General Pump MK Owner Manual - Manual (Page 11)

GENERAL PUMP
A member of the Interpump Group
MK SERIES
Page 11
9.4
Hydraulic Connections
In order to isolate the system from the vibrations produced
by the pump, we advise to build the first section of the duct
near the pump (both for intake and delivery) with flexible
hose. The consistency of the intake section must allow to
avoid deformation caused by the depressurization
produced by the pump.
9.5 Pump Feeding
MK pumps must always be installed under positive head,
i.e. they must receive water by gravity or by forced feed-
ing, and never suck from a lower level. The pumps can
tolerate minimum NPSH even as low as 1 m. (3.28 ft.),
however, to obtain a better volumetric efficiency and
above all to avoid cavitation, the minimum NPSH avail-
able, measured at the pump inlet flange, will have to be at
least equal or higher than the values shown in the chart
below.
9.6 Suction Line
For the pump’s correct operation, the suction line must
have the following characteristics:
1. Minimum internal diameter as indicated in the diagram
in paragraph 9.9, and in any case equal or greater than
the pump head’s value.
Along the duct, avoid localized diameter reductions
that may cause pressure drops with subsequent
cavitation. Absolutely avoid 90 0 elbows, connections with
other hoses, bottlenecks, counter-slopes, upside down “U”
shaped curves, “T” connections.
2. The selected lay-out must allow to avoid cavitation.
3. It should be perfectly airtight, and built in a way that
guarantees perfect sealing over time.
4. Avoid pump emptying when stopping (even partial
emptying).
5. Do not use hydraulic-type fittings, 3 or 4 way fittings,
adapters, etc. , since they may hinder the pump’s
performance.
6. Do not install Venturi tubes or injectors for detergent
intake.
7. Avoid the use of standing valves, check valves, or any
other type of one-way valves.
8. Do not connect the by-pass line from the valve directly
to the pump suction line.
9. Provide appropriate baffle plates inside the tank in
order to avoid water flows coming from both the by-
pass and feeding lines may create turbulance near the
tank’s outlet port.
10. Make sure that the suction line is perfectly clean inside
before connecting it to the pump.
11. The pressure gauge for checking booster pressure
must be installed near the plunger pump’s outlet port,
and always after the filters.
The version may be changed only by special-
ized and authorized personnel by carefully
following the instructions in the repair manual.
9.3 Version Change and Reducer Positioning
A right version pump is defined when: observing the
pump from the head side, the PTO shank of the pump
shaft is on the right side.
A left version pump is defined when: observing the pump
from the head side, the PTO shank is on the left side.
See fig. 5.
Furthermore, it is possible to position the reducer in 5
different positions, both on the right and left sides, as
shown in fig. 6.
The reducer’s position may be changed only
by specialized and authorized personnel by
carefully following the instructions in the
repair manual.
fig. 6
MK40A MK45A MK50A MK55A MK60A MK65A
NPSH
r
(ft)
14.8 18 21.3 24.6 26.2 29.5
For the pumps with higher displacement (MK55A-60A-
65A), it is strongly recommended to use a booster pump
to avoid cavitation, in view of the geometry on the
hydraulic section and of the remarkably high flow rates.
The booster pump must have the following specifications:
flow rate at least double the rated flow rate of the pump,
and pressure between 30 to 40 PSI (2 to 3 Bar). These
feeding conditions must be respected in all running condi-
tions.
Booster start-up must always precede plunger
pump start-up. In order to protect the pump,
we advise to install a pressure switch on the
feeding line after the filters.
Ref 300669 Rev.B
05-13