Question 226Steam Plants - Assistant Engineer

The correct answer is D) undercut the existing brick around the area to be patched. The reason this is the correct answer is that undercutting the existing brick around the area to be patched helps to create a secure, interlocking fit for the plastic refractory wall patch. This prevents the patch from falling into the furnace of the D-type boiler. Undercutting the brick provides a mechanical attachment for the patch, rather than relying solely on the adhesive properties of the plastic material. The other answer choices are not as effective for securing the patch. Mixing the plastic with concrete may not provide a strong enough bond, reinforcing with metal mesh could be difficult in the confined boiler space, and attaching anchor bolts to the furnace casing would not create the necessary interlocking fit with the existing brick.