Does brass+glass SPG require any checks/service?

[elgoog]

Hi -

Scenario 1 = used SPG. Anything I should look for other than it "works" and shows the right tank pressure? Maybe leave it on the tank for a few minutes to see if there are any changes?

Scenario 2 = new SPG. Does this get checked at all during the usual regulator service?

Thanks in advance,
elgoog

 

[claymore]

The only service for an SPG is to replace the HP spool or the o-rings on the spool between the hose and SPG.

 

[GrumpyOldGuy]

With any SPG, I would check to a known source at relatively low pressure on occasion. I use an SPG but a 2nd known good reg works too.
Most people check 0 (pegged / useless) and full, what you really want to know is how accurate it is at the end of the dive and is the error linear.
Sometimes old SPG's can get sticky in the low range, which is bad. A linear error reading low is not as big of an issue as reading high or being sticky.

 

[elgoog]

The only service for an SPG is to replace the HP spool or the o-rings on the spool between the hose and SPG.

Sounds good.

what you really want to know is how accurate it is at the end of the dive and is the error linear.
Sometimes old SPG's can get sticky in the low range, which is bad. A linear error reading low is not as big of an issue as reading high or being sticky.

How would you test for the "stickiness"? Hooking it up to a tank and then slowly bleeding it to close to empty? I imagine this test isn't done often.

 

[Tbar]

How would you test for the "stickiness"? Hooking it up to a tank and then slowly bleeding it to close to empty? I imagine this test isn't done often.

Connect a second high pressure gauge that is known to be accurate across the range. Using a full tank, open the tank, this will fill the hoses with HP gas. Close the tank. Do the gauges read the same pressure? Now you can slowly bleed the air, you could use the purge on a regulator with a gentle touch or if you had an inline second stage adjuster you could fine tune the second stage to just free flow. At points through the gauge range stop releasing air and compare the gauges. If you want to check for 'sticky' release the air slowly and watch the gauge needle for a smooth movement. I have has a gauge that was correct at 200bar but 20bar out at 50bar.

There is no need to use the full cylinder of gas.

 

[Bob DBF]

I have a reg with 2 HP ports so it's easy to check one SPG against another, reduce pressure slowly insuring the gauges track pressure together and does not stick anywhere. Make sure 0# reads correctly.

Hooking it up to a tank and then slowly bleeding it to close to empty? I imagine this test isn't done often.

The test is usually done after you notice the gauge acting hinkey, or just stays stuck. Or your looking to buy a used one or, in my case, decide to use an old one laying around that has not been used for ages.



Bob

 

[GrumpyOldGuy]

Sounds good.


How would you test for the "stickiness"? Hooking it up to a tank and then slowly bleeding it to close to empty? I imagine this test isn't done often.

No its not common. Most of the time, I just check the tank ending pressure against my SPG and all is good. All you need to do for sticky a spg is to take a spent tank, and drain it down from the 500-800PSI until you have to 100 (or zero if its due for a vip). You should see a steady drop. This type of failure is rare and I am not proposing you need to be regular about this, but then again good dive gear can last decades and gets abused so weird things can happen. My oldest gear is 1978 and I am not even into vintage gear which is much older. I am sure my ideals are not common. I use minimal gear but keep it well maintained and do enough self testing that I am highly confident my gear will not give me an issue during a dive. I have yet to abort a dive due to gear issues. Testing needs to be done at the extremes, high and low. As a good diver, you probably are rarely using the tank below 500, so testing that on occasion is good.Testing with a full tank is part of every dive.

 

[tbone1004]

Once a year when VIP time comes around and reg rebuild time comes around, I will drain a tank with a reg on it and my back gas pressure gauges on there to make sure they are bleeding correctly. The ideal scenario is to do it with doubles so you can get the 4 spgs that are typically used in tech sidemount, 2 backgas, 2 stage. Deco bottles don't really matter other than it's full or it isn't which is why I use button gauges. With the 4 gauges in, I'll set a slight freeflow, and let them drain down checking every 20 minutes or so to see and mark variation on the gauges at different pressures. This is entirely overkill, but they ahve to get drained and draining via second stage is less obnoxious than tanks bleeding.

 

[elgoog]

Awesome information, thanks everyone!!