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mcapps1
Participant

Join Date: Nov 2006
Posts: 4

Gas Regulator Spring Problem

03/22/2007 4:12 PM

Given Info: Spring 1 has a spring rate of 580 lbs/in and spring 2 has 740 lbs/in from a test our vendor performed. Only differences are: #1 has .004" diff. in wire dia., .012" difference in free length, and .002" difference in solid height (#1 at .960" SH and # 2 at .962" SH).

Problem: Both springs were placed in the same regulator and spring #1 passed the test by meeting 500 psi (minimum) while #2 failed at 375 psi. How can a lower rate spring perform better than the higher rated spring? Could it be the free length difference, or spring #2 over powered inlet pressure to were it bottoms out before desired spec?

If you have any ideas I'd appreciate it.
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Tom Kreher
Power-User

Join Date: Nov 2006
Location: Oregon
Posts: 238
Good Answers: 5
#1

Re: Gas Regulator Spring Problem

03/23/2007 2:50 AM

In only differences you did not mention the outside diameter of the springs. If spring #2 had a larger O.D. you may have some mechanical interference cutting the force to the diaphragm or piston.

If a spring were to go solid and hold the valve open your secondary pressure would approach primary (high pressure out) pressure pronto unless flow was very high.

I would have spring #2 retested or throw it away. It is a puzzle not a spring.
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Anonymous Poster
#2

Re: Gas Regulator Spring Problem

03/23/2007 3:19 AM

No expert here but springs are supposed to exhibit approximately linear behavior. The force is a constant x spring compression distance. Sounds like the spring has a weak section due to manufacturing defect or was rated incorrectly by the vendor.
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garth
Guru
Australia - Member - New Member Engineering Fields - Mechanical Engineering - New Member

Join Date: Sep 2006
Location: NSW Australia
Posts: 1101
Good Answers: 23
#3

Re: Gas Regulator Spring Problem

03/23/2007 9:21 AM

What do you mean failed at 350 psi ? Do you mean it could not produce more than 350 psi at max compression [ not bottomed out] ?

In which case it cannot be a 740 psi spring

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jmart23
Guru

Join Date: Jun 2006
Posts: 501
Good Answers: 8
#4

Re: Gas Regulator Spring Problem

03/23/2007 9:45 AM

Is this regulator adjustable - just screw the adjustment in to add pressure? and to adjust for the difference in solid hight.
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