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SurfLung
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Sticking Whip Valve?

Fri Jan 19, 2018 11:23 am

Sticking Fill Whip Valve?
- I was filling tanks recently, changing tanks while the compressor was running. I connected an empty tank and opened the tank and the whip valves. This is where the fill needle slides down to whatever pressure is left in the empty tank. I looked away for a second or two and looked back to see that the needle was at 3000 psi. The empty tank was one of my vintage 1800 psi ones so, I snapped to attention and quickly turned off the compressor. Twisting the whip and tank valves had no affect... The needle stayed at 3000 psi until I close the valves, bled off the pressure, and disconnected the fill whip. I then opened the fill whip valve and the pressure bled out normally. Trying again, everything worked fine and the tank filled without any problem. This happened once while filling tanks last Summer, too.
- Is it possible my fill whip valve seat could stick closed even though it was twisted open?
- After writing this description, I'm wondering if maybe it was the TANK valve... I don't remember if it was this same tank when it happened last Summer.
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Re: Sticking Whip Valve?

Fri Jan 19, 2018 11:52 am

I have had this happen. It would happen if I pressured up the whip with the whip valve open and then opened the tank valve. I am not sure why or how but it appears pressure prevents the tank valve seat from moving. The seat is not directly connected to the threaded valve stem and there may be just enough play in the coupling between the stem and the seat to appear that the valve is open but pressure in the whip is holding it closed. After this happen several times I now make it a practice to open the tank valve before the whip valve.
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Re: Sticking Whip Valve?

Sat Jan 20, 2018 12:42 am

Most valves are designed for air to normally flow in one direction when being opened. Pressure from the wrong direction does tend to extrude the soft valve seat from the brass carrier as the valve is being open. Common problem on US DIvers J-valves, but others are affected as well. Also the common Sherwood/Dacor line valves. Not just Scuba tank valves. I see it often. Good to to always open a tank valve before opening the fill line valve.
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Re: Sticking Whip Valve?

Mon Jan 29, 2018 1:40 pm

Hey Thanks for the advice Captain and AntiqueDiver. I've been traveling and didn't see your responses until now. That makes a lot of sense... It definitely was with a tank that had the old style J-Valve... Even old enough for the 1/2" tapered thread. And, I had breathed the tank down to just about ZERO pressure. So, I should open the tank valve before I open the whip valve... I will try that.

Sea Hunt Jerry called me to say he had the same thing happened to him when filling his triples. He said there was a repair/upgrade to that valve that solved it. But if just opening it first solves it, I see no reason to do any repairs.

I think I will do a little experimenting. If I empty the tank out and try filling it cascade style from a 3000 PSI AL80, I can repeat the experiment a few times to get a consistent result with the valve starting in the closed and opened positions. :idea:
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Re: Sticking Whip Valve?

Mon Jan 29, 2018 4:34 pm

If that soft seat extrudes too many times due to "backward" air pressure getting behind it I would suspect it may get even looser with time, and maybe become more prone to getting out of place. Just a thought. If you have a replacement seat and carrier I'd suggest installing it.

I know of two "possible" instances with those seats (the one with the hole through it) extruding during use and blocking or greatly restricting flow. That's just a "MAYBE" that it happened, because the divers involved could have failed to turn on their air properly. Or maybe they turned their air on and some helpful-but-ignorant divemaster on the boat turned it back off accidently. I will never know for sure, but I was present on one of those times, and did open up the valve, finding that the seat material was well worn, deeply indented from much use, and a little loose in the brass carrier.

I think USD put the hole in there to solve an extrusion problem somehow pertaining to the reserve, but it ended up causing them to allow air pressure to get behind the seat and dislodging it when a fill valve is opened before the tank valve. There is probably more to that story somewhere.

We also sometimes see well worn Sherwood type line valves have the soft seat extrude when opened with air pressure entering from the wrong direction. Take a look at one of those valves and you will see an arrow cast into the body pointing in proper flow direction. These seats don't even have the small center hole like the USD tank valves do.

I'd like to hear from others who have witnessed similar events.
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Re: Sticking Whip Valve?

Mon Jan 29, 2018 8:32 pm

You guys are right. I tested the valve several times and sticks closed every time if I don’t open it first. Fills fine when the tank valve is opened first.

I’m going to disassemble the valve and see if the seat needs replacing.
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Re: Sticking Whip Valve?

Mon Jan 29, 2018 8:50 pm

Well, to add more to the cantankerous valve cases, today I ran into an old 50's K-valve that would not take air even if opened up before the fill line valve. The cylinder was dead empty, I opened the tank valve a turn and half or so as I usually do, then opened the fill line valve. No air movement. Tried it several times with same results.

I was pressed for time so did not open the offending valve up yet, just replaced it with another. Curious to find the cause, but expecting to find a really loose seat.
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Re: Sticking Whip Valve?

Fri Feb 02, 2018 1:28 pm

This shows what can happen inside the valve if pressure is applied from fill line before opening tank valve... especially on the USD J-valve:
IMG_3035.JPG
This shows a normal USD J-Valve seat on the left. The other was intentionally exposed to pressure from the fill hose before opening the tank valve. As the tank valve was opened the seat extruded. I did not turn the tank valve back off, or the seat would have been pushed back into normal position. I just bled the air off and disassembled the tank valve with it still in the open position. It clearly shows the soft seat extruded into a position that will block the incoming air flow.

More information about this just posted on the Tanks and Valves section.
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Re: Sticking Whip Valve?

Sat Feb 03, 2018 11:40 am

Does the seat have a hole in the center of it. The hole is supposed to stop it from extruding. It's possible some valves were rebuilt with the incorrect seat.
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Re: Sticking Whip Valve?

Sat Feb 03, 2018 9:26 pm

captain wrote:
Sat Feb 03, 2018 11:40 am
Does the seat have a hole in the center of it. The hole is supposed to stop it from extruding. It's possible some valves were rebuilt with the incorrect seat.
Yes, there is a hole in it. This is actually the correct seat specified for the J-valves.
I remember hearing the same story about the hole preventing extrusion, but it really doesn't make sense to me. Because these were only used on the J-Valves (no hole in the K-valve seat) it leads me to believe the problem they were trying to solve was being cause in some way by the reserve system. I would like to know more facts about the reason for the hole.

Really look at the actual path of air pressure coming from a fill hose with the tank valve closed. It enters the hole, potentially letting pressure get between the seat and the carrier. When the tank valve is then opened the air flow from the fill hose exerts pressure behind the soft set. It is not all that unusual for that pressure to push the soft seat outward from its normal position, holding it against the orifice. I think it's possible the soft material shrinks a little with age and gets just loose enough in the carrier to dislodge. I have seen it a number of times.

Same thing can happen with line valves that are subjected at times to air flow from the "wrong" direction. We see hundreds of Sherwood type line valves when dealing with fill systems from fire departments, dive shops, etc. Commonly see a few each year that are installed contrary to correct air flow because of convenience in positioning of the male and female threads on the valves. With time and a lot of use they can exhibit very similar issues with extrusion, and there are no holes in them. The air pressure from reverse flow is able to get around behind the seat and result in partial extrusion. Only see one or two a year.
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Re: Sticking Whip Valve?

Sun Feb 04, 2018 11:09 am

The reason may be because if the J wasn't in the fill or down position and the valve opened and the whip opened pressure could be forced behind seat and when the J was opened the trapped pressure would extrude the seat. The hole relieves the trapped pressure when the J is opened.
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Re: Sticking Whip Valve?

Sun Feb 04, 2018 1:11 pm

As you say, seems like it had something to do with the reserve. Just logic about only using them on the J's seems to confirm that.
I don't know why they thought the fill pressure wouldn't do the same... but of course closing the tank valve resets the seat before actually mounting a reg and going diving. It should stay in place then, so it wouldn't be as potentially dangerous as an extrusion and air blockage when opening the reserve during a dive would!
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Re: Sticking Whip Valve?

Tue Feb 06, 2018 12:59 pm

My valve is the 1/2" J-Valve but my seat has no hole...
Seat1.jpg
- The indentation wraps itself around and over the orifice so completely, I can see why external pressure seals it in place... By comparison, the tank side of the orifice is a vacuum of whatever the amount of external pressure happens to be.
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