Level control chambers

Level control chambers are fitted externally to boilers for the installation of level controls or alarms, as shown in Figure 3.7.11.

The function of the level controls or alarms is checked daily using the sequencing purge valves. With the handwheel turned fully anticlockwise the valve is in the 'normal working' position and a back seating shuts off the drain connection. The handwheel dial may look similar to that shown in Figure 3.7.12. Some handwheels have no dial, but rely on a mechanism for correct operation.

The following is a typical procedure that may be used to test the controls when the boiler is under pressure, and the burner is firing:

• Slowly turn the handwheel clockwise until the indicating pointer is at the first 'pause' position. The float chamber connection is baffled, the drain connection is opened, and the water connection is blown through.
• Pause for 5 to 8 seconds.
• Slowly move the handwheel further clockwise to full travel. The water connection is shut-off, the drain valve remains open, and the float chamber and steam connections are blown through. The boiler controls should operate as for lowered water level in boiler i.e. pump running and / or audible alarm sounding and burner cut-out. Alternatively if the level control chamber is fitted with a second or extra low water alarm, the boiler should lock-out.
• Pause for 5 to 8 seconds.
• Slowly turn the handwheel fully anticlockwise to shut-off against the back seating in the 'normal working' position.

Sequencing purge valves are provided by a number of different manufacturers. Each may differ in operating procedure. It is essential that the manufacturer's instructions be followed regarding this operation