Thrush GTU - Manual (Page 2)

Suction Piping
The diameter of the suction pipe should be at least that of the
pump suction nozzle. Use of a smaller diameter pipe will
result in loss of heat due to friction.
All joints must be tight to maintain the prime on the pump.
Elbows installed in any position at the suction nozzle have a
tendency to distribute the liquid unevenly in the impeller eye
and may cause a reduction in capacity, create an undesirable
thrust condition, or cause noisy operation. Therefore, elbows
should not be used at the suction nozzle. If this is unavoid-
able, long radius elbows should be used in place of standard
elbows wherever possible. This is because of their superior
flow characteristics.
If reducers are necessary, they should be of the eccentric type.
They should be installed directly at the suction nozzle, with the
taper at the bottom to prevent air pockets from forming
(see Figure 2). Straight taper reducers should never be used in a horizontal suction line because of
the air pocket that is formed at the leg of the reducer and the pipe (see Figure 2).
If a strainer is installed on the suction line, it should be checked periodically to insure that it does not
obstruct flow to the pump. If the suction line does become sufficiently blocked, severe damage to
the pump will occur.
Discharge Piping
The discharge pipe diameter should be at least as large as the diameter of the pump discharge
nozzle. The size of the discharge pipe to be used is dependent upon the application.
The same cautions mentioned concerning elbows applied at the pump suction also apply to elbows
placed on the discharge piping.
If an increaser is needed at the pump discharge, it may be of the straight taper type.
Shut-Off Valves
Shut-off valves should be installed on both the suction and discharge lines to facilitate service. The
suction valve should only be used for shut-off, NEVER TO ADJUST PUMP FLOW. One may
therefore us a gate valve. The discharge valve, however, may be used to throttle the pump. IF
SO, IT SHOULD NOT BE A GATE VALVE. Instead, it should be a globe, ball, or butterfly valve.
Expansion Joints
Expansion joints are used primarily to prevent the transmission of piping strain caused by thermal
expansion and contraction, piping misalignment, pressure changes, or other causes, to the pump
casing. They can also be used to eliminate the transfer of noise from the pump to the system. It is
recommended that either the flexible metal type or the convoluted rubber bellows type with limit
bolts be used. Simple rubber expansion joints, which cost less, tend to deteriorate, making frequent
replacement necessary.
For the GTU model end-suction pump, rigid base mounting with flex-connections at suction and
discharge is recommended.
Operation
NOTE: CENTRIFUGAL PUMPS SHOULD NEVER BE STARTED OR RUN DRY. OPERATING A
PUMP DRY WILL CAUSE SCORING OF THE MECHANICAL SEAL, RESULTING IN PREMATURE
SEAL FAILURE. TO PREVENT THE PUMP FROM BEING RUN DRY, IT SHOULD ALWAYS BE
PRIMED BEFORE STARTING.
Shut-Off
The pump should never be operated at a shut-off head condition (no-flow). This can cause over-
heating, and result in damage to the pump. If the pump is to be run at a no-flow for an extended
period, provisions must be made for a relief by-pass. (Consult Factory)