Rotary Drilling Rig Crowd Cylinder KA4 Relay Diagnosis

A rotary drilling rig crowd cylinder that will not move can suggest a failed auxiliary pump, blocked valve section, damaged cylinder seals, or an electrical command problem. Because each possibility can lead to expensive disassembly, the inspection should compare unaffected functions and verify the control path before major components are replaced.

In this field case, the crowd cylinder had no motion or moved very slowly. Replacing the 1D and 3D solenoids did not change the symptom. Other functions remained normal, the auxiliary hydraulic supply checked normally, and inspections did not find a fault in the M4 section or cylinder seals. The remaining evidence led to the KA4 relay in the changeover circuit. Replacing KA4 restored crowd movement.

The Crowd Cylinder Had No Motion or Moved Very Slowly

The reported complaint was specific to the crowd-cylinder function. Depending on the operating attempt, the cylinder showed no motion or moved very slowly. Other machine functions were normal, which immediately made a complete hydraulic-system failure less likely.

A local fault could still exist in the electrical command, the changeover circuit, the relevant solenoids, the M4 valve section, the crowd cylinder, or the hydraulic supply serving this path. The diagnosis therefore needed to separate a missing command from a component that received a command but could not pass oil.

The source does not provide a reliable public model, year, operating hours, or location. Those details are not inferred. For a buyer, the useful evidence is the documented relationship between the affected crowd function and the unaffected machine functions.

Primary symptom: the crowd cylinder had no movement or moved very slowly.
Comparison result: other machine functions operated normally.
Possible causes included command, changeover, valve, cylinder, and supply faults.
The inspection proceeded by ruling out each path with recorded checks.

Replacing the 1D and 3D Solenoids Had No Effect

The 1D and 3D solenoids were replaced, but the change had no effect on the crowd-cylinder symptom. This result prevented the replacement itself from being mistaken for a repair. A new or serviceable component does not prove the diagnosis unless machine behavior changes in the expected way.

Because the other functions were normal, the team continued tracing the dedicated crowd path. The unchanged symptom after the solenoid work indicated that the cause was elsewhere in the command or hydraulic chain.

For a used-rig buyer, ask for before-and-after function videos whenever electrical or hydraulic components are replaced. A parts list alone cannot show whether the replaced item caused the fault, whether the command reaches it, or whether the final function has returned to normal.

The 1D solenoid was replaced during diagnosis.
The 3D solenoid was also replaced.
The crowd-cylinder fault remained unchanged after both replacements.
The diagnostic path continued instead of declaring an unsupported repair.

Supply Pressure, the M4 Section, and Cylinder Seals Checked Good

The auxiliary pump and relief pressure were checked and found normal in the source procedure. Combined with the normal operation of other functions, this evidence reduced concern about a general auxiliary-supply shortage or an incorrectly relieving circuit.

The team then inspected the M4 section and the crowd-cylinder seals. The M4 section and cylinder seals were good, so neither inspection produced a physical explanation for the loss of crowd movement. These checks were important because they ruled out two repair paths that would have required further hydraulic disassembly.

No numerical pressure values are reported in the source facts supplied for public use, so none are added here. A modern inspection record should preserve actual gauge readings, test points, oil temperature, engine condition, and the service limits used for comparison.

The auxiliary-pump condition was checked and treated as normal.
Relief pressure was checked and treated as normal.
Inspection found the M4 section serviceable.
The crowd-cylinder seals were also found serviceable.

Auxiliary pump inspected during rotary drilling rig crowd-cylinder diagnosis

Combined M4 valve and solenoid bank inspected during crowd-cylinder fault isolation

The Changeover Path Led to the KA4 Relay

With the main hydraulic candidates reduced, the technicians traced the changeover path used by the crowd function. That path used KA4 to complete the required control changeover. A failed relay could therefore interrupt the command even though pumps, pressure control, valve hardware, and cylinder sealing remained available.

KA4 was replaced, and the crowd cylinder returned to normal movement. The successful functional response tied the original complaint to the failed relay and explained why replacing 1D and 3D had produced no effect.

The report does not provide relay-coil resistance, terminal voltage, or contact-drop measurements. Those values are not invented. For stronger handover evidence, technicians should document input command, relay actuation, contact continuity under load, output voltage, and a complete crowd-extension and retraction test after replacement.

The crowd changeover path used the KA4 relay.
The earlier hydraulic checks left the changeover command as the supported next target.
Confirmed corrective action: replace KA4.
Recorded result: replacing KA4 restored crowd movement.

What a Buyer Should Request for a Crowd-Function Fault

During a pre-purchase inspection, operate the crowd cylinder through its working range and compare it with other auxiliary functions. Record whether movement is absent, slow, intermittent, or different by direction. The test should show the control input, cylinder response, and any warning or input-state information available on the display.

If the repair involves a relay or solenoid, request circuit-tracing evidence rather than only a photograph of the new part. Useful records include connector condition, command voltage, relay input and output, pressure checks, and the unchanged or changed behavior after each substitution.

Kepler Machinery uses this sequence to reduce unnecessary major-component replacement: define the symptom, compare normal functions, confirm hydraulic supply, inspect the local valve and actuator, trace the electrical changeover path, and verify the repaired movement under controlled conditions.

Test crowd extension and retraction and compare both directions.
Record unaffected functions to demonstrate available hydraulic supply.
Trace relay and solenoid commands before replacing major hydraulic parts.
Require a complete post-repair function test before shipment.

Isolate the Changeover Path

The crowd-cylinder complaint was narrowed by comparison rather than assumption. Replacing the 1D and 3D solenoids had no effect, while other functions, auxiliary supply, relief behavior, the M4 section, and the cylinder seals checked normal. That evidence shifted attention to the changeover circuit.

The path used KA4, and replacing the failed relay restored crowd movement. For an overseas buyer, the case demonstrates why small electrical-control components should be verified before pumps, valve sections, or cylinders are condemned.

Safety Note

Crowd-cylinder diagnosis involves heavy moving structures, electrical controls, and pressurized hydraulic oil. Testing and repair must be performed by qualified personnel using the machine-specific service procedure. Secure attachments, establish an exclusion zone, release stored pressure before opening the circuit, isolate electrical power where required, and keep personnel clear of cylinder and linkage movement.