Product Categories
- XCMG Horizontal Directional Drill
- Filling Machine
- Joystick
- Machinery Parts
- Used Forklift
- Kalmar Port Machinery Spare Parts
- XCMG Spare Parts
- Solenoid Valve
- Sany Port Machinery Spare Parts
- Linde Port Machinery Spare Parts
- Konecranes Port Machinery Spare Parts
- Fantuz Port Machinery Spare Parts
- Liebh Port Machinery Spare Parts
- HysXX Port Machinery Parts
- HDD Rig Accessories
- Foton Tractor Parts
- Cumm Engine Parts
- Filters
- Plasma Consumables
- Material Handling Machine
- Tractor
Kalmar DRF Reach Stacker Boom Automatic Retraction Fault Quick Repair
Fault description
The customer reported that a DRF450 front crane could not extend its boom during use, but could extend it at a very slow speed. After the boom was extended, it would automatically retract. The other movements of the locomotive were normal, and no fault code appeared.
Troubleshooting
When the locomotive has a fault but there is no fault code, start the inspection from the working principle of this fault function.
According to the logical flow of the input signal of the hydraulic function of boom extension to the required output signal, the first step is the input signal of the aviation handle in the cab. Enter the display screen diagnostic menu and check the parameters of the aviation handle:
When the aviation handle is in the middle position, the middle voltage of the boom lifting potentiometer is 2.45V, which is normal;
The middle voltage of the boom extension potentiometer is 1.07V, which is wrong.
When the locomotive is normal, the middle voltage of the aviation handle potentiometer should be 2.5V (actually there is a slight deviation). When the boom is retracted, the aviation handle moves to the left, and the potentiometer voltage changes from 2.5V to 0.5V, that is, when the boom telescopic potentiometer voltage is lower than 2.5V (excluding the inactive area), the boom will begin to retract.
The boom telescopic potentiometer voltage of this locomotive is 1.07V, which is significantly lower than 2.5V. Even if the aviation handle is not operated by anyone, the boom will automatically retract, which will also affect the potentiometer voltage value when the boom is extended, so the boom extension speed will be slow.
The middle voltage of the telescopic potentiometer of the aviation handle of the locomotive is lower than the normal value. The following problems may exist:
(1) The mechanical rotating part of the potentiometer of the telescopic part of the aviation handle may be stuck, and the rotating part needs to be cleaned and lubricated;
(2) The aviation handle is faulty, resulting in incorrect middle voltage of the potentiometer when the handle is in the middle position;
(3) The connection line between the aviation handle and the main computer is worn and short-circuited with other lines or grounded. During the use of the locomotive, due to the vibration of the locomotive, the damaged line short-circuited and the voltage was abnormal;
(4) The main computer of the locomotive is damaged. Check the above four possible reasons one by one:
(1) First check the mechanical rotating part of the potentiometer of the telescopic action of the aviation handle. No jamming was found. Lubricant was added by the way. It was normal;
(2) Unplug the aviation handle cable plug and measure the resistance value of the aviation handle telescopic sliding potentiometer. The total resistance value of the potentiometer is 5KΩ. The output resistance value is 2.5KΩ in the middle position. When the aviation handle moves to the left or right, the output resistance increases or decreases from 2.5KΩ, indicating that the aviation handle is normal;
(3) Check and measure the wiring harness from the aviation handle to the main computer. No problem was found in the line (because the line is fixed in the cab, the probability of damage is very low). Normal;
(4) Check the main computer, according to the aviation handle circuit diagram:
First, measure the main computer K7:2 pin, the aviation handle potentiometer 5V reference voltage, normal;
Then measure the main computer K7:4 pin, the boom extension potentiometer signal voltage, 1.066V, the same as the display screen diagnostic menu data, indeed abnormal, judge the signal voltage has leakage;
Suspect the main computer K7:4 pin internal leakage, disconnect the main computer plug X007 No. 4 pin wire and the main computer connection, and then measure the aviation handle end 0074 wire voltage, 2.46V, the voltage at this time is normal voltage, thus determined that the main computer internal fault.
Solution
Replace the main computer, all functions of the locomotive returned to normal, delivered for use.
Case summary
This failure was caused by the internal damage of the main computer affecting the feedback of the aviation handle potentiometer circuit. After checking the drawings, we learned that in the absence of other optional functions, the three function groups of the aviation handle, lifting and lowering (P1), extending and retracting (P2), and spreader rotation (P3), are controlled by the voltage signal of the potentiometer input to the main computer.
When the aviation handle is in the middle position, the three potentiometers send a 2.5V middle voltage signal to the main computer, letting the computer know that the aviation handle is not doing anything at this time. The main computer will not send a PWM signal to the proportional solenoid valve, and the boom and spreader will not have hydraulic action.
If the main computer detects that the feedback voltage signal of the aviation handle deviates from 2.5V, the control system will output a PWM signal to the proportional solenoid valve in proportion to the corresponding voltage signal to control the execution of the hydraulic action.