Sherwood dry bleed contaminated piston

[fmerkel]

As indicated in an earlier post all forms of chemical cleaing (rubbing alcohol, acetone, MEK, Simple Green, plain water, boiling water) have come to naught>no bubbles.
So I started taking a small diamond tip bit on a dremel to it. Remove a little > test > repeat. I must have done that a dozen times, each time cleaning before the dremel and cleaning after. FINALLY I got bubbles, measured at about 40cc/min. A bit more than spec, but a lot better than nothing. Hooray!

I let it sit overnight, tested the next day again just to watch it bubble > NOTHING!!! Huh?
What's going on here?
Took it apart, visual inspection is OK. Washed with simple green, 5" in a warm water ultrasonic, put back together > nothing.
I'm kind of frustrated.

 

[underH2Oman]

I always considered that design as questionable for the reason you mentioned, and I don't understand why Sherwood just stopped supporting their customers with at least new pistons for these models.

You can get a new/replacement piston for this regulator.

 

[fmerkel]

I've been appraised of that option. Right now I'm kind of on a mission to see if I can overcome this problem. The reg itself is not a critical component, it's been sitting for years and I have others that I can use if needed.
Thanks though.

 

[axxel57]

You can get a new/replacement piston for this regulator.

Man, thanks a lot!!

Years ago when I was asking for a customer, Sherwood didn't have them.

After your post yesterday I checked again, and right, the pistons are available.....

 

[chillyinCanada]

Glad to hear it! I've been diving my old Sherwood Maximus for 22 years. Last year it wasn't dry bleeding despite two separate services. Finally got it to the true Sherwood expert in these parts and now works again, like new!

 

[KeithG]

Glad to hear it! I've been diving my old Sherwood Maximus for 22 years. Last year it wasn't dry bleeding despite two separate services. Finally got it to the true Sherwood expert in these parts and now works again, like new!

chilly, can you reveal the expert?

can someone provide further detail about piston availability? are these "new old stock", used or newly manufactured? are they available for direct purchase (not thru a shop)? i have a first stage that just needs a new piston.

 

[keyshunter]

I believe that they are newly manufactured. But, even if they are NOS, all you might need to do is to replace the 2 o-rings. It is unlikely that the teflon HP seat has been compromised by age.

 

[fmerkel]

eBay, ~ $45 with shipping. Appears to be NOS - Sherwood Scuba Regulator HP First Stage Piston Part Dive 3601-10

 

[rsingler]

I've been appraised of that option. Right now I'm kind of on a mission to see if I can overcome this problem. The reg itself is not a critical component, it's been sitting for years and I have others that I can use if needed.
Thanks though.

Kindof neat that this thread has continued this long. Comments re: flaws in the design concept are valid (corrosion, salt crystals, silicone plugging the bleed filter), but Sherwood had a pretty elegant solution forty years ago.
The new design with a completely dry system with compensating pressure supplied by a Schrader valve is also cool, but the transmitting rods to put pressure on the piston also beg for impaired motion due to corrosion.
Divers just don't take care of their gear, and Sherwood's design has tight tolerances. Kindof like a Sig-Sauer vs a Colt 1911 semiautomatic pistol.

Anyway, re: the very first question, this sintered filter really isn't repairable. 150 psi differential just can't be controlled with a micro drilled hole down to 20 cc/min. Too bad they "upgraded" the old replaceable ceramic filter with the permanent sintered metal one.
I'll look for a serviceable used piston in the shop.
I know how you feel, though. Things like this just "oughta be fixable." Alas, not in this case. If repeated hot ultrasonic cleaning with phosphoric acid and solvent soaks didn't do it, then the thousands of tiny press are just too clogged. Sorry, but previous grinding probably didn't expose a fresh surface as much as it flattened and closed the layer beneath it.

PM me with questions if you like.

Rob

 

[rsingler]

..thousands of tiny pores...