Burners should be visually inspected to ensure proper operation once per shift. Conditions that need to be corrected include flame impingement on tubes and supports, abnormal flame dimensions and pattern, oil drippage, and smokey combustion. In addition, the burners should provide an even heat distribution. Poor firing from unbalanced burners can cause serious deterioration of the heating elements and setting. Defective burners that can not be repaired in service should be replaced so that they do not lead to premature failure of other components. Obtain the burner drawings from the burner vendor. The drawings will include the installation tolerances, tile diameter and tip drilling information.
Burner plugging problems sometimes can be solved by proper sizing of the fuel drum and demister pad, heat tracing the fuel gas delivery lines, and providing filters or coalescing systems. Regardless, deposits should be analyzed to determine if the source of the plugging can be identified and eliminated.
The following guidelines are general recommendations for maintenance outage inspection. Always consult the guidelines from the burner vendor.
a. The burner tile is an air orifice. It controls the amount of air flow. Since it is extremely desirable to have even air flow to each burner, the tile dimensions are critical. Typical installation tolerance is ± 1/8 in. (0.32 cm) on the diameter as shown on the burner drawing. Measure the diameter in three to four locations. Most round tiles are installed as a slight oval shape. This will result in poor fuel-air mixing and a bad flame shape. Burner tiles should not be cracked or spalled. The use of a plywood template helps set the tiles in the proper diameter and concentricity. The burner tile must be centered on the gas tip to obtain uniform fuel air mixing. Typical installation tolerance is ± 1/8 in. (0.32 cm). Poor installations result in bad flames.
b. Check the burner drawing for the number of tip drillings and the drill bit size of the port. Use drill bits to check the proper hole size and the proper included angle of the drillings. Do not mix parts from other burners. Be sure to install tips with high-temperature anti-seize compound.
c. The installation tolerance on gas risers is typically ± 1/8 in. (0.32 cm) on horizontal spacing and ± 1/8 in. (0.32 cm) on vertical spacing. Bent gas risers can cause these dimensions to be wrong. A common problem is different lengths on the gas risers. Many burners are designed such that the gas jets intersect in the center of the burner. The tips usually have arrows or cutouts to aid in tip orientation. Welding rods can be a valuable check for alignment.
d. Air dampers and registers should be checked for operability. Sticking air registers and dampers are a problem. Sometimes, dry graphite lubricant can improve air register operability. Penetrating oil, grease fittings and the addition of bearings to damper shafts can improve operability.