TESTING MORE SAFETY VALVES

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Trainman4602
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TESTING MORE SAFETY VALVES

Post by Trainman4602 » Sat Jun 30, 2018 8:41 pm

Hi All
I just finished another run of safety valves. It seams I am getting more request for higher set pressures. In the video I just finished setting a valve for 140# with a 4 # re seat pressure.

I get questions about the valve leaking but this is not what is is doing . When the pressures is near the pop off point the valve will "simmer" the closer to the set pressure the more it simmers until the pressure reaches the set point and then it will pop. The re seat or blow down is set but the blow down ring.

Here is a video of it in action.

BTW the boiler finally blew more tubes I was barely able to finish the run. I'll have to re tube it before the next run

Send me a PM if you would like to receive a pair of valves. I can set them from 95# to 140# in 5# increments only nothing in between. The pressure gauge on your locomotive is not that accurate and there is generally a 5% plus or minus error factor allowed by most clubs anyway.

The valves are $175.00 ea. includes shipping in the USA

https://www.youtube.com/watch?v=rbZbt2SOZ-E

ALLWAYS OPERATING MY TRAIN IN A SAFE MANNER USING AUTOMATIC AIR BRAKES

BClemens
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Re: TESTING MORE SAFETY VALVES

Post by BClemens » Mon Jul 02, 2018 5:42 pm

To reiterate what Dave says:

Why is My Valve Opening Early?

A question we commonly receive is why a valve appears to open, or actuate, earlier than expected. Often, we find that the valve is not, in fact, opening early. Rather, the perception that it is actuating early is due to a misunderstanding of set pressure.
What is set pressure?

The set pressure, also called the opening pressure, of a safety or relief valve is the inlet pressure at which the valve begins to open as required by code.

The definition of set pressure depends on the type of valve and the service:

For steam service and most valves used in air or gas service, set pressure is defined as the pressure at which the valve makes a loud, audible “pop.”
For some valves in air or gas service, set pressure is defined as the pressure at which the first audible signal appears.
For liquid service, set pressure is defined as the pressure at which the first vertical steady stream of liquid appears.

A valve should be set to open at the maximum allowable working pressure (MAWP) of the vessel the valve is intended to protect. There is some tolerance to actual set pressure, which means that a valve set at 100 psig may open slightly above or slightly below this level.
Why does my valve open before it reaches the set pressure?

The first step is to determine if your valve really is opening early. Sometimes safety and safety relief valves appear to open before they reach the set pressure — there may be an audible or visible release of fluid between the seat and the disc. This is known as “simmer” or “warn,” and it is not the same as a full open.

Simmer, or warn, occurs when a valve opens slightly, discharging only a small percentage of its rated capacity. For example, direct spring-operated safety valves may simmer or warn at 90% of the nameplate set pressure. A valve that is simmering is not considered open.

The next step is to check your gauge to ensure that it is reporting the set pressure correctly. The gauge should be calibrated properly and located upstream of the valve, close to the valve inlet. Rapid increases in system pressure can make it appear that a valve is opening early because the gauge can’t accurately report the pressure.

If you still believe your valve is opening early, assess the operating factors that might be contributing to the situation. Valves are factory set using standard conditions, and factors like high temperature, vibration, and back pressure can cause them to open early. These conditions can be compensated for using cold set pressure, aka cold differential test pressure (CDTP). Learn more about CDTP from the National Board.

This is a simple copy and paste - but does amply support what Dave is being explicit to explain about pop-off valves - they 'simmer' as they reach pop-off pressure. The term "pop off'' would seem to mean it reaches set pressure and opens....but not...it simmers a bit before mechanical is overdone by static. These sets of physics were designed by the same being that made ice float and heat rise, I often thank God for all of that....worldly engineers may forget and tangle those simple laws.

all the good,
bc

Steve Alley
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Re: TESTING MORE SAFETY VALVES

Post by Steve Alley » Tue Jul 03, 2018 10:13 pm

Dave Just got the safety's you sent, Nice craftsmanship. I am sure there going to work as advertise.
Steve Alley
Allen Models

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Trainman4602
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Re: TESTING MORE SAFETY VALVES

Post by Trainman4602 » Thu Jul 05, 2018 11:04 am

thanks steve
ALLWAYS OPERATING MY TRAIN IN A SAFE MANNER USING AUTOMATIC AIR BRAKES

Phil Tucker
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Re: TESTING MORE SAFETY VALVES

Post by Phil Tucker » Tue Aug 14, 2018 9:51 pm

I received a pair of safeties from Dave Sclavi and finally tried them out. They are excellent. The first one lifts consistently at 120PSI on the button with a satisfying pop. The re-seat is sharp and tight and there is no weeping. Glad someone is supplying the hobby with high quality products. I strongly recommend these.

Glenn Brooks
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Re: TESTING MORE SAFETY VALVES

Post by Glenn Brooks » Wed Aug 15, 2018 1:02 am

Dave, what is the intake diameter on your safeties? I need one with 1/2” or maybe 5/8” pipe. Have to go measure tomorrow to confirm.

Thanks
Glenn
Moderator - Grand Scale Forum

Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

Ahaha, Retirement: the good life - drifting endlessly on a Sea of projects....

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Trainman4602
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Re: TESTING MORE SAFETY VALVES

Post by Trainman4602 » Wed Aug 15, 2018 9:15 am

Hi Glenn
The safety valves are machined with a 1/8 NPT thread. To adapter to 1/2 NTP I sell a stainless steel reducer bushing for an additional $5.00
no such thing as 5/8 pipe the next size would 3/4 NTP.
ALLWAYS OPERATING MY TRAIN IN A SAFE MANNER USING AUTOMATIC AIR BRAKES

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Trainman4602
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Location: New Jersey

Re: TESTING MORE SAFETY VALVES

Post by Trainman4602 » Wed Aug 15, 2018 9:16 am

Hi Phil Thanks for the compliment I'm glad you like them.
ALLWAYS OPERATING MY TRAIN IN A SAFE MANNER USING AUTOMATIC AIR BRAKES

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