Page 302 - Wastewater Solids Incineration Systems

Incinerator Maintenance 263

condition is caused by a slagged-up burner tile. If left uncorrected the shell can be
seriously damaged.
On incinerators without shell insulation the operator should check the entire sur-
face for hot spots. The operator should also check for shell cracks, particularly in the
skew-back bands at each hearth. Should a skew-back band crack completely through,
the arch of that hearth will settle down and quickly fail. Immediate repairs should be
made.
The operator should also check the shell for corrosion in the vicinity of all
hearths. Serious corrosion can occur from the inside of the shell because the shell
temperature is at the dewpoint. Operators should check for all of these conditions
during every shift.

1.8 Refractory Repair and Replacement
The quality of all repairs and modifications inside an incinerator affects equipment
life. If high-quality material is used and installation is performed in a professional
manner, service life of the refractory work will be substantially extended.
Installation of refractory brick hearths is a complex process and should not be
compared with laying bricks in a building wall. The bricklayer or contractor must be
trained in the art of incinerator refractory and should have the required experience.
This person should have a thorough knowledge of the many refractory materials,
temperature limits, strengths, curing procedures, construction procedures, and emer-
gency hot work techniques.

1.8.1 Brick Shapes
A hearth is constructed with many individual bricks arranged in concentric rings
starting from the outside and progressing inside the hearth. There are two types of
bricks used for hearth construction: special shaped and standard sized. The advan-
tages to using standard-sized brick are
• Consistent modulus of rupture throughout a lot. Standard-sized bricks are
machine made and are packed at higher pressure, which produces a high-
strength brick. Special-shaped bricks are traditionally hand-filled and packed.
As a result, modulus of rupture values have varied so much that failures have
occurred after very little running time.

• Reduction in spare brick stocking to only one size when using a standard-
sized brick. With special-shaped bricks, each ring of bricks is a different size.