![background image](http://html1.mh-extra.com/html/gardner-denver/pzg-7/pzg-7_operating-and-service-manual_3692422031.webp)
15-600 Page 26
compound gasket seals end of liner against valve
chamber. When replacing a valve chamber it is
necessary to remove the discharge manifold. Also
remove screws holding suction manifold to the
chamber being replaced. Loosen, but do not remove
suction manifold screws in the other two chambers.
Suction manifold can be dropped enough to clear
gaskets. These members are to be securely bolted to
the new valve chamber before it is finally tightened
against frame connecting flange. Be sure manifold
gaskets are in place.
LINER CLAMP AND LINERS
- When liner clamps are
reinstalled or replaced, it is advisable to check cylinder
to frame stud nuts and tighten if necessary. Refer to
pages 31 and 32 for proper torques.
Nuts holding liner clamps in place should not be
overtightened as distortion of the clamp and liner bore
may result. Recommended torque values are shown
on pages 31 and 32.
Change size of pistons and liners as volume and/or
pressure requirements change. See rating charts on
pages 12 thru 15.
Liners are replaced by removing the liner clamp. Liners
should be cleaned and oiled after removal to protect
against rusting during storage, so they can be used
again.
Pump liners are to be clean both inside and out when
installed. Also clean the liner clamp bore and lightly oil
all surfaces.
Use new gaskets when installing liners and be sure to
clean all surfaces against which the gaskets fit. Liners
or valve chambers may be cut by leaking gaskets.
PISTONS
- Single-acting pistons consist of a steel
piston body with insert retained by a washer and snap
ring.
Pistons, with piston rods, can be removed or installed
through suction valve opening after valve upper guide
is removed by turning it 90_. Valve spring must also be
removed. 7” pistons on PZG, PZH and PZJ pumps
must be removed through frame. In the 7500 PSI high
pressure fluid cylinders, 6” diameter is the maximum
that can be removed through the suction valve
opening. Larger diameters must be removed through
the frame.
It is recommended that a piston and rod assembly be
kept ready for replacement. This is a practical time-
saver.
PISTON ROD
- Piston rods are manufactured of high
carbon steel. They are electrolytically plated to protect
against corrosion. They are provided with a knurled
section so rod can be held while tightening piston nut.
It is important that piston rod nut be tightened to
recommended torque shown on pages 31 and 32.
Piston rod to piston fit is straight. Piston fits against
flange on piston rod with on “O” ring gasket to prevent l
connecting flanges and pilots. DO NOT use a
screwdriver or cold chisel to separate the flanges - turn
the pump slightly.
For pumps with threaded piston rod to push rod
connection, tighten to torque specified on pages 31
and 32.
PISTON WASHING SYSTEM
- The piston washing
system is vital to the satisfactory performance and life
of pistons and liners. The complete system must be
kept in good operating condition. Washing fluid should
be maintained in good condition and should be
replaced when contaminated to the point where free
circulation is impaired. This is of utmost importance
and should be impressed upon all operators of the
pump.
Water supply lines should be permanently attached to
the openings provided in the circulating pump and the
tank. Water is then quickly available as a washing fluid
or to flush out the lines by operating the proper valves
in the piping system.
The piston washing fluid may be varied according to
conditions and operator’s preference. Water makes a
suitable washing fluid under most conditions. Good
results can be obtained using water with one-half
gallon (1.9 liters) of soluble oil per tank of water within
the closed system. A light oil gives good results under
some conditions, and can be used under severe
freezing conditions.
The more fluid circulated, the better; however, it should
be regulated by a valve in discharge line of the
centrifugal circulating pump to prevent splashing and
being blown about.
MAINTENANCE OF VALVES
- In order to keep the
pump in its best operating condition, it is necessary to
examine the suction and discharge valves occasionally
to see that excessive wear or cutting by the slush or
mud has not impaired their efficiency. Any worn or
damaged parts should be replaced.
This is especially true with regard to the inserts.
Standard inserts are made from urethane and are the
part of the valve which should be changed most
frequently. They are much cheaper than the valves and
seats, and if the inserts are renewed as soon as they
begin to fail, the more expensive steel parts will last
much longer. Routine inspection of valves every two or
three days is recommended.