What is Safety Valve | Boiler Mounting and Accessories

BOILER MOUNTINGS AND ACCESSORIES

Boiler mountings are the devices mounted on the boiler surface for safe operation, efficient working, control steam generation and easy maintenance of the boiler.

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

Two safety valves
Two water level indicators – Click here for more information
A pressure gauge
A steam stop valve
A feed check valve
A blow-off cock
An attachment for inspector’s test gauge
A man hole
Mud holes or sight holes

Safety Valves

Function:

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.

Location

A safety valve is generally mounted on the top of the shell.

As per boiler regulations every boiler must be fitted at least with two safety valves.

Types

Dead weight safety valve.
Lever safety valve.
Spring loaded safety valve.
High steam and low water safety valve.

Spring Loaded Safety Valve

For locomotives and marine engines both the lever and dead-weight types are unsuitable for obvious reasons, and the valve must be spring loaded, as such valve is unaffected by vibration or deviations from the vertical

Illustrates what is known as Rams bottom spring loaded safety valve. It consists of two separate valves and seating’s having one lever, bearing on the two valves, and loaded by a spring, the spring being placed between the valves. The tension on the spring can be adjusted by the nuts. By pulling or raising the lever the operator/driver can relieve the pressure from either valve separately, and ascertain it is not sticking on the seating. One disadvantage of the spring-loaded safety valve is that the load on the valve increases as the valve lifts, so that pressure required just to lift the valve is less than that required to open it fully. From this reason is some cases it is arranged that the area acted on by the steam is greater when the valve is open than the valve is closed.