c. Pressure Gauge Cock
Generally, this valve is a ball valve. It is used to isolate pressure gauges installed along
the water pipe lines.
Main pipe line
Pressure gauge
Impulse tubing loop
Gauge cock (Ball valve)
The gauge cock is only opened during pressure measurement. When not in use, the valve
is closed to prevent prolonged pressurising to the gauge, therefore preventing damage
to the gauge itself. It is also closed when changing a new gauge.
d. Safety Relief Valve [Optional]
The valve will open when the pressure exceeds a set value to prevent over pressuring the
system which may cause damage. Normally, this is used when the system is running
hot water (mini chiller in heating mode/reverse cycle) in a closed piping. The hotter the water
temperature, the higher is the pressure due to expansion.
Such valves are also useful for protection against sudden pressure shocks, e.g. water
hammering, and overpressuring from water fill system.
If the system is with an open piping and external tank, this valve may be exempted.
The setting of the valve should be at least 10% higher than the expected maximum operating
pressure. It should be installed at the location where this pressure may be expected to
occur, e.g. near any expansion tanks or pump discharge lines.
Pipe the exhaust from the relief valve to an external drain.
Section 3 Page 53
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