check valves and counterbalance valves can be employed to hold the
load in the raised position.
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-compen-
sating pumps, air 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 devel-
oped for each of the hydraulic systems in your plant. By performing
these tests, your systems will operate safer and at maximum 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.
Continuous flow out of a bleed valve may indicate worn piston seals.
