Throttle valves?

[mcandrew1894]

Ok guys and gals,

What are you using for throttle valves these days.

I took the family out for a cruise today...running well for a good hour...all of a sudden there was a "tink" and the engine came to full stop.....no steam....on shore wind picking up....and we were getting closer

I quickly went through the list of things that first came to mind...nothing.

I then realized, that something in either the main steam stop or the throttle valve must have failed. By now, the safety was lifting and my daughter bless her heart, didn't like the noise to say the least, so I had my wife drop anchor and open the fire box doors while I closed the ash pit up....I put in some water with the hand pump as that will settle the boiler down.

OK so whats up?

I tried closing the mainsteam stop, and it closed. That left the throttle valve as the culprit.

Just then a boat came along side and offered a tow....I reluctantly agreed.....I didn't know what I would find under the valve bonnet, the wind was picking up a bit...and my daughter was scared.

We got the boat on the trailer and we went home. Once there I pulled the thottle valve bonnet ( a 300 psi globe valve). Sure enough the valve, made in two pieces threaded together so as to float on the stem for alignment, had come disassembled. The steam pressure slammed the loose piece shut against the seat and stopped steam tight! I would classify that as SUB OPTIMAL!

I pulled it out and just screwed the two pieces back together.....but THAT valve is coming out! as is any other valve made that way on my boat.

So What are you all using for thottle valves these days?....so I can order one....NOW.

Dave

PS yeah I should have mounted the valve the other way round ...but I still don't like the design.

[fredrosse]

I have used gate valves for throttling service in steam, this has always worked well. I know handbooks often say gate valves should not be used for throttling flow, but I have never had any problems here, even when heavily throttling 150 psi steam for months continuously on a 300 lb bronze gate valve.

Another (perhaps more modern) valve is a rated ball valve, they are inexpensive, and many are rated for 150# SP.

[mcandrew1894]

Thanks for responding Fred,

I'm torn...globe or something else.

The valve is a Nibco, and I am thinking about a United with a T sloted disk.

However, If I can prove to myself that the Nibco will, if properly installed, fail open at the thottle...no where near as bad as failing closed as I can start stop and reverse with the link... I'll stay with it...but I still don't like it.

I am seriously considering a ball valve and ditch this nonsense.....I''l check the various suppliers and see what's available.


Dave

[froya66]

Hi Dave

I use a ball valve with a modified handle (plastic removed ) so it does not look to modern.

I like the idea of controlling the steam flow from full open to closed within 1/4 of a valve turn, especially during manoeuvring.

Best regards
Jørgen Hansen

[artemis]

Thanks for responding Fred,

I'm torn...globe or something else.

The valve is a Nibco, and I am thinking about a United with a T sloted disk.

However, If I can prove to myself that the Nibco will, if properly installed, fail open at the thottle...no where near as bad as failing closed as I can start stop and reverse with the link... I'll stay with it...but I still don't like it.

I am seriously considering a ball valve and ditch this nonsense.....I''l check the various suppliers and see what's available.


Dave

All boiler steam carries some particulates in it and these can cause severe scoring of a valve disc or seat. Look at the cutaway drawing of a globe valve and trace the passage of steam (and particulates). Good example is the scoring of a whistle valve seat. A gate valve is a simplified form of of the throttle valve used on many small steamships and it is preferable to the globe valve because it is less susceptible to the type of seat scoring that will cause globe valves to leak. There should ALWAYS be a Main Steam Stop Valve at the boiler so that steam to the engine can be totally shut off - the movie "Sand Pebbles" for a graphic description of the outcome for leaky main steam valves.

[mcandrew1894]

Artemis,

I have some time running big stuff. My boiler has a main steam stop for the engine and an Aux steam stop for everything else. but their either open or closed....never in between

Throttling the engine from the main steam stop "Walve" is a serious PITA if I'm to steer as well.....I'd rather throttle the boat in with the link

My friend Will told me today that he has had a ball valve in his boat as a throttle for the past twenty years.....SOLD!
Thanks for the input guys..

Dave

[artemis]

Artemis,

I have some time running big stuff. My boiler has a main steam stop for the engine and an Aux steam stop for everything else. but their either open or closed....never in between

Throttling the engine from the main steam stop "Walve" is a serious PITA if I'm to steer as well.....I'd rather throttle the boat in with the link

My friend Will told me today that he has had a ball valve in his boat as a throttle for the past twenty years.....SOLD!
Thanks for the input guys..

Dave

You misunderstand -- I've come across several steamboats that had NO main steam stop walwe. The throttle valve was it. I'd NEVER work on an engine that had steam if there was no stop valve between it and the boiler.

As long as the ball valve is rated for the pressure and steam, I've heard only good things about ball valves. Create a wood handle - split - to fit over the metal handle, drill through and through-bolt with a flat head screw and a countersunk hex nut, preferably in brass.

[mcandrew1894]

Point taken....forgive my flare.

Running without a Main steam stop valve is NOT good practice.....We agree.

You should ALWAYS be able to isolate your boiler and your engine from eachother.

.....and for those of you who have'nt picked up on "walve"....I suggest you get the movie.....it must be experienced...it can't be explained. .


Dave

[mcandrew1894]

The ball valve worked great ...made up a nice "period" looking handle for it and it functioned perfectly.....

Now for the rest of the list of things I want to change.....

Dave

[artemis]

Point taken....forgive my flare.

Running without a Main steam stop valve is NOT good practice.....We agree.

You should ALWAYS be able to isolate your boiler and your engine from eachother.

.....and for those of you who have'nt picked up on "walve"....I suggest you get the movie.....it must be experienced...it can't be explained. .


Dave

My earlier main steam stop valve comment was also to ensure you have a way to shut off steam to the throttle valve. I have heard of a couple of instances where enough "stuff" was picked up between the boiler and the throttle valve to cause scoring of the throttle valve seat (easy to do in a ball valve) and consequent leaking of steam. No problem to replace if one has a good "Main Stem Stop Wahv"