KRAL DL3 Series, Operating Instructions Manual

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5 Function description
5.3 Assignment pump station - pump
5.3 Assignment pump station - pump
DL3 NE DL4 NE DS1 NE DS3 NE DS4 NE
1800 15 3200 32 150 5 900 15 1600 32
2300 20 4000 42 240 5 1100 20 2000 40
2900 26 6000 54 320 10 1500 26 3200 32
400 7.5 1800 15 4000 40
500 10 2300 20 6000 54
750 7.5 2900 26
1000 10
1300 13
Tab. 9: Assignment pump station DL/ DS - pump NE
5.4 Reversing valve
If the lever of the reversing valve 6 is in one of the two side positions, the respectively other line of the
station is separated from the fluid circuit so that the strainer of this line can be opened and cleaned. If
the lever is in the centre position, both lines are connected to the fluid circuit. The delivery rate can thus
be increased through parallel operation of the two pumps. If only one pump is being operated, the
second pump can be cut in automatically if the delivery rate or the pressure drops at the active line. In
order to ensure a uniform distribution of the operating hours, an interval-controlled automatic switch-
over between the two pumps is also possible in this valve position. The non-return valves ensure that
the respective pump that is stopped does not begin to rotate backwards.
5.5 Overflow valve
1 2 4 5
8 7 6 9
3
Fig. 6: Overflow valve
1 Screw plug
2 Adjusting screw
3 Pressure spring
4 Seal ring
5 Reversing valve lever
6 Suction-side connection
7 Valve ball
8 Control block
9 Pressure-side connection
The overflow valve is integrated in the control block and ensures that very high pressures that could
result in housing parts bursting do not arise.
The overflow valve is purely there as a safety element for the pumps and should not be used for control
or regulation purposes such as maintaining pressure. If the valve is kept open for too long under ad-
verse operating conditions (high differential pressures and/or low viscosities) it will only take a few
minutes for the overflow valve and the valve seating to become damaged. As a result, the overflow
valve will leak permanently and there will be a corresponding reduction in the delivery rate. In addition
to this, circulation through the overflow valve for too long results in excess heating of the pump. This
reduces viscosity and can ultimately lead to pump failure.
It therefore has to be ensured at the system by a safety valve that the maximum operating overpres-
sure always lies under the opening pressure of the overflow valve.
Notice The opening pressure of the overflow valve is set to 110% of the differential pressure in the factory.
The overflow valve is accessible through a screw plug 1 and can be adjusted from the outside Ä Dur-
ing operation, Page 22.
Operating instructions OID 06en-GB Edition 2019-11 11