Kalmar DCE80-100E, Technical Handbook

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All trucks
Technical Handbook
Hydraulic Cylinders
Service
9279 02-09
Publ.
Gr. S.
12 70
Double action piston seals
Double action seals function with pressure from both directions,
e.g., in a steering cylinder.
The whole of the surface within the cylinder pipe is the sealing
surface, it is therefore extremely important that this surface is not
damaged in any way.
Be very careful when fitting the piston in the cylinder pipe to avoid
any damage to the seal from the threading in the cylinder pipe.
Dismantling
1. Remove guide rings and support rings.
2. Move the sealing body over to one side of the sealing groove.
3. Press up the materials so that there is a gap between the seal
and the piston.
4. Without damaging the surface of the piston, cut the seal off
with a knife.
5. Carefully check the seal to discover any damage that can
have caused leakage. This can be achieved most easily by
bending over the seal section by section and checking the
sealing surface with a finger nail.
Fitting
1. All double action piston seals are constructed in the same
way, a middle sealing body, thereafter support rings and final-
ly, guide rings, see illustration.
2. First fit the sealing body, thereafter the support rings and final-
ly the guide rings - everything must be done by hand, without
the use of tools, in order to prevent damage.
Repairing the piston rod surface
The smallest damage to a piston rod can be enough to cause
leakage. The chromium plating has a thickness of 20-50
µ
and
can be worked on to repair smaller damage. This can be a viable
alternative to costly dismantling.
1. Locate the damage with finger tips and finger nails.
2. Use a small, finely polished, panel beating hammer and work
in the material from the area surrounding the damage, work
from the outside in towards the damage.
3. Instead of a sharp mark, there will now be a more even irreg-
ularity in the chrome surface.
4. Polish with emery cloth, in stages, use grades from 240 - 600.
Wrap the emery cloth around a file to support the cloth well.
N.B. Sufficient chrome must always be visible at the point of
damage.
5. It is important, before both dismantling and fitting, to repair
small dents and other physical damage so that they do not
damage the cylinder head.
6. For larger damage to a piston rod:
– fill the damaged area with a weld
– completely remove all welding cinder
– file down the weld to the same level as the chrome surface
– polish to an even finish with emery cloth
KL1015
1
2
3
4
4 3 6
5
1. Moving sealing surface against cylinder
pipe
2. Static sealing surface against piston
3. Guide ring
4. Support ring
5. Head of piston
6. Cylinder pipe
KL1016
3
4
1
1
1. Piston rod
2. Chrome surface
3. Damaged surface
4. Finely polished hammer
2