Sherwood regs

[matt_unique]

I say no. The bleeder on a sherwood first stage is specifically identified as a one way bleeder valve. This means that whether or not the reg is pressurized, there will not be any bubbles entering the reg. I know guys that use both practices of leaving the bottle off and on, and a sherwood reg should not make that decision.
Don't believe me? http://www.sherwoodscuba.com/regulators.html scroll a little down.

The dry bleed system is one way but according to my Sherwood service tech this would not prevent water entering beyond a certain depth. The pressure on the air space inside the first stage would be huge as we all know with depth and there would be a limit at which point water would enter. I'm not a tech but it makes logical sense to me. I would not rely on the one way design feature to replace the designed practice of having the reg constantly pressurized.

In April of this year I was testing my trim in the shallows with some new gear and descended down to about 15' without turning my stage bottle. I thought for sure it was flooded and brought it in for service the next day. The Sherwood tech opened it up and it was dry as a martini thankfully. He thought it would have flooded if I had gone much deeper than that even though it has a one way design.

--Matt

 

[MikeFerrara]

The check valve on the dry air bleed isn't much of a valve and I wouldn't trust it to keep water out.

I prefer not to use them on stage bottles or decompression bottles but I have and didn't have a problem other than they will bleed down when charged and turned off. In theory that could result in water getting in the first stage by way of the second stage. Still not turning the bottle off is just plain dumb because if a a little leak developes you could end up with no gas when you need it.

I've used sherwoods for a long time just because I have some but the dry air bleed is a pain and the regs aren't what I'd call high performance. I wouldn't buy any more.

Another interesting thing about the sherwood is the way that they fake it being a balanced first stage (other than the brute of course).

 

[rescuediver009]

The dry bleed system is one way but according to my Sherwood service tech this would not prevent water entering beyond a certain depth. The pressure on the air space inside the first stage would be huge as we all know with depth and there would be a limit at which point water would enter. I'm not a tech but it makes logical sense to me. I would not rely on the one way design feature to replace the designed practice of having the reg constantly pressurized.

... The Sherwood tech opened it up and it was dry as a martini thankfully. He thought it would have flooded if I had gone much deeper than that even though it has a one way design.

--Matt

Negative Matt. The bleeder is a cap type valve. So one way means one way. The deeper you go the tighter the seal. I will not give at a deeper depth. think of the type of cork that sits in a bottle that is not just a cylindrical cork. Instead it has a portion at the top of the cork that is of a wider diameter. This way there is no way to loose the cork inside the bottle. No matter how hard you push the valve will not go in. The Sherwood bleeder is the same way. IT WILL NOT LEAK !

As for what Mike said, sherwoods were never intended to be high end technical regs. They are built tough and serve the rec diving population well. Don't get me wrong I wouldn't trade my Apeks or your Atomics for one though.

 

[jonnythan]

A one way bleeder valve? If it plugs up under pressure from outside, why not just keep it plugged up all the time and make it a sealed system?

 

[rescuediver009]

A one way bleeder valve? If it plugs up under pressure from outside, why not just keep it plugged up all the time and make it a sealed system?

Because then it would be an unbalanced piston. This is the only way to get the best of both worlds. The reg is sealed and is balanced at the same time. The only other types of pistons that can achieve this are the flow through types. Even then they have the holes on the outside to allow the water pressure to balance the reg.
The more pressure holdsing the bleeder shut, the more air pressure is exerted inside the first stage to balance the reg.
Basically instead of allowing the water pressure to build and influence the IP in the reg, air does it.

 

[jonnythan]

Interesting.

 

[WarmWaterDiver]

Rescue, I'm on board with you. The industrial equivalent is a spring loaded check valve - the cracking pressure is the critical element. This only needs to be set at 1 PSI or less as it's a differential pressure to keep the air from "bleeding out" once the intermediate chamber pressure is closely approaching the ambient pressure. I don't know what the Sherwood tech's manual or specs on their particular design is for cracking pressure, but the concept is valid. So long as the intermediate chamber was initially pressurized by turning the tank valve on before again turning it off, this should suffice for the depths I'm diving. The differential pressure would still be in the direction of not having water enter the first stage via the second stage.

For my use application, which isn't on my back gas, the reg and the tank it's attached to wouldn't be used at 'great' depth for oxtox reasons anyway, so I think I'm just being prudent using the Sherwood on the sling bottle instead of the back gas (the whole point of why it was on the sling bottle).

Thanks everyone for your contributions to my question.

 

[rescuediver009]

Rescue, I'm on board with you.

Thanks everyone for your contributions to my question.

In the words of Austin Powers... ah thank you...

 

[MikeFerrara]

Because then it would be an unbalanced piston.

Not really. The Brute is non-balanced but it still has the dry air bleed.
The air bleed is what allows the reg to sense the ambient pressure to maintain an IP of target IP + anbient. Most piston regs just let water directly in.

Balancing referes to the correction for tank pressure changes. In an unbalanced first stage the IP will change with tank pressure because the tank pressure acts to try to either open or close the valve depending on the reg design. Therefor IP changes as tank pressure changes.

The Sherwood uses a springs rather than with direct gas pressure like most regs to balance.

This is the only way to get the best of both worlds. The reg is sealed and is balanced at the same time. The only other types of pistons that can achieve this are the flow through types. Even then they have the holes on the outside to allow the water pressure to balance the reg.

The dry air bleed is just a way to seal a piston reg.

 

[rescuediver009]

Not really. The Brute is non-balanced but it still has the dry air bleed.

I was referring to the Blizzard in question not a brut.

The Sherwood uses a spring rather than with direct gas pressure like most regs to balance.

They are not really springs they are conical discs. And they work in conjunction with the moving orofice. not present on the Brut.

The dry air bleed is just a way to seal a piston reg.

Don't get me wrong it does that too, but it also acts as a regulator keeping the IP just above ambient as explained in previous posts.
I think that the sherwood site has a little more info. www.sherwoodscuba.com/regulators