9
www.imo.se
AC
F/
U
C
F5 2
01
9.
12 e
n-
G
B
, I
D
-N
o.
: 1
63
-0
44
/B
bar
Fig. 12 Gauges
Gauges
Gauges for monitoring the pump’s working
conditions are recommended. These gauges should
be placed readable as close to the pump’s in- and
outlet flanges as possible. On standard pumps,
series ACE, LPE, ACG/UCG, ACF/UCF and LPQ,
there are gauge connections for both in- and outlet.
Pressure relief valve
All systems with screw pumps should be equipped
with a pressure relief valve installed immediately
adjacent to the pump.
In the standard versions of IMO AB low pressure
pumps, this pressure relief valve is an integral part
of the pump to protect the pump against excess
pressure.
This relief valve is intended for momentary
protection of the pump against overpressure. It is
neither intended to be a system pressure control
device, nor used as a flow regulation device.
When liquid is circulated through the valve it is
heated up in proportion to the set pressure level and
the percentage of by-passed liquid.
Up to 50 % by-pass can generally pass for unlimited
periods of time without harming the pump except
when pumping low viscosity media.
If more than 50% recirculation is anticipated, a value
specific to each application should be determined by
closely monitoring the pump body temperature.
For flow less than ~50 m
3
/h
- 100% by-pass can only be tolerated for less
than about 3 minutes, provided the viscosity &
temperature is within the limit of the pump type.
For flow higher than ~50 m
3
/h
- 100% by-pass is tolerated less than 30 seconds.
Note that an open valve can cause noise.
If the pump is operating in line with a separate
pressure control valve (see fig. 14), the setting of the
relief valve should be high enough to not to interfere
with the control valve.
Likewise, if two pumps are operating in parallel, the
setting should be such that interference between the
two valves is avoided.
Pressure testing and flushing
The system must be flushed and pressure tested
before connecting the pump. If corrosive liquid, such
as water is used, the system must be thoroughly
drained, dried and protected against corrosion after
having been flushed.
! Oil leakage may make the floor slippery
and cause personal injury.
Fig. 13 Pressure relief valve
Fig. 14 External control with pressure relief valve
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