Construction machinery operates in harsh environments, and the vibration and impact generated during operation can easily cause electrical system faults. If electrical system faults in construction machinery are not repaired promptly, they will affect construction progress. Based on years of maintenance experience, the author has summarized 9 emergency repair methods for electrical faults in construction machinery.

1. External power supply method

When the DC power supply is interrupted due to an open circuit in the control circuit or auxiliary circuit, or damage to an electrical component (such as a DC power supply), the external power supply method can be used for emergency repair.

For example, an HBT30 concrete pump in operation suddenly stopped working. Inspection revealed that its DC24V transformer had burned out. Because the construction site was in a remote suburb and no spare parts were available, it was decided to borrow the battery of a concrete mixer truck as the power source so as not to affect operations. The specific procedure was as follows: first prepare a 2-core cable 20 m long with a cross-sectional area of 2.5 mm2 or more, then disconnect the DC24V power output terminal on the concrete pump, then connect one end of the prepared 2-core cable to this output terminal and install alligator clips on the other end. Connect the 2-core cable to the battery of a nearby concrete mixer truck via the alligator clips, and the concrete pump can be started to continue working.

2. Temporary isolation method

When an electrical component in a circuit is damaged, the damaged component can be temporarily isolated (disconnected) from the circuit, and the circuits on both sides can be connected directly.

For example, an Atlas 352E hydraulic rock drilling jumbo in operation suddenly stopped, and the fault display showed a phase loss in its circuit. A multimeter measurement showed no phase loss in the upstream distribution box circuit, but phase loss at the cable collector reel, so the problem was determined to be inside the cable collector reel. Upon disassembly, the contact surface of the conductive copper ring in the collector reel was found to be burned and eroded. After inquiry, no parts were available in stock domestically, and overseas ordering would take 3 months. To repair the machine as quickly as possible, it was decided to remove the cable inlet and outlet terminals on the conversion connector and connect the outlet terminal directly to the upstream distribution box circuit. Although the cable then had to be manually reeled in and out before each operation, normal production was not affected.

3. Temporary wiring method

If a circuit or an electrical component is damaged and causes the circuit to be disconnected, the temporary wiring method can be used.

For example, an AL500 dry/wet concrete spraying machine suddenly failed to travel. A preliminary inspection showed that the solenoid valve controlling the machine's travel was normal, and that the problem was only with the power supply to the solenoid valve. Tracing the fault location step by step would take a long time. To put the concrete spraying machine into use quickly without affecting subsequent operations, it was decided to use the temporary wiring method. The details were as follows: first disconnect the original circuit, then temporarily run a wire directly from the battery to the solenoid valve, and then connect a switch in the middle of this wire to control the circuit on and off.

4. Short-circuiting method

Open-circuit faults in the electrical systems of construction machinery include broken wires and loose connections, poor contact and cold solder joints at contacts, and blown fuses. When an open circuit is determined to exist in the circuit and conditions for repair are not available on site, a well-insulated wire can be used to short-circuit the open-circuit location, thereby eliminating the fault.

For example, when a MEYCO Potenza dry/wet wet spraying machine was in operation, the swing arm failed to move. Testing determined that the cause was an open circuit in the remote-control cable related to the swing arm. If there is no spare wire in the cable, the following emergency repair method can be used: remove the broken wire, and run a cable 20 m long with a cross-sectional area of 1.5 mm2 or more along the direction of the remote-control cable, connecting one end to the swing arm handle and the other end to the cable connector.

5. Emergency substitution method

When electrical components on construction machinery such as relays, ordinary switches, and proximity switches fail, the electrical components available on hand can be fully utilized and the emergency substitution method can be adopted for repair.

For example, the ignition switch of a Kawasaki 85ZIV loader in operation was damaged. Purchasing this ignition switch would take 3 months. To avoid affecting production, a similar domestically made ignition switch can be used as an emergency substitute.

6. Forced manual method

When the automatic mode of the electrical system of construction machinery fails, the forced manual method can be adopted to forcibly switch a component with manual control to a certain working state and lock or position it, so as to ensure that other components or systems can work normally. For some solenoid valves without manual operating levers, as long as it is feasible in terms of hydraulic principle, tools such as a screwdriver can be used to push the valve spool to the working position, so that the construction machinery can continue to work.

For example, a concrete pump truck in operation suddenly stopped working. Inspection revealed that the pressure-regulating solenoid valve coil of the truck had burned out, and no replacement parts were available on site. At this time, a suitable screwdriver can be used to push the spool of the pressure-regulating solenoid valve to the working position, restoring the hydraulic system to normal and ensuring that the pump truck can continue operating.

7. Patching and repair method

When electrical components of construction machinery such as switches, buttons, and relays are damaged and no spare parts are available, in order to reduce downtime, methods such as adhesive repair and patching can be used to repair them so that the construction machinery can continue working. After the spare parts arrive, a thorough repair can then be carried out.

For example, an LWL-80 electric hydraulic slag raking machine failed to run its motor. Careful inspection revealed that the contacts of the motor's AC contactor were severely burned and eroded, and no spare parts were available on the site. The emergency treatment method at this time was as follows: remove the burned contacts, polish them with fine sandpaper, and reinstall them after the contact surfaces are smoothed.

8. Cannibalization method

In the electrical systems of construction machinery of the same type, some electrical components are interchangeable. When a component in the electrical system fails, an electrical component temporarily not in use on the same machine or another machine of the same model can be removed to replace the failed component, thereby achieving the purpose of emergency repair.

For example, a Fangyuan HBT60A concrete pump in operation suddenly failed to work normally. Testing revealed that there was an electrical signal at the PLC input terminal of the machine but no electrical signal at the output terminal, indicating that the fault was in the PLC. To avoid affecting operations, the PLC from another idle concrete pump of the same model was installed, and the concrete pump resumed working.

9. Modification and repair method

When electrical components on construction machinery are damaged and there are no spare parts in stock or the original imported parts are expensive, the modification and repair method can be used.

For example, the remote control of an AL500 dry/wet concrete spraying machine suffered from damaged electrical components, unresponsive operation, and aging wiring. The remote control was judged to have no repair value. Replacing it with an original imported remote control would cost more than 60,000 yuan and have a long delivery cycle. Based on electrical control principles, we modified the remote control circuit. The modified remote control cost only more than 2,000 yuan, yet its performance and service life were comparable to those of the imported part.

Flexibly applying various emergency repair methods can effectively reduce the adverse impact of sudden faults on production, shorten fault downtime, and improve machinery utilization. However, emergency fault repair is, after all, temporary repair and cannot achieve the best results, so temporary repairs must not be treated as permanent repairs. In particular, when removing parts from other machinery for emergency repair, maintenance records must be kept properly, and relevant parts must be reported and purchased as soon as possible so as to restore the original machine's technical performance as quickly as possible.