Displacement Pump Service - Graco Fast-Flo A Series Instructions-Parts List Manual

Displacement Pump Service

CARBON STEEL DISPLACEMENT PUMPS, with leather,
polyethylene, or PTFE packings
This procedure covers the following displacement
pumps. Refer to the parts drawings on the indicated
pages for an illustration of your pump.
• Model 215953, page 18.
• Model 215956, page 18.
• Model 215954, page 19.
• Model 215957, page 19.
• Model 237254, page 20.
• Model 237449, page 21.
• Model 237255, page 22.
Before You Start
1. Disconnect the displacement pump from the air
motor as explained on page 11.
2. Be sure you have all the necessary repair parts on
hand to reduce downtime.
3. Repair Kits are available. For best results, use all
the new parts in the kit even if the old parts look
good. Refer to the parts drawing for your pump.
Intake Valve
1. Unscrew the intake valve housing (23) from the
cylinder (13), using a strap wrench. Disassemble
the valve and clean and inspect all parts.
NOTE: On Models 237254 and 237255, inspect the ball
(28) and seat in the housing (23) for wear or nicks.
2. Replace parts as necessary. Reassemble as shown
in the applicable parts drawing.
Piston Valve
1. Using a strap wrench, grip the cylinder (13) near the
outlet housing (6) and unscrew it from the housing.
Pull the cylinder down off the piston. Check the
inner surface of the cylinder for scoring or wear by
running a finger over the surface or holding the part
up to the light at an angle.
2. Loosen the lower nut (16) and unscrew the valve
housing (18) from the connecting rod (17). Unscrew
the piston stud (22).
307427ZAF
3. Clean and inspect all piston parts. Replace parts as
necessary. Reassemble the piston parts as shown,
being sure that the lips of the u-cup packing (21) are
facing up. Screw the piston stud (22) into the valve
housing (18) and torque to 31 N•m (23 ft-lb).
4. When reassembling the piston to the connecting rod
(17), screw the connecting rod all the way into the
displacement rod (15). Tighten the upper nut (16)
against the displacement rod and torque to 33 N•m
(24 ft-lb). Adjust the lower nut (16) to allow 3.1 mm
(0.125 in.) free travel for the disk (19).
Throat Packings
1. Remove the cylinder (13) and piston as explained
previously. Remove the packing nut (1) and pull the
displacement rod (15) out of the top of the outlet
housing (6). Inspect the outer surface of the
displacement rod for scoring or wear by running a
finger over the surface or holding it up to the light at
an angle.
2. Remove the throat packings from the outlet housing
(6).
3. Clean and inspect the parts for wear or damage.
Lubricate the packings before reassembly. Install
the parts one at a time, in the same position as
before. The lips of the v-packings must face down
against fluid pressure.
NOTE: On displacement pumps 215953, 215956, and
237254, install the two leather v-packings (4) below the
single PTFE v-packing (3).
4. Leave the packing nut (1) loose until the
displacement rod (15) has been installed.
CAUTION
Insert the displacement rod from the top of the outlet
housing to prevent shearing of the packings.
5. Tighten the packing nut just enough to prevent
leaking. Overtightening can damage the packings.
6. Reconnect the displacement pump to the air motor
as explained on page 11.
Displacement Pump Service
17