Operating instructions
Speed, Pressure, Temperature
Suitable safety measures must be taken at the plant to ensure that the speed, pressure and
temperature of the pump and the shaft sealing do not exceed the limit values given in the Data
Sheet. The given admission pressures (system pressures) must also be sufficiently high.
In addition, the pump must be protected against pressure surges such as can be caused by
switching off the plant quickly (e.g. by non-return valve on the pressure side, flywheel, air vessel).
Permitted forces on flanges
Basically, the suction and pressure lines should be such that the forces on the pump are kept to a
minimum. If this is not feasible, the figures given in the Appendix „Permitted forces and
moments“ should not under any circumstances be exceeded.
NPSH
When entering the impeller, the liquid being handled must have a minimum pressure NPSH to
prevent cavitation or breaking off of flow. This requirement is met if the unit NPSH value
(NPSHA) is well above the pump NPSH value (NPSHR) under all operating conditions.
Attention must be paid to the NPSH value in particular when liquids close to boiling point are
being handled. If the value falls below the pump NPSH value, this can lead to damage resulting
from cavitation or serious damage from overheating.
The NPSHR for each pump type is given in the sheets of characteristic curves. We can supply
leaflets for calculation of NPSH values on request.
Sealing, Flushing, Cooling
Suitable facilities for the regulation and monitoring of sealing, flushing or cooling are to be
provided.
When handling dangerous liquids or if temperatures are high, care should be taken to ensure that
the pump ceases operating if the sealing, flushing or cooling system fails.
Sealing, flushing and cooling systems must always be operational before the pump is started up.
They should not be taken out of operation until the pump has stopped, provided that the nature of
the operation allows this at all.
Minimum flows
If the pump is started against a closed pressure line valve, it should be noted that the power taken
up by the pump is transmitted to the liquid handled in the form of heat. This can cause the liquid
to heat up excessively within a relatively short time, which will then cause damage to the pump's
internal fittings. After the pump has reached operating speed, the discharge valve should therefore
be opened as quickly as possible. If operating conditions mean that Q = Ø is unavoidable, or if hot
water is circulating, a free flow non-return valve, or, on smaller systems, a by-pass pipe, should be
provided. We should be pleased to advise on determining the minimum flow or designing the by-
pass line.
Protection against running dry
The pumps must not run dry under any circumstances, since overheating can damage pump
components (e.g. mechanical seals).
Pa 100/3-en
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