Gast 55R Series - Manual (Page 5)

Gast will NOT guarantee field-rebuilt product
performance. For performance guarantee, the
product must be returned to a Gast Authorized
Service Facility.
Service Kit contents vary. Most contain gasket and filter
parts.
SERVICE KIT INSTALLATION
Ꮨ
Disconnect electrical power supply cord before
installing Service Kit.
If product is hard wired into system, disconnect
electrical power at the circuit breaker or fuse box
before installing Service Kit.
Vent all air lines to release pressure or vacuum.
Failure to follow these instructions can result in
death, fire or electrical shock.
WARNING
Electrical Shock Hazard
Compressor Head Reassembly:
NOTE: The kit contains two different cylinder/cup
assemblies. The assemblies can be identified by the
direction of the piston cup lip (see Fig. 2) The pressure
cylinder piston cup is positioned with the lip toward
the head.
10. Locate the pump mounting pad nearest to the motor.
Install the new cylinder/cup assembly into the pump
mounting pad and over the piston.
NOTE: The pressure cylinder/cup assembly must be
installed nearest to the motor for long shaft bearing
life.
11. Place the retainer over the piston cup. Reinstall the
cleaned phillips head screw you set aside earlier,
using Loctite 222 or equivalent. Torque the screw to
26-30 lb-in.
12. Install a new O-ring in the groove in the pressure
cylinder. Install a new pump head gasket in the
groove in the pump head ( see Fig. 3).
13. Place the valve plate on the pump head so that the
recessed intake valve is exposed (faces away from
the pump head) as shown. Be sure the valve plate is
oriented so the recessed intake valve coincides
with the intake chamber.
14. Using the four phillips head screws you set aside
during disassembly, reinstall the pump head and valve
plate on the mounting pad nearest to the pump.
Position the pump head and valve plate according to
your labeling. Torque the screws to 26-30 lb.-in.
Vacuum Pump Head Reassembly:
NOTE: The kit contains two different cylinder/cup
assemblies. The assemblies can be identified by the
direction of the piston cup lip (see Fig. 2). The
vacuum cylinder piston cup is positioned with the lip
inward, away from the head.
15. Locate the pump mounting pad farthest from the
motor. Install the new cylinder/cup assembly into the
pump mounting pad and over the piston.
NOTE: The vacuum cylinder/cup assembly must be
installed farthest from the motor for long shaft
bearing life.
16. Place the retainer over the piston cup. Reinstall the
cleaned phillips head screw you set aside earlier,
using Loctite 222 or equivalent. Torque the screw to
26-30 lb-in.
17. Install a new O-ring in the groove in the vacuum
cylinder. Install a new pump head gasket in the
groove in the pump head (see Fig. 3).
18. Place the valve plate on the pump head so that the
recessed intake valve is exposed (faces away from
pump head), as shown. Be sure the valve plate is
oriented so that the recessed intake valve coincides
with the intake chamber, as shown. Refer to the flow
arrows stamped on the pump head.
19. Using the four phillips head screws you set aside
during disassembly, reinstall the pump head and valve
plate on the mounting pad farthest from the pump.
Position the pump head and valve plate according to
your labeling. Torque the screws to 26-30 lb-in.
Check that all external accessories such as relief
valves and gauges are not damaged before
re-operating product.
If pump still does not produce proper vacuum or pressure,
send unit to a Gast Authorized Service Facility for repair.
1. Disconnect electrical power to pump.
2. Disconnect air supply and vent all air lines to
release pressure or vacuum.
Pump Head Assembly:
3. Label the head so you can reposition it correctly during
reinstallation. Remove the four phillips head screws at the
corners of the pump head, then remove the head and valve
plate. Set the screws aside for later reassembly.
4. Use needle nose pliers to pull the rubber valves from the
valve plate, and discard them.
5. Remove the phillips head screw at the center of the piston
cup retainer ( the “head” of the piston) and remove the
retainer. Clean the screw and set it aside for later
reassembly.
6. Remove the cylinder and piston cup as a unit from the body
of the pump.
Valve Installation
7. Clean the valve holes in the valve plate. Do not make any
scratches or burrs in the edges of the valve holes.
8. Install the new valves from the opposite sides of the valve
plate ( see Fig. 1). Insert the valve stem through the center
hole of the group of small holes at each valve location.
With needle nose pliers, gently stretch the valve stem to
pull the ball on the stem through the other side of the valve
plate.
9. Use diagonal cutters to trim off the excess valve stem above
the ball as shown.