Effect of Heating/cooling on spring steel

[Kmclean]

Hi Everyone, Wondering if any body has any information on the below.

I work in a company which has a glue delivery system, within this there is pressure relief valves which are set using a spring and then air pressure to the one end which sets your 'relief' pressure, for example air pressure of 4 bar onto the pressure relief means it will activate if pressure inside the tank exceeds 80bar.

As the glue sets it becomes near impossible to clean, the only way we do this is placing the valve into an oven at 4-500c to burn the glue out of it.

I was wondering what effect this would have on the spring (spring steel) and how much it would effect its performance? (if the 4bar pressure would still give a relief pressure of 80bar, or it would weaken this significantly). Once these have been in the oven they are brought out and left to cool down at room temperature.

Any Information would be appreciated.

 

[EdStainless]

You need to know what stress relief temperature was used on the spring when it was manufactured.
I would expect this temp to be in the range of 250C-425C depending on the alloy.
Going above the original temp will cause relaxation of the spring.
The spring rate will not change, but the free length and travel limits will.

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P.E. Metallurgy, Plymouth Tube

 

[Kmclean]

Thanks for the Reply!


For the use i am using it then, as the spring rate is the same it will compress the same amount that it would of before being placed in the oven. As the valve relies on this pressure on the spring to seal the valve until said pressure opens it, then it should operate the same, regardless of the free length of travel?

Unless the spring increases in size so much that it needs to be compressed more to fit into the valve/casing therefore giving more initial pressure on the spring before adding additional air pressure onto it?

If this makes sense to any one else?

 

[chicopee]

Have you thought about using a solvent bath to clean out the glue from the spring?

 

[EdStainless]

I am worried about stress relaxation resulting the spring getting shorter and not applying enough force.
If the spring has any load on it when heated it will start getting shorter.

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P.E. Metallurgy, Plymouth Tube