General information
15
VALVE MAINTENANCE
The valve is a very delicate mechanism, so the system operator must check its efficiency. If necessary, contact a technician
authorised by the manufacturer.
It is good practice for the safety valves installed to protect the plant:
–
to be operated (once a week) with system pressurised, by activating the manual lifting lever of the shutter
–
to have their calibration checked once a year, directly on the system or with bench test
–
to be subjected to overhaul every two years
–
to be replaced after ten years of operation
m
IMPORTANT
The safety valves are designed and built to operate without lubricant; simply keep them clean and efficient. Always
refer to the specific manual.
SAFETY PRESSURE SWITCH
The pressure switch is equipped with a single-pole switch, of which the position of the contact depends on the pressure on the
relevant connection and on the value set. It is calibrated at a higher pressure compared to the maximum one of the pressure
transmitter, but always lower than the opening pressure of the safety valve.
The safety pressure switch intervenes in case of steam pressure regulator failure (adjustment pressure switch or pressure
transmitter) and permanently stops the burner.
1
Main shaft
2
Main spring
3
Differential shaft
4
Differential spring
5
Reset spring
6
Activation lever
7
Bellows
8
Pressure connection
9
Reset button
10
Differential knob
11
DIN plug
12
Micro-switch
13
Micro-switch bracket
14
Adjustment knob
m
IMPORTANT
The safety pressure switch is calibrated and sealed during generator construction.
Operation
When the system pressure exceeds the set value, the pressure switch automatically stops the plant.
The failure of the internal bellows decreases the cut-in pressure of the pressure switch by about 3 times with respect to the set
value, causing the plant to stop.
The failure of the external bellows decreases the cut-in pressure of the pressure switch by about 3 bar with respect to the set value,
to guarantee an intrinsically safe operation.
Cooke Industries - Phone: +64 9 579 2185 Email: [email protected] Web: www.cookeindustries.co.nz
