Two Steam Boiler System/ Need help

Randy Berg_2

Need help please, went to a job yesterday, system is a two boiler steam system. Boiler # 1 is a Smith gas fired, 89.6 hp, #2 is a Weils Mclain rated at 91 hp. I just love these Friday afternoon calls. The call was that Boiler # 2 was flooded and the condensate pump would not shut off. When I got there I found #2 boiler operating or running but not making steam, and #1 was overfilled. I checked the normal things like a welded contactor for the pump, low water control, and also for a defective float. Found no problems. Found header was flooded with water as well. Drained and fired up both boilers, and both came up to operating pressure of 5 psig. After talking to the the contact person at the school this has been a ongoing problem, and has become worse this winter, which has been a cold one here in MD. I have downloaded the near boiler piping for both boilers, and after looking at this I feel that the piping is incorrect for both boilers. Will check that out on my return trip on Monday. Does it sound like I'm on the right path? Someone has installed traps on the main steam lines in the boiler room to force the condenstate out of the main. Also I saw that there is some bad traps in ths system due to the steam comimg out at the condensate pump. All feedback will be helpful.

Steamhead

A couple of questions

1. Is that a "condensate" pump or a "boiler-feed" pump? The difference is the condensate pump is operated by a float in the receiver tank, and the boiler-feed pump is controlled from the boiler.

2. Does the system really need 5 PSI to operate? This could be the cause of the steam in the receiver. Try cranking it down.

3. There should be no need to "force" the condensate from the steam main. It should drain by gravity.

Where in Maryland is the school located? Anywhere near Baltimore?

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Randy Berg_2

It is a boiler feed pump that is operated by the McDonald Miller 150 one set of contacts. The other is tied into the operating control circuit to shut thr burner down on low water. As for the pressure settings both boilers were set at 7 lbs with a diff of 4.I set both to 5 psig/ diff of 3 The school is located in Washington County. It seems like this problem has been with this job since the Smith boiler was installed three years ago, they got fed up with the contractor that installed this boiler. Also what makes it worst is that the contact person has only been at this school for alittle over a year. No history as to why the orignial had to be replaced.

Dan Law

A couple of more ?

Does each boiler have it's own feedwater pump? (common reciever I presume)
Are the boilers staged in any way?

Randy Berg_2

Both boilers have there own feedpump, and they are tied into a energy mangement control system, which from what he stated that the boilers alternate every day and both run when the temp drops below 20 degrees. Onr boiler operates one day then the other the next day. Yes it is a common tank

Steamhead

Randy

e-mail me- I can come out and give you a hand if you'd like. Baltimore isn't that far away. But I'm going to Wetstock so we might have to wait till I get back!

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Ben_3

Randy

I agree with Steamhead as far as your pressure being to high, Two pipe steam should usually cut out by 2 psi. Those traps on the mains are probably for venting the air from the mains over to the dry return. You need to evaulate all your traps and replace as needed in the off season if there are to many to do in one day. Also check if someone added a trap to the dry return mains. I see this all the time, reciever vent pipe starts to blow steam and someone thinks they can just master trap all the return lines. This needs to be removed if there is one there. Have fun! P.S. CRANK THE PRESSUR DOWN.

Dan Law

Flooding boilers

I've seen this before. The BMS guy thinks he can stage the boilers similar to HW
boilers. The standby boiler in effect becomes a huge radiator / receiver. The cool
water in the standby boiler condenses the steam from the running boiler.
Exposed to the entire surface of the water level in the standby, it does what
steam wants to do - condense, "flooding" it. Eventually you end up with water in
the header as you describe.

Traps can be piped off a convenient boiler tapping, or in the equalizer line, slightly
above the water line,
and discharge back to the receiver. (See Lost Art under multiple boilers) While
this does keep the boiler from flooding,
it does nothing for the wasted energy consumed running steam & condensate
around in circle
from the running boiler, to the standby, to the receiver, and back to the feed water
to the running again. I can envision the standby boiler's (now a condenser)
condensing capacity to be large compared to the running boiler’s generation
ability. This could explain your finding of the running boiler not producing any
steam on your arrival. I'll be it was making steam, it was just being condensed by
it's neighbor as fast as it was made.

Compared to this, keeping both boilers on line
strikes me as a better
option. If one boiler can safely maintain building
temps, you could isolate the other from the header, assuming you have the
vavling arrangement. Then manually alternate the boilers on a weekly schedule.

The whole process can be automated of course, but the cost / benefit is
questionable.

Hey, if this is the scenario in play here, you'll look like a hero on the fuel
consumption review. Might be politically astute to ask the clerk to give you the
before and after fuel records. Bet you might pick up a lifetime contract.

Dan

Steve Lucero

I have seen this problem time and time again. This one could be multple problems. If these are cast iron sectional the take off piping may be installed improperly. With tandem boilers the idle boiler will fill with condensate. A.S.M.E. states it is permissable to install a high level trap to relieve the excess back to the make up tank. The Fargo public schools actually have their boilers alternate every 2 - 3 hours and it works well. Steam traps that fail can cause the boiler water to be induced from the boiler and some times cause the boiler to trip out on low water. Water treatment can be a problem but usually not. I would definitly repair the traps first because this will increase the load on the boiler and induce the boilerwater. If they have day-night set back make sure that different sections of the building are phased in so that there is'nt one big load change on the boiler which will again cause water to be induced. You can usually tell if this is a problem when about 9 or 10 in the morning the condensate reciever overflows. Personally I would start with the traps.

Randy Berg_2

I want to say thanks to all the input on this problem. After doing some investigation on this system found alot of problems. There is 33 traps that are defective, the near boiler piping on both boilers are incorrect, also the ph and conductive of water in both boilers are very high. No one told them they need to blow down the boilers at least once a week. The energy mangement system is not swiching the boilers as needed, also it is not staging them. I'm going to meet Johnson Controls on the jobsite on thrusday to get that problem corrected. Also the school has given me the ok to replace all the defective traps, when the boilers are shut down, also I have a water treatment company coming in as well. I advised them that the near piping on both boilers are not correct, and they are bring in a engineer to look at that.