IP flutter on a sealed diaphragm 1st stage

[greeniguana]

I have an RG1208 that makes a vibrating sound when breathed and the IP does a wide ranging rapid vibrating flutter/oscillation between 110 and 170 PSI. It doesn't just drop 10psi and return. The IP when it's at rest is stable at 135

Any idea what the problem is? I took it apart to overhaul but I don't see anything. The seat face doesn't look different than any others I've done.

 

[runsongas]

have you removed the diaphragm already and checked the valve lifter and body?

 

[greeniguana]

have you removed the diaphragm already and checked the valve lifter and body?

Yes. Nothing unusual. Right amount of lube, nothing missing. Diaphram in good shape.

 

[runsongas]

no binding of the valve lifter or hp seat through their regular travel distances? if so, i would just go ahead with the rebuild and see if the behavior goes away

 

[rsingler]

I would polish the shaft of the pin hat. That's the only place I can think where binding would allow IP to surge past the setting. The HP seat shaft is well lubed, and the pin doesn't make contact with anything in transit.

 

[greeniguana]

It is getting rebuild.

The pin hat stem and seat shift are in good shape and no movement restrictions

 

[greeniguana]

Rebuild fixed it. I think something was wrong with the HP seat face. It did not look the same as others I've replaced.