92
NOISY PUMP
Air in the system: Check ttings, cracked hoses, and other
parts on the pump intake. Check hydraulic tank. The tank
must be kept 3/4 full.
NOTE: Never ll hydraulic tank completely full at any time.
System drainage will cause the tank to overll and spill out.
Cavitation (vacuum in pump): Check for clogged or
restricted intake line or plugged air vent in tank.
Loose or worn pump parts: Look for worn gaskets and
replace if necessary. Check for clean and proper uid.
Stuck pump vanes, valves, pistons etc: Disassemble and
clean thoroughly. Avoid the use of les, emery cloth, steel
hammers etc, on a machined surface. Products of uid
deterioration such as gums, sludges, varnishes and lacquers
may cause sticking. Use solvent to clean parts and dry
thoroughly before reassembling. If parts are stuck by
corrosion or rust, they will probably have to be replaced.
Pump out of alignment with drive: Check alignment.
Misalignment may be caused by temperature variation.
OVERHEATING
Viscosity too high: Check recommendations. Unusual
temperature conditions may cause uid of proper viscosity for
working temperature to thicken too much on the way to the
pump. In this case, use of a uid with higher viscosity index
may cure trouble.
High discharge pressure: Such parts may cause undue
friction. Look for signs of excessive friction. Be sure all parts
are in alignment.
Low oil: Assure oil level is proper, at least 3/4 full. If the tank
is low, less uid will be available to carry away the heat,
raising the oil temperature.
PUMP NOT PUMPING
Pump shaft turning in the wrong direction: Shut down
immediately. Some types of pumps can turn in one direction
only.
Intake clogged: Make sure tank is cleaned periodically. Fluid
must be kept 3/4 full.
Air leak in intake: If any air is going through pump, it will
cause noise. Pour uid over points suspected of leakage; if
noise stops, you have found the leak.
Oil too heavy: If uid is too heavy, some types of pumps
cannot pick up prime. Fluid that is too heavy can do great
damage to hydraulic systems. Drain and rell with oil of the
proper viscosity.
LOW PRESSURE IN SYSTEM
Relief valve setting too low: With an improper setting, uid
may ow from the pump through the relief valve and back
to the tank without reaching the point of use. To check relief
setting, block pressure line beyond relief valve and check line
pressure with a pressure gauge.
Relief valve stuck open: Clean dirty relief valves (see
maintenance.) A stuck valve may be an indication that the
system contains dirty or deteriorated hydraulic oil.
Broken, worn or stuck pump parts: Install pressure gauge
and block system just beyond relief valve. If no noticeable
pressure is developed and relief is okay, look for mechanical
trouble in pump. Replace worn and broken parts.
Valves sticking or binding: Check suspected parts for
mechanical problems such as misalignment, bent, worn etc
then look for signs of dirt, sludge, varnishes and lacquers
caused by deterioration.
Sluggishness when machine is rst started: Sluggish-
ness is often caused by uid that is too thick at starting tem-
peratures. If you can put up with this for a few
minutes, uid may thin out enough to give satisfactory
operation, but if it does not thin out or if surrounding
temperature remains relatively low, you may have to switch
to a uid with a lower pour point and lighter viscosity. Under
severe conditions, immersion heaters are sometimes used.
SERVICING HYDRAULICS
To Next Page
Loading...