Reducing valve

1hvacman

I have two reducing valves feeding the same unit small one is set at 20 psi larger one is set at 17 psi both work fine alone. When I use both together pressure goes up to 35 psi. Don’t know what to check

1hvacman

They are Spence reducing valve E main and D pilot

Jamie Hall

They can't work alone, at least not to control pressure. This brochure: https://www.spenceengineering.com/PDFs/D353010X012_Spence_Overview_Brochure.pdf shows how the Spence ED pressure reducing valve works. The most obvious thing to check first is the setting of the adjusting spring -- which you can't check alone. It has to be in the system. Nor is it possible to check it correctly with no flow, as the pressure reducing valve will indeed reduce (and hold, up to the maximum rated flow) the downstream pressure, but it that pressure is already high for some reason, you can adjust that spring all day and nothing will happen (well, not true -- you can raise the downstream pressure, but not lower it).

Allow some flow through the system, then adjust the spring so the downstream pressure is correct. If the valve won't control the downstream pressure, or the pressure is erratic, there are other problems -- control line damaged or plugged, for instance, or a failed diaphragm in either the pilot of the main, for examples.

1hvacman

The valves are parallel not in series. Hope I said that correctly

Jamie Hall

If they are in parallel, it's not a Spence ED setup. It's something else. Don't know what. Unless it is an ED system with a remote pilot -- which can look sort of like a parallel setup?

1hvacman

1hvacman

Just replaced this one Friday other one is larger

EBEBRATT-Ed

Usually the trouble is in the pilot assembly. How is the sensing line piped? I would think one control is fighting the other control.

1hvacman

One sensing line with a tee it feeds both

1hvacman

I’ll get some pictures tomorrow of the setup I’m working on. Thanks for being helpful

Jamie Hall

In the picture, I see E -- with the red spring -- and D, and the bleed line. I don't see the sensing line. and I'm not sure the bleed is connected to both ports near the valve itself? In principle you can use one sensing line Teed off to run two pilots. but I'd rather use two sensing lines.

EBEBRATT-Ed

I have not looked up any Spence information but I think one sensing line is a no-no.

jumper

Not that they're fool proof either; steam to steam generators are less troublesome than pressure reducing stations. PRV s are often too large.

1hvacman

Sorry it’s taken me this long to respond. Just got back to the job today.


The sensing line is running uphill from the pilots. But it has been this way since 1991. Without this problem I’m having now. Any help will be appreciated.

Dale_3

This looks like a typical 1/3 2/3 set up. If the problem only shows up when the 2/3 valve is in play I would start there. Isolate the 1/3 valve and see what happens when you back the pilot spring nuts all the way out. It looks like you are remotely sensing something but I can't tell where from the pics. If the 2/3 valve is still feeding after being backed off totally we need to start pulling the downstream tube bends off to see if we are getting steam past the pilot valve or the main valve. Also, if the sensing line is stopped up it can run up. Better pics and a little more info might help. good luck

EBEBRATT-Ed

Check he sensing line off the pilot valves. The sensing line can have no water in it. It cannot run up hill it has to pitch down to drain. Can't tell if the sensing line is teed to both valves it should not be. They have to be separated and pitched down.


Or it could be plugged. It doesn't matter how long it's been that way wrong is wrong

dopey27177

It appears that you have a red spring in the pilots. That spring is used for high pressure only. The pressure you are operating at requires a spring that will control steam pressure from 5 to 25 psi.
That spring is orange in color and is classified as medium pressure Part number 5-05003-0.

I do not know what the amount of steam in pounds per hour is needed, that is critical in determining which valve is the primary valve and which valve is the the booster when the steam demand becomes greater.

If 20 psi is needed set the primary valve at 22 and the secondary valve at 20 this way when the primary valve can not supply the needed pressure (drop below 20 the secondary valve will kick in),

What is needed on the system is an electric safety pilot if there is an overide in pressure pressure occurs set that safety to 25 psi assuming the safety valve is set at 30 psi.

Jake

dopey27177

It appears that you have a red spring in the pilots. That spring is used for high pressure only. The pressure you are operating at requires a spring that will control steam pressure from 5 to 25 psi.
That spring is orange in color and is classified as medium pressure Part number 5-05003-0.

I do not know what the amount of steam in pounds per hour is needed, that is critical in determining which valve is the primary valve and which valve is the the booster when the steam demand becomes greater.

If 20 psi is needed set the primary valve at 22 and the secondary valve at 20 this way when the primary valve can not supply the needed pressure (drop below 20 the secondary valve will kick in),

What is needed on the system is an electric safety pilot if there is an overide in pressure pressure occurs set that safety to 25 psi assuming the safety valve is set at 30 psi.

Jake

1hvacman

Thanks I’ll check on that.   If primary pressure is 125 psi. Do I still need the orange one

dopey27177

At 125 pressure you need the red spring. That's high pressure.
sorry did not see the 125 inlet pressure requirement.
Again find the valve that is primary, usually the larger one, set it at 20 psig and the smaller one at 18 psig.
the small valve will remain shut until the large one cannot supply the proper pressure.
Consider installing electrical pilot operated safeties to shut down the prvs in an over pressure condition.

Jake