Hydraulic uncoiler fault isolation
Use a symptom-first inspection path when the hydraulic station runs but the mandrel does not expand, does not contract, moves in the wrong direction, moves unevenly, or cannot hold the coil as commanded.
What Does “Wrong Expansion or Contraction” Mean?
A useful fault report describes the observed response rather than only saying the hydraulic uncoiler is “not working.” The hydraulic power unit may run while the mandrel or expansion drum remains stationary, moves opposite to the selected command, moves slowly, stops partway, creeps after release, or reaches position but cannot retain the coil securely. These symptoms do not have the same cause.
| Observed symptom | Likely fault group to investigate | Evidence to record |
|---|---|---|
| No expansion and no contraction | Command power, permissive/interlock, pump delivery, relief path, common blocked line, or disconnected linkage | Mode, alarms, valve indication, pump sound, gauge reading under the approved test procedure |
| One direction works; the other does not | Directional command, solenoid/valve spool, one hose/port, cylinder seal path, or mechanical interference | Which command fails, valve indication, direction, stopping point and repeatability |
| Slow, weak or intermittent motion | Low supply, contamination, air, leakage, worn pump, relief setting, temperature/viscosity, or binding | Oil condition, temperature, sound, visible leakage, pressure trend and load state |
| Mandrel moves but will not hold | Internal leakage, valve leakage, cylinder/seal condition, linkage wear, or incorrect mechanical adjustment | Position loss over time, coil state, pressure decay and linkage movement |
| Uneven or jerky expansion | Segment/linkage contamination or wear, bent/damaged parts, poor lubrication, cylinder/linkage misalignment, or unstable hydraulic flow | Which segment lags, marks, debris, abnormal sound and unloaded versus loaded behavior |
Use This Inspection Order
- Record the event before resetting. Note the exact selector/button command, operating mode, interlock state, alarms, coil loaded/unloaded condition, previous maintenance and whether the fault appeared suddenly or gradually.
- Confirm the correct machine and documents. Match model, serial number, hydraulic schematic, electrical drawing, ordered mandrel/coil-car/support options and any approved modifications.
- Perform only permitted external checks. Look for visible leakage, damaged hoses, loose connectors, abnormal sound, heat, contamination and the indicated oil level. Use the specified oil and inspection range from the project documentation.
- Separate command from hydraulic response. An authorized electrician/technician should confirm whether the correct control output reaches the directional valve and whether permissives or interlocks are blocking the command.
- Verify pressure and flow by the released test method. Use installed test points and rated instruments. Compare the result with the machine hydraulic documentation; do not invent a generic pressure value.
- Inspect the valve and hydraulic path. With energy controlled, check the directional valve, relief path, filters, lines and ports for contamination, sticking, blockage, damage or incorrect connection.
- Inspect cylinder and mechanical transmission. Check the cylinder, pins, wedges, segments, guide surfaces and linkage for leakage, wear, deformation, binding or loss of connection.
- Repair, clean or replace only the confirmed cause. Parts must match the drawing/BOM, pressure/function rating and machine revision. A component that physically fits is not automatically compatible.
- Retest in controlled stages. Prove correct direction and smooth travel unloaded where the approved procedure allows, then complete the specified guarded material trial and acceptance record.
When the Hydraulic Station Runs but the Mandrel Does Not Respond
Check whether a command is actually reaching the valve
A running motor or pump only proves that the power unit has started. It does not prove that the controller has released the motion, that the correct solenoid is energized, or that the directional spool has shifted. Record the control indication and let authorized personnel compare the command with the electrical and hydraulic drawings.
Check supply condition without opening a pressurized connection
Low indicated level, external leakage, abnormal pump noise, excessive heat or contaminated oil can support a hydraulic-supply diagnosis, but the acceptable level, oil type, temperature and test pressure belong to the specific machine documentation. Never crack a hose or fitting as an improvised flow test.
Separate valve/line faults from cylinder/linkage faults
If the correct valve command and approved pressure/flow evidence are present, isolate and inspect the downstream path. A blocked line, sticking valve, internal cylinder leakage, disconnected pin, worn wedge, contaminated sliding surface or mechanical interference can produce similar operator-visible symptoms.
Why One Direction May Work While the Other Fails
Expansion and contraction normally use different directional valve states and opposite cylinder flow paths. When only one direction fails, compare the two command states rather than replacing the pump first. The difference may be a control output, solenoid, valve spool, hose/port, cylinder seal path, linkage position or mechanical obstruction. If hoses or valve parts were recently replaced, confirm routing and part identity against the released schematic before further testing.
What Should Be Checked After Repair?
- Correct expand/contract direction for each control command;
- Smooth travel through the approved range without binding, impact or segment lag;
- No external leakage and no unacceptable position/pressure loss;
- Mandrel/linkage fasteners, guards, supports and interlocks restored;
- Coil retention and centering confirmed with the approved trial material;
- Repair part, setting, test result and responsible sign-off recorded.
What Information Helps HENLI Diagnose the Fault?
Send the machine model and serial/nameplate, hydraulic and electrical drawing references, coil weight/width/thickness/ID/OD, loaded or unloaded condition, exact command and response, alarms, photos/video, visible leakage, sound/temperature observations, indicated pressure from an approved test, recent maintenance and any replaced valve, hose, seal or linkage part.
Frequently Asked Questions
Can I keep cycling the expansion command to free a stuck mandrel?
No generic article can authorize repeated cycling. Stop if movement is abnormal, the coil is insecure, pressure behaves unexpectedly, or parts bind. Control stored energy and inspect through the approved procedure.
Does a running hydraulic pump mean the pump is healthy?
No. It confirms rotation only. Delivery, pressure, relief flow, contamination, internal leakage and mechanical load still require documented checks.
Should filters be replaced on a universal time interval?
Use the component and machine maintenance criteria, condition indicators, oil analysis or the project schedule. Do not replace parts on an invented universal interval.
Can the machine be tested with a coil immediately after repair?
Only after the approved unloaded checks, guarding/interlock restoration and test plan are complete. The responsible personnel should control the material trial.
Send the Symptom Evidence Before Replacing Parts
HENLI can review the identified machine, command sequence, hydraulic/control evidence and coil data to separate the likely fault path and prepare project-specific service guidance.
