Needle Valve Design

[Scubadude_LA]

Looking into needle valves for PP blending, couple of concerns/questions.

After researching Parker and Hoke I see there there are different style tips on the needle (blunt, etc). Is one better than the other for blending?

If one is aquired, do parts need to be changed to be HP O2 compatible? Or is just a cleaning needed? I guess the better question would be do valves like Parker and Hoke already have the proper components in them, or separation of the incompatible components from the HP O2 area of the valve?

Having trouble determining how "slow opening" the different models are, not sure what to look for.

If another needle valve would be dedicated to continuous blending only, how big a concern is the valve design at the low pressure in that scenario?

Maybe some guru here can suggest a make/model?

 

[SCUBA_Phil]

Scubadude_LA,

How are you going to use it? In a whip, part of a panel? If it's a whip, I would just buy one pre setup with a Sherwood valve or you can build your own.
Here is the valve I would buy :High Pressure Inline Valve 1/4" male - 1/4" female 6000 PSI Max" Valves & Regulators

If it's a whip: Standard Filler Whip

Here is what I actually bought (It was part of my booster package) "Deluxe Fitting and Hose Kit"
http://www.divegearexpress.com/rebreathers/booster.shtml

And yes, I would O2 clean it.

 

[Scared Silly]

I would not use a std fill whip valve like the Sherwood for controlling O2. You want a needle valve which opens slowly and reduces adiabatic compression.

If you look carefully you will find that needle valves often come O2 compatible. At least two from Parker are that way. I would buy one of them.

 

[Scubadude_LA]

Trying to replace a junky one used to control O2 flow to a stick. Typically 50psi input pressure running no more that 2cfm.