Burner Testing – Gas Burner Operation
The following tests should be carried out on several test gases blended to simulate the normal and extreme ranges of expected fuel gas quality. Generally a three-component mixture of natural gas, propane and hydrogen is used to duplicate the expected ranges of specific gravity, heating value and hydrogen content of the fuel gas.
1. Move from maximum to minimum heat release maintaining design draft and 2% oxygen in the flue gas. Develop the capacity curve of fuel header pressure vs. heat release, where the latter is measured by a meter on gas flow rate. Estimate and record the size of the flame core (i.e., the steady outline of visible flame) and the extent of visible wisps of flame.
2. At design draft, establish the minimum heat release below which 2% oxygen cannot be maintained in the flue gas.
3. At design draft and with the air registers set for 2% oxygen at normal heat release, increase the gas pressure until the flame becomes unstable. (It may not destabilize before reaching the maximum available pressure.) Repeat with air registers full open and at maximum draft. Estimate and record the flame size at these conditions. This test helps set the maximum gas pressure.
4. At maximum draft (damper full open) and with the air registers full open, reduce the gas pressure until the flame on one of the gas tips goes out or, in premix burners, until the flame drops into the mixer throat. This test helps set the minimum gas pressure.
5. At maximum draft (damper full open), reduce the gas pressure to the desired minimum gas bypass pressure with the air registers closed. Bang the air registers full open to make sure the flame doesn’t blow out. If it does, a design change is needed.
6. For combination oil-gas burners, set the gas header at the minimum flow bypass pressure. At maximum draft and with the air registers full open, go through at least two cycles of oil burner ignition, shutoff, and steam purge to make sure the gas flame doesn’t blow out. If it does, a design change is needed or the minimum flow bypass pressure has to be raised.