Cleaning Sherwood First Stage Laser Drilled Flow Control

[rsingler]

Thank you very much for the information! However, that is for cleaning the *piston* with the sintered-metal insert. Those are pretty much acknowledged as being completely uncleanable.

I'm asking about the laser-drilled insert that goes into the body. This was a mid-1990's improvement in the design with a late-1990's improvement to the laser-drilled insert. Here's a quote from the SRB5300 Assembly and Maintenance Guide:



The problem is, I tried cleaning the insert in an ultrasonic cleaner, and of 6 of them, zero improved. So I must be missing something. Hence my question.

I know I can replace them. But I'd rather learn how to clean them -- I have a *lot* of Sherwood regulators...

The tiny laser drilled hole is open, or it's not. You made the comment in an earlier post: "no air bleed". If you can see a tiny speck of light thru the hole, there MUST be air bleed, or there's a separate problem going on.
Now if the bleed is present, but below specification, that is a function of the hole diameter and/or the effectiveness of your U/S and solution.

If there's zero bleed, but you can see light thru the hole, there must be an obstruction in the pathway to the little rubber bleed plug.

If there's light visible, I'd switch from vinegar to phosphoric acid. You can get food grade phosphoric acid on Amazon. Start at 3% and then double it. Add a few drops of Dawn and a few drops of antifreeze to help penetration. Warm it.

Let us know!

 

[tmassey]

I had previously tried blowing/sucking through them, but got no results (which makes sense: it takes >100 PSI to move 20cc/min!).

Getting to see light visible through them was tricky. That hole is *SO* small that the light is very difficult to see unless it's bright, and then you're usually overwhelmed by the light from *around* the screw. I made it work by holding them in my right hand, behind my left hand with a tiny crack between two fingers -- a crack smaller than the diameter of the screw. You could probably do the same thing with a piece of cardboard or aluminum foil: put a hole in it smaller than the screw, and put the screw behind that.

In any case, that allowed me to see that of the 6 screws I'm dealing with, 3 had light and 3 did not. I put one of them with a visible hole into a reg real quick (no filter on the screw and just hand-tight) and found that it's generating 7cc/min. Way below spec, but with the hand-tight there may be a much lower IP. So, maybe something was improved?

I know that Sherwood recommends a curious blend of 1000 cc water, 60g sulfuric acid and 60g potassium dichromate, but I don't have that lying around (or a source to acquire it), and hexavalent chromium is not healthy stuff anyway, so I usually stick with 50% vinegar (or 2.5% acetic acid). Phosphoric acid, Dawn (which is great stuff) and antifreeze is a new one on me. What does the antifreeze (ethylene glycol I assume) do?

Home Depot has Kleen Strip Phosphoric Prep and Etch, which according to the MSDS (link below) is 35-45% concentration phosphoric acid for $16 for a gallon. Amazon has 8oz (1/16 of a gallon) of 10% food-grade phosphoric acid for $9 Prime, but I don't want to wait! (The MSDS for Krud Kutter Concrete Clean and Etch seems to show it to be similar.)

Does anyone think there'd be a problem with using the Kleen Strip product (diluted 10:1)?

Of course, right after giving the formula for their magic cleaning solution, Sherwood then says the following:

Cleaning solutions recommended by ultrasonic cleaner manufacturers: The preferred choice.

So maybe I should give that a chance, too! (But I'm not finding a good source for anything other than jewlery cleaner locally.)

Anyway, I'll see if I can hut down the supplies tomorrow and let you know how I make out.

Klean Strip MSDS: http://www.kleanstrip.com/uploads/documents/GKPA30220_SDS-401.5.pdf
Krud Kutter MSDS: https://www.rustoleum.com/~/media/DigitalEncyclopedia/Documents/RustoleumUSA/TDS/English/CBG/Krud Kutter/msds/concentrates-and-outdoor-cleaners/ce-concrete_clean _etch.ashx

 

[Couv]

950 ml of 85% Food Grade Phosphoric Acid | eBay dilute as necessary.

Add the dish soap to work as a surfactant, the anti-freeze as a penetrant.

 

[rsingler]

950 ml of 85% Food Grade Phosphoric Acid | eBay dilute as necessary.

Add the dish soap to work as a surfactant, the anti-freeze as a penetrant.

What @couv said

I actually tried the Krud-cutter in an early batch of home brew Lawrence Factor Wash. So if you can't wait, it'll probably be okay. But you never quite know what else is in those products.

As for the consequence of low bleed rate, if you had a VERY rapid descent, with a bleed rate of 7 cc/min, and an IP chamber volume of 3 cc, then it might take 25 sec for IP to recover. In other words, if you instantaneously descended to 99 ft (4 atm = 59 psi), your delivered IP to your second stage might temporarily drop to 80 psi.
A G250 would barely notice the difference, and the same is probably true of an Oasis.
And it would recover in 25 sec, EXCEPT that there is a little risk of water entering via the rubber bleed plug as you suck IP down further with a breath.
But in practice, no significant risk at all, IMO.

Still, it's worth the effort to keep trying. Keep us informed!

 

[ams511]

I had previously tried blowing/sucking through them, but got no results (which makes sense: it takes >100 PSI to move 20cc/min!).

Have you tried using compressed air either out of a tank or a can to blow out the hole? I know it is small but if you do it in a bag then you won't lose the part if it blows away.

 

[BRT]

Have you tried using compressed air either out of a tank or a can to blow out the hole? I know it is small but if you do it in a bag then you won't lose the part if it blows away.

If compressed air would do it I think the 3000# in the tank would succeed.

 

[grf88]

If compressed air would do it I think the 3000# in the tank would succeed.

It is only subjected to IP in the reg not 3000psi.

 

[BRT]

It is only subjected to IP in the reg not 3000psi.

OK, only shop air pressure then.

 

[ams511]

OK, only shop air pressure then.

Sorry that is what I meant, the intermediate pressure not the tank pressure.

 

[BRT]

Sorry that is what I meant, the intermediate pressure not the tank pressure.

No need to be sorry, you were correct.