| SYMPTOMS |
CAUSES |
CORRECTIONS IN DESIGN |
REMEDIES IN THE FIELD |
| Noisy Pump |
Cavitation |
Specify a larger intake pipe. |
Use a larger suction strainer
Use lower viscosity oil. |
|
Restricted Suction |
Suction needs to be at least
50% larger than the discharge
pipe. Place the pump not more than 24 inches above the oil level.
|
Clean the suction strainer |
|
Air leak at intake |
Keep suction lines simple. |
Pour oil over the joints when
The pump is running and spot
Joint where pump runs quietly. |
|
Air leak at intake shaft packing |
Use flexible drive coupling with Stiff
tank top for rigidity. |
Lubricate or renew packing.
Accurately align pump shaft. |
|
Air drawn into system from tanks |
Place suction and discharge pipes
on opposite sides of baffle plate.
Check oil requirements of circuit against delivery of pump.
|
Raise oil level in the tank.
Discharge below oil level.
Does oil have an anti-foam additive? |
| Get started NOW! Call
or email us now. (Click here for our contact page). |
| Noisy Pump |
Worn valves, vanes
Pistons, gears, etc. |
Use filters as often as practical |
Renew worn parts
Clean filters. |
|
Sticking valves
Or vanes |
Incorporate Filter in system. |
Check for impurities or metal particles in oil.
Clean filters. |
| Excessive heating of pump |
Internal pump leakage |
Use pumps well below their upper pressure limits. |
Renew worn parts, such as gears, vanes, pistons,
valves, etc. |
|
Internal leakage caused by thin oil |
Specify closer tolerances and finishes, or higher
VI oil.
Increase cooling capacity.
|
Use heavier bodied oil.
User higher VI oil.
Check pressure relief valve setting.
Check pressure relief valve for leaks. |
|
Insufficient clearance of moving parts |
Check assembly of pump parts. |
|
| Pump flow low |
Pump parts worn Out or system
bypassing Oil. |
Check orifice in relief valve |
Renew
worn parts |
|
| Erratic & sluggish
Operation |
Oil viscosity too high. Not
enough Horsepower. |
Check
needed power input – HP goes up with very high viscosities. |
Use
lower viscosity oil. |
|
| Pump low pressure |
Short circuit in Pump or system is Bypassing |
|
Check seal between inlet and
outlet ports of pump. Check orifice in relief valve |
|
| Low or no pressure In the
system. |
Relief valve jammed Or
orifice plugged |
Reset pressure setting after |
cleaning relief valve. |
|
 |
Low oil |
Provide site glass. |
Add oil. |
|
| Fluctuating PSI |
Air or water in System, No back Pressure. |
Provide 5 – 10 lbs. Back pressure
relief valve (foot valve), on Return
line. |
Check seals and pipe connections.
Check for jams or obstructions in System (collapsed hose?). |
|
| Erratic movements |
Insufficient oil in System
or Improper kind of Oil. Water or air Present. |
Check
oil requirements of total cycle.
Provide site gauge. |
Check vent valve. Check oil
level. Test oil. |
|
| High pressure Below expectations |
Relief
valve not functioning Properly.
Internal Pump leakage, |
Check capacity of spring (if
direct operated). Use proper viscosity oil. |
Check poppet for sticking and
Spring for proper adjustment. Use proper oil. |
|
| Get
started NOW! Call or email us
now. (Click here for our contact
page). |
|
| High pressure Below
expectations |
Excessive
frictional loses in system. Oil Velocity too high |
Use as few pipe bends as
possible. Adhere to ideal radius of pipe and tubing bends. Area of ports, holes |
Tubing and piping to be
consistent With an oil velocity of 15 fps on Pressure lines. 10 fps on return
lines. |
|
| Frequent leaks in Lines |
Vibration
in machine. |
Design in more brackets and |
Fasten oil lines securely.
more supports |
|
| Overheating
of oil (efficient normal Operating temp is About 130° 140° Degrees F). |
Too
much oil blowing over the relief valve.
(Pump too large for the
system) |
Pump
capacity to be at least 10 To 15% larger than requirements. |
Check relief valve for pressure
and Leakage. Check pressures at which pump should operate. Add heat
exchanger. |
|
| |
Insufficient oil or oil level too
low. |
Increase capacity of oil tank To
at least 34 times the pump. |
Add oil |
|
| |
Highpressure help too long. |
Use small pump for high
pressure |
And high volume pump for low pressure. |
|
| |
Oil too
light |
Specify
correct SSU oil. |
Use
heavier oil. |
|
| |
Obstructions or restrictions to
flow of |
Avoid sharp bends in pipelines
especially in copper tubing. |
Check position of control valve
For neutral location and overloads. |
|
| |
Oil in
pipeline |
Specify ideal bending radius. |
Pump parts may be worn. Check
backpressure valve for high pressure. |
|
| Excessive leakage In system
(internal). |
Oil too light, valves Pumps
worn out. |
Specify correct
viscosity & correct Viscosity. |
Check
clearances. Use heavier oil If leakage
is still excessive. |
|
| Irregular, erratic or
Uncertain feeds. |
|
Check
control valve for proper Positioning.
Check linkage and cam Adjustments |
Check for excessive internal
leakage. Check kind of oil used use
recommended oil. Check external pilot pressure if |
|
| Slow acting machine |
Starting temperature of Oil is
too cold. |
Provide immersion heaters. |
Set controls so that oil is blown
Across relief valve until it heats. |
|
| |
Oil is too heavy, causing
Excessive frictional Resistance in system. |
Increase size of plumbing. |
Use
lighter oil. |
|
| Jerky operation
of Working cylinders, Motors,
etc. |
Friction in seals Friction in
ways. |
Provide pressure at both ends of
Cylinder. For servo systems, specify “Low Friction” type seal. |
Check oil level, may be too low.
See that packing is not binding. Check for worn or scored rods, Seals, and
broken piston rings. |
|
| Get
started NOW! Call or email us
now. (Click here for our contact
page). |
|
| Jerky
operation of Working cylinders,
Motors, etc. |
Air
in the system |
Provide bleeder port in the
top |
Bleed the cylinders. cylinder. |
|
| Rapid traverse of
Reversing valve Troubles. |
|
Springs of check valve too weak,
recalculate. Provide dashpot or Springs in ends of valve. Floating Spool
mounted horizontally. |
Check for broken springs. Valve
plunger depressed too far. Cams and /
or rollers worn. Valve Remaining
partially open. |
|
| Acceleration
too Slow |
|
Taper on spool too long and
gradual. Use check valve to bypass. |
Check relief valve setting. |
|
| Acceleration
too Fast |
|
Taper on spool too short. Use metering valve in addition to dashpot. |
|
|
| 3 and
4way valve troubles. Overheating of
Solenoid operated Valves; indicated by Hum or buzz. |
|
With plunger or spool in home
Position, solenoid should have
completed stroke and rest dead Provide clearance between solenoid link
and valve plunger (1/64”). |
Excessive
wear of spools or body, Broken springs. Leaky seals. Binding resulting from
varnish costing. Replace valve. |
|
| Check
valve trouble Flow Control |
|
Mount in a vertical position |
Check condition of valve seat. If
Worn or ball of poppet is in poor Condition, reseat new ball.
Replace
valve. Pressure compensator binding, |
|
| Flow
Control Troubles Metering valve not
Functioning properly |
|
Provide lock to set position for desired
feed. |
Pressure compensator binding,
caused by dirt. Plungers worn.
Clean
orifice, polish spool.
Dirt lodged in
eccentric grooves Or orifice. |
|
| Metering
valve not Functioning properly |
|
Provide lock to set position for
desired feed. |
Dirt lodged in eccentric grooves
Or orifice. |
|
| Needle
valve will not Control or shutoff. |
|
|
Needle valve worn; regrind and
Relap or replace. |
|
| Fluctuating pressure Of
relief valve |
|
|
Relief
pressure control spring broken / worn. Check for proper adjustment.
Clean
orifice.
Check pilot cone. |
|
| Pressure reducing |
|
Drain
line to be open directly to Tank; do not connect to return line |
Spring adjustment fault. Drain
line closed. Broken springs. |
|
| Get
started NOW! Call or email us
now. (Click here for our contact
page). |
|
| Solenoid
Failures: |
|
|
|
| Solenoid
Failure |
When a solenoid is held at inrush
current for an extended period of time, the solenoid overheats and eventually
burns out. The heat produced by the
solenoid melts the nylon. This melted
nylon flows in around the plunger and causes it to stick in some
positions. This mechanically blocks
the valve from shifting. |
Cause of failure includes: |
|
|
| Melted Nylon |
|
1. Excessive force needed to
shift spools |
|
|
|
2. Both solenoids energized at
the same time on a double solenoid valve. |
|
|
|
3. Cycle rate too high – not
cooling properly. |
|
|
|
4. Voltage too high or too low. |
|
|
| Solenoid
Buzzing |
When the solenoid plunger is kept
from bottoming out, the solenoid will have a tendency to buzz. This buzzing is created by the pulsating AC
current magnetism being opposed by a hydraulic spool force and a spring force
causing the plunger to move in and out |
Cause of failure include: |
|
|
|
1. Excessive force required to
shift the spool |
|
|
|
a. Contamination adds to spool
shifting forces. |
|
|
|
b. Valve spool silting |
|
|
|
c. Flow specification of valve
being exceeded. |
|
|
|
d. Excessive spring centering or
spring offset force. |
|
|
|
2. Low Voltage. |
|
|
|
3. Damaged coil |
|
|
|
4. Split Solenoid laminations. |
|
|
| Brittle
Solenoid Leads |
The continual use of the solenoid
over a period of time will leave the wire insulation brittle. This creates the possibility of insulation
and / or wire breakage which may lead to shorting out of the solenoid |
Cause of failure include: |
|
|
|
1. The leads are affected by
heart generated by the solenoid. This
situation is aggravated by high ambient temperatures. |
|
|
|
2. Type of hydraulic fluid may be
eating / affecting the insulation. |
|
|
|
3. Cutting fluid used by the
machine could be destroying the insulation. |
|
|
| Solenoids
Exposed to Fire Resistant Fluids |
Exposure of solenoids to fire
resistant fluids such as Phosphate Esters, will cause shorts between the coil
windings. These fluids will also
dissolve the coil’s varnish and solenoid’s black paint. The fluids will also affect the lead wire
insulation by causing it to become spongy and eventually drop off. This condition can be avoided by purchasing
solenoids or coils that are compatible with the caustic fluids. |
Cause of failure: |
|
|
|
1. Chemical reaction with the
solenoid. |
|
|
| Solenoid
Failure – Coil burns Out |
Continuous inrush current melted
nylon |
Causes
of failure include:
1. Mechanical blockage
2. Low line voltage
3. Excessive
ambient temperature
4. Excessive cycle rate.
5. Excessive / high line
voltage. |
|
|
| Solenoid
failure – Shorting |
|
1. Coolants containing metal
chips
2. Voltage transients
3. Fire resistant fluids |
|
|
| Solenoid
Failure – Mechanical Destruction |
|
1. Over voltage
2. Excessive
cycle rates
3. Overzealous mechanic. |
|
|
| Shorted
Solenoid |
A solenoid used in or near water
based coolants that are saturated with fine metal particles is susceptible to
shorting between the coil lead wire junctions |
Cause of failure include:
1.
Soaking of the coil with coolant. |
|
|
