Overpressure/dump valve question

[sharkey01]

I have a Dive Rite smb with an overpressure/dump valve. The valve has 3 pieces that screw together; the bottom 2 pieces/rings screw together form a seal on the sausage opening and the upper piece houses the spring and seal.

After completely cleaning and reassembling for the first time it seems if the top section is twisted all the way down (tight) the spring fully compresses and the dump function is disabled. If I leave the upper ring loose, the dump is functional. But, the system is not snugged up tight and so it doesn't seem right. I know, I should have paid closer attention when I took it all apart... did I lose a spacer? Does anyone have any pointers?

 

[Hallmac]

I don't have one to verify but I will take a shot.


When you disassembled the lower two pieces could a rubber seal have been present on the inside.

The seal would look like a rubber washer.

 

[Splitlip]

I don't have one to verify but I will take a shot.


When you disassembled the lower two pieces could a rubber seal have been present on the inside.

The seal would look like a rubber washer.

Don't think so. But good call. That would be the case on an inflator elbow, but not, at least with my Halcyons, DSMB.

I am thinking , cross threading. Seems to happen to me when I do mine. The parts OP mentioned are it AFAIK.

 

[Cave Diver]

These might help:

If you think the issue might be cross threading like one poster mentioned, when you assemble the pieces, screw them backwards using slight pressure until you feel and hear a "click" when the threads of the two pieces line up and drop together into the starting position. Stop, and then slowly tighten it in the correct direction. This helps keep from cross threading and damaging plastic parts.

 

[Hallmac]

Don't think so. But good call. That would be the case on an inflator elbow, but not, at least with my Halcyons, DSMB.

I am thinking , cross threading. Seems to happen to me when I do mine. The parts OP mentioned are it AFAIK.

Halcyon and Dive rite are rarely designed the same. Dive rite, If I am not mistaken, continues to use the designs that Hughes Industries started when they were producing items for everybody.

However, you could be correct, another cause could be a puck that is catching the outer lip and cocking.

 

[sharkey01]

These might help:

If you think the issue might be cross threading like one poster mentioned, when you assemble the pieces, screw them backwards using slight pressure until you feel and hear a "click" when the threads of the two pieces line up and drop together into the starting position. Stop, and then slowly tighten it in the correct direction. This helps keep from cross threading and damaging plastic parts.

Well the problem is not xthreading, but with the fine threads I can see how that'd be easy enough to do.

The photo titled "bcd_over_pressure_valve" in CD's post above indicates there IS a washer of some sort that I'm missing. Strangly, in that diagram there is no numerical callout (???). And, a washer inside would make the problem worse.
Anyway, further investigation and comparison with a DR wing's dump valve innards shows that the SMB valve puck is ~1.5mm taller. Interesting also: the shorter puck off the wing works.

Time to get in touch with Dive Rite.

 

[Randy43068]

It would appear from what I see in your picture that there is something preventing the round rubber gasket from making full, and flat contact with it's holder. Is the knot in the string sitting such that that is preventing the rubber gasket from laying completely flat against it's holder?

This is such a simple design, the error and correction cannot be difficult.

 

[sharkey01]

Problem is that the seal does not break when the string is pulled. Screwing the top down completely seals the valve. There is no movement possible at all inside. So it seems either I have the wrong puck, or there is an outside washer that I'm missing that would allow the top to tighten down without fully compressing the spring.

 

[Randy43068]

Did it work correctly when new?

 

[sharkey01]

Yes, and so it narrows down to
1. I lost a piece
2. I have it reassembled incorrectly
I can get it to work if I back off about 2-3 threads.