Serrated washers on steel conduit

[Rocboni]

Whats the opinion in serrated washers with galv steel conduit? I was always taught at college to have one in between coupler and accessory and coupler and trunking, wether being used as the cpc or a separate cpc.

I was at a job today where they are installing a trunking/conduit system but are not using serrated washers, I mentioned it but basically got told to shut up! Couldn't really come up with a good answer, they just said it's not being used as the earth. I said it could carry significant fault current so the system need some to be mechanically and electrically sound.

 

[Rosco]

Isn't that why we bond the trunking or metal box or conduit box that said conduit is attached to? I've never used serrated washers or been told to do so.

 

[soms]

I'm interested to hear what others think about things like this. We are taught that metal conduit and trunking must be earthed regardless of whether or not it is used as a c.p.c. (as it is an exposed conductive part) and that you should achieve electrical continuity throughout the containment system. However, we have not been taught to use of serrated washers. Another one is scraping paint of metal backboxes etc. Reminds me to refer to the text books I have (mixture of old JTL/CITB and some new) and see what is said.

 

[westward10]

I like seeing serrated washers as you say just because a separate cpc is incorporated it is just important the conduit is effectively earthed. Of course a correctly installed system should ensure continuity but I do like them.

 

[Rocboni]

I like to see them aswell, but not a good reason. If it was my job they would be fitted, but not much I can do!

 

[LankyWill]

I went in the wholesaler the other to get some for a large swa gland, the look of dismay from the bloke behind counter was priceless. He said we dont stock any serrated washers....

 

[westward10]

I have had trouble getting brass nuts and bolts for banjos recently.

 

[7029 dave]

Okay, what the hell is a serrated washer.?

 

[westward10]

Okay, what the hell is a serrated washer.?

Serious.

 

[7029 dave]

Serious.

Never heard of the term.Got a pic?

 

[westward10]

Never heard of the term.Got a pic?

Can't do this putting picture up bits. How about shake proof washer, same thing, Google it.

 

[7029 dave]

Just googled it, and can say don't see the connection with conduit work or any kind. Never used them in my day.

 

[buzzlightyear]

not used them in long time

 

[westward10]

Just googled it, and can say don't see the connection with conduit work or any kind. Never used them in my day.

You can get them in conduit sizes and fit between the coupler and enclosure, makes for good continuity.

 

[7029 dave]

You can get them in conduit sizes and fit between the coupler and enclosure, makes for good continuity.

What is wrong with bush and coupler, bush spanner used of course.?

 

[drzsta]

Never used them in any conduit system. Why would a competently installed conduit run with threaded fittings require serated washers for earth continuity?

Anything painted I rather get good contact with an earth prep tool like G&j Hall manufacture.

 

[7029 dave]

Never used them in any conduit system. Why would a competently installed conduit run with threaded fittings require serated washers for earth continuity?

Same, folk can't be arsed today to spend a bit of time cleaning the accessory up to obtain good continuity.

 

[westward10]

As I said in #4 a well installed system shouldn't need them but I still like them.

 

[Marvo]

Okay, what the hell is a serrated washer.?

They're known as star washers in this neck of the woods. Generally used to provide a mechanical lock for a nut especially in a vibration environment. Do they actually do anything to improve earth impedance on steel conduit systems? I've never seen them specified to improve the impedance of a joint, my initial thoughts would be that they may even decrease the contact area or maybe could strip the galvanising off one of the surfaces and accelerate corrosion so could even be detrimental... (**tin hat on**)

 

[Des 56]

Just googled it, and can say don't see the connection with conduit work or any kind. Never used them in my day.

Here,here
Not only have I never seen or heard of washers (serrated or otherwise) being used on a conduit system,the action of introducing two extra surfaces to retain continuity (where no action should be required) seems to be making the continuity and effectiveness of passing a high current worse.
If it was the case it is a better practice why were we not doing so decades since