MTH M50 SERIES - Recommended Spare Parts; Installation; Location; Foundation

entrance velocity in the pump. If a
pump requires more energy (or NPSH)
than is available at a given capacity,
the pressure at the inlet will fall below
the vapor pressure of the pumped
liquid and loss of performance will
result as the liquid vaporizes.
P
s
= Pressure in the suction vessel in
PSIA.
P
vp
= Vapor pressure of the pumped
fl uid in PSIA.
H
s
= Static height of the pumped fl uid
above (+) or below (-) the centerline of
the pump in feet.
H
f
= All friction losses from the vessel
f
= All friction losses from the vessel
f
to the pump in feet.
NPSH = 2.31( )+ H
s
- H
f
For boiling liquids, P
s
and P
vp
are
equal. This item then becomes zero
and can be omitted from the equation.
1D6 Noise
Regenerative turbine pumps typically
produce a high pitched whine that
increases in intensity as the differential
pressure produced in the pump
increases. While high frequency
sound is attenuated more easily than
lower frequencies, piping structures
and the fl uids in them readily transmit
noise. Motors, bearings, and other
rotating components add to the noise
and sometimes create objectionable
harmonics.
Adequate support for the inlet and
discharge piping is important for noise
reduction.
1D7 Freezing
When ambient temperatures drop
below the freezing point of the fl uid
in a pump, consideration should be
given to heating, insulating, or draining
the pump. If you choose to drain the
pump, and it will only be for a short
period, fi rst remove the drain plugs,
Page 503
P
NPSH = 2.31( )+ H
P
NPSH = 2.31( )+ H
NPSH = 2.31( )+ H
s
NPSH = 2.31( )+ H
- P
NPSH = 2.31( )+ H
- P
NPSH = 2.31( )+ H
NPSH = 2.31( )+ H
vp
NPSH = 2.31( )+ H
sp. gr.
NPSH = 2.31( )+ H
sp. gr.
NPSH = 2.31( )+ H
Valves in the outlet piping of a
regenerative turbine pump should
always be open as far as possible
when the pump is started. This will
reduce the start-up load on the pump
and motor. Never start the pump with
the discharge valve closed.
Inlet valving should be open when
starting any pumping system. Without
some fl uid in the pump, it can gall
and lock up the impellers. Violent
pump failure will result from continued
operation with the inlet valve closed.
1D4 Priming
Regardless of whether self-priming
equipment is used or not, always fi ll the
pump and vent it of air before starting,
for best seal and pump life. Under
most circumstances, regenerative
turbine pumps can be made to self-
prime as long as a
small amount of
fl uid can be recirculated through the
impeller and the fl uid doesn’t heat up
noticeably.
1D5 NPSH (Net Positive Suction
Head)
The NPSH required varies with every
size and capacity of pump. The NPSH
required by your unit can be obtained
from the performance curves or from
your MTH representative.
If the NPSH available is not equal to or
greater than that required by the pump,
it must be increased or a different
pump selected. The usual method for
increasing NPSH is to raise the static
head on the pump inlet, (H
s
).
By defi nition, NPSH means: “net
positive suction head” above the
vapor pressure of the pumped liquid
available at the centerline of the
pump. It should always be given in
feet of pumped liquid. The NPSH is
actually a measurement of the amount
of energy available in the pumped
liquid to produce the required absolute
then drain the inlet and outlet lines.
Carefully blow out the pump with
compressed air to clear all internal
cavities of fl uid.
1E Recommended Spare Parts
FOR CRITICAL SERVICES - a duplex
installation, with two identical pumping
units in parallel, is the safest and many
times the most cost effective choice.
FOR IMPORTANT SERVICES - a
standby pump, ready for installation is
advised.
Special pricing and new pump
warranty is offered for factory
rebuilding. Turn around time can be as
short as one or two days for standard
models.
FOR ROUTINE MAINTENANCE
- only the mechanical seals and a
complete set of “O” ring gaskets are
recommended. Should additional
components show wear, they are
available from stock at the factory.
FOR SERVICING A PUMP THAT
DOES NOT PRODUCE RATED
HEAD - mechanical seals, “O” ring
gaskets, impeller, and channel rings.
FOR REBUILDING A PUMP - all the
components required for servicing,
plus bearings, shaft, and drive keys
for fl exible coupled pumps, should
be obtained. A factory rebuild
should be considered whenever your
disassembly indicates rebuilding is
necessary, as this is usually more
economical.
The factory recommendation for
spare parts are all of those listed for
rebuilding a pump, and are shown on
the exploded view drawings for each
individual type of pump.
Installation
2.
M50 • L50 SERIES
FLEXIBLE COUPLED PUMPS
CLOSE COUPLED PUMPS
A.
Location
B.
Foundation
C.
Leveling
D.
Alignment
E.
Piping
F.
Typical Installation
In order to insure that pumping
equipment is installed properly and
to obtain reliable pump operation,
it is recommended that only
experienced, qualifi ed erecting
engineers undertake this task. Read
the instructions thoroughly before
beginning.
2A Location