First fill with Alkin Issue with gauge "plug"

Today I did my first fill on SCBA tank. I started at 1000 psi in SCBA. Started the Alkin W31 (AW31) and then filled to ~3000 psi. Here's what happened:
I turned the W31 off, closed valve on SCBA, I then opened the Alkin drain valves for condensate and left them open. I then closed the "lever valve" at the end of the AW31 with "Foster" coupler. When I did this I heard a loud pop from the fill adapter (TUXING CGA347 Paintball Filling Station) connected to the SCBA tank and my neighbor felt something hit him.. We both looked at each other and said "what was that." We didn't know what it was then I saw a small rubber "plug" ~1/4 in diameter on the floor in front of the "AW31" Looked a little further and the plug apparently was discharged from the top of the pressure gauge when I closed the AW31 fill valve at end of hose.
Apparently I did something wrong. Any ideas?
 
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Today I did my first fill on SCBA tank. I started at 1000 psi in SCBA. Started the Alkin W31 (AW31) and then filled to ~3000 psi. Here's what happened:
I turned the W31 off, closed valve on SCBA, I then opened the Alkin drain valves for condensate and left them open. I then closed the "lever valve" at the end of the AW31 with "Foster" coupler. When I did this I heard a loud pop from the fill adapter (TUXING CGA347 Paintball Filling Station) connected to the SCBA tank and my neighbor felt something hit him.. We both looked at each other and said "what was that." We didn't know what it was then I saw a small rubber "plug" ~1/4 in diameter on the floor in front of the "AW31" Looked a little further and the plug apparently was discharged from the top of the pressure gauge when I closed the AW31 fill valve at end of hose.
Apparently I did something wrong. Any ideas?


@markT I’m not familiar with your style of SCBA valve. I’m thinking if it’s a plug from the gauge it sounds like what keeps the glycerin in the gauge. I’ve heard a pop before when I didn’t screw the DIN fitting into the SCBA tank valve securely and the o-ring blew out when the DIN 300 fitting and valve separated. I’ve never filled using roster fittings. Can you photograph the parts you’re describing?

My order of operations differed slightly. After closing the SCBA valve I bleed the fill line and disconnect it. Then I open the 1st and 2nd stage valves before turning the compressor back on. After filling my last tank and running it without a load, I turn it off again and open the valve on the water separator. I also firmly hold the fill whip with one hand and open the fill line valve to discharge the HPA in the fill line. Once the water separator and fill line have drained, I may run the compressor for another minute or so, turn it off and close the water separator valve.Next I unplug the compressot and let it cool off. Finally I place it in its storage space and cover it.
 
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Here's what I have connected to the SCBA tank. I gave my neighbor the SNBA tank with the Tuxing fill adapter connected to it so I cannot provide pictures. ( sorry) I will try and follow your method going forward and see what happens.
tuxing.png
 
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It’s the gauge on the “Tuxing.” We didn’t see and glycerin and I’m not sure the gauge had it in the first place. I med to watch some more videos and write down the process. It seemed in my mind that what I did made sense but not really sure if it was me or CH made Tuxing.
@markT I suggest following the steps that apply to your compressor in the Alkin video series. I typed my process out. As for the Tuxing fill set, I don’t know much About their products.
 
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It’s the gauge on the “Tuxing.” We didn’t see and glycerin and I’m not sure the gauge had it in the first place. I med to watch some more videos and write down the process. It seemed in my mind that what I did made sense but not really sure if it was me or CH made Tuxing.
Typically, if a gauge pops its plug, it is leaking air out of the front of the gauge. I popped a plug on my 2nd stage Alkin gauge, and air was bubbling through the glycerin, Alkin sent me a new replacement gauge.
 
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When you move the Alkin lever from horizontal (open) position to vertical all you are doing is relieving the pressure from the Alkin fill hose to the fill assembly. It is doing the same thing as opening the bleed valve on your fill assembly. You are depressurizing the fill valve assembly so the Alkin hose can be detached under no pressure. So it wasn't an incorrect procedure on your part that caused the gauge plug to pop off. I can't imagine what happened to you other than it was coincidental. It indicates a leaking defective fill valve gauge but it should have happened before you flipped the lever up.

After I fill with my Alkin I close the tank valve first, shut off the compressor power switch, flip up the Alkin hose lever, detach the lever from the tank, drain the left side tower drains, then the right side air filter drain, then I release the pressure in the Alkin fill hose by moving it from vertical back to horizontal.
 
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When you move the Alkin lever from horizontal (open) position to vertical all you are doing is relieving the pressure from the Alkin fill hose to the fill assembly. It is doing the same thing as opening the bleed valve on your fill assembly. You are depressurizing the fill valve assembly so the Alkin hose can be detached under no pressure. So it wasn't an incorrect procedure on your part that caused the gauge plug to pop off. I can't imagine what happened to you other than it was coincidental. It indicates a leaking defective fill valve gauge but it should have happened before you flipped the lever up.

After I fill with my Alkin I close the tank valve first, shut off the compressor power switch, flip up the Alkin hose lever, detach the lever from the tank, drain the left side tower drains, then the right side air filter drain, then I release the pressure in the Alkin fill hose by moving it from vertical back to horizontal.
Great information sir! I have asked my neighbor ( his tank and fill assembly) to check the gauge in question by inserting the fill probe into his Gamo Urban and open the SCBA valve and check the gauge for pressure.
I’ll keep on him and see what the verdict is. Thanks again!
 
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