Shaft Seal Run-In Period; Motor Start/Stop; Reference Readings Of Monitoring Equipment; Maintenance - Grundfos NK Serie Montage- Und Betriebsanleitung

10.6 Shaft seal run-in period

The seal faces are lubricated by the pumped liquid, meaning that
there may be a certain amount of leakage from the shaft seal.
When the pump is started for the first time, or when a new shaft
seal is installed, a certain run-in period is required before the
leakage is reduced to an acceptable level. The time required for
this depends on the operating conditions, i.e. every time the
operating conditions change, a new run-in period will be started.
Under normal conditions, the leaking liquid will evaporate. As a
result, no leakage will be detected.
Liquids such as kerosene will not evaporate, and drops will be
visible, but this is not a shaft seal failure.
Mechanical shaft seals
Mechanical shaft seals are precision components. If the
mechanical shaft seal of a recently installed pump fails, this will
normally happen within the first few hours of operation. The main
cause of such failures is improper installation of the shaft seal or
the pipe for barrier liquid and/or mishandling of the pump during
installation.
Stuffing box
The stuffing box gland must not be too tight during startup in
order to let sufficient liquid lubricate the shaft and the packing
rings. Once the stuffing box housing and the stuffing box gland
have reached approximately the same temperature as the pump
parts, the running-in of the stuffing box gland is complete. If the
stuffing box leaks too much, retighten the gland slightly and
evenly while the pump is running. To ensure continuous
lubrication, a few drops should always drop from the stuffing box
to protect the packing rings or shaft sleeve. We recommend 40 to
60 drops/minute.

10.7 Motor start/stop

Max. number of motor starts per hour
Frame size
2
56-71 100
80-100 60
112-132 30
160-180 15
200-225 8
250-315 4

10.8 Reference readings of monitoring equipment

We recommend taking initial readings of these parameters:
• vibration level - use SPM measuring points
• bearing temperature - if sensors have been fitted
• inlet and outlet pressure - use pressure gauges.
The readings can be used as reference in case of abnormal
operation.
Number of poles
4 6
250 350
140 160
60 80
30 50
15 30
8 12

11. Maintenance

Warning
Before starting work on the product, switch off the
power supply. Make sure that the power supply
cannot be accidentally switched on.

11.1 Pump

The pump is maintenance-free.
11.1.1 Mechanical shaft seals
Mechanical shaft seals are maintenance-free, working almost
without any leakages. If any considerable and increasing
seepage occurs, the mechanical shaft seal must be checked
immediately. If the sliding surfaces are damaged, the entire shaft
seal must be replaced. Mechanical shaft seals must be treated
with the greatest care.
11.1.2 Stuffing box
If the stuffing box leaks too much and cannot be further tightened,
the stuffing box must be repacked. After removal, clean and
check the shaft sleeve, chamber and stuffing box gland. For
further information, see the service instructions for NK.
11.1.3 Replacement of packing rings
3
Fig. 29 Sectional view of a stuffing box
Pos. Description
1 Stuffing box gland
2 Packing ring
3 Distribution ring
Follow these steps when replacing the packing rings:
1. Loosen stuffing box gland and remove it.
2. Remove old packing ring, distribution ring, if any, and packing
rings behind the distribution ring, using a packing ring hook.
3. Insert two new packing rings one at a time. Push them firmly
into position, staggering the joints 120 degrees.
4. Insert distribution ring, if any.
5. For D24/D32, insert one, and for D42/D48/D60, insert two
more packing rings, staggering the joints 120 degrees. If no
distribution ring is used, two extra packing rings will be
required.
6. Reinstall stuffing box gland.
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