There are several fittings and mountings on a boiler.
Mountings
2. Manhole
3.
Mudhole
4.
Safety
Valve
5.
Main
Steam Stop Valve (Crown)
6.
Blow
down valve.
7.
Level
Gauge glass
8.
Level
Controller
9.
Sequence
Controller
10. Explosion Door
11. Fusible Plug
12. Auxiliary air vent valve
Pressure Gauge
A dial pressure gauge (Bourdon Tube) is mounted on the front face of the boiler. It indicates the pressure in the boiler.
Manhole
A manhole is an elliptical opening provided at the top of the shell. Usually while in operation the manhole is covered with a manhole ring. A manhole is an opening provided for maintenance/repair.
Mudhole
Mudhole is provided in the boiler (near the blowdown valve) so that when the boiler is drained, the solid particles could be cleaned off.
Safety Valve:
Safety Valves are provided on the boilers to ensure safe operation. These valves are set according to the highest working pressure in the boiler. The safety valve pops open as soon as the pressure in the boiler rises above the set point. As an additional safety feature along with Boilers two safety valves are provided, such that even if one fails the other pops open releasing the pressure.
Steam Stop or
Crown Valve
The valve that supplies steam to the process from the boiler is called the Crown valve. This valve is kept closed when the boiler is just started to build the pressure required by the process. After the pressure is build as required then the valve must be opened gradually to its full capacity. The crown valve should always be kept fully open once the pressure is built.
Blowdown Valve
The blowdown valve is used to blow down the water in the boiler when the TDS (Total dissolved solids) level in the boiler feedwater increases beyond the permissible value. Generally, boiler operators perform the blow-down manually. Blowdown is a loss because hot saturated water is drained. Therefore, care should be taken to avoid excess blowdown. Manually blow-down is done per shift for a few minutes considering the TDS level. The blowdown valve must be sized properly according to the boiler capacity.
Gauge Glass
Gauge glass is used to indicate the water level in the boiler. Most boiler manufacturers provide only one water level indicator.
Sequence
Controller
The sequence controller is side-mounted and houses all the electrical switches and relays. It controls the sequence of operations. It also houses the controls of the burner operation. It sets the damper position through a damper motor to supply the correct air-fuel ratio.
Fusible Plug
It is basically a safety feature. In case if all the controls fail and the water level starts dropping which results in a rise in metal temperature of the boiler, after a while the fusible plug melts and the water from the shell falls over the flame and extinguishes the flame. This plug operates only when all other electrical controls fail.
Explosion Door
It also a safety feature. It is provided at the exit of the flue gases. In case the chimney gets blocked, or the flue gases could not pass through the chimney, the explosion door opens, and the flue gases pass out.
Auxiliary Air Vent Valve
This valve is mounted along with safety and crown valves. It is used to vent air after shut-down or during a starting up of the boiler.