General information
14
VALVE MAINTENANCE
The valve is a very delicate mechanism, so the system operator must check its efficiency. If necessary, contact a technician author-
ised 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 transmit-
ter) and permanently stops the burner.
2
1
5
6
4
4
3
1
Sealed anti-tampering cap
2
Polyamide cover
3
Stainless steel bellows
4
Pressure connection G 1/2 A
5
Protection class IP 66
6
2 x PG 13.5 cable diameter 6 - 14 mm
7
SPDT interchangeable contact system
m
IMPORTANT
The safety pressure switch is calibrated and sealed during generator construction.
Operation
When the pressure exceeds the set value, contacts 1-4 close and contacts 1-2 open. Contacts go back to their initial position when
the pressure drops below the set value, minus the differential value (fixed at 1.2 bar).
I
II
1
4
2
IS
D
M
1
4
2
1
4
2
I
Alarm triggered by the increase of the pressure above the set value.
II
Alarm triggered by the decrease of the pressure below the set value, minus the differential value.
IS
Scale setting.
DM
Mechanical differential.
Cooke Industries - Phone: +64 9 579 2185 Email: [email protected] Web: www.cookeindustries.co.nz
