updates/Changes to 1st stage?

[Sherwood SCUBA rep.]

1. The dry air bleed system is what allows the first stage to sense the ambient pressure. So the answer is yes, it is the mechanism that tells the first stage how deep it is. As you descend ambient pressure increases and more air flows into the chamber until it starts bleeding air. This will increase the IP in the first stage. If the Dry Air Bleed is not functioning on your first stage, take it to your LDS. The service on it is pretty easy.

2. The belleville washers (there is only one spring in the first stage) are what make the orifice a moving orifice. As pressure is reduced in the tank the moving orifice pulls away from the piston allowing the IP to remain the same throughout the dive.


Hope this helped.

 

[tfsails]

This served to verify my suspicions. I work as a service tech for a Sherwood dealer and have rebuilt many Sherwoods (as well as other brands). Actually, your system is pretty ingenious and trouble-free as long as the tech knows not to dip the piston (old) or dry bleeder (new) into the ultrasonic cleaner. I've had a spate of bad ones recently and had to replace a few of the above parts.
I knew the belleville washers were washers, but taken together, they serve as a spring--and they seem to work quite well!
Thanks for your help.

TF

 

[skdvr]

So why can't the old pistons go into a ultrasonic cleaner? I can understand the drybleeder. I guess I have never seen an old piston of a Sherwood 1st (Well what is OLD)

Thanks
Phil

 

[keyshunter]

So why can't the old pistons go into a ultrasonic cleaner? I can understand the drybleeder. I guess I have never seen an old piston of a Sherwood 1st (Well what is OLD)

Thanks
Phil

The older Sherwoods had the dry bleed orifice integral with the piston. Essentially, there was a hole in the piston with a scintered filter permanently fitted in place. About the mid '90's, Sherwood changed the body, so that a replaceable bleed orifice was machined into it. The piston no longer needed to be replaced if the filter was plugged. The orifice unit was merely unscrewed, and replaced. Later, the integral filter in the replaceable orifice was changed to an easily replaceable foam? filter. If this filter is blocked, just the filter, and not the entire orifice is changed.

Back in the bad old days, I pounded the hell out of two Sherwoods in almost daily use. They were "carefully" cleaned (read occasionally squirted with the hose when the boat was being washed), and tossed into the cabin. I almost never had a problem with the piston integrated bleeds, since I was very careful about keeping water out of the inlet. But, if I did, I would soak the piston in vinegar, and that seemed to solve the problem. I suspect that if clean solution is used in an ultrasonic, no damage would be done, but scintered filters are rather difficult to clean properly, and, depending upon what was blocking it, the cleaning might not be successful.

 

[tfsails]

That's the problem: used ultrasonic cleaner will have a film of oil on the surface that means absolutely nothing to any piece of any regulator except the Sherwood sintered bleed orifice. This film will coat the sintered metal and clog it up, rendering it inoperative. If this happens to an older reg's piston, your only option is to replace the piston. With a newer reg where the bleeder is in the body, you can replace the bleeder and fix the problem.

Not even new cleaner with heat will unclog the orifice. The only choice that I've seen is to replace it. Fortunately, pistons are not that expensive.