ICI - Innovative Creations, Inc. AX - Manual (Page 8)

ACCESSORIES
6
2.1.4 Safety valves
These valves have the function of discharging steam
when the maximum design pressure of the boiler is
reached.
The valves used on boilers can be of the type Lever and
weight (Fig. 5) or Spring (Fig. 6).
The boiler operator must pay much attention to the safety
valves and carry out careful and diligent maintenance.
The safety valve is the most important and sensitive
accessory on the boiler and represents the best
guarantee that the internal pressure of the boiler does not
exceed the design pressure.
As during normal operation of a boiler, the safety valve
never acts, it is good practice to check that the valve is
free, i.e. that the valve plug is not stuck to the seat, by
acting on the side lever (spring valves) or on the
horizontal lever carrying the weight (lever and weight
valves) until the valve starts to discharge steam.
WARNING
On first start-up, you must verify that safety valve
adjustment is made to the boiler design pressure.
Generally the spring safety valve is supplied already adjusted, while the lever
and weight type must be adjusted by moving the weight along the lever until the
opening pressure value corresponds to the boiler design pressure.
The safety valve installed on steam boilers must have the discharge piped to
outside the boiler room. Particular care must be taken in designing the
discharge line; we show some here.
• The discharge line should e of diameter at least equal to that of the
discharge flange on the safety valve.
• Only wide radius curves must be used in the discharge line.
• The entire discharge line must be built to avoid the formation of
condensation locks. There must be therefore adequate slopes to ensure
complete drainage.
Particular care must be taken if the valve seat and plug are to be ground; if this
operation becomes necessary due to leaks, use abrasives based on silicon
carbide or oil based carborundum. Carry out the first grinding operation using
fine grain abrasive, finishing with a very fine grain abrasive.
2.2 LEVEL
2.2.1 Level indicator gauge
The level indicator consists of a pair of valves connected to a sight glass box containing a prismatic glass.
This device is connected to the boiler both above and below the normal water level, while the lower part is
fitted with a purge valve so that any sludge can be removed, to keep the glass clean. Using these valves, the
efficiency of the level control system can be verified periodically by carrying out the following operations:
• Open for a few seconds and then close the purge valve. If the water disappears from the sight glass and
then appears again with ample level oscillation, then it can be considered that the level operates correctly.
If on the other hand the water returns slowly or stops at a level differing form the preceding level, then on of
the communications may be obstructed. To make sure which of the two is obstructed, and to attempt a
purge, close the steam valve leaving the water valve open, then open the purge valve. This valve must
release water taking with it any sludge formed in the pipes. Then close the water valve and open the steam
valve: steam should be released from the purge valve. Closing the purge valve and leaving the two water
and steam valves open, the water should return to the initial level. If this does not occur, the
communication pipes between the level and the boiler must be cleaned.
Fig. 5
Fig. 6