Thrush HVGTB - Manual (Page 2)

MOUNTING
PIPING
SUCTION PIPING
DISCHARGE PIPING
PRIMING THE PUMP
FLOODED SUCTION PRIMING
The pump will not operate satisfactorily until is is primed. All air must be expelled from the suction
piping and pump casing and replaced by the liquid to be pumped. There are several methods of
priming pumps. The one selected will depend on the specific requirements.
This method of priming a pump is relatively simple. The liquid source is located above the pump and
all that is necessary to prime the pump is to open the air vent valve or plug in the pump casing and to
crack the isolating valve in the suction line. The suction line and pump should be filled slowly until a
steady stream of liquid is observed flowing from the air vent. After the pump is operating, it is
recommended that the air vent valve or plug be opened again to insure that all air has been expelled
from the pump casing.
Long radius elbows should be used in place of standard elbows wherever possible, because of their
superior flow characteristics. Elbows installed in any position at the suction nozzle have a tendancy to
distribute the liquid unevenly in the impeller eye and may cause a reduction in capacity which creates
an undesirable thrust condition or creat noisy operation. Eccentric reducers should be installed
directly at the suction nozzle, with the taper at the bottom to prevent air pockets from forming.
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.
The discharge piping diameter should be the same as, or larger than, the discharge nozzle diameter.
The size of the discharge pipe to be used is dependent upon its application.
PROPER PIPING ALIGNMENT IS ESSENTIAL BEFORE CONNEC TION IS MADE. PIPING
ALIGNMENT SHOULD NEVER BE ACHIEVED BY FORCE, THIS COULD PROCUCE STRAIN ON
THE PIPING AND TH E PUMP CASING. NOTE: Centrifugal pumps should never be started or run
dry. Operating a pump dry will cause scoring of the mechanical seals, resulting in premature
seal failure. To prevent the pump from being run dry, it should be primed before starting.
Thrush In-Line pumps conserve floor space, simplify piping and can be serviced without discon-
necting piping. The proper installation of these pumps is to install them as a part of the piping. The
pumps must be free to travel with the expansion and contraction of the piping. In-line installation
eliminates the problems normally encountered in aligning piping to a base mounted unit.
SUPPORT OF THE HVGT SERIES PUMPS SHOULD ALWAYS BE CONNECTED TO TH E PIPING
RATHER TH AN T O TH E PUMP CASING. The line-mounted feature eliminates the need for installing
flexible pipe connectors at either the pump suction or discharge. Isolating valves should be installed
at both the pump suction and discharge to permit servicing of the pump without draining the entire
system. Make certain the space around the pump is sufficient to give clearance for removing the
pump assembly from the casing. Also the space around the pump should be large enough for
general accessibility and ventilation. The same criteria and formula for selecting piping supports are
used with the additional consideration that the weight of the pump is concentrated at one point in the
piping.
The piping practices you follow will directly affect the efficiency and power consumption of your pump.
Pay particular attention to the seemingly insignificant details involved in piping for they make the
difference between a good and bad installation. BOTH THE SU CTION AND THE DISCHARGE
PIPING SHOULD BE INDEPEN DENTLY SU PPORTED NEAR THE PU MP. LIBERAL USE OF PIPE
HANGERS AND SUPPORT BLOCKS WILL PREVENT EXCESSIVE STRAIN ON THE PU MP
CASING AND ON THE PIPE JOINTS. T he suction diameter should be at least the same diameter as
the suction nozzle on the pump and preferably larger. All joints must be tight to maintain prime on the
pump.