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4.4.5. PRESSURE MAINTAINING VALVE
DESCRIPTION
A pressure maintaining valve is mounted at the outlet of the
filter system P21.
It ensures that pressure is built up in the filter even from the
start of delivery, thus achieving a constant, optimum filtra
tion. It will also guarantee proper working conditions for the
final stage cylinder.
The pressure maintaining valve is adjusted to 150 ±10 bar
(2,175 psi).
3
2
1
Fig. 31
Pressure maintaining valve
MAINTENANCE
The pressure maintaining valve (Fig. 31) is adjusted at the fac
tory to the required pressure and normally does not require
regular maintenance or readjustment. In case of readjust
ment becoming necessary, loosen jam nut (2) and set screw
(3). Adjust screw (1) to the required pressure using a suitable
screw-driver.
Clockwise = increase pressure
Counter-clockwise = decrease pressure
4.4.6. SAFETY VALVES
DESCRIPTION
All three compressor stages are protected by safety valves as
follows
24
Instruction Manual w Junior II
1st stage
2nd stage
The safety valve for protection of the last stage is mounted
on top of the filter system P21 and is adjusted to the operat
ing pressure of the unit (see chapter 1, Technical Data), 225
bar (3,200 psi) for the standard units, 330 bar (4,700 psi)
for models -H or -HU. All safety valves are sealed at the fac
tory.
If one of the intermediate pressure safety valves blows off,
the valves in the next stage are not closing properly, affording
valve check. The cause of the trouble is usually the inlet valve
of the next stage. See also chapter 4.4.8.
MAINTENANCE
Checking function
The final pressure safety valve has to be checked regularly.
For this purpose the safety valve can be vented manually.
Turn knurled knob on top of the valve clockwise until valve
blows off (Fig. 32).
This just ensures that the valve is functional and will release
pressure in case of a malfunction. To check the blow-off pres
sure value refer to "Blow-off pressure check".
Venting
Fig. 32
Venting the final pressure safety valve
Checking blow-off pressure
Check blow-off pressure of the final pressure safety valve reg
ularly, see maintenance schedule chapter 4.3. Pump unit to
final pressure with shut-off valve closed until safety valve
blows off. Check blow-off pressure of safety valve at pressure
gauge. If deviation is 10% or more, replace safety valve.
4.4.7. PRESSURE GAUGE
DESCRIPTION
The compressor unit is equipped with a final pressure gauge
(Fig. 33). The red marking on it shows the max. allowable op
erating pressure.
9 bar (130 psi)
80 bar (1,160 psi)
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