# Needle Valves - Before or after the solenoid?



## Acrantophis (10 Mar 2009)

Guys following the solenoid that went bang in my face, I took the plunge and brought a replacement. Cheers to those of you who forwarded the recommendations. 
http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... gory=20756 
Took receipt of one of the above yesterday and having looked at the connections (air connections) today I am posed with a quandary. The original solenoid was positioned between the regulator and the needle valve, the one pictured can only be connected after the needle valve via tubing. Is this going to be a problem? I suspect not but would preffer your opinions. Also what thread sealant would you recommend for producing an airtight seal on the threads? PTFE tape or gasket sealant? The stuff I cleaned off the threads was like superglue, dry, brittle, and translucent.


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## Egmel (10 Mar 2009)

After is fine, not sure about sealant, I don't use any.


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## plantbrain (10 Mar 2009)

Pipe thread compound, or teflon tape sometimes, always add after the solenoid, this way the leaks are minimized. Some argued that the pressure changes when the solenoid is on/off, changes the flow rates, but I've not found that to be true with decent needle valves. Pressure still changes once gas starts flowing, so after seems best IME, IMO.

Regards, 
Tom Barr


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## TLH (10 Mar 2009)

You can use tubing to join them bits but you don't have to. The whole lot can be screwed together if you place the solenoid after the needle valve.

Here is the link to instructions for fitting. It's in German but the pics explain it well enough.

http://www.lunapet.net/Anleitungen_PDF/ ... noid_D.pdf


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## Acrantophis (10 Mar 2009)

Thanks for the drawing, for some reason they didn;t provide me with the details to that  :? 

The problem I have is that I have to many male ended threads, the only option is to either lay my hands on an adapter which will enable me to connect two male threaded elements together. Or otherwise the solenoid will have to go in line after the needle valve. I have a box of pneumatic fittings at work so I will have to see what I have in there tomorrow.


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