After a Year of Workarounds: Schramm Drilling Rig Control Repair in Williston

According to the customer, another service company had previously said there was no repair available for the issues. We did not review that company’s diagnostic records, so that statement is included only as customer-reported history.

What we could verify was that the problems were real, and that they did not all have the same cause.

This Schramm TXD500 drilling rig had three primary complaints:

• The top-drive rotation brake was intermittent or inoperative.
• The jib boom would not extend or retract.
• The power unit could not be started or controlled properly from the driller’s station.

After living with the symptoms for roughly a year, it would have been easy to consider them permanent quirks of the machine. Instead, each complaint was separated into its own diagnostic path.

One machine, three different problems

Modern drilling equipment combines operator controls, programmable controllers, electrical outputs, solenoid coils, pilot pressure, hydraulic valves, and mechanical components.

For a hydraulic function to operate, a command generally has to travel through several stages:

• The operator activates a control.
• The PLC recognizes the command.
• The controller sends an electrical output.
• A solenoid coil operates the pilot or pressure-control valve.
• Pilot pressure shifts the hydraulic valve.
• Hydraulic flow moves or controls the function.

A failure anywhere in that path can make the problem look purely hydraulic. A function that will not move could be caused by a switch, wiring, PLC output, coil, programming error, pilot-pressure problem, hydraulic cartridge, main valve, or mechanical failure.

Replacing the complete hydraulic assembly without knowing where the command stopped would have been an expensive guess.

Top-drive brake: A coil that failed under load

The service work included reviewing hydraulic schematics, control information, and the rig’s Valtronics pilot-valve system.

Access to the valve bank and controller required working from a man basket on the mast. The wiring, PLC cabinet, coils, pilot valves, and related components were inspected.

A diagnostic laptop was connected to the machine, communication with the control system was established, and command outputs from the driller’s controls were checked. Other functions operating from the same hydraulic block still worked, helping narrow the search.

Testing found that the affected electrical output dropped when the solenoid coil was placed under load. Further troubleshooting identified a partially shorted coil.

A known-good coil was substituted to confirm the circuit’s response. The pressure-control cartridge was also removed and tested with a known-good component. A pressure gauge was installed so the working pressure could be set and verified.

The repair was not simply “replace a coil.” It required confirming:

• The operator command reached the controller.
• The output was present without a load.
• The output changed when the coil was connected.
• The coil had an internal electrical problem.
• The pressure-control component operated correctly.
• Hydraulic pressure was properly set and verified.

Jib boom: When programming stops a hydraulic function

The inoperative jib boom required a different approach.

Additional Valtronics service information was obtained so the actual pilot-valve and winch-control parameters could be compared with verified settings.

The initial jib-spool configuration displayed an impossible flow value. That finding pointed toward incorrect or corrupted programming rather than a plugged hose, damaged cylinder, or failed main hydraulic valve.

Before changing anything, the existing program was saved. The affected valve-control component was then replaced and programmed using the verified parameters. Once the correct configuration was installed, the affected function responded again.

This is an important part of modern oilfield equipment repair. A hydraulic valve can have electrical power and be mechanically capable of moving, but the function may still remain inoperative if the controller is commanding an incorrect flow value.

Replacing the cylinder, hoses, or complete valve bank would not have corrected a controller-parameter problem.

Starting controls: Following the electrical command

The inability to start or control the power unit became the third diagnostic path.

Testing showed that the control button was producing an output to the PLC. That eliminated the button itself as the immediate cause.

Inspection then found a tripped breaker supplying the Murphy gauge and control circuit. After the breaker was reset, the fuel-level display returned and the engines could again be started and controlled from the ground controls.

A tripped breaker does not automatically mean an engine, starter, or controller has failed. It means the protective circuit has opened. If the breaker trips repeatedly, the circuit needs further inspection rather than repeated resetting.

PLC signals and faults were monitored during operational testing following the diagnostic work.

Why these problems lasted so long

Long-standing equipment problems are not always caused by one major failure. They can persist because intermittent symptoms cross the boundaries between electrical, hydraulic, electronic, and mechanical systems.

In this case, the documented findings were separate:

• A partially shorted coil affected one electro-hydraulic function.
• A controller with an impossible flow parameter prevented the jib from responding correctly.
• A tripped breaker interrupted the gauge and starting-control circuit.

Treating all three complaints as one failure could have resulted in unnecessary parts replacement while leaving other symptoms unresolved.

Breaking the machine into testable sections made the problems manageable:

• Was the operator command reaching the PLC?
• Was the controller producing an output?
• Did that output remain stable under load?
• Was the valve receiving pilot pressure?
• Were pressure and flow set correctly?
• Did the programmed parameters match verified service information?
• Were the necessary protection and power circuits active?

Each answer narrowed the search until a repairable cause was identified.

What operators should document

When equipment develops an intermittent control problem, useful information includes:

• Which control station was being used
• Whether the failure is constant or intermittent
• Which related functions still work
• Whether the engine loads down without movement
• Whether the symptoms change as the machine warms up
• Whether gauges or displays shut off
• Whether breakers or warning indicators change state
• What happened immediately before the failure

Do not open energized control cabinets or work around pressurized hydraulic components unless trained and authorized. A clear report of what the machine did is often more useful than an attempted repair that changes the evidence.

A year-long problem is still worth diagnosing

This Williston-area drilling-rig repair was not completed by replacing one large assembly and hoping it corrected every complaint.

It required hydraulic schematics, live PLC communication, electrical testing under load, pilot-valve inspection, hydraulic pressure verification, controller programming, and operational testing.

The crew had lived with the symptoms for approximately a year. Systematic oilfield equipment diagnostics showed that the machine had several identifiable and repairable faults, not one permanent, unrepairable condition.

Mondak Equipment & Hose provides advanced diagnostics and oilfield equipment repair through its Williston operation. If your drilling rig, forklift, telehandler, aerial lift, or construction machine has an intermittent hydraulic or electronic-control problem, contact Mondak for equipment-level troubleshooting.