11
Parker Hannifin
Cylinder and Accumulator Division Europe
Maintenance Bulletin
'Mill Type' Cylinders
MA3 Series
Standard and Low Friction Piston Seals PN and PF Kits
Figs. 5 and 6
1
Remove the old seals and wear rings from the piston, taking
care not to damage the seal grooves. Carefully clean all parts.
2
Examine the cylinder bore and piston for signs of scoring.
If either is damaged, it must be replaced.
Chevron Piston Seals – PLL Kits, Fig 7
Note: Piston/rod assemblies are accurately trued during ma-
nufacture using factory jigs and measuring equipment. Parker
Hannifin cannot accept responsibility for any failure or damage
that results from reassembly by unauthorised personnel.
1
The chevron-type piston is made in two parts and assem-
bled on the piston rod, with the chevron seals and bearing ring
clamped between the two parts. Drill out the locking pin (55)
between the piston and rod.
2
During disassembly, the piston rod must be prevented from
turning, either by locking the rod end thread or by clamping the
piston rod in a soft-jawed vice.
Warning:
any damage to the polished surface of the piston rod
will lead to early failure of the gland seals. Unscrew and remove
the outer part of the piston (17b)
from the piston rod.
3
Noting the quantities and sequence in which the old seals
and bearing ring are assembled, remove them from the piston.
Remove the rod/piston O-ring. Slide the inner part of the piston
from the rod and remove the second rod/piston O-ring.
4
With the piston assembly removed from the piston rod, the
cushion sleeve should be examined for signs of damage or
wear. Note that the cushion sleeve must be free to move on the
piston rod.
5
Thoroughly clean and inspect both parts of the piston, the
piston rod and the cylinder bore. If any wear or damage is pre-
sent, the affected parts must be replaced.
Reassembly – Piston and Seals
Standard Piston Seals – PN Kits Fig. 5
PN kits contain a step-cut, filled polyamide seal (125), an ener-
gising ring (126) and two wear rings (127), plus cylinder body
O-rings (26), and back up washers (47) where fitted.
1
Install the energising ring (126) followed by the polyamide seal
(125). Position the wear rings (127) in their grooves.
2
Lubricate the cylinder body with light oil and insert the piston.
Low Friction Piston Seals – PF Kits Fig. 6
PF kits contain an outer, filled PTFE seal (131), an energising
ring (132) and two split wear rings (133), plus cylinder body O-
rings (26), and back up washers (47) where fitted.
1
Install a new split wear ring (133) in the shallow groove at one
end of the piston.
2
Working from the same end, slide the energising ring (132)
over the wear ring and into the central groove.
3
From the other end of the piston, install the second wear ring.
4
Heat the outer seal (131) in boiling water and stretch it by
hand until it will just fit over the wear rings. Push the seal over
the wear ring and into the central seal groove, on top of the
energising ring.
5
Apply O-ring grease to all rings, compress them with a ring
compressor and slide the piston into the cylinder body.
Chevron Piston Seals – PLL Kits Figs. 7 & 8
PLL kits comprise a bearing ring (142), two each of the chevron
header rings (143a) and back-up rings (143c), and a number of
chevrons (143b). In addition, a pair of rod/piston O-rings (46)
and a pair of cylinder body O-rings and back-up washers (26
and 47) are also included. The number of chevrons supplied
varies with cylinder bore size.
Fig. 8
From the contents of the chevron piston seal kit, identify the
chevrons and divide into two equal sets to fit on either side of
the central bearing ring (142). Confirm from the notes made
during disassembly (step 3 above) that the correct number of
chevrons is available.
1
Ensure that the cushion sleeve is correctly positioned on the
piston rod, with its tapered face towards the cylinder's head
end, and that it is free to move.
2
Lubrica Cylinder Assembly Figs. 1-7
The cylinder should be reassembled as follows:
3
During assembly of the piston to the piston rod, the rod must
be prevented from turning, either by locking the rod end thread
or by clamping the piston rod in a soft-jawed vice.
Warning:
any damage to the polished surface of the piston rod
will lead to early failure of the gland seals.
4
Lubricate and install the chevron header ring (143a), chevrons
(143b) and chevron back-up ring (143c) onto the shoulder of
the inner piston, noting from figure 7 that the lips of the chevron
seals face outwards from the centre of the piston.
5
Referring to figure 7, repeat step 4 on the outer part of the
piston, and slide the bearing ring (142) onto the outer piston
until it abuts the back-up ring. Ensuring that the seals and
bearing ring do not become dislodged during assembly, slide
the outer part of the piston onto the rod and tighten using the
face-type pin wrench. Drill a new locking pin hole between the
piston and rod, drive the replacement locking pin into the pin
hole and peen the end to secure.
6
Lubricate the piston and cylinder bore with light oil. Insert the
piston into the bore, ensuring that the forward-facing lips of the
chevron seals do not become twisted on entering the tube.
