Service; Calculation Of Minimum Inlet Pressure; Disposal - Grundfos DNP series Montage- Und Betriebsanleitung

11. Service

If a pump has been used for a liquid which is injurious
to health or toxic, the pump will be classified as con-
taminated.
If GRUNDFOS is requested to service the pump, GRUNDFOS
must be contacted with details about the pumped liquid, etc. be-
fore the pump is returned for service. Otherwise GRUNDFOS can
refuse to accept the pump for service.
Possible costs of returning the pump are paid by the customer.

12. Calculation of Minimum Inlet Pressure

The minimum inlet pressure "H" in metres head required during
operation to avoid cavitation in the pump can be calculated from
the following formula:
H = p x 10.2 – NPSH – H – H
b f
p = Barometric pressure in bar.
b
(The barometric pressure can be taken as 1 bar).
In closed systems p
bar.
NPSH = Net Positive Suction Head in metres head
(to be read from the NPSH curve on page 87 at the
highest flow the pump will be delivering).
The maximum flow rate must not exceed the values
stated for each individual pump on page 86.
H = Friction loss in suction pipe in metres head.
f
H = Vapour pressure in metres head, see page 86.
v
t = Liquid temperature.
m
H = Safety margin = 0.5 metres head.
s
If the calculated value of H is positive, the pump can operate with
a maximum suction lift of "H" metres.
If the calculated value of H is negative, a minimum suction head
of "H" metres is required during operation of the pump to prevent
cavitation.
Example:
p = 1 bar.
b
Pump type: DNP 50-200, 50 Hz.
3
Flow rate: 70 m /h.
NPSH (from page 89): 2.5 metres head.
H = 3.0 metres head.
f
Liquid temperature: +90°C.
H (from page 86): 7.2 metres head.
v
H = p x 10.2 – NPSH – H – H
b f
H = 1 x 10.2 – 2.5 – 3.0 – 7.2 – 0.5 = –3.0 metres head.
This means that a suction head of 3.0 metres is required during
operation.
Inlet pressure calculated in bar: 3.0 x 0.0981 = 0.30 bar.
Inlet pressure calculated in kPa: 3.0 x 9.81 = 29.4 kPa.
74
– H
v s
indicates the system pressure in
b
– H [m head].
v s

13. Disposal

Disposal of this product or parts of it must be carried out accord-
ing to the following guidelines:
1. Use the local public or private waste collection service.
2. In case such waste collection service does not exist or cannot
handle the materials used in the product, please deliver the
product or any hazardous materials from it to your nearest
GRUNDFOS company or service workshop.
Subject to alterations.