Calling old-timers - stumped on valve

[cme]

I was at a site earlier and was looking at the existing heating water plant for retro-fitting pneumatic controls to DDC.

There are 2 3-pass firetube boilers, 40 yrs old (defunct mfr), retubed and w/ newly installed burners. Prob 100 hp or so. No water treatment to be found.

No backflow preventer on the cw makeup either.

Anyway, the boilers are piped reverse ..... return into the top and supply out the bottom. Somebody put new valves on the pipes and did some modifications.

There is this ITEM on the return pipe right before an elbow and valve at the top of the boiler. This is the return side. The item is about 18" long with horiz water connections and a bolted top. There are 2 pressure gauges on it. The tag says "Superior Combustion Thermal Protection Valve".

It looks similar to a Sarco FT450 super capacity F&T trap.

This is a HW system.

What is it?

 

[MikeHalloran]

All I can think of, and this is complete conjecture, is that it's an excess flow valve, meant to substantially reduce the water flow in the event of a burst pipe, and avert personal injury.

But it makes no sense to put such a thing in the return line...



Mike Halloran
Pembroke Pines, FL, USA

 

[JStephen]

I find a few references to a "Thermal protection valve" that "prevents pump from overheating", but once again, no reason to have it where it's at.

 

[imok2]

I believe this is what you have:
"The control logic for all four temperature control valves options is the same. The flow of supply water from the boiler is allowed to flow into the system provided the return sensor is above the setpoint, in this case 135F. The flow into the system from the "boiler envelope" will increase as the valve opens or the pump speed increases, provided the return sensor is satisfied. If the temperature in the return line decreases, the valve will continue to close to maintain a safe condition. In the case of the variable speed injection pump, the pump speed will decrease to maintain the same safe condition. Although this is a rather simple explanation, the control algorithms can be very sophisticated since satisfactory performance is expected".

http://www.burnham.com/news/Archived-Articles/dontneglect.cfm

 

[cme]

The item says "valve" but there is no actuator, just 2 pressure gauges on the one side. It looks like that steam trap I noted.

The pumps are constant speed.

 

[MikeHalloran]

I think imok2 is saying that it's an automatic flow control valve that responds to temperature, restricting the flow when the return water is cold, sort of like the thermostat in a car engine. If that's true, the two pressure gages should read the same when the system is up to temperature, but should have different readings right after the system starts.



Mike Halloran
Pembroke Pines, FL, USA