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Boiler Mountings - An Overview

These are different fittings and devices which are necessary for the operation and safety of a boiler. These devices are usually mounted over the boiler shell.

In accordance with the Indian boiler regulation, the following mountings should be fitted to the boilers.

Two safety valves

The function of a safety valve is to release the excess steam when the pressure of steam inside the boiler exceeds the rated pressure. As soon as the pressure of steam inside the boiler exceeds the rated pressure, the safety valve automatically opens and excess steam rushes out into the atmosphere till the pressure drops down to the normal value. A safety valve is generally mounted on the top of the shell.


Two water level indicators

The function of a water level indicator is to indicate the level of water in the boiler constantly. It is also called water gauge. Normally, two water level indicators are fitted at the front end of every boiler. Where the boiler drum is situated at considerable height from the floor, the water gauge is often inclined to make the water level visible from any position.

Pressure gauge

The function of a pressure gauge is to measure the pressure exerted inside the vessel. The gauge is usually mounted on the front top of the shell or the drum. It is usually constructed to indicate up to double the maximum working pressure. Its dial is graduated to read pressures in kgf/sq. cm (or bar) gauge (i.e., above atmospheric). There are two types of pressure gauges: (i) Bourdon tube pressure gauge and (ii) Diaphragm type pressure gauge. A pointer, which rotates over a circular graduated scale, indicates the pressure.

Steam stop valve

This is perhaps the heaviest and most critical of all valves in a boiler and the one that experiences in full superheated steam. The steam stop valve is a heavy-duty isolating gate-type valve of the same size as the main steam line or a size smaller. An SSV can be a wedge gate, parallel slide or venturi type.

Feed check valve

The function of a feed check valve is to control the supply of water to the boiler and to prevent the escaping of water from the boiler when the pump pressure is less or the pump is stopped. The feed check valve is fitted in the water space of the boiler, slightly below the normal level of the water.

Blow-off cock

A blow off cock or valve performs the two functions: (i) It may discharge a portion of water when the boiler is in operation to blow out mud, scale or sediments periodically. (ii) It may empty the boiler when necessary for cleaning, inspection and repair. It is fitted on the boiler shell directly or to a short branch pipe at the lowest part of the water space. When more than one boiler are working, and they drain in the same waste pipeline, an isolating valve is necessary to prevent the discharge of one boiler, from entering into the other.

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