Belvi washer

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ptonsparky said:
What is the typical installation method for belvill washers. Point of contact and another full turn?
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Belleville?
Think it might depend on application.
I've seen them mostly used in stacks where they are back to back to form a a disk spring assembly on heatsinks for pressure-mounted semiconductors.
There is a tell-tale tab that gets just loose when the springs are correctly compressed.

For copper bars, we use high tensile bolts and a torque wrench.
 
zbang said:
Enough to load/flex the washer but not so much as to flatten it.
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"Exactly halfway between uncompressed and flat." Very quantitative. :)
That gives you the greatest expansion and contraction range without losing pressure.

If it will be used mainly at a temperature different from room temperature, you want to make sure that it neither loosens nor bottoms out at that temp.
 
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zbang said:
Ah, you caught me before the edit :)
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Edit time expired, so:

PPS: They must always be used in pairs (total = even number) with the concave side out at each end. That way there is no friction at the perimeter to mess up the contact force as the washers compress and expand.

PPPS:The source documents zbang provided describe use of single Bellville washers, which is quite good for most thermal expansion situations. It is only when you have to go to more than one washer to give enough range that the pair configuration comes into play.
Piling up Belleville washers nested (all facing the same way) does no good at all (except maybe to allow a somewhat higher contact force than the washer is actually rated for.)
 
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GoldDigger said:
PPS: They must always be used in pairs (total = even number) with the concave side out at each end. That way there is no friction at the perimeter to mess up the contact force as the washers compress and expand.

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Not that I've read any real technical papers on installation, but don't you have that backwards? Shouldn't it be convex side out, concave side in?
 
Put them in any way you like, as long as each one bends away from the ones it touches.

Only when there are several in a stack (making little 'UFO's') can the assembly as a whole act as a spring. Ordinary spring rules apply: the more the stack is compressed, the more energy is stored.

To illustrate:

()()()() is 'best'

)()()()( works

)))) or (((( isn't much better than a stack of simple flat washers in preventing things from coming loose.
 
renosteinke said:
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)()()()( works

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But you lose most if not all the compressive strength of the last washer under the bolt head or nut... unless you have a heavy duty large flat washer(s) between them, which pretty much leads to the pairs should be installed cup to cup.
 
Smart $ said:
But you lose most if not all the compressive strength of the last washer under the bolt head or nut... unless you have a heavy duty large flat washer(s) between them, which pretty much leads to the pairs should be installed cup to cup.
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You do not exactly lose the compressive strength, you lose the spring travel. And if you use a large flat washer it may just bend anyway and permanently deform.
 
ptonsparky said:
What is the typical installation method for belvill washers. Point of contact and another full turn?
Click to expand...

We as an electric/water utility belong to an organization called EUSERC. It's function is to write manufacturuing requirements for service equipment. Belleville washers are used in most of the switchgear equipment we deal with. Literally all of the manufacturers have specific torque requirements for the various type of "beveled" washers they supply. The torque value is required to be posted in the compartment where the washers are used. Bottom line, check with the equipment manufacturer if you want the correct info. Rule of thumb is fine, but in a liability type of environment, any damage or fires determined to be caused from improper torque can leave a contractor wide open to a fat lawsuit settlement. Why risk it.
 
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