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Throttle Valve, what to use?

Posted by Dusty 
Throttle Valve, what to use?
July 16, 2023 06:46AM
I've been trying to decide what design or type throttle valve to use on my monotube boiler; ball, butterfly, plunger, etc.

So I'm asking members of this forum, what are you using? What holds up to 400o F steam at 400 psi ?
Re: Throttle Valve, what to use?
July 16, 2023 08:10AM
This should work for you; tried and true with 125 years service record.
Re: Throttle Valve, what to use?
July 16, 2023 08:55PM
Thanks for suggesting the Stanley valve; I had looked at the Stanley valve earlier and wondered why it was so complex. Reading through the explanation of how it functions, the stem valve opens first, and at that point, it's really the cylinder valve that controls steam flow. After the throttle stem moves far enough to begin moving the cylinder's hole into alignment with the valve body, thereby allowing steam to flow through the cylinder valve, it appears the stem valve is doing little to nothing to control flow, all the work is done by the cylinder valve, yes?

So, why not just rotate the cylinder valve thru 90o to open and close the valve, much as a common ball valve works? I've seen this rotating design used for high pressure fuel valves, so I'm wondering, why not use this rotating design for steam? Your thoughts?

Edited 1 time(s). Last edit at 07/16/2023 10:01PM by Dusty.
Re: Throttle Valve, what to use?
July 17, 2023 10:34AM
It's kind of a bear to make a valve like that work --- you need really tight seals to keep it from leaking when the valve is closed. On the other hand, you don't need to be quite so tight when throttling.
Re: Throttle Valve, what to use?
July 17, 2023 08:33PM
Thanks for the explanation Frustated, now the sliding cylinder valve combined with the stem seat valve inside the Stanley assembly makes sense. And you're absolutely right about how challenging it is to make a rotating valve that doesn't leak around the cylinder; many years ago I made a fuel valve similar to the one in my drawing,...working pressure was only 90 psi and I was never able stop all the leakage.

I cant help but wonder if garden-variety ball valves sold for plumbing use could handle the heat? The stainless steel models certainly look like they would have no problem with pressure well above 500 psi, but the packing material in all the valves I've examined appears to be nylon or some other common plastic, which likely wouldn't hold up to 400oF. Has anyone tried using these valves?
Re: Throttle Valve, what to use?
August 17, 2023 09:20AM
Hi Dusty,
I'm using a ball valve arrangement on my 10 HP Stanley build. Tony Grzyb used this arrangement for years on his Delora steam buggy. Secrete is to come out of the boiler with 3/8" pipe and expand to 1/2" pipe. Put a union inline before the ball valve and this reduces the temp to within limits that this yellow handled valve can handle. Also, Ron Rogers has a similar arrangement on his Locomobile.

It is very workable to interface with the handle. BTW, I plan to use super heat after the valve to raise up to the 400 *F. I'll be running a 400/400 machine (*F/PSI). You can raise to the challenge of interfacing your mono-tube with a similar practice. Go for it!

You can also go an expensive stainless ball valve. Chuk Williams (LSR record holder for piston steam) uses this valve on a regular basis on his T steam car.

What ever you feel comfortable with, try it. However, make sure you account for a fail safe condition. Try to think ahead a little bit.

Hope this helps,
Kind regards,

Re: Throttle Valve, what to use?
August 17, 2023 02:18PM
My 10 HP Stanley Throttle Drawing is on the Stanley Steamers site under Rollys EX build.

Re: Throttle Valve, what to use?
August 17, 2023 09:32PM
Rolly, Thanks for pointing out your valve CAD drawing, I would never have found it otherwise. Your workmanship is amazing !!

Rick.H, thanks for the info on your & Tony Grzyb's use of commercial ball valves.

After considerably more Googling online, I found that different manufactures place different temperature limits on their valves, even though they all seem to be using PTFE for the seals.
ProLine specs most of their valves at 600 psi but only 300oF, likely due to their use of PTFE as seating material.
RS offers what looks like exactly the same valve but rates their valves at 1000 psi at 200oC (400oF.
Dernord ball valves are rated for 1000 psi & 410oF.

The plastics industry rates PTFE up to 550oF.

At this point, I think Rick.H has the right idea; give it a try (while staying safe). The worst that will likely happen is the valve leaks and I've lost whatever money I spent on the valve.
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All files from this thread

File Name File Size   Posted by Date  
Steam Valve.jpg 151.5 KB open | download Dusty 07/16/2023 Read message
Throttle Ball Valve.jpg 115.9 KB open | download Rick.H 08/17/2023 Read message