Change in Spring Properties over 40 Fdegs

[todcaesar]

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

 

[NickE]

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

 

[NickE]

Linky Dinky:
thread367-58751
ne

 

[JoeTank]

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

http://www.tankindustry.com

 

[TVP]

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=MIL5-H.xml&br=3

MIL-HDBK-5H available as individual chapters

http://assist.daps.dla.mil/quicksearch/

MIL-HDBK-5J (latest revision) - HUGE download!

 

[martintw]

Tod,

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

Martin