Service manual

13
D.7.5 Suction Strainer /Filter
Pump life is related to liquid cleanliness. Suction strainers or filters should be installed
in all systems to prevent entry of large contaminants into pump. See Figure 9.
Purpose of a suction strainer or filter is for basic protection of internal pumping
elements. It should be installed immediately ahead of inlet port. This location should
provide for easy cleaning or replacement of strainer element. Appropriate gages or
instrumentation should be provided to monitor pump pressure. Pressure drop across a
dirty strainer must not allow inlet pressure to fall below NPIPR. General guidelines for
strainer sizing are as follows:
When pumping relatively clean viscous liquids (over 5000 SSU), use 10 to 12 mesh
screens or those with about 1/16 inch (about 1 ½ mm) openings.
When pumping relatively clean light liquids such as distillate fuels, hydraulic oil and light
lube oils, use suction strainers of 100 to 200 mesh.
When pumping heavy crude oils, use 5 to 6 mesh strainer screens or those with about
1/8 inch (3 mm) openings.
When pumping relatively clean distillate fuels in high pressure fuel supply systems, use
25 micron “absolute” filters for three screw pumps and 10 micron “absolute” filters for
gear pumps.
Make sure size/capacity of strainer or filter is adequate to prevent having to clean or
replace elements too frequently.
CAUTION ATTENTION
Before connecting pump to system, all system piping must be thoroughly flushed to
remove debris which accumulates during fabrication, storage, and installation. Imo
pumps should not be used for flushing. One large, hard particle may cause internal
damage, possibly requiring a pump overhaul. Pay particular attention to suction
line between suction strainer and pump to be sure it is clean.
Strainer
Valves
Pressure Gage
Pressure Gage
Figure 9 - Ideal Strainer Arrangement