Parker HAS Series, Manual, Page: 122 / 125

Hydraulic and Electrohydraulic Actuators
HAS Series Analog Drives Manual
125 Parker Hannifin Corporation
Cylinder Division
Des Plaines, Illinois USA www.parker.com /cylinder
Catalog HY08-4005-M3
Cylinder Safety Guide
3.1.2 – Cylinders operating in an environment where air drying materi-
als are present such as fast-drying chemicals, paint, or weld splatter,
or other hazardous conditions such as excessive heat, should have
shields installed to prevent damage to the piston rod and piston rod
seals.
3.1.3
– Proper alignment of the cylinder piston rod and its mating
component on the machine should be checked in both the extended
and retracted positions. Improper alignment will result in excessive rod
gland and/or cylinder bore wear. On fixed mounting cylinders attaching
the piston rod while the rod is retracted will help in achieving proper
alignment.
3.1.4 – Sometimes it may be necessary to rotate the piston rod in
order to thread the piston rod into the machine member. This operation
must always be done with zero pressure being applied to either side
of the piston. Failure to follow this procedure may result in loosening
the piston to rod-threaded connection. In some rare cases the turning
of the piston rod may rotate a threaded piston rod gland and loosen it
from the
cylinder head. Confirm that this condition is not occurring. If it does,
re-tighten the piston rod gland firmly against the cylinder head.
For double rod cylinders it is also important that when attaching or
detaching the piston rod from the machine member that the torque be
applied to the piston rod end of the cylinder that is directly attaching to
the machine member with the opposite end unrestrained. If the design
of the machine is such that only the rod end of the cylinder opposite
to where the rod attaches to the machine member can be rotated,
consult the factory for further instructions.
3.2 Mounting Recommendations
3.2.1 – Always mount cylinders using the largest possible high tensile
alloy steel socket head screws that can fit in the cylinder mounting
holes and torque them to the manufacturer’s recommendations for
their size.
3.2.2 – Side-Mounted Cylinders – In addition to the mounting bolts,
cylinders of this type should be equipped with thrust keys or dowel pins
located so as to resist the major load.
3.2.3 – Tie Rod Mounting – Cylinders with tie rod mountings are
recommended for applications where mounting space is limited. The
standard tie rod extension is shown as BB in dimension tables. Longer
or shorter extensions can be supplied. Nuts used for this mounting
style should be torqued to the same value as the tie rods for that bore
size.
3.2.4
– Flange Mount Cylinders – The controlled diameter of the rod
gland extension on head end flange mount cylinders can be used
as a pilot to locate the cylinders in relation to the machine. After align-
ment has been obtained, the flanges may be drilled for pins or dowels
to prevent shifting.
3.2.5 – Trunnion Mountings – Cylinders require lubricated bearing
blocks with minimum bearing clearances. Bearing blocks should be
carefully aligned and rigidly mounted so the trunnions will not be sub-
jected to bending moments. The rod end should also be pivoted with
the pivot pin in line and parallel to axis of the trunnion pins.
3.2.6 – Clevis Mountings – Cylinders should be pivoted at both ends
with centerline of pins parallel to each other. After cylinder is mounted,
be sure to check to assure that the cylinder is free to swing through its
working arc without interference from other machine parts.
4.0 Cylinder and Accessories Maintenance, Troubleshooting
and Replacement
4.1 Storage – At times cylinders are delivered before a customer is ready
to install them and must be stored for a period of time. When storage is
required the following procedures are recommended.
4.1.1 – Store the cylinders in an indoor area which has a dry, clean and
noncorrosive atmosphere. Take care to protect the cylinder from both
internal corrosion and external damage.
4.1.2
– Whenever possible cylinders should be stored in a vertical
position (piston rod up). This will minimize corrosion due to possible
condensation which could occur inside the cylinder. This will also mini-
mize seal damage.
4.1.3 – Port protector plugs should be left in the cylinder until the time
of installation.
4.1.4 – If a cylinder is stored full of hydraulic fluid, expansion of the
fluid due to temperature changes must be considered. Installing a
check valve with free flow out of the cylinder is one method.
4.1.5 – When cylinders are mounted on equipment that is stored
outside for extended periods, exposed unpainted surfaces, e.g.
piston rod, must be coated with a rust-inhibiting compound to prevent
corrosion.
4.2 Cylinder Trouble Shooting
4.2.1 – External Leakage
4.2.1.1 – Rod seal leakage can generally be traced to worn or
damaged seals. Examine the piston rod for dents, gouges or
score marks, and replace piston rod if surface is rough.
Rod seal leakage could also be traced to gland wear. If clearance
is excessive, replace rod bushing and seal. Rod seal leakage can
also be traced to seal deterioration. If seals are soft or gummy or
brittle, check compatibility of seal material with lubricant used if
air cylinder, or operating fluid if hydraulic cylinder. Replace with
seal material, which is compatible with these fluids. If the seals
are hard or have lost elasticity, it is usually due to exposure to
temperatures in excess of 165°F. (+74°C). Shield the cylinder
from the heat source to limit temperature to 350°F. (+177°C.) and
replace with fluorocarbon seals.
4.2.1.2 – Cylinder body seal leak can generally be traced to
loose tie rods. Torque the tie rods to manufacturer’s recommen-
dation for that bore size.
Excessive pressure can also result in cylinder body seal leak.
Determine maximum pressure to rated limits. Replace seals and
retorque tie rods as in paragraph above. Excessive pressure can
also result in cylinder body seal leak. Determine if the pressure
rating of the cylinder has been exceeded. If so, bring the operat-
ing pressure down to the rating of the cylinder and have the tie
rods replaced.
Pinched or extruded cylinder body seal will also result in a leak.
Replace cylinder body seal and retorque as in paragraph above.
Cylinder body seal leakage due to loss of radial squeeze which
shows up in the form of flat spots or due to wear on the O.D. or
I.D. – Either of these are symptoms of normal wear due to high
cycle rate or length of service. Replace seals as per paragraph
above.
4.2.2 – Internal Leakage
4.2.2.1 – Piston seal leak (by-pass) 1 to 3 cubic inches per
minute leakage is considered normal for piston ring construction.
Virtually no static leak with lipseal type seals on piston should be
expected. Piston seal wear is a usual cause of piston seal leak-
age. Replace seals as required.
4.2.2.2
– With lipseal type piston seals excessive back pressure
due to over-adjustment of speed control valves could be a direct
cause of rapid seal wear. Contamination in a hydraulic system
can result in a scored cylinder bore, resulting in rapid seal wear. In
either case, replace piston seals as required.
4.2.2.3 – What appears to be piston seal leak, evidenced by the
fact that the cylinder drifts, is not always traceable to the piston.
To make sure, it is suggested that one side of the cylinder piston
be pressurized and the fluid line at the opposite port be discon-
nected. Observe leakage. If none is evident, seek the cause of
cylinder drift in other component parts in the circuit.
4.2.3 – Cylinder Fails to Move the Load
4.2.3.1 – Pneumatic or hydraulic pressure is too low. Check the
pressure at the cylinder to make sure it is to circuit requirements.
4.2.3.2 – Piston Seal Leak – Operate the valve to cycle the cylin-
der and observe fluid flow at valve exhaust ports at end of cylinder
stroke. Replace piston seals if flow is excessive.
4.2.3.3 – Cylinder is undersized for the load – Replace cylinder
with one of a larger bore size.
4.3 Erratic or Chatter Operation
4.3.1
– Excessive friction at rod gland or piston bearing due to load
misalignment – Correct cylinder-to-load alignment.
4.3.2
– Cylinder sized too close to load requirements – Reduce load or
install larger cylinder.
4.3.3
– Erratic operation could be traced to the difference between
static and kinetic friction. Install speed control valves to provide a back
pressure to control the stroke.
4.4 Cylinder Modifications, Repairs, or Failed Component – Cylinders
as shipped from the factory are not to be disassembled and or modified.
If cylinders require modifications, these modifications must be done at
company locations or by the Company’s certified facilities. The Cylinder
Division Engineering Department must be notified in the event of a
mechanical fracture or permanent deformation of any cylinder component
(excluding seals). This includes a broken piston rod, tie rod, mounting
accessory or any other cylinder component. The notification should include
all operation and application details. This information will be used to provide
an engineered repair that will prevent recurrence of the failure.
It is allowed to disassemble cylinders for the purpose of replacing seals or
seal assemblies. However, this work must be done by strictly following all
the instructions provided with the seal kits.