Cleaning Sherwood First Stage Laser Drilled Flow Control

[BRT]

OK, so this is an adventure! Make sure you have some coffee, it's a long one!

When we last spoke, I had 6 clean flow control screws. They first had 10 minutes in ultrasonic with ~3% phosphoric acid and a little Dawn (less than 1/4 tsp in 10oz). Light check. Those that were still clogged had another 10 minutes. When I was done, I could see light through all of them. Great! So time to test.

A few notes about testing. I tested the first one with the first stage end cap tightened properly. That gave me an IP of 125psi (these are Blizzards and tuned for icewater). I then re-tested with the end cap hand tight, which left it about 1/16" from fully screwed down. Turns out that this doesn't make a difference at all: same IP, same flow results. Good to know: it's a lot faster testing without using a big wrench...

Also, hitting the purge button on the reg for, say, a full second or so causes the bubbles to completely stop. It takes a good 5+ seconds for the bubbles to start again. Interesting: it seems that in normal operation that one-way valve will need to keep the water out for at least a little bit.

Back to the results. Of the six, one performed well below spec (7cc/min), three performed slightly below spec (17cc/min), one performed within spec (25cc/min) and one was actually past spec (35cc/min).

I decided to work on the three slightly below spec They were all within 16-18cc/min and would give me an opportunity to see how more cleaning affected them. I ran them through 10 minutes of ultrasonic in the phosphoric acid again. Pulled them out and rinsed them. Put then back into the reg: no bubbles on two, and very weak bubbles on the third (well below what it was before and didn't even bother to measure)!

What was the difference? Well, for one thing, I had quickied out on the rinse. So, I redid them, this time going through my full O2-style process (which I did last night). Another thing: I hadn't dried them. Last night they air-dried. Today, there might have been a droplet in them. I wouldn't normally think of that as a problem, but that is a *really* tiny hole to try to push air *and* water through... So I blew them out with tank air.

Somewhat better: one was at 17 cc/min, one at 20 c/min, and one was clogged, and I couldn't see light through it (which I could when the rinse was done). So maybe there's a reason Sherwood put a filter upstream of these?

For the two clogged ones, I whipped up a new batch of cleaning solution, this time 1:5 (or ~6% phosphoric acid) and less than 1/4 tsp Dawn to 10oz solution. Another 10 minutes, then full O2 rinse process, then quick blow dry. I can see light.

After testing: better results! One was 20cc/min and one was 22cc/min. Nice!

So I now have six unclogged flow elements! The process seems to have worked. But it's really picky. Seeing as I had six of them, it was well worth the effort. If I only had one? I'd be tempted to simply buy a replacement -- especially once I had bought a spare one on the shelf that I could use immediately and not have to wait on the replacement.

For the future, I'd go with: 1:5 Klean Strip to Hot water (10oz total), <1/4 tsp Dawn. 10 minutes ultrasonic. Look for light. Repeat if no light. Full O2-style rinse process. And it does work!

Hopefully I can simply keep these guys bubbling and won't have to go through this for a while!

Thanks. Great to have a roadmap.

 

[rsingler]

There's another thread percolating right now on regs for extreme cold water. I thought it worth sharing this link:
Cold Water Regulator Blues
How about that Sherwood picture!!!
It's a shame they haven't gotten better press. Of course, their little SR-1 blip didn't help, but the SR-2 is a worthy follow-on.
Different dry engineering, but just as inventive.

 

[ams511]

Rob, I remember reading somewhere about the regulators used in the Antarctic diving program. There were using old style (SRB 3600) Sherwood Maximus regulators that were modified by reducing the IP and adding the heat transfer fins from the Blizzard (which I thought was odd because I thought the Maximus had them already. One thing I remember from the article is that a regulator needs to be retested if they are redesigned. I think that is why they were using older rather than the newer version. The newer version was not as good under the ice.