Installation
42
TT Twin-Screw Pump -
Installation, Operation & Maintenance Manual
commissioning (temporary) suction strainer can be
removed.
Recommended operating (permanent) strainer
mesh size:
• Viscosity≤450 SSU (86 cSt) use 40 mesh
• Viscosity>450 SSU (86 cSt) use 20 mesh
• Viscosity>1000 SSU (216 cSt) use 12 mesh
If more than one pump operates from
the same liquid source, check that
separate suction-piping lines are used
for each pump.
This recommendation helps you to achieve a higher
pump performance and prevent vapor locking
especially with light volatile fluids
If necessary, make sure that the
suction piping includes a drain valve
and that it is correctly installed.
Assure adequate insulation is applied
for liquids with specific gravity less
than 0.7.
Low specific gravity fluids typically have high vapor
pressures and are sensitive to thermal gain from
the heat flow through uninsulated piping. To
assure sufficient NPSHa is these application
insulation is strongly recommended.
Liquid source below the pump
Check
Explanation/comment
Checked
Make sure that the suction piping is
free from air pockets.
This helps to prevent the occurrence of air and
cavitation in the pump inlet.
Check that the suction piping slopes
upwards from the liquid source to the
pump inlet.
This helps to eliminate any air from the pipework
Check that all joints are air-tight.
Air leaks increase the effective NPSHr of the pump
Check that a device for priming the
pump is installed
– such as a foot
valve is installed.
Use a foot valve with a diameter that is at least
equivalent to the diameter of the suction piping.
Foot valves are not usually required when handling
liquids of higher viscosity
Liquid source above the pump
Check
Explanation/comment
Checked
Check that an isolation valve is
installed in the suction piping.
This allows closure of the suction line during pump
inspection and maintenance.
Make sure that the suction piping is
free from air pockets.
This helps to prevent the occurrence of air and
cavitation in the pump inlet.
Check that the piping is level or slopes
downward from the liquid source.
This helps to eliminate any air from the pipework
Make sure that no part of the suction
piping extends below the suction
flange of the pump.
This helps to eliminate the possibility of trapped air
pockets forming in the pipework
Make sure that the suction piping is
adequately submerged below the
surface of the liquid source.
This prevents air from entering the pump through a
suction vortex.
