Stainless needle valves (PTFE seats)

[scotsman]

Not sure if everyone has noticed but while i was searching for stainless needle valves for my valved reflux i noticed they were all PTFE seated. I know that this forum frowns upon plastics so thought id let you all know. Maybe i have missed something but still concerned about buying them. Might go with the treated brass option. Let me know what you all think.
Thanks
Vince

[minime]

Not sure if everyone has noticed but while i was searching for stainless needle valves for my valved reflux i noticed they were all PTFE seated. I know that this forum frowns upon plastics so thought id let you all know. Maybe i have missed something but still concerned about buying them. Might go with the treated brass option. Let me know what you all think.
Thanks
Vince

Welcome Vince
Yes we are all well aware of the issue with valves but unfortunately there's not much we can do as there are no affordable alternatives. The brass valves have buna rubber seals which are not impervious to alcohol at all so you're much better off with the stainless as the teflon seals are very alcohol tolerant.

[HookLine]

Short version:

Can't have an LM or VM still without a valve.

Can't have a valve without a seal material.

Only seal materials available are rubber, fibre, nylon or PTFE.

PTFE is way better than the others for alcohol (and pretty well every thing else).

Brass valves use rubber, fibre, and nylon for seal materials. Brass also needs to be treated to remove any surface lead.

Stainless valves use only PTFE seals, and stainless is a much better material than brass anyway (much tougher, machines more accurately, and doesn't need de-leading).

Needle and gate valves have least amount of seal material in contact with alcohol.

Therefore, if you want the most inert seal material, and the least amount of seal material, get a stainless needle valve (for LM), or gate valve (for VM).

The only real downside of stainless is its cost, but it is worth it. You only got to buy a stainless valve once, they last a lifetime or three.

[pigroaster]

Does anyone have a good supplier to order this item? Usa or Canada would be super.

[minime]

Does anyone have a good supplier to order this item? Usa or Canada would be super.

http://www.mcmaster.com/" onclick="window.open(this.href);return false;" rel="nofollow

be prepared, they ain't cheap

[scotsman]

Thanks heaps for your information guys. I have no issues in gettin the stainless valves as we have them at work (Fitter and turner). Was just worried. Well ill stick with the stainless. Thanks again.

[MtRainier]

I'm coming in a bit late on this topic, but I was trying to put together a parts list and wanting to avoid any non-metal in my distillate line. I work in research where we don't worry so much about the valve material dissolving in alcohol, but we do vacuum applications and we want materials that don't out-gas when you hook them up to the turbopump. We use stainless steel bellows valves such as the SS-4BG from Swagelok (http://www.swagelok.com/search/product_ ... art=SS-4BG. They ain't cheap, but there is no teflon anywhere in the valve.

There's even one up on ebay right now cheap. It's vintage, but new, and looks like about half the valves in our lab with 1/4" tube compression fittings which use copper ferrules.

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0001968384

Could be a great buy for someone looking for a good safe valve that's entirely stainless.

[CoopsOz]

That looks like a good buy.

[HookLine]

We use stainless steel bellows valves such as the SS-4BG from Swagelok (http://www.swagelok.com/search/product_ ... art=SS-4BG" onclick="window.open(this.href);return false;" rel="nofollow. They ain't cheap, but there is no teflon anywhere in the valve.

A good alternative. Thanks for that.

[punkin]

Got a lovely little half inch valve from one of our members today, it has teflon seals on the stem, but jeez, you'd have to be a wily little wisp of vapour to find em....



The bottom washer is stainless, so the vapour would have to squiggle past it (flush fit) just to get to the teflon, then it'd have to condense and tray to drip back out past the rest of the vapour before it could make your testicles drop off.

[CoopsOz]

Who's selling valves? Got any more?

[HookLine]

before it could make your testicles drop off.

Uh oh. That would explain a lot. (Too much info?)

[Adverse Effects]

Got a lovely little half inch valve from one of our members today, it has teflon seals on the stem, but jeez, you'd have to be a wily little wisp of vapour to find em....



The bottom washer is stainless, so the vapor would have to squiggle past it (flush fit) just to get to the teflon, then it'd have to condense and tray to drip back out past the rest of the vapor before it could make your testicles drop off.

you could replace the Teflon with 0.5mm gasket paper or if you are really keen make some out of densely packed hemp just like the really old taps in houses had where if they where leaking you could tighten a nut on the top of the body and they would crush the hemp in them tighter ans seal

Edit: in fact you could remove all the washers except the top and bottom ones then pack the area in between them with hemp from a Hessian potato sack tha way you could tighten the nut on top to compress it to make it seal

[Dnderhead]

to jump in hear a minit-- they have packing that is cotton -impregnated with graphite most hardware/plumbing should carry

[punkin]

I got no interest in trying to improve this tap. It's a damn beauty the way it is. I have plenty of valve packing in the shed, and i tell ya there's no way i'd puposely introduce that stuff into my still. The graphite is in a kinda grease that gets everywhere and i have no idea what that stuffs made from.

Like i said, i believe it's only stainless in contact with all but microscopic amounts of vapour.

[fran151]

This one seems to be the old chevy truck for stainless steel needle valves. Right in the middle of the road on price. Isn't anything fancy but will do the most adequate job. http://www.mcmaster.com/#4995k42/=yu3r5i" onclick="window.open(this.href);return false;" rel="nofollow

[Hound Dog]

This one seems to be the old chevy truck for stainless steel needle valves. Right in the middle of the road on price. Isn't anything fancy but will do the most adequate job. http://www.mcmaster.com/#4995k42/=yu3r5i" onclick="window.open(this.href);return false;" rel="nofollow

85$ !?!? Holy crap! shop around a bit......
http://www.ebay.com/itm/Parker-1-2-SS-S ... 1ea41a2110" onclick="window.open(this.href);return false;" rel="nofollow