big old Crane boiler

DasBoot

Greetings:

     I'm working on an old Crane water boiler, model # 14-402, 2,210,000 BTU.  Natural gas.  Hoping to find info on the orifice size, and manifold pressure.  It has 13 flat cast iron burners, and just seems to have way too much fire in there:  flames are lazy yellow, curl back on themselves, and I just brushed 5 gallons of black soot out of it.  Thank you in advance!

Mark Eatherton

Normal is...

3.5" W.C. at the manifold.



As for orifice sizing, it depends on your elevation, and fuel source.



4% deration per 1000 feet above sea level determines the proper input.



Derated gross input divided by the number of burner orifi will tell you how many btu's/burner you need, and then you can size the orifi based on the density and caloric content of the gas you are dealing with. The appliance was most probably shipped with sea level orifices, and if you are less than 2,000 above sea level, then no change would be necessary.



Lazy flames could also be an indication of a lack of primary air, as dictated by the lack of a draft to draw air through the appliance, which can be a symptom of plugged flue gas passages (sounds like you already discovered that) or poor chimney draft, or excessive negative pressure countering natural draft tendencies. Could also be that the primary shutters are closed way down...



Do you have a flue gas analysis?







ME

Tim McElwain

At 2,210,000 with 13 burners

each one at below 2,000 feet is 170,000 BTU"s per burner at 3.5" W.C. at a specific gravity of .6 and a BTU content per cubic foot of 1050 BTU's you need a size "A" orifice or 17/64ths for each burner..



Do you have a gas meter that you can clock the burner?



The flame situation is of much concern along with all the soot. I would take the boiler apart and check the sections and give it a good cleaning.



Mark ask if you have done a combustion test that is definitely a must along with the other things he mentioned..

DasBoot

that crane boiler

We are at 1,100 feet altitude here, so that is not an issue.  Orifices are drilled at 1/4 inch.  Manifold pressure is 3 1/4 inch WC.  It's natural gas.  I could do a combustion test, but since it's currently filling the room with about 40 ppm CO, I know the combustion ain't good, and want to clear up this nasty rolling yellow flame before I bother with the combustion test.

    Room has a power combustion air supply, and it is functioning.

What I was first worried about is the previous techy might have drilled out the orifices, or messed with the manifold pressure and took 'em out of spec, but it sounds like they're really close to where they belong.

     They chimney is a large masonry stack, which is clear of obstruction.  The boiler is vented to the chimney with a manifold of 3) 14 inch metal pipes merging to a 28 inch metal horizontal pipe, and they're all wrapped with asbestos...........i've gotta figure a way to check the horizontal run for obstruction without tearing into asbestos.  I'm thinking of either finding a camera on a flexible cable and sending it up from below, or finding a small child and sending it down from above.

(okay, I'm joking about one of those)

Can anyone locate an original manual from this boiler?

 

Mark Eatherton

Good luck on the manual...

Unless one of these guys who collects them has a copy, I don't think you will be able to find one. The orifices are fairly close, and minor adjustments at the manifold pressure can be made to fine tune, but I would not exceed 10% in manifold adjustments. If 3.5" is normal, then I would not go lower than 3.15".



While you are using your snake cam, might not be a bad idea to take a look deeper up in the heat exchanger to see what kind of soot accumulations you have up there.



Having the mechanical room positively pressurized may also be causing some of your CO issues. Excess air will quench the flames, and cause CO production. U suspect you still have some soot further up in the heat exchanger impeding flue gas flow.



Another option, would be to block the fixed draft hood off, set a barometric damper and roll out switches, and adjust to -.02" WC stack pressures BEFORE the baro damper.



I'd also make an attempt to adjust the combustion air blower so that you are pressuring the room at +.01" W.C. Otherwise, if there ever was a major CO spill, you could be forcing it into living spaces...



ME

DasBoot

barked up the wrong tree

Turns out the nasty flame in there was not because of the burners and gas pressures and stuff.

  Last year they replaced a water heater in the same room.  The new one has sealed combustion, and the old one was vented into the same horizontal run with the boiler.  Way up in the tangled pipes and conduits, the 12 inch round pipe from the old water heater was left open.  It was pulling a lot of air, and leaving insufficient draw for the boiler.  Capping that almost instantly cleaned up the flames in the boiler.  I'll do combustion analysis today.

   Thanks for responses.  This board rocks.