Service maintenance – Great Plains CDS-JohnBlue NGP Series Pumps User Manual

Page 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