Pressure Reducing Valve Replacement (Gordo & Steamhead)

Steamhead (in transit)

that unless the customer is close enough to the power plant(s), it is cheaper to dump the condensate (after metering it, of course) then to pump it back to the plant(s).

The corrosion issues of the return piping factor into this equation, also.

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Steamhead (in transit)

Boilers Arn't the Only Thing That Get Oversized

The Zion Church in Downtown Baltimore is heated with Steam. The main church was built in 1809, and the steam was added 100 years later. Sometime in the 1950s, the boiler was removed and the building complex was put on the district steam grid.

By all reports, it has knocked and banged ever since.

All Steamed Up was called in because the over-pressure and the water hammer had caused so many leaks that the main church was starting to look like Yellowstone National Park.

We capped off the major leaks for now, but the over-pressure was still an issue. In the basement, we found that the pressure reducing valve for the main zone had been "line-sized". That is to say a 3" PRV had been installed on the 3" line. This valve had failed in the open position. The connected load was found to be less than 800 lbs. per hour. The incoming steam pressure is 35 psi.

The 3" valve (BANG!) can pump out over 6000 lbs. of steam (BANG!) per hour at 547 miles per hour (BANG! BANG!).

We sized the replacement valve at 1 1/4". We tested it with compressed air and modified the new control pilot valve to work with the existing motor/lever control system.

We made a Size Mock-up and lined up a welder for the day. The job went relatively smoothly. And so far we expect, for the first Christmas Eve in over 50 years, the church to be...


quiet.







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Steamhead (in transit)

And we hope

to get fuel-savings numbers on this project too, as we have for several others.

We will also compare the two remaining PRVs to the loads they serve- we have no doubt they're also oversized, just a question of how badly.

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The Steam Whisperer (Formerly Boilerpro)

I would suspect......

Judging by your picture of the church, that the system is way oversized too. 800 lbs/hr seem like a lot of heat for such a small space.

boilerpro

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Ross_7

Spence valves

Hey Guys,

Nice job on the piping! I see that you also use Spence pressure reducing components. We use them pretty exclusively here at the university. We have 85# steam central distribution reduced down to 4-7# for the buildings. Which I think is way too high for most of our applications. My concerns usually fall on deaf ears. I like Spence components though, we've had good luck with them.

Ross

Brad White_203

Beautiful!

Going from 3" to 1.25".... almost a "what were they thinking?" moment.. Now you are ending 50+ years of Hammer Chorus...I hope they sing an aria of the Hallelujah Chorus in your honor.

Excellent work and methodology, Frank and Gordo! I particularly like the copper pilot lines. Hand bent I take it and not stock pre-bent? Dang, they look so good.

We too specify Spence valves almost exclusively. There are a couple of projects on the boards now, one a Vari-Vac system which we want to get back in line.

What I am wondering, to control at the lower pressures we all crave, we are going to use a D-5 pilot, with that larger diaphragm. Is that what you are using or more to the point, how stable and low can you get the standard D pilot to go?

The other thing your post illustrates is how these valves are so often "up there", sandwiched between themselves and hard to access, but you prove that it can be done.


One question if you do not mind: Relief valve or trip valves, what do you normally use in Baltimore? We use enough trip valves here, just curious.

joe lambert_2

D-5 Pilot

The low range pilot works fine, it is the E valve that has trouble with very low pressures. If possible, use the E2, which has a rubber diaphragm instead of metal and is meant for INLET pressures less than 15 psig. However, you can fool the system a little by using the condensate pots between the pilot and diaphragm to collect some condensate, cool it, and not melt the thing. There are these pots on this church job.

Brad White_203

Thanks, Joe

Good info.

We only specify the E series as our inlet pressures average 125 PSIG, but this is good to know. So those pots- are those the can-looking devices? We have one on the side of the E5 trip valve.

Baltimore/Maine Doug_4

Gordo, how is BGE

measuring steam delivered, by condensate?

David Nadle

\"Quiet\" is good...

but "silent" is better ;-)

Steamhead (in transit)

The Street Steam

is currently supplied by Trigen (a Johnson Controls Co). BGE sold the steam system off years ago. The district steam system has changed hands a few times since.

Yes, on the low pressure systems, the condensate is metered and dumped. That's why Baltimore's Inner Harbor never freezes.

Pictured below is Trigen's reverse water meter in Zion church.

On the newer, high pressure (125 psi) systems, the incoming steam is metered.

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Steamhead (in transit)

Thank you, Mr. White

Yes, Spence is Good Stuff. I have had bad experience with Hoffman pilots. TOTAL JUNK.

The copper pilot lines come with the Spence valve pre bent (more or less) and with nuts and furrels. Spence likes to use an odd tube size, 5/16" o.d.. Hoffman uses 1/4"o.d..

For this Zion Church job, the regular D pilot was chosen over the D-5 for several reasons: (1) It was available now, not 5 weeks hence. (2) It could be field converted to the obsolete type "W" pilot to fit the customer's control system, and (3) Since the existing near-PRV piping was much less than optimal, the fine control supposedly obtainable by the D-5 pilot would most likely not be possible.

I do like the D-5 because it is difficult (but not impossible) for some fool to crank above 10 psi. The D style can go to 30 psi.


The type E valve is available in stock and has a stainless steel diaphragm and doesn't need that condensation "can" to protect the "rubber". Properly sized, the type E valve appears to provide stable low enough pressure even with the type "W" pilot.

We like safety relief valves, if possible. Question: Will a Trip valve shut down a stuck-open E valve?

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Brad White_191

Trip valves

Hi Gordo-

The trip valves don't control the E valves, they just drop closed in an over-pressure condition. We specify these with the P125 trip pilot.

Now, there may be a way to interface them, I really do not know. We see trip valves as our fallback device when a relief valve and vent to a safe location is not practical. In high rise work, this is a huge help! But given a choice, yes, ASME relief valves if we can.

We are currently having a debate in the office on whether the trip valve goes first in line or after the main valve. Any thoughts?

Also, on the regular D pilot, how low can you go, 30 being the high limit? I did not know the D-5 had that much lead time and we have some experimenting to do soon!

Steamhead (in transit)

Oh, sorry

I thought you were referring to the P125 when you mentioned a "trip valve". What's the Cv rating of a main "trip valve"? I guess I would put it after the pressure reducing valve to take advantage of the orifice pressure reduction safety factor of the PRV. Who makes a good trip valve?

The 5 week lead time was a bit of hyperbole. It's more like 3 weeks on any special order from Spence. And every order from Spence is special.

According to Spence, the D can go down to 3 psi. With a special (3 week away) vacuum spring, it can go down to 30" Hg with a high of 15 psi. This application was not recommended by the factory.

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Steamhead (in transit)

Stille Nacht

Heilige Nacht, indeed.

The Zion Church in Baltimore still gives its services in German.

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Brad White_191

Cv of Trip Valve

The trip valve, Gordo, as far as I know, is also an E valve but without a reduced seat. It is sized for minimal pressure drop (it has but one function after all) and this is taken into account in the total pressure drop chain, however minor it is.

Thanks for the info on the range of the D pilot! We want to crank this Vari-Vac system down from 7-9 lbs. (yes, indeed) to as low as we reliably can go... I could live with 3 lbs. as we do have various "exposure zone valves", which will take that down further...

joe lambert_2

Pot

They use the pots on the E5 because it, too, has a non-metallic diaphragm. FYI: here in NYC for Con Ed steam we sometimes use (for budget concious customers) a solenoid in line with the pilot that is activated by a manual reset pressure switch used as a safety shut-off. With a two stage PRV, this passes muster with Con-Ed and saves lots. Still not quite as safe as a separate safety shut-off valve,though. However, even using the E5 before the PRV's, we still use a steam solenoid and pressure switch to shut it off. For added safety, we often use the pressure limiting pilot on the primary PRV, too.

Steamhead (in transit)

Mr. Lambert

Do you have pictures of your PRV set-ups? Please share! Thanks!

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nicholas bonham-carter

dumped condensate

that seems wasteful, i wonder why they couldn't recirculate it?

maybe the energy conservation police will have that in their sights, along with the double-hung thermostat! --nbc