KRAL KV - 5.8 Overflow valve

5 Function description
5.5 Overflow valve
Housing Type Description
KFN/KFT/KVT Flange arrangement: Overhead flange PN6/PN16
KFA Flange arrangement: Overhead flange in special design
PN16
Tab.5: Housing variants
5.5 Overflow valve
3 42
1
Fig.5: Overflow valve
1 Screw plug
2 Adjusting screw
3 Pressure spring
4 Valve body
The integrated overflow valve ensures that very high pressures that could result in housing parts burst-
ing do not arise.
The overflow valve is purely there as a safety element for the pump 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24.
Notice o A function test of the overflow valve at least every 5 years is essential for the safe operation Ä Dur-
ing operation,Page24.
o Scope and if necessary shorter test intervals must be specified by the operator-owner in accord-
ance with the requirements and national provisions (for example Austrian Ordinance of Safety and
Health (BetrSichV)).
o The first function test must take place directly after the commissioning.
o After longer downtimes (> 4 weeks) the function of the overflow valve must be tested again.
Operating instructions
OIK 09en-GB Edition 2019-11
11