Boiler's fluttering gas tubes

Schvenzlerman

I have a gas-fired Weil McLain LGB-6 steam boiler. It has a series of parallel metal tubes to which a manifold (in photo foreground) feeds gas. Gas emits from an open slot (not seen in photo) at the top of these tubes and burns under the boiler. Two of the tubes periodically misfire and burn not only through such slots, but also at the manifold end with a fluttering or whooshing sound. I'd like to know why. I checked the tubes and they are clean with no obstruction and straight without being banged up.

Dave in QCA

those are called Burners

Those tubes are called burners.  I can see from the picture that the burner furthest to the left is not positioned correctly.  Is there more than one like this, bit could be part of the problem.



Also, just curious, are you burning nat gas or propane?  Excess air being fed to the burner air inlet causes the flame to lift on nat gas, but on propane, it does the opposite, causing the flame to intensify right at the burner, causing the burner to overheat and sometimes causing ignition inside the burner tube.

Schvenzlerman

You got the right idea

We burn natural gas, but your other description fits what happens; there is ignition inside the burner tube.



Yes, it is the two burners at the far left where this occurs. I will adjust the furthest-left burner so that it fits like the others. How would one go about reducing excess air being fed to the burner air inlet

Dave in QCA

excess air

Excessive air in the burner is not the problem if firing on nat gas.  I would get your burners lined up correctly.  In fact, it might be a good idea to remove them and really clean them out.  Use a brush or vacuum cleaning to make sure that all of the slots in the top of the burner are clean so the burner is burning properly.  If partially clogged, this can also cause the problem.

Dave in QCA

also

It appears in your picture, that the coverplate located just above the burners is not installed in the correct position.  It appears that the left hand side is higher than the right.

Schvenzlerman

clarify please

"The coverplate located just above the burner" refers to a vertical plate that shields the wiring area from the open flame area?

Dave in QCA

Cover plate

Yes, that is correct

ttekushan_3

I've seen this on the LGB

under several circumstances.  1) leaks between sections causing rust and rusty flakes to restrict the fine slots at the top of the burner, 2) the boiler was modified to operate with only one ignition module and therefore only had one point of ignition on the far end, and 3) the internal regulator on the PV MV  Honeywell gas valve has gone bad-- meaning that the turn-on of the gas is no longer a gentle two stage affair, but a sudden "woooof"-- and  will cause the gas to burn within the tube, especially on a cool start.



Most troubling in scenario 3 is that the manifold pressure may not be regulated anymore.  I recommend that you get a technician there to look at the wiring and be sure that the manifold pressure is not exceeding the  3.5" w.c. specified.

Abracadabra

LGB

I've had lots of experience with LGBs







Check that each burner tube is clean.  

Check that each orfice is clean and not blocked.

Verify gas pressure is within spec.  I believe the WM shipped two versions of the burner for natural gas.  One for 6" WC and one for 3.5" WC.