Regulator Creep Question

[MikeAllen]

When a regulator has “creep” does the indicated pressure increase or decrease? I would think it increases but want to make sure. I have an Impact M3 and pressures in both regulators are pretty consistent but they do vary a little at times. I think it’s probably temperature and other atmospheric influences like barometric pressure but want to make sure, and I also want to know more about this topic.

 

[2L8]

Mike, you are correct. Temperature variations should only cause slight differences in your second reg set pressure. I can't say what those differences might be at your location, but they are real. Many variables contribute to the changes in pressure from your baseline fill and reg setpoint, which should be between 40-60bar for stability. I would guess TX at any time of year does not have the same temperature swings as I have here in Colorado. That being the case, your reg differences will not be similar. 0 to 5-6bar is my comfort zone with my M3 and mk2. Plus or minus 5-6bar from my baseline is a concern and will require troubleshooting I would say. If it's outside those parameters, you might have a faulty reg, which will be another problem to solve. If that is the case, FX should send you a "reg re-build kit" part # 9121

Patrick

 

[MikeAllen]

Thanks Patrick! Here in Central Texas our temperature swings only about 30 degrees - from 78F to 108F! Can't wait for Fall!

 

[nervoustrig]

When a regulator has “creep” does the indicated pressure increase or decrease? I would think it increases but want to make sure.

Correct, the regulated pressure can only climb over time. For the most part it may be due to creep (valve squeezed mostly closed but not quite 100%) or due to the temperature climbing.

If the pressure falls due to a leak or a temperature decline, the regulator simply opens to “top up” the pressure.

 

[MikeAllen]

Thanks nervoustrig!

 

[Ca_Varminter]

Reg set Pressure variance is just a given factor of mechanical device...
Temperature is one of the main causes... Especially sudden change...
Reg Creep, the rising of the pressure over time, is usually caused by damaged sealing surface..
In the case of the M3, most likely is the Delrin piston!
In all the years I have worked on different models of Regs... Polishing the sealing surface is Very Important...
Just head over to YouTube, checkout Ernest Rowe's videos about this....
Good Luck,
Stuart

 

[MikeAllen]

Thanks Stuart. I do understand the principle but have very little change in reg pressure. I have also seen Ernest’s videos. My main reason for the post was to confirm what I “thought” I knew about this. Thanks to you and the others for all of this great information!

 

[Centercut]

Correct, the regulated pressure can only climb over time. For the most part it may be due to creep (valve squeezed mostly closed but not quite 100%) or due to the temperature climbing.

If the pressure falls due to a leak or a temperature decline, the regulator simply opens to “top up” the pressure.

I've seen regulated pressure decrease as temperature increased. I think it has to do with the "swell" of the delrin seat or brass valve pin on some regulators (not sure which one changes with temperature). As the gap between the valve pin and seat decreases, the set point of the reg. decreases... This happens as you shoot the gun, not when its just sitting with a static pressure. So I've seen when going from 75 degrees to well over 100 degrees on Huma regs. a decrease of almost 10 bar.

 

[Motorhead]

The WEAK LINK is IMO the material ( Metals ) that make up the Regulators Body and that of Inner Spool.
The bevel springs not so much.
Regulators & how they work is very simple, Pressure bears against the larger (LP) side of spool causing it move towards seat.
ANY CHANGES to the distance spool travels getting to the seat WILL CHANGE SET POINT !!!
If say Reg body is Aluminum it will expand with heat actually increasing the length of itself, same with the inner spool which we see a lot of Brass ones.

These two materials have different rates of thermal expansion be it cold to hot or visa versa.
It takes only .001's of an inch to see a set point change be it seat height or spring preload.

JMO ...

 

[MikeAllen]

Great information Motorhead - thank you!