Testing Procedure - Enerpac P-391 Instructions De Service

■ Assembly
Refer to Repair Parts Sheet L-1771 and use Repair Kit number P-391K2.
Important: Set relief valves before assembling pump. Use new parts from the pump repair kit when
assembling pump.
FLEX PLUNGER STYLE: The old, solid style plunger has been replaced by the flex plunger. With the flex plunger
style, the P-391, 1004 and P-392, 1005 use the same type of base. When servicing the P-392, 1005, you will install a
bypass valve in the base and put a 7/32" check ball in the low-pressure check assembly. When servicing the P-391,
1004, the 7/32" inlet check ball is not used and a pipe plug is installed in place of the bypass valve. Refer to NOTE
in Repair Parts Sheet L-1771.
1. Replace relief valve(s) inside the pump base.
a. Older, solid plunger pumps require
replacement gasket(s) from kit. Torque to
60 to 70 in-lbs.
b. Newer, two-piece flex plunger pumps have
relief valves with 1/8" NPT threads. Gaskets
are not required. Torque to 10 to 12 ft-lbs.
2. Replace oil filter screen if necessary.
3. To install check assemblies, replace the 7/32"
and 5/16" check balls, spring, and spring cap
from the repair kit. Reseat check balls if
necessary. Torque the pipe plugs to
28 to 34 ft-lbs.
4. Before installing the release valve assembly,
remove and replace the spindle o-ring and the
7/32" check ball. Reseat ball if necessary. Put
roller bearing grease on the o-ring before
installing. Tighten the machine screw with a
5/32" Allen wrench.
5. When you re-assemble the reservoir, install a
new round reservoir o-ring when you position
reservoir onto the pump base. Be sure reservoir
is properly placed on the location pin.
a. Drop cap assembly chain through reservoir fill
port. Loop chain around the tie rod and
thread tie rod into pump base.
b. Replace end cap gasket and put end cap
onto end of reservoir.
c. Using new copper gasket, tighten the acorn
nut to 15 ft-lbs.
6. Install plunger assembly. For two stage
plungers (P-392, 1005), replace the o-ring and
back-up rings on both small and large pistons.
For single stage plungers (P-391, 1004), replace
the oil seal back-up ring and the o-ring.
Note: Put roller bearing grease on the plunger
before replacing oil seal and installing the piston
into the bore.
7. Install handle by inserting the new beam pin
into the beam pin hole on the pump base and
through the beam and handle assembly. Secure
the beam pin with new retaining ring.
a. For older solid plunger pumps, install plunger
clip and cross pin, with the flat of the cross
pin against the top of the plunger. Apply
bearing grease at this location.
b. For newer two-piece flex plunger pumps,
apply roller bearing grease to the cylindrical
shaped cross pin. Insert the cross pin into
the beam pin hole of the pump base, and
through the plunger and handle.
8. Refill the reservoir with the appropriate volume
of Enerpac hydraulic oil.
Pump is now assembled. Follow Testing Procedure
below to verify operation.

■ Testing Procedure

Test setup: connect (1) high-pressure hose, (1) 0-
15,000 psi gauge, and (1) 10-ton single-acting
cylinder to the hand pump.
1. Single stage pump: (P-391, 1004) set high-
pressure relief valve to 10,000-10,500 psi.
2. Two stage pump: (P-392, 1005) set the low-
pressure relief valve to 200-275 psi; set high-
pressure relief valve to 10,000-10,500 psi.
3. Test for loss of pressure. Operate the pump to
build pressure to 9,000-9,500 psi and watch
pressure gauge to see if pump maintains
pressure. The maximum drift or pressure drop
allowable is 250 psi in 10 seconds.
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