IP Sweep and Drift

[padudle]

Hello I have a 10 year old Sherwood Oasis balanced piston regulator whose intermediate pressure seems to be out of spec. When I breathe from the second stage the IP drops down to about 135 and then sweeps back to 150 when I stop breathing. After that the pressure continues to slowly drift up to about 170 psi over about 10 seconds.

The spec on reg is 135 to 150 for static IP so I am planning to take my reg in for servicing.

Do you agree that high intermediate pressure is a sign of possible 1st stage problems?

Can anyone describe the likely causes for such IP drift?

Thanks,

Pete

 

[DA Aquamaster]

The Ip drop during inhalation from 150 psi to 135 psi is normal and is just a function of flow rate of the first stage.

The IP creep from 150 to 170 psi however is not normal and indicates a leaking high pressure seat and/or orifice.

 

[Charlie99]

And if you submerge both of your 2nd stage regs, you might find that the reason the IP creep stops at 170psi is because that's when one of your 2nd stages opens up a little bit and lets out the air that is squeaking by the leaking high pressure seat and/or orifice.

I've encountered several divers on boats that thought they had a problem with their 2nd stage because it "has a little tiny freeflow". When that tiny little freeflow or bubbling stops for a few seconds each time you breath on the 2nd, it makes it pretty clear that the problem is IP creep, even without using an IP gauge.

 

[padudle]

Hello All

I took the regulator into the LDS to check out the problem with my 1st stage. It looks like the orifice that presses against the rubber seat was badly corroded. The technician took it apart right in front of me and the business end of the orifice was all green and funky. It had only been 2 years since the last overhaul.

I dropped by the next day after the part had been cleaned in the ultrasound and with a magnifying glass you could see that the lip of the orifice had a little chunk missing. This just made it impossible for the rubber seat to seal completely so a little bit of air kept leaking past between breaths.

Now I am wondering how I abused my regulator so that the orifice corroded away. It looks to me that saltwater got into the 1st stage. I always dry and install the dust cap when removing from the tank valve. The LDS owner told me that I should always hang a wet regulator with the 2nd stages down so that any saltwater drains away from the 1st stage. I guess I try to do that from now on.

The LDS ordered a new orifice for me but Sherwood sent the wrong part. This meant that my reg was not ready for my trip to San Andres, Colombia. Graciously the LDS loaned me a reg to use while my was in the shop. Sherwood asked for a digital photo of the part so they can send the right thing. Anyway I guess its a happy ending.