Kunkle safety valves

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makinsmoke
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Kunkle safety valves

Post by makinsmoke » Fri Aug 14, 2020 7:21 am

I have a friend trying to communicate with the Kunkle folks. Not being an engineer or steam pressure vessel expert he is having a difficult time.

We know the working pressure of the boiler and other obvious things, but apparently Kunkle needs something called Pounds per Hour.

Is anyone available that can talk or email with him to help him break the language barrier?

Thought of you first Bill Shields.

Thanks,
Brian

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pat1027
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Re: Kunkle safety valves

Post by pat1027 » Fri Aug 14, 2020 9:09 am

Pounds [of steam evaporated] per hour is a boiler capacity rating, I'm guessing they are looking at sizing a valve.

https://www.engineeringtoolbox.com/boil ... _1115.html

https://www.industrialcontrolsonline.co ... sion-table

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Dick_Morris
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Re: Kunkle safety valves

Post by Dick_Morris » Fri Aug 14, 2020 6:06 pm

My recollection is that the compact 1/2" Kunkle that is often used for live steam locomotives is actually sold/ASME rated for use on unfired pressure vessels. Assuming you are looking for a safety valve for a boiler, Kunkle probably wouldn't mention this as an option. I read somewhere that this valve was rated for fired vessels at one time but for some reason the certification was revised to only cover unfired vessels.

Glenn Brooks
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Re: Kunkle safety valves

Post by Glenn Brooks » Fri Aug 14, 2020 8:30 pm

Yep, Dick is correct. Basically these “non fired” 1/2” Kunkle valves are now rated for use on things like steam pipes that attach to a boiler, but aren’t themselves fired. No idea why the change...

Kunkle does make a vertical discharge valve, model 6182 in sizes ranging from .5” up to 4” diameter. They are a bit taller than the old traditional ones, but ASME certified.

https://www.valvesdepot.com/collections ... valve-6182

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SZuiderveen
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Re: Kunkle safety valves

Post by SZuiderveen » Fri Aug 14, 2020 9:19 pm

It has to do with the costs of certification maintenance. The No. 1 Kunkle is still the same, but other Kunkle valves cover this fired vessel range, so they only have a “U” stamp now. Our local state inspectors (Maryland) know this and give us no problem at annual inspection.

Steve

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NP317
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Re: Kunkle safety valves

Post by NP317 » Fri Aug 14, 2020 11:16 pm

I have a bit of a quandary about a safety valve.

The Blackstaffe water tube boiler on my steam launch is presently using the original pair of small safety valves made and installed by Cliff Blackstaffe himself.
Of course they have been recently serviced, tested and adjusted, and are working perfectly, being designed for the output of this boiler.

The Northwest Steam Society (west coast of the USA) "requires" steam boat boilers to have an intact seal indicating certification by an "authorized" service facility.

I can not find any safety valve meeting that requirement that is small enough for the boiler. The smallest commercial safety valves would dangerously drain the water level before it could shut off. Simply not safe to use.

Anyone have a potential solution to aim my direction?
Thanks.
RussN

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Dick_Morris
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Re: Kunkle safety valves

Post by Dick_Morris » Sat Aug 15, 2020 5:51 am

I believe that 1/2" is the smallest that ASME certifies. I got around that by using a 1/2" Kunkle mostly hidden in the steam dome cover with a 1/8" model valve next to it on a nipple to clear the dome cover. The little valve relieves the steam and the big one make it comply with the regulation.

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cbrew
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Re: Kunkle safety valves

Post by cbrew » Sat Aug 15, 2020 8:32 am

NP317 wrote:
Fri Aug 14, 2020 11:16 pm
I have a bit of a quandary about a safety valve.

The Blackstaffe water tube boiler on my steam launch is presently using the original pair of small safety valves made and installed by Cliff Blackstaffe himself.
Of course they have been recently serviced, tested and adjusted, and are working perfectly, being designed for the output of this boiler.

The Northwest Steam Society (west coast of the USA) "requires" steam boat boilers to have an intact seal indicating certification by an "authorized" service facility.

I can not find any safety valve meeting that requirement that is small enough for the boiler. The smallest commercial safety valves would dangerously drain the water level before it could shut off. Simply not safe to use.

Anyone have a potential solution to aim my direction?
Thanks.
RussN
Russ, wouldnt this fall under hobby boiler?
If it is not live steam. its not worth it.

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NP317
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Re: Kunkle safety valves

Post by NP317 » Sat Aug 15, 2020 10:06 am

Chris:
Marine boilers are usually US Coast Guard certified. There does not seem to be a "hobby boiler" classification for marine use.
Sort of a black hole of regulation. I suspect that is why the NWSS has set up their own requirements: Trying to avoid government regulations.

I have gone ahead and used a version of the Kitsap Live Steamers Boiler Test record sheet, to record my own inspections and tests for this boiler.
We'll see what transpires when I take the boat to a NWSS meet. When they start having meets again...

A picture is attached of the boiler with the side sheet removed for inspection of the water tube coils.
RussN
Thistle Boiler2.jpg

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Bill Shields
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Re: Kunkle safety valves

Post by Bill Shields » Sat Aug 15, 2020 6:03 pm

Brian:

you really don't need my help after all the info supplied by others....which is germain...but in layman's terms in a way that people can understand:


What Kunkle is looking for is not pressure..but HOW MUCH STEAM does the boiler generate so that the valve can pass the steam necessary to keep the pressure under control.

Imagine a small valve on a HUGE BOILER. The valve would POP, but the boiler could make more steam than the valve can release...and you end of with an explosion anyway because in essence, the small valve is just a 'leak' to the huge boiler.

or a HUGE VALVE on a small boiler...every time the valve would open, the boiler would lose so much steam that the pressure would drop significantly below the valve reset pressure...and the valve would RAT-TAT-TAT and beat itself to death.

Hence...the valve needs to be sized to the boiler...or sometimes TWO or THREE valves (or more) are needed. Look at a picture of a NYC Niagara...IIRC some 6 safety valves on top....not always set at the same pressure...but the total 'POUNDS / HOUR' is greater than what the boiler can produce.

The cumulative steam passing capacity of all of the valves needs to be just greater than the steam CREATION CAPABILITY of the boiler.

This is why some clubs run an ACCUMULATION TEST...they make the boiler owner fire the boiler as hot as possible, lift both safety valves and determine that the valves, doing their thing, can keep the boiler pressure under control.

So...what is the 'POUNDS / HOUR' of the friend's boiler?

That is the question....one which is not terribly easy to calculate on a model boiler.

Generally, a 1/2" Kunkle valve will pass more than enough steam...the question is what happens when it POPs...does the boiler pressure drop too suddenly?

Having to put an orifice under the valve is not an uncommon practice to keep from passing too much steam...but totally frowned upon (for obvious reasons) in many areas.
Too many things going on to bother listing them.

Asteamhead
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Re: Kunkle safety valves

Post by Asteamhead » Sun Aug 16, 2020 2:27 pm

Hello Bill,
Thank you for your good and precise explanation of this subject! :)
Regarding the question of boiler steaming capacity, I found this simple rule of thumb (in case it seems to difficult to make a life test):
Locomotive boilers of usual construction can produce about their raw (empty) weight as steam per hour :idea:
Looking at any full size locomotive or most of our model engines - this would fit.
Size means volume which corresponds pretty good to steaming capacity.
By the way, testing the steaming capacity of a boiler equipet with a superheater can be harmfull at standstill (with no flow of steam to the cylinders) :!:
Just my two cents
Asteamhead

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Fender
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Re: Kunkle safety valves

Post by Fender » Sun Aug 16, 2020 4:37 pm

I would also add that putting a restrictor plate / orifice between the boiler and the safety valve is likely to produce the rapid on/off cycling mentioned earlier. The orifice causes the pressure to drop underneath the valve as soon as it opens, causing it to re-seat, then pressure returns, opening it, etc.
Dan Watson

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