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Change in Spring Properties over 40 Fdegs

Change in Spring Properties over 40 Fdegs

Change in Spring Properties over 40 Fdegs

(OP)
I have a relief valve (10psi,3/4 in, used for lube oil) that has been giving us problems. I am certain the problem is caused by the change in viscosity of the oil over the ranges of 60-100 deg F. However, a number of people I work with believe the spring(steel)stiffness is changing. I am sure the change is negligible; however, I have not been able to quantify it. None of my reference books give me any help.

Can anyone give me a rough value?

Thanks,  Tod

RE: Change in Spring Properties over 40 Fdegs

Some one posted a link or reference to the modulus change for different steels with respect to temperature.  I'll search and link into it if I can find it.

I also don't off hand think that the spring would be changing more than 1-4% in stiffness by modulus change w/ temp esp since your temps are so very low.

nick

RE: Change in Spring Properties over 40 Fdegs

Linky Dinky:
Thread367-58751
ne

RE: Change in Spring Properties over 40 Fdegs

The ASME Code, Section II, has tables of how the Modulus of Elasticity varies with temperature.  The steels do not vary much at all over a temperature range of 100 degrees F.  Perhaps you should indentify the materail and check out the Code information.

Steve Braune
Tank Industry Consultants
www.tankindustry.com

RE: Change in Spring Properties over 40 Fdegs

As NickE already said, the change in elastic modulus over the temperature range of 60-100 F is negligible.  MIL-HDBK-5 (revision H or J) does not have data specifically for spring alloys like music wire (SAE 1080-1095) or Cr-Si (9260, 9254, etc.), but the change in modulus for these grades will be very similar to other medium to high carbon steels that are included such as 4140.  I would be more inclined to look at viscosity or other system level effects, as change in spring rate seems like a non-issue.  By the way, if you want to obtain MIL-HDBK-5, use either of the following links:

http://www.grantadesign.com/cgi-bin/stat-tree.cgi?src=M...
MIL-HDBK-5H available as individual chapters

http://assist.daps.dla.mil/quicksearch/
MIL-HDBK-5J (latest revision) - HUGE download!

RE: Change in Spring Properties over 40 Fdegs

Tod,

Apart from Oil viscosity are you sure no vaporisation is occurring - especially if some water has got into the oil.

Martin

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