JETStream X Series - Lubrication

22
Operation Manual
Technical Notes
*** Driver selection and coupling selection re-
quires engineering analysis of torsional loads
and vibra- tions (TVA). Jetstream can supply
the mass- elastic data for the pump but it is
customer’s responsibil- ity to perform TVA of
the system. Coupling failure, engine damage,
and powerend damage can result from incor-
rect coupling selection.
****All pumps have a minimum inlet pressure
necessary to prevent cavitation.
Additionally, Jetstream (and many other)
pumps have a maximum allowable inlet pres-
sure. Excessive inlet pressure will not affect
the operation or life of the uid end, but can
negatively affect the power end.
The connecting rods are equipped with plain
bearings where they contact the crankshaft.
These bearings require lubrication to sur-
vive. When the crankshaft rotates and pulls
the crosshead backwards through the suc-
tion stroke, the force between the connect-
ing rod journal bearing and the crankshaft
decreases greatly. This reduction in force
and the rotation of the crankshaft causes oil
to be drawn into the small space between
the connecting rod journal bearing and the
crankshaft. As there is no oil pump in the
3000/3600/4200/5200 series, this is the only
mechanism that lubricates the journal bear-
ings.
High pressure on the plungers during the suc-
tion stroke can prevent oil from being drawn
into the space between the connecting rod
journal bearing and the crankshaft. The lack of
lubrication can cause journal bearings to fail
in only a few hours. This problem is worse with
large plungers, high inlet pressure, and low
speeds.
Following Jetstream’s maximum allowable
uid end inlet pressure of 75 psi and mini-
mum pump speeds of 200 rpm for the 3000,
183 rpm for the 3600, and 173 rpm for the
4200 and 5200 series will prevent this type of
failure.