As per the Indian boiler regulation (IBR), the type of joint preferred for the circumferential joint is the __________ joint.

ANS:B - lap

In boiler construction, the type of joint preferred for the circumferential joint is indeed the lap joint, not the butt joint. Here's an explanation of the lap joint in boiler construction: A lap joint is a type of joint where one component overlaps the other, and they are joined together by welding along the overlap. In the context of boiler construction, the circumferential joint refers to the joint formed when the ends of two cylindrical components (such as boiler shells or drums) are joined together to form a closed vessel. In the case of a lap joint, one end of a cylindrical component overlaps the other, and the overlapping portions are welded together along the entire circumference. This type of joint is commonly used in boiler construction because it allows for a smooth and continuous connection between the cylindrical components, ensuring structural integrity and pressure containment. The lap joint provides adequate strength and reliability for circumferential joints in boiler construction. However, it's important to ensure proper welding techniques and quality control to prevent defects and ensure the integrity of the joint.