750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual
8-31
8.19 — Opening and Closing Doors
8.18.4 — Rear Door
The rear door is a steel shell lined with insulation material and refractory board.
Burned or discolored paint on the outer surface of the door does not necessarily indicate refractory trouble, but
may be an indication of other conditions such as:
• Leaking gaskets.
• Improper seal.
• door retaining bolts insufficiently or unevenly tightened.
• Repainted with other than heat resistant paint.
Therefore, before assuming that the refractory requires reworking:
• Check condition of the gasket.
• Check for cracks in refractory material.
• Check tightness of door bolts.
It is normal for refractories exposed to hot gases to develop thin “hairline” cracks. This by no means indicates
improper design or workmanship. Since refractory materials expand and contract to some extent with changes in
temperature, they should be expected to show minor cracks due to contraction/expansion, recessing themselves
when the refractory cools. Cracks up to approximately 1/8” across may be expected to close at high temperature. If
there are any cracks that are relatively large (1/8” to 1/4” in width), clean and fill them with high temperature
bonding mortar.
After opening the rear door, clean the flange surface of the door with a scraper or wire brush. Clean the surface of
the refractory carefully with a fiber brush to avoid damaging the surface. Remove all dried sealing material. Wash-
coat the lower half of the rear door refractory prior to closing, caring not to apply too thickly.
8.19 — Opening and Closing Doors
8.19.1 — Opening Front or Rear Door
Before opening the doors, tighten the nut on the davit arm to create
slight tension. This will minimize sagging and facilitate opening of the
door. After opening either door, check the gaskets and seating sur-
faces. Replace the door gaskets if they are hard or brittle. Clean the
sealing surfaces of the door and tube sheet.
FIGURE 8-34. Tighten the Davit Nut
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