The longitudinal joint of a boiler shell is always a

Question

Question

This question was previously asked in

UKPSC JE Mechanical 2013 Official Paper I

Answer 1

Explanation:

Longitudinal Butt Joint For Boiler Shell

There are two types of riveted joints in a cylindrical boiler shell.
They are called longitudinal butt joint and circumferential lap joint.
The plate of the boiler shell is bent to form the ring and the two edges of the plate are joined by a longitudinal butt joint.
This longitudinal joint is usually a double-strap triple-riveted butt joint.
The longitudinal joint makes a ring from the steel plate.
The circumferential joint is used to get the required length of the boiler shell by connecting one ring to another.
For this purpose, one ring is kept overlapping over the adjacent ring and the two rings are joined by a circumferential lap joint.
Boilers and pressure vessels are cylindrical vessels. They are subjected to circumferential and longitudinal tensile stresses.
It can be proved that circumferential stress is twice the longitudinal stress.
Therefore, the longitudinal joint should be stronger than the circumferential joint and butt joint is used for the longitudinal joint.