Great Plains CDS-JohnBlue NGP Series Pumps - Manual (Page 10)

© 2013 CDS-John Blue Co. 10
SERVICE MAINTENANCE
Proper maintenance of the NGP pump will ensure a service life for many years. Rebuilding and / or servicing
check valves, piston flange packing, piston rod packing, and crankcase components is an economical way to
ensure optimum service. This type of service is simple, and can be done by almost all end users. The parts list
and schematic section shows the position of all service kit items, which includes all seals, packing, and gaskets.
Gasket kits and component parts can be ordered through any authorized CDS – John Blue distributor.
CLEAN AND INSPECT CHECK VALVES
 Remove the valve cap exposing all 4 check valves. Take care in
removal to notice the orientation of the valves. Discharge valves
use a tighter spring and are on top, flat side in. Suction valves use
a weaker spring and in the bottom, flat side out.
 Valves should be removed by hand, do not use a screw driver or
pry-bar as damage can result. Push each valve disc off its o-ring
seat ensuring that the spring reseats each disc evenly and that no
debris is present. Inspect the o-rings for cuts or cracks which
could allow air to enter or cause the discs to not seat properly.
 Check the port o-rings positioned near the top and bottom of the
inboard cylinder in an oval shaped groove. This o-ring should not
be removed unless visible damage is present. The o-rings should
be fully installed in the groove with no cuts or cracks. Once all valves are checked for debris or damage and
o-rings are in position, re-install valves in proper orientation, replace the cover, and tighten the bolts evenly.
PISTON PACKINGS
 With valve cover removed, remove the ½” long bolts securing the
outboard cylinder. Remove the outboard cylinder exposing the
piston – gaskets, washer, and packing.
 Remove the first piston – packing, gasket, and washer; notice the
orientation of the packing lip. Remove the second piston gasket
and packing from the inboard cylinder; again noticing the
orientation of the packing lip.
 Inspect the packing and replace if necessary, gaskets should
always be replaced once removed. The piston - packing should
be pliable and without cracks or nicks to perform properly.
 Clean the cavities of both the inboard and outboard cylinder as
well as the valve cap while disassembled. Discoloration of the
plunger and / or lateral scoring of the piston can be deceiving, but
not necessarily detrimental.
 Inspect piston for deep grooves, radial scoring, or severe abrasion. The best method is by feel.
 Assemble in reverse manner taking care for proper orientation of the piston – packing, gaskets, and washer.
Piston – packing
Piston – gasket
Piston – washer
Piston – gasket
Piston - packing
Suction Valves
Discharge Valve