Never permit the pressure drop through the strainer to exceed
the normal operating value recommended by the manufacturer.
( c ) S t r a i n e r s . C l e a n strainers, i f provided, at established intervals
as recommended by the specific manufacturer. When starting a new system,
s t r a i n e r s require frequent cleaning until the system is free from foreign
( d ) P a r a l l e l O p e r a t i o n . Pumps operating in parallel should have similar
c h a r a c t e r i s t i c curves in the operating range. I f that is not the case, the
pump that develops the greatest head will pump most of the water. This
c o n d i t i o n may be corrected by throttling the discharge valve until the head
developed by the pump is reduced to the required value. A better solution is
o b t a i n e d by installing a calibrated orifice in the pump discharge line after
the valve. The orifice is designed to decrease the pump head as necessary,
which permits operation with a fully open discharge valve.
( e ) Stuffing Box Adjustment. T i g h t e n stuffing boxes evenly to prevent
excessive leakage, but do not overtighten. E x c e s s i v e friction can overheat
and damage the pump shaft or shaft sleeve and the packing. Set the gland
loose enough to allow a trickle of water leakage through the stuffing box.
This lubricates and cools the packing which prevents it from overheating and
s c o r i n g the shaft or shaft sleeve.
( f ) L u b r i c a t i o n . When oil rings are used for lubrication, make sure
t h a t oil level is maintained, as specified by manufacturer, and that the rings
keep turning. Use only the amount and type of oil approved by the
manufacturer for the service intended. R e g u l a t e bearing cooling water, if
u s e d , to maintain oil within safe operating limits. I f the bearing is
overcooked, atmospheric moisture may condense in the bearing housing,
c o n t a m i n a t i n g the oil. I f there is no specific information from the
manufacturer, consider a maximum operating temperature of 150F for babbitted
s l e e v e bearings and 180F for antifriction bearings. D r a i n o i l p e r i o d i c a l l y
gasoline or kerosene, then add new oil. Use clean tools and cloths; do not
use waste materials. When grease-packed, antifriction bearings are used, be
sure not to over grease the bearings as this may result in overheating.
U s u a l l y , antifriction bearings should be packed-one-third full with a proper
grade of bearing grease. For average operating conditions, add 2 or 3 ounces
of grease at intervals of 3 to 6 months. U s e a safety fitting or remove drain
plug when adding grease to prevent overgreasing.
( g ) Irregular Performance. Watch for any abnormal pump operation.
Check bearing temperatures, pressure gauges. and flow indicators periodically,
and compare with normal operating conditions. Observe st u f f i n g boxes to see-
t h a t sufficient water leaks through the stuffing box for proper cooling and
Watch for abnormal noise, overheating, and v i b r a t i o n s . Check
a n c h o r bolts for tightness; loose bolts may cause vibrat ion and misalignment.