Stiff Fill Knobs?

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g1138

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Scuba Instructor
Divemaster
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Location
Bay Area, in CA
# of dives
500 - 999
We have a fill station at our Aquarium that all the volunteers and staff use to fill their cylinders.
The fill knobs used to be real stiff to turn, so I recently serviced them. Had been about a year and some change since the last. Changing out the HP seat, oring, copper washer, and two teflon washers. I wiped down the threads, made sure they were clean and put it all back together. Used a bit of Tribolube on the oring.
Night and day difference, you could turn them with just your finger tips when filling.

About a month after they became stiff again. Not as bad as before, but it's still more than I'm used to on other fill stations.

The station is set up in a separate room from the compressor and has a fill rate limiter. So with that being said, the volunteers and staff can fling the knobs all the way open and closed with out a care in the world.
I know quite a few really crank the knobs tight open and tight closed.

Was wondering if that has something to do with the fill knobs becoming real stiff.
Any input on maintenance or preventative to keep this from happening so quickly is much appreciated.
We go through about 300-430 fills a month between two fill whips.
 
It sounds like you have a few Gumps that don't know their open from their closed. :confused: By forcing the fully open position (which some seem to think is closed till they discover otherwise ) the lower shaft which is made of brass can distort the threads downwards making for a tighter turning action.

Over tightening will destroy the seat material a bit sooner............makes me wonder how some of these people cope (survive ) underwater! :shakehead:

Write operating instructions for the literate ones and tape it to the panel.
 
Thank you.
I think it has more to do with, "if I don't turn it all the way it will fill too slow".

Seems I should reiterate that they only need a quarter turn on and a light turn off. It fills the same no matter how far you turn it.
So would it be a seat replacement you're saying, or should I also replace the shaft?
 
Sounds like you need training class first.

Sent from my SCH-I545 using Tapatalk
 
The lower shaft incorporates the seat, it's the threaded brass plug with the slot on one end and seat on the other.

Gotcha. I thought you were mentioning the seperate metal shaft that connects above that whole unit.
Thanks again.
 
1/4 turn valves will solve all problems. Throttle with the cylinder valve, or the needle valve on the fill panel. That's what the needle valve is built for.
 
Frank, do you have a source or link for 1/4 turn HP valves with 1/4 NPT? I would love to replace all my old knob fill valves.
 
Hard to throttle the tank valves when they're in a blast chamber. =]

Needle valve is in a completely separate room and controls airflow to our Partial Blending blast chamber and work bench. Can't have my volunteers or staff messing with that component.

I'll go with the cheapest route first. Re-training.
 
https://www.shearwater.com/products/perdix-ai/

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