More throttle questions

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kvom
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More throttle questions

Post by kvom »

Having finalized on my overall design, I find that the reach rod to activate the globe valve will be 2-pieces that will pivot slight in the vertical plane. One will be 5" long, and the other approx. 7" depending on the placement of the turret.

I have a good quantity of 1/4" brass rod, so I would like to use it for this purpose. As the rods are exposed to steam, they should not corrode as steel would. The pivot and the valve connector would be SS pins secured with small brass cotters. The valve crank is also brass.

Any faults here?

Since the entire mechanism will be above the boiler tube, everything will be relatively simple to remove for maintenance or repair.
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Trainman4602
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Re: More throttle questions

Post by Trainman4602 »

Sounds like you have made up your mind already.
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tburzio
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Re: More throttle questions

Post by tburzio »

Well, aside from corrosion, thermal expansion is a problem. My throttle is a screw type (Japanese style) and works great almost all the time, but ever so often it will stick closed when I fire up. You have to turn the valve really, really hard to overcome the initial resistance, then it's fine. A design of a throttle should plan for this thermal expansion problem, and be robust enough to withstand the force you need to get her unstuck and going.
kvom
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Re: More throttle questions

Post by kvom »

My question is primarily about the proposed materials. I could use SS for the rods if the brass wouldn't work, but I'd have to buy that.

At the turret the gland will be bronze, and I am assuming that the packing material would accomodate any expansion of the rod.
tburzio
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Re: More throttle questions

Post by tburzio »

kvom wrote:assuming that the packing material would accomodate any expansion of the rod.
Huh, that's what I thought too... :mrgreen:
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Fender
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Re: More throttle questions

Post by Fender »

Brass in a boiler can be a problem because of de-zincification. I would recommend another material.
Dan Watson
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kvom
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Re: More throttle questions

Post by kvom »

I did some research on the de-zincification issue.

To be clear, the rods in question are not IN the boiler but connect the steam dome and the turret. I am assuming that they will not be in contact with much liquid water, and only with steam during the time a typical steamer is in use. Is the de-zincification a real issue in this case?

Alternate materials would be SS or 260 brass, which is supposedly corrosion-resistant. I've read lots on here about not using SS for steam use, but once again is the limited usage here an issue?
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John_S
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Re: More throttle questions

Post by John_S »

All of the linkage (rod, cotter pin, and two levers/arms) from the throttle on the backhead to the ball valve in the steam dome on my mogul is 340 SS.

Stainless only comes into question when used to build the actual boiler.
kvom
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Re: More throttle questions

Post by kvom »

I assume you meant 304 SS. :?:
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Fred_V
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Re: More throttle questions

Post by Fred_V »

kvom wrote:I did some research on the de-zincification issue.

To be clear, the rods in question are not IN the boiler but connect the steam dome and the turret. I am assuming that they will not be in contact with much liquid water, and only with steam during the time a typical steamer is in use. Is the de-zincification a real issue in this case?

Alternate materials would be SS or 260 brass, which is supposedly corrosion-resistant. I've read lots on here about not using SS for steam use, but once again is the limited usage here an issue?
i have a brass ball valve with a brass lever in the dome of my Chloe (not built by the plans) and also a brass plate above to defuse priming. it has been run since 1996 and neither part shows any de-zincification.
Fred V
Pensacola, Fl.
kvom
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Re: More throttle questions

Post by kvom »

Good to hear that Fred. The globe valve body is some variety of brass or bronze regardless of the rod material.

I checked my supply of brass rod to discover that it's all 5/16 and 3/8, not 1/4. Since all the other parts were draw assuming 1/4 reach rod, I'm just going to order some SS rod.
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Harold_V
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Re: More throttle questions

Post by Harold_V »

kvom wrote:I assume you meant 304 SS. :?:
It must be. I've been in the shop for eons and have never heard of 340 stainless. There is an alloy designated as 347, however.

Here's a link that will show the common 300 series alloys.

http://www.spiusa.com/Ref001/300prop1.html

Harold
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