replacing mk200 hp seat

[halocline]

The question is, what happens with the IP as it's leaking? If your leak is coming from the ambient chamber, on this reg it has to be from the IP chamber (I think) which means as it leaks either the IP is dropping until the piston moves and 'burps' it back up, or it's creeping, which in this case might look like its staying put at 140, because it means air is leaking out of the ambient chamber as it's also leaking in from the seat.

It really helps to have a clear picture in your head how the air flow goes. You're positive the leak is coming from the ambient chamber holes? Meaning, you've bubble tested it and there's no doubt?

 

[runsongas]

The leak is constant enough that there really isn't any burping action. I can feel the leak coming from the ambient holes if I cover them with my fingers. If it was the seat, then it would have to be sealing really badly for it to leak like this right? else I should see the IP increase till the piston moved far up enough in the chamber to seal it off?

 

[halocline]

Please try two things.

1. Get an IP gauge (maybe you have one) and watch it while you pressurize the reg. Take note of any movement. If the seat is sealing but air is leaking from the IP chamber, the IP should go down as air leaks out of the IP chamber until it gets low enough for the piston to move, refilling the IP chamber and the process starts over. It might be happening pretty quickly, I really don't know. If it's a bad enough leak I guess the seat would never lock up. That would be like having an open LP port or a major freeflow in a 2nd stage. If the seat is leaking the IP would creep up until it forced a leak at one of the piston o-rings.

2. Submerge the reg while pressurized and see exactly where the bubbles are coming from. It's surprisingly difficult to locate an air leak without doing this.

 

[runsongas]

Well I am not sure which suggestion did it, but it finally pressurized after I used polish on the chamber, replaced the orings again, and flipped the hp seat (both sides were used so I picked the side that looked in better shape). The IP is a little higher than before (around 145 or so), so I may need to play with shimming the piston. Thanks for all the help and advice guys!

 

[halocline]

The IP is a little higher than before (around 145 or so), so I may need to play with shimming the piston. Thanks for all the help and advice guys!

A new seat should take care of that. When you pressurize the reg, watch the IP gauge for movement. Then tap the purge a few times and watch again. It should lock up quickly and solidly at the same IP every time. Often a nick or old groove in the seat will cause it to creep a little, maybe not lock up at the same pressure every time, stuff like that.

I would set the IP around 145 at a very full tank, 3000 or maybe even a little higher if you have a HP tank. On this reg the IP will drop close to 20 PSI throughout the supply range, so a tank at 300 should read 125 or so. If you're getting 145 with a tank that doesn't have much air in it, you need to lower the IP as you'll be way above the range with a full tank. To lower the IP you remove shims, not add them. (You might realize that) if you are getting 145 with a low tank pressure and no shims, get a new seat, they're very cheap for this reg, and try that.

 

[ams511]

90 duro viton from sterling seal and supply

I would try a 70 or 75 duro even if it from a hardware store just to see if it seals.

 

[runsongas]

I understand that removing a shim decreases the psi (as there is less distance needed for the piston head to move in order to close). There is a little bit of creep (about 3 psi or so after 5 min) but it is locking up at the same pressure at least. I have 2 shims on it right now per the schematic configuration from frogkick. Asking my LDS to sell me a generic seat may be an adventure in of itself.

 

[halocline]

I understand that removing a shim decreases the psi (as there is less distance needed for the piston head to move in order to close).

Not exactly, the shims basically compress the spring a bit more. This puts a little more spring pressure holding the seat off the orifice ( meaning the 1st stage valve is open) and requires proportionally more air pressure to push the piston so that the seat contacts the orifice. IP is the the amount of pressure needed to close the 1st stage valve.

Your IP measurement can't be evaluated without knowing what the tank pressure is.

I would really suggest you get the Vance Harlow book on regulator repair. You'll enjoy it and some of your questions will be answered.