Preventing Needle Valve Damage

[GDHLEWIS]

So my local BSAC dive club is having a continual issue regarding the needle valves on its panel. The issue is gas blenders keep over tightening the needle valves and damaging them. These people are properly trained and have continual reminders that finger tight is all that's needed, but alas that is clearly too much information for some people.
Does anyone know of mechanical way to prevent the valves being over tightened? Some form of stop to prevent it being turned to far? Or maybe another type of valves?

Cheers

 

[happy-diver]

Yeah get rid of the needle valves

 

[GDHLEWIS]

Yeah get rid of the needle valves

do you have an alternative ?

 

[tbone1004]

they are probably not needle valves, most likely line valves similar to the design on a scuba tank. If they are used just for on/off then you can replace them with quarter turns which are great for selecting which banks you want to pull from. I would keep the line valves for the final valve going to the tank so you have some control over flow rate.

 

[GDHLEWIS]

they are probably not needle valves, most likely line valves similar to the design on a scuba tank. If they are used just for on/off then you can replace them with quarter turns which are great for selecting which banks you want to pull from. I would keep the line valves for the final valve going to the tank so you have some control over flow rate.

They are defiantly needle valves

 

[tbone1004]

They are defiantly needle valves

weird choice for a cascade system, usually you would reserve needle valves when you need precision flow control like when we are PP blending, but even then you often have a line valve to control "on/off" so you aren't cranking on the needle valves when you need to stop flow. As much as I'd like to say there is an engineering solution to this problem, you're probably going to just have to put better training in for the tank monkeys....

 

[GDHLEWIS]

weird choice for a cascade system, usually you would reserve needle valves when you need precision flow control like when we are PP blending, but even then you often have a line valve to control "on/off" so you aren't cranking on the needle valves when you need to stop flow. As much as I'd like to say there is an engineering solution to this problem, you're probably going to just have to put better training in for the tank monkeys....

Training is the next step, was just hoping an Engineering solution could be found as well

 

[rjack321]

Exactly how are you using needle valves in your panel? They are not meant to be used as on-off valves and no matter how delicate you are, the metal needle to metal seat will fail quickly. If you want on-off control, you need a soft seat valve.

My swagelok needle valve on my CCR has a stop to prevent it from closing all the way.

I would add actual soft seat on-off valves and then replace the flow control needle valves with something using a stop which completely prevents needle to seat contact. 0.2 LPM at full pressure is enough to ensure that the needle isnt contacting the seat

 

[GDHLEWIS]

Needle valves are for the flow control side of the panel. How long are such things supposed to last ? These specific valves have lasted less than two years used a fair amount through the week

 

[tbone1004]

Needle valves are for the flow control side of the panel. How long are such things supposed to last ? These specific valves have lasted less than two years used a fair amount through the week

As stated above, in a fill panel, you should only have a needle valve if you are doing partial pressure filling to control the oxygen and/or helium. They should be used in conjunction with line valves which are the soft-seat valves mentioned above and those provide more than adequate flow control from the banks. 2 years of regularly use of a needle valve sounds about right if they are being misused as they are in this implementation.
Send pictures of the panel, but I'm 99% sure they should/could be replaced with either a 1/4 turn ball valve or a soft-seat line valve which will last about a decade with heavy daily use. The line valves are functionally identical to the valve in the scuba tank for reference.