No Steam Traps? and lots of water hammer.

Greg Kousidis

Thanx for the insight guys.

Could these "orifices" be located in the radiator valves themselves?, I don't see anything obvious on the piping run, upstream or downstream of the radiation.

All of the radiators seem to dump their condensate down to a condensate line on the ground floor. This line doesn't seem to have any pitch to it, it runs along the wall, the length of the building approximately 12 inches off the ground. It then enters the boiler room where it is then trapped upward into the bucket trap I previously spoke of. Is this what you call a wet return? And if so, why was it trapped upward, in essence raising the condensate water level on the ground floor?

Greg Kousidis

I have been asked to look into various heating problems at a local elementary school. I'll do my best to describe the situation.

The building is three stories tall and roughly 80 ft. long. It is heated by an oil fired steam boiler that replaced an existing fire-tube boiler with a gravity return. I was initially told by the custodian that he has always had difficulty heating the farthest rooms on the third floor, and has replaced the air vents in that area several times. He runs the boiler at about three pounds of steam pressure and says that when he tries to increase to 4 to 5 pounds, the water hammer makes it sound like the building is coming down.

Most of the larger radiators and fan coil units in the building DO NOT HAVE STEAM TRAPS! How can this be?

The building used to be controlled with pneumatic radiator valves (now defunct). These valves look as they had been installed on both the supply and return side of the radiators, so when the t-stat in the room satisfied, it closed both valves. Does this make sense?

The gravity condensate line was not piped back to the new boiler, instead it was run into a small receiver tank. The tank discharge is piped into the boiler and is most likely cycles on by the water level control on the boiler.

I also notice that prior to entering the receiver tank, the condensate line was piped upward (trapped)into a large F&T steam trap. The custodian said this was installed because there was a large amount of steam blowing by and exiting the receiver overflow line. This trap was later raised in height to where it now stands at about 5 1/2 ft. high which is just above the boiler water line.

Some questions I have are as follows:

1.What should the steam pressure be for a building of this length and height?

2.Why is the steam not reaching the farthest rooms?

3.Why so much water hammer with an increase in steam pressure.

4.Could the main bucket trap I spoke of be malfunctioning thereby holding back condensate? The trap has a wye strainer located up-stream.

Thank you for any opinions anyone may have.

hot_rod

How did the air get out

on the original installation? That trap impedes the air removal in your current setup. If the air can't get out, the steam can't get in.


I think that you might need to do something about the line to the trap that holds water.

I also think that you need to find out what used to control the inlets and outlets of the radiators. That clue might be the big one. Something used to keep the steam out of the return piping before that main trap was installed. Something.....

The steam can't get into the radiators because the steam in the returns and supply piping won't let the air out. The pressure in both pipes is the same. The water in the return (aggrevated by the trap that doesn't drain the return completely) hammers back and forth by the action of the steam that is there but shouldn't be.

8 ounces of pressure (1/2 psi) is enough pressure for a 400 foot long steam main. You size steam mains to drop 2 ounces per 100 feet. Of course, that is figuring that the return is at 0 psi and piped correctly. If you have to use steam to blow the air through that trap, you need some pressure, and you can count on some cold spots because not all of the air can get out.

I would look for a way to keep the steam from reaching the return piping beyond the radiation. Orifices in the inlet valves, or traps on the outlets. Then I would move that end of main trap to the end of the supply main, not the return main. Lastly, I would repipe so that the return held absolutely no water which would let the air vent out freely through the tank vent.

Noel

Art Pittaway

Orifice traps

Look at the piping downstream and see if there is a funny looking fitting, sometimes stainless, sort of blends into the piping. If so, it's a highly engineered hole in a piece of steel. The people that sell these things pray on school districts that don't spend money on good maintenance but can spend capital on wonderful projects. Sometimes the project is a sucess because the 20 year old traps were shot and anything was better than nothing. But, when it goes wrong they will do all sorts of things to "fix" the system. I have seen some pretty strange piping changes. Dig into the history, and look it over carefully before you make changes. See if the school has any original prints in a corner of the store room.
Good Luck
Art

[Deleted User]

Saw a job

that sounds something like this years ago.

It had originally started life as a vapor system w/ an alternating receiver. Then the boiler got changed and the receiver (what the h___ is this thing) met the scrap man. Many plumbers & heating types later, an imagineer met the job.

He removed the pressuretrol & installed a vaporstat. He piped the wet return, only, directly to the boiler with a Hartford Loop. The "A" Dimension was very generous. New vents on the end of the mains. The dry return, w/ a vent at the top, was piped into a small condensate receiver, and the return condensate was pumped into the equalizer well below the loop entry. Operated @ about 6 oz cut off.

No radiator traps. I don't recall what was there. But. No steam @ the receiver. Quick to heat and quieter than a church mouse.

I was only there twice. Our oil price got too high for the customer. Just an idea you might like to chew on.

steamman

steamman

orifice traps stick again

It sound's like there may be orifice traps in the school. The problem with orfice traps is that they are sized on average load (a school has a varying load). The only place that I have seen orfice traps work in on U.S. SHIP's (Navy, ect). The reason why is because they have a constant load. I would say that if the furthest rooms in the school are not heating, it is either that the radiators are air bound or full of water. Sense Orifice traps have extrem difficulties handling air and high loads of condensate you might want to invesagate the orifice traps futher.

Steamhead

Orifices

could have been located on the supply or the return- early Trane Vapor systems had them built into the radiator return elbows. After it became practical to control a coal-fired boiler within a few ounces, supply-side orifices came into use.

I think your basic problem is air. Except for the "2-pipe, air-vent system", most 2-pipe steam installations routed air from the rads into a dry (above the boiler waterline) return, from which it was vented in or near the boiler room.

Your condensate line on the ground floor sounds like a wet (below the waterline) return, with the trap at the pump serving to keep water in the return (false water line). Did this return always approach the boiler- old one as well as new one- below the waterline?

Think like air. If you were air, could you get out of that system?

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Greg Kousidis

Hi Noel,

I neglected to mention that the bucket trap has an air vent piped into the upper port.

hot_rod

Air

Where to start....

Let's look at a system that works. If it had traps or orifices on the return side of the radiators, the steam would fill the mains, then fill the radiators, until the whole system was pressurized to the last trap. That would leave air and NO PRESSURE on the outlets of all of the radiators and in all of the return piping. The radiators (yes, even those cold ones) vent air and water into that empty pipe.

Even if the orifices are at the inlets, the return is unpressureized and empty.

Then someone put a trap at the tank on the return. As long as that air vent is open, there is a little pressure difference between the supply and the return. Radiators can vent and can fill with steam. Once that air vent shuts, those cold radiators have the same pressure on both pipes, and nothing moves in or out of them. They stay cold.

At some point, we need to discover what was there before the trap and the boiler were installed.

It really is important to find out. The other details are interesting, but until we understand what you are supposed to have, we can't really make any reccomendations on a cure. Something USED TO keep the returns unpressurized....

Noel

Dale

I think Dan

tells a story like this from Alaska, someone put a low spot in front of a condensate receiver, I think the fix was to drain the return to the condensate receiver which is piped to the outdoors so no pressure can build up in the return piping. If the old system had no receiver and the rads all dropped to a wet return then no traps are needed.

Greg Kousidis

The configuration you describe seems to make the most sense. The radiators do in fact all drain down into the wet return. I believe this line ran directly back into the old bte in the oiler. The custodian did say that the trap was installed to stop the steam that was blowing back thru the wet return. He also said that the trap was later raised in height. It know sits about 5 1/2 feet above the ground. This is obviously raising the return water level. Why did they do this?

The more I ramble on, the more I get confused....What do you think?






You mentioned that traps would not be needed, can you explain this? What happens when the steam comes around and comes in contact with this condensate in the return?

[Deleted User]

Can you clarify

some of what you said.

Are there two separate returns? One for the main drips and one for the radiators? Or, only one common return?

Less important: what type of trap @ the condensate pump? You said F&T & then Bucket.

Is it possible that the radiators are equipped w/ radiator return ells (impulse check, ball check union, union elbow return, etc.)? They were the forerunner of traps in the days of vapor.

Just pieces of the puzzle that might help.

Greg Kousidis

Hi Ron,

There is one common wet return and all the condensate lines drain straight down into it.

The main steam trap is an F&T and I was given another piece of the puzzle today which may explain why it was installed.
The condensate line originally drained back directly into the old boiler. It just so happens that this boiler was located in a pit unlike the replacement which sits on the ground. This of course means that the new boiler water level is higher than the original (approx. 5 feet high).
This is probably why the need for a receiver. I think the condensate line would be drained empty if it was piped directly into the receiver without the trap (the tank would repeatedly fill and pump). The trap is probably providing a false water line as mentioned in one of the prior responses.

What do you think?

[Deleted User]

I thought about the pit

as I was driving home last evening. Looks like someone did not do their homework when installing the newer boiler.

Still wonder how the radiator air was vented from the single return. Maybe there were traps on the main line drips. That return line would have been a dry return. Then the line would have been vented before it dropped down to the the Hartford Loop. Then the consideration would have been the "A Dimension" from the bottom of the return to the boiler water line.

Looks like someone will have to install F&T Traps on the main line drips. Pipe the return into a condensate return pump w/ an inlet at or below the return line level. Ditch the master trap. Install a vaporstat & set @ 8 oz. You might also consider installing m/l vents on the mains before the drips. There will be a lot of water and air trying to pass through that return on each start. The m/l vents should reduce the overcrowding.

Might even have to install radiator traps. But, I would try the above first. Good luck, if they let you do it.

P.S. Any reduction in that return line size @ the receiver, if the inlet is smaller, should be w/ an eccentric reducer.