Page 300 - Wastewater Solids Incineration Systems

Incinerator Maintenance 261

Rabble arm socket failure results in the arm falling out of the socket and jamming
against the next rabble arm. This failure requires an incinerator shutdown to remove
the broken arm/socket and repair of the socket (see section 1.8.8, Rabble Arm
Replacement, for shutdown repair action).
Ash and/or slag buildup on top of the rabble arms may add excessive weight to
the arm and can damage the arms and central shaft. This buildup should be removed
on a regular basis.
1.4.4 Upper and Lower Center Shaft Seals
The upper and lower center shaft seals are typically filled with sand. Additional sand
must be added to the seals on a regular basis. Recently, a number of WWTPs have
replaced sand with steel shot. Because of the density of the steel shot, it does not have
to be replaced as often as sand.
1.4.5 Thermocouple Repair and Replacement
Thermocouples within the incinerator must be cleaned, calibrated, and repaired on a
regular basis. Thermocouples should be replaced on an as needed basis.
1.4.6 Calibration and Repair of Analyzers
Oxygen analyzers, total hydrocarbon (THC) analyzers, and carbon monoxide ana-
lyzers have to be calibrated on a daily basis and repaired on an as-needed basis. An
adequate supply of spare parts should be retained on site and the equipment should
be replaced as necessary.

1.5 Hot Work Cleaning and Repairs
Some cleaning and repair work can be performed without a complete shutdown
(cool down to ambient temperature). To perform “hot work,” the feed must be
stopped and the cake within the incinerator must be allowed to burn off. After this is
accomplished, the central shaft is stopped and the burner flames turned off. The
entire incinerator should be under a negative draft to prevent hot gases from flaring
out of inspection doors and lance tubes.
Maintenance workers should be equipped with high-temperature clothing,
gloves, and face protection and be properly trained. A backup person with proper
gear should also be in attendance. The tools required are typically custom-made long
handled chisels, pry bars, lances, and hoes.
The following types of “hot work” jobs can be performed without shutting down
(however, special care must be taken to protect workers):