Bushing

[mstrlucky74]

Had someone tell me that the "Provide bushing and locknuts made of galvanized malleable iron" means it has to be MIGB. Is that true? Thanks

 

[nickelec]

Migbs are metallic insulated grounding bushings. They do make them In malleable galvanized as well as standard steel see attached pics one is malleable galvanized and one is not

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[jumper]

That spec does not say they always have to be grounding bushings. They do make plain metallic bushings.

 

[nickelec]

They also make both types without the grounding lug from what I read it looks like there just requesting that whatever bushings you do use are required to be galvanized

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[MAC702]

I agree. Sounds like they are just making sure you don't use cheap cast stuff.

 

[jumper]

I agree. Sounds like they are just making sure you don't use cheap cast stuff.

Maybe, I was more of the opinion that the spec wanted to make sure plain plastic was not used in general and metallic grounding bushings were used if required or needed.

 

[raider1]

Maybe, I was more of the opinion that the spec wanted to make sure plain plastic was not used in general and metallic grounding bushings were used if required or needed.

I agree,

I read that as they do not want plastic bushings as well.

Chris

 

[Fulthrotl]

I agree,

I read that as they do not want plastic bushings as well.

Chris

the metal ones are problematic, as you can't cut them as easy
and put them on after the wire is pulled.

:ashamed1:

 

[jumper]

the metal ones are problematic, as you can't cut them as easy
and put them on after the wire is pulled.

:ashamed1:

Well, there is that little snag..........

 

[K8MHZ]

I agree. Sounds like they are just making sure you don't use cheap cast stuff.

Both of those look cast to me. The one on the left looks like a sand casting, and the one one the right
looks like a die casting.

Edit to add: I don't think the die cast product is iron. I think it's pretty difficult to die cast iron.

 

[K8MHZ]

Here are some in a catalog.

http://www.emersonindustrial.com/en...ded-conduit-bush/threaded_conduit_bushing.pdf

 

[K8MHZ]

That spec does not say they always have to be grounding bushings. They do make plain metallic bushings.

The spec also specifies malleable iron. Not just any metallic bushing will suffice.

 

[K8MHZ]

Locknuts available here:

http://www.cooperindustries.com/con...og-pdfs/conduit-locknuts-sealing-locknuts.pdf

 

[jumper]

The spec also specifies malleable iron. Not just any metallic bushing will suffice.

Those are the cheapest IIRC. Who would buy steel or worse SS ones if they were not speced?

 

[K8MHZ]

Those are the cheapest IIRC. Who would buy steel or worse SS ones if they were not speced?

I'll bet the die cast metallic bushings are cheaper.

 

[jumper]

I'll bet the die cast metallic bushings are cheaper.

You are prolly correct. I really did not pay that much attention, my mind went to SS or steel.

 

[MAC702]

I forgot the title of the thread was about the bushings specifically. I was reading the specification and my mind went to the difference between these two types of materials, especially with locknuts.

 

[Carultch]

Both of those look cast to me. The one on the left looks like a sand casting, and the one one the right
looks like a die casting.

Edit to add: I don't think the die cast product is iron. I think it's pretty difficult to die cast iron.

The die cast one is die cast zinc. Zinc is the base material, rather than the anti-corrosion coating as it usually is.

The iron one is specifically malleable iron that is zinc plated. It could be made the way cast iron is made, but it is not made by die casting. Die casting is a process that is typically used with non-ferrous metals. Aluminum, Magnesium, Copper, Zinc, Tin, Lead, and alloys of the above.

 

[Carultch]

Those are the cheapest IIRC. Who would buy steel or worse SS ones if they were not speced?

I know the reasons for spec'ing the SS ones, but what exactly is the advantage to spec'ing the steel or malleable iron bushings over the die cast zinc counterparts? What functional purpose do they do, that the die cast zinc ones do not?

A bushing is usually inside the enclosure, so outside influences like air, water, salt, and physical damage would rarely matter to a bushing. Some may be exterior, when the conduit is open air sleaving.

 

[MAC702]

...what exactly is the advantage to spec'ing the steel or malleable iron bushings over the die cast zinc counterparts? What functional purpose do they do, that the die cast zinc ones do not?....

You can get them a lot tighter with less worry about breaking them. Wouldn't think it would be as critical with bushings as it is with locknuts, but still.