Figure 34. Piston Inspection.

ARMY TM 10-4610-309-14

MARINE CORPS TM 10802A-14/1

0053 00

TACTICAL WATER PURIFICATION SYSTEM (TWPS)

UNIT MAINTENANCE PROCEDURES

HIGH PRESSURE PUMPS

19. Inspect and (if necessary) replace the pistons as follows:

NOTE

The pistons are free-floating in the cylinder liners. They rely on positive feed

pressure to push them downward during refill and are then pushed upward by the

cam and piston cluster during the pump stroke. Each piston has specially

designed low friction, high-pressure seal and wear sleeves installed onto them. If

any one of the pistons needs replacement, the whole piston assembly should be

replaced.

a. Inspect the spherical end of the pistons for damage. Damage may include flattening,

discoloration or cracking. Replace the piston assembly if any of this damage is found.

b. Measure the length of the piston. If it is shorter than 2.969 in., discard and replace the

piston assembly.

c. Inspect the piston wear rings and the pistons for scratching or scoring. Replace the

assembly if needed.

d. Inspect the piston seals. If a seal is torn or otherwise deteriorated, replace the piston

assembly.

e. Carefully clean and rinse all components with clean, fresh water before reinstalling into

the pump.

PISTON

PISTON SEAL

PISTON WEAR RING

Figure 34. Piston Inspection.

CAUTION

Once the pistons are properly seated into the body, do not turn the cam shaft for

any reason. Failure to observe this caution may result in serious damage to the

pump.

NOTE

The ball end of the pistons goes down against the cups on the face of the piston

cluster.

Install the pistons and push all pistons down through the body into the dimples in the

piston cluster (see Figure 35).

g. Install the large O-ring on the outer edge of the piston body.

0053 00-30