Why are boiler manholes elliptical in shape?

Boiler manhole is the hole through which maintenance personnel enter the container during boiler maintenance or supervision. To install, disassemble, clean and overhaul the internal devices of the equipment. The structure of hand hole and manhole is basically the same, consisting of a short barrel section and a blind plate.

The boiler manhole-lids are mounted from the inside of the boiler so that the boiler pressure will help to keep them tight. Hence the manholes have to be elliptical in shape to make it possible to take the lid out from the boiler.

Because the stress concentration is low, the diameter of both ends will be smaller. Therefore, in order to facilitate people to enter the drum, the shape of the manhole of the drum is elliptical.

In order to prevent leakage, the installation quality of manholes must be strictly required. The flange and cover plate are processed with sealing water lines, and attention should be paid to protection during construction to avoid oil leakage during use. Each time the manhole is removed, a mark should be made to avoid dislocation when re-installing, which will affect the tightness.