Blocked positive pressure valve in first stage

[Michel Dumont]

Hello there, I have a SRB3600 Sherwood reg and the positive pressure one way valve is not functioning on the first stage piston. Besides using an ultrasonic cleaner, what else can I do to allow air to flow through again? I have attached a picture taken from the service manual showing the positive air purge valve on the piston, although the manual says that absence of bubbles proves the system is not working, there is no suggestion on how to clean or repair. Is that piston fixable?
Many thanks

 

[knotical]

I'm unaware of any method to unclog the sintered filter.
Paragraph 5.4.2.2.c in my copy of the manual says the piston must be replaced.
Based on the picture you posted, I assume we have the same manual.
sorry

 

[Michel Dumont]

I'm unaware of any method to unclog the sintered filter.
Paragraph 5.4.2.2.c in my copy of the manual says the piston must be replaced.
Based on the picture you posted, I assume we have the same manual.
sorry

Yup, thanks for the quick info, I missed that in the manual. Will look for a replacement unit.
Many thanks.

 

[Couv]

Could you place the piston in an ultrasonic cleaner and get good results? In another thread cleaning sintered filters was discussed and that method seemed to work.

See post 33 in this thread: http://www.scubaboard.com/forums/repairing-your-own-gear/320118-mk5-mk10-body-cleaning-brush-4.html

 

[Texfrazer]

When I had Sherwood training a fairly long time ago, any piston with a clogged valve was supposed to be replaced. There was no mention of any means to clear it (though I've heard that some people have some success with the ultrasonic cleaner).

 

[knotical]

The last two posts in this thread: http://www.scubaboard.com/forums/sherwood-scuba/222028-updates-changes-1st-stage.html seem to indicate that some folks have had some success with the ultrasonic cleaner – but that it's a bit of a crap shoot depending on the reg's history.

The small pore size of these filters and whatever is clogging them would both factor in.

 

[keyshunter]

I have tried soaking a piston in vinegar, and once had an LDS give one a whirl in the ultrasonic--with limited success. Both methods partially worked. Because the actual orifice is so small (compared to the size of the screen), success depends upon what is blocking it, and how badly it is blocked. Personally, if I still had and wanted to dive one of the older Sherwoods, I would just buy a new piston. In the later, round bodied Sherwoods, with the orifice in the body, a blockage is MUCH easier to deal with.

 

[axxel57]

Keyshunter, what could be possibly MUCH more easier to deal with a blockage of the flow restrictor screw. The hole is laser drilled and extremly fine. So if it is blocked I haven't found any method to clear the path, so buying one of those screws and replace them is the only solution I have found. Did you find a way to clean the orifice of the flow restrictor screw? I tried ultra sonic, it doesn't work.
If you have a good idea, that would be helpful, I got the next about 15 Sherwood regs waiting on the workbench.

 

[daz88]

you need a bigger hammer!

 

[keyshunter]

axxel,
The reason I say it is much easier to deal with is that you can replace the dry bleed screw instead of the piston. In later round bodied first stages the dry bleed screw has a very efficient foam(?) puck in place of the scintered filter, and one does not need to replace this screw. The easily replaceable foam disc is included in the later Sherwood service kits. If you retrofit the newer screw (with foam puck), dealing with a blocked filter is simplicity itself. I know of no way to clear a blocked dry bleed orifice.