad connection does not improve the connection.

 

[weressl]

Many people say never if the original installation was torqued properly. My old company did maintenance for an American Express computer center. An entire building filled with computer equipment. They would periodically shut down all of the PDU's and we would re-torque every CB as part of their routine maintenance. They thought it was a good idea.

The OP was asking about MCC's. Other equipment may have different requirements, however all electrical equipment manufacturers design their products in the US so that the current carrying bolted connection should require initial torquing to the predetermined level. These connections are designed to self-compensate for the thermal expansion contraction when operated within the defined mabient temperatures. Equipment subject to excessive vibration have other, additional design criteria.

 

[weressl]

ZOG nailed it:

Terminations are historically OVER TORQUED by electricians seldom to ever under torqued. Connections are missed and not tightened but once the man with the wrench tightens he bears down with all he has.

In cases where re-torquing is recommended the value is usually less that the original torque setting.

IR and repair as necessary, torquing a bad connection does not improve the connection.

Overtorqued connection will DEFINETLY develop hot spot if it is operated in the 75%+ load range.

Could you post a link where re-torquing to a lower limit is recommended?

 

[ce2two]

ce2two sparky

ce2two sparky

mcc's /traffic signals cabinets or whatever ,everything has a torque rating ,preventive maintenance will save a lot of headaches.....do it by the book (oem) ........one wire not torqued in a signal cabinet then it goes on flash ,that's when fun begins ha,ha, the nightmare really??????????????//

 

[dbuckley]

If the MCCs have bolts on the end for lugs then on installation once the bolt is torqued draw a line with a sharpie across the bolt, nut, and lug. Then if the nut moves it is noticable.

Shutting down data centres for retorquing is so last century, marking the bolts and thermal imaging has made it unnecessary.

 

[76nemo]

What about a thick layer of nail polish? You can't break a "Sharpie" mark. You can break a polish thread.

 

[zog]

If the MCCs have bolts on the end for lugs then on installation once the bolt is torqued draw a line with a sharpie across the bolt, nut, and lug. Then if the nut moves it is noticable.

Shutting down data centres for retorquing is so last century, marking the bolts and thermal imaging has made it unnecessary.

Alot of data centers use continous IR monitoring, in fact in the UK it is a design standard for data centers.

 

[haskindm]

My understanding is that - if I properly torque a connection today, and come back tomorrow and re-torque it to the same value, and then come back the next day and re-torque it to the same value, etc., etc. - I will eventualy cut through the conductor and will never have over-torqued the connection. It seems to me that re-torquing is a bad PM procedure.

 

[jamieb]

Thanks alot guys for the input!! certainly do appreciate it

 

[R Bob]

ZOG nailed it:

Terminations are historically OVER TORQUED by electricians seldom to ever under torqued. Connections are missed and not tightened but once the man with the wrench tightens he bears down with all he has.

In cases where re-torquing is recommended the value is usually less that the original torque setting.

IR and repair as necessary, torquing a bad connection does not improve the connection.

I was on a job the other day where a VA Power crew was connecting the line on a CT. They were using a socket and ratchet.

I asked one of the guys if they ever use a torque wrench. He laughs and says that they just crank it down until it clicks, then it's torqued!

 

[brian john]

I was on a job the other day where a VA Power crew was connecting the line on a CT. They were using a socket and ratchet.

I asked one of the guys if they ever use a torque wrench. He laughs and says that they just crank it down until it clicks, then it's torqued!

I once offered a torque wrench to a PEPCO CT installer just so he could see how much he was over tightening the hardware, his buddy told me in no uncertain terms to F off.