stack analysis

Jesse_3

I was hoping someone could explain to me the process of performing a stack analysis to calculate efficiency of boiler. Thanks.

Joe V

Stack analysis...

... Can tell you what's going up the chimney. If you have a percentage of raw gas, then your burners aren't burning the fuel completely which is an inefficiency.

It can also measure the temperatures of the exhaust gases and tell you how much heat is used to produce steam and how much is going up the stack which is another inefficiency.

I participated in a stack analysis with the EPA at a coal mine. They had a rolling laboratory with a boom to lower their sensors into a stack. They said our burners were inefficient-too much hydrocarbons. After troubleshooting, I found the contractor cross treaded a couple 1-1/4inch unions above the burner which dumped raw gas into the chimney. It was an industrial drier where the burners are positioned in the airstream in the equipment.

Jim Davis_7

Stack analysis is a means of increasing the efficiency of boilers and checking starting and ending results. They are not very good at calculating the actual efficiency because their are too many unknowns. The key is that every appliance needs to run within a certain set of guidelines based on what the equipment is doing. The lower the O2 the more efficient. The lower the CO the cleaner the burn but 0 ppm CO it not necessarily where we want to run. CO just needs to be below 100ppm and stable. Flue temperature is a function of what we are trying to heat. If we are making steam the flue temperature needs to be higher than if we are making hot water. If we are making 180 degree hot water the flue temperature should be higher than if we are making 160 degrees hot water. Atmospheric boilers operate with O2 readings between 6-9% while power burners should operate between 3-6% O2. Low flue temperatures do not necessarily mean higher efficiency. Each type of equipment has different ranges. In most cases when tuning up equipment properly the calculated efficiency will either go down or stay the same. The efficiency difference is the the changes in O2 and Stack temperature. It is simple once you learn it but I can't explain all the parameters in a post that takes me 2 days to teach in a class. You can call me at 800-633-7058. Bacharach does have a website that gives you some good information but does not really explain how to get from one set of readings to another or how totally diagnose all the situations you need to know.

Joe V

...a means of increasing efficiency: well put.