MACHINERY LUBRICATION- INDIA SEPTEMBER-OCTOBER 2019 | Page 24

HYDRAULICS
valve. Care should be taken so all
personnel are away from the bleed valve
prior to turning on the pump. If there is
continuous flow, the piston seals or
barrel may be worn. If no flow exists,
recharge the accumulator to the proper
dry nitrogen level.
Check Hoses
Check all system hoses for the proper
length and wear. Hoses rarely burst due
to the rated working pressure being
exceeded but rather because of a poor
crimp or rubbing on a beam, another
hose, etc. Hose sleeves are available
from a variety of manufacturers if
rubbing cannot be avoided. Hoses
generally should not exceed 4 feet in
length unless they move with the
machine.
Also, examine the system piping to
verify that a hose is installed prior to
connecting to a valve bank or cylinder.
The hose will absorb the hydraulic
shock generated when the oil is rapidly
deadheaded. One exception to this rule
is that hard piping should be used when
connecting to a vertical or suspended
type of load. Pilot-operated check
valves and counterbalance valves can be
employed to hold the load in the raised
position.
Continuous flow out of a bleed valve may indicate worn piston seals.
bleed valves and accumulator dump
valves. The tank lines of these valves
should be checked regularly with a
temperature gun or infrared camera to
verify that the valves are closed and no
oil is being lost back to the reservoir.
A reliability and preventive maintenance
schedule should be developed for each
of the hydraulic systems in your plant.
By performing these tests, your systems
will operate safer and at maximum
Inspect Clamps
Inspect system clamps to confirm they
are the correct type for hydraulic lines.
Beam and conduit clamps are not
acceptable, as they will not absorb the
shock generated in the piping or tubing.
Clamps should be spaced approximately
5 feet apart and installed within 6
inches of the pipe or tubing termination
point.
Valve Testing
On any system, one or more valves will
be closed while the system is operating.
These include relief valves used with
pressure-compensating pumps, air
22 | September - October 2019 |
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efficiency while reducing unexpected
downtime.
About the Author
Al Smiley is the president of GPM Hydraulic
Consulting Inc., located in Monroe,
Georgia. Since 1994, GPM has provided
hydraulic training, consulting and reliability
assessments to companies in the United
States, Canada, the United Kingdom
and South America. Contact Al at gpm@
gpmhydraulic.com.