Displacement Pump Service
STAINLESS STEEL DISPLACEMENT
PUMPS, with polyethylene, leather,
or
r
packings
This procedure covers the following displacement
pumps. Refer to the parts drawings on the indicated
pages for an illustration of your pump.
D
Model 215–955
page 27.
D
Model 215–958
page 28.
D
Model 236–991
page 29.
D
Model 237–253
page 30.
D
Model 237–256
page 31.
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.
2. Inspect the ball (28) and seat in the housing (23)
for wear or nicks.
3. 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.
On Models 215–955, 236–991, and 237–253, loos-
en the lower nut (16) and unscrew the valve hous-
ing (18) from the connecting rod (17). Unscrew the
piston stud (22).
On Models 215–958 and 237–256, remove the
cotter pins (29) from the ball stop pin (30). Re-
move the ball stop pin and unscrew the piston stud
(22) from the displacement rod (15). Be careful not
to drop the ball (25).
3. Clean and inspect all piston parts. Be sure to in-
spect the ball (25) and its seat on the piston stud
(22) for wear or nicks. Replace parts as necessary.
Reassemble the piston parts as shown,
being sure
that the lips of the u-cup packing (21) are facing
up. Torque as specified on the applicable illustra-
tion.
NOTE:
On Models 215–955, 236–991, and 237–253,
when reassembling the piston to the connecting rod
(17), screw the connecting rod all the way into the dis-
placement 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 ball (25).
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 out-
let 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 hous-
ing (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.
4. Leave the packing nut (1) loose until the displace-
ment rod (15) has been installed.
CAUTION
Insert the displacement rod from the top of the out-
let 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.
PTFE
