1. Appearance check
The purpose of the appearance of the inspection is to affect the normal and reliable operation of the hydraulics system appearance of the design and installation of the quality of the general initial inspection, in order to find and correct early. The main contents are.
1) hydraulic pumps, cylinders, valves and other hydraulic components of the connection and the host of the corresponding parts of the installation is correct and reliable.
2) system of hydraulic components, piping and pipe joints in the location of the installation, adjustment, inspection and repair.
3) The height of the liquid level in the tank, the tank structure and the type of working fluid are in accordance with the requirements.
4) Check whether the test instruments for monitoring the system, such as pressure gauges, tachometers, and dustproof, anti-pollution and other related devices are in good condition.
5) Check whether the motor rotation of the hydraulic pump is easy and even.
2. No-load test
The role of the no-load test is to make the entire hydraulic system in the operating conditions without workload, a comprehensive check of the hydraulics system of the circuit and the control and regulation of all parts of the work of the device is normal and reliable, whether the work cycle meets the requirements at the same time also for the load test to prepare for the system is to ensure reliable operation of the necessary steps. No-load test can be carried out in accordance with the following rules.
1) before the no-load test, in addition to the oil tank oil injection, should also be injected into the pump oil. Injection tank oil should reach the specified level height; to the pump inlet oil injection, should pay attention to the direction of rotation of the pump, and the hand toggle coupling, really to the pump outlet oil without bubbles until; hydraulic motor and the pump with oil drain port, should be through the drain port for the shell filled with oil.
2) cleaning cycle, for the system of servo valves, proportional valves, hydraulic cylinders and motors, should use a short-circuit transition plate to isolate it from the cycle circuit; accumulator, pressure square sensor and pressure relay should be removed, the joints with a stud blocking, so that these components out of the cycle circuit.
3) no-load test, the relief valve control pressure shall be adjusted to maintain the oil is circulating to overcome the pipeline resistance of the lowest value; flow valve pressure reducing valve shall be adjusted to the maximum opening.
4) the beginning of the no-load test, the system will be placed in the ‘stop’ (or ‘unloading’) position, so that the hydraulic pump according to the unloading circuit work, start the hydraulic pump. At this time, check the hydraulics pump oil pipe in the pressure gauge needle is stable in the ‘0’ position or point out the corresponding pressure; hydraulics system parts should not appear harsh noise: the surface of the oil in the tank should not indicate that the system sucks in air bubbles.
5) Slowly adjust the relief valve to the specified pressure value. Place the system in the starting position to allow the machine’s workpieces to undergo maximum stroke reciprocating movement. This procedure aims to expel any accumulated air from the hydraulic system. Check that all safety protection devices, such as safety valves and pressure relays, function correctly and reliably. You can verify this by moving the machine’s working parts at a slow speed to a rigid block (or using other methods) and observing the pressure gauge in the corresponding pipeline to ensure that the safety protection device operates reliably under the specified pressure. Also, inspect the hydraulic system parts for any external leakage. After a period of no-load, check whether the liquid level of the tank drops within the specified height range.
6) According to the design requirements to achieve the machine working parts of the unloaded operation, in order to check the machine working parts in accordance with the correctness of the specified work cycle coordinated action.
At this time, the main content of the check is as follows:
1. Verify the correctness and continuity of the automatic work cycle sequence.
2. Check the accuracy of the travel distance of the executive element within the work cycle.
3. Assess the reliability of various interlocking devices.
4. Measure the maximum speed of the executive element.
5. Ensure smoothness in starting, direction changes, and speed switching. The movement should be free of crawling, jumping, or impact phenomena.
In the hydraulics system after continuous no-load operation for a period of time, check the temperature rise of the working oil temperature, should not exceed the specified value. Observe the stability of the pressure gauge reading in the working oil circuit during the full stroke of the actuating element. Once you confirm that the hydraulics system and all hydraulic mechanisms can work uninterruptedly, normally, and reliably, you can proceed with the load test.
7)Coordinate with the electrical debugging work cycle. Check that the coordination and sequence of each action are correct. Additionally, verify the smoothness of the system.
8) Run the hydraulics system continuously for a period of time, generally 30 minutes. During this time, check the temperature rise of the fluid. The temperature rise should remain within the allowable value, typically between 35°C and 60°C for working oil.
3.Load test
The load test is generally conducted with a load less than the maximum. If everything operates normally, proceed to test with the maximum load. This approach helps avoid equipment damage and other accidents.
1) The purpose of the load test is to check the maximum load pressure and power consumption. It also aims to ensure that noise and vibration levels are within the permissible range. Additionally, the test evaluates the stability and reliability of the entire hydraulic system and its components under load conditions.
2) The load conditions of the test should be adjusted to be consistent with the actual working conditions of the machine. For hydraulic systems with a working pressure lower than 16 MPa, set the test pressure to 1.5 times the working pressure. This ensures that the system is tested under appropriate conditions. For systems with a working pressure higher than 16 MPa, set the test pressure to 1.25 times the working pressure. Check the load pressure according to the reading of the pressure gauge. Follow the steps and main contents of the aforementioned no-load test. Then, check the correctness and reliability of the machine’s action.
Ensure that you conduct this check under load conditions or during the automatic work cycle. During the load test, increase the pressure step by step. Stabilize each pressure increase for 2 to 3 minutes. Once the test pressure is reached, hold the pressure for 10 minutes. Afterward, reduce the pressure to the working level. Perform a comprehensive inspection of all welds and interfaces in the system. Ensure there is no oil leakage and that the pipeline does not exhibit permanent deformation to qualify.
4) To ensure safety, avoid hammering the pipeline during the load test. Additionally, do not perform open flame operations within 5 meters of the test area. If a failure occurs, address it only after relieving the pressure.
5) Under load conditions, test the speed of movement and its stability. For machine tool type equipment, test the stability of movement at low speed is particularly important. You can calculate the power consumption based on the measured load pressure, movement speed, and torque.
6) During the load test of the hydraulic system, you should pay attention to the temperature rise in the hydraulic components and the tank. This temperature rise should not exceed the specified value.
7) You can adjust the hydraulic system according to the contents listed in Table 6-4. Additionally, the methods for these adjustments are provided in the same table.
| Table 6-4 Hydraulic System Adjustments | ||
| Adjustment parameters | Regulated components | Adjustment range and requirements |
| Working pressure of the hydraulic pump | Safety and relief valves for hydraulic pumps | 10%~20% greater than the working pressure of the actuating element |
| Pressure at fast stroke | Safety valves for hydraulic pumps | To be 15%~20% greater than the actual pressure required for rapid travel |
| Secondary working pressure | Pressure reducing valves | Should meet the requirements of the working mechanism |
| Working pressure of the pressure relay | Springs in pressure relays | Be lower than the working pressure 0.3~0.5MPa |
| Unloading pressure | Safety and relief valves | Unloading pressure should be less than 0.1 ~ 0.2MPa, the use of unloading hydraulic pump as a control or lubrication system energy, unloading pressure should be in the range of 0.3 ~ 0.6MPa |
| Sequence of reversing or switching of the actuating elements | Travel switches, pilot or directional valves, blocks and bumpers | Switching sequence and its precision should meet the requirements of the working parts. |
| Speed of movement of the working parts and their smoothness | Throttle valves, variable pumps or hydraulic motors, guide bars and plates, lubrication systems, seals | Smooth movement, no shock and vibration, no external leakage allowed. Load speed reduction should not be more than 10~20 per cent |
4. Dynamic test
The main parameters of the hydraulic system constantly change during operation. Starting, reversing, and unloading conditions cause these parameters to vary. These changes are important factors that affect the performance of the hydraulic system. You should create conditions to complete the system dynamic test. The dynamic analysis of the system should be verified. Additionally, research and exploration of similar system designs are important. The goal is to seek directions for improvement.
The dynamic test items include:
1. The test of the commutation transition process of the executive element.
2. The self-excited vibration test of the hydraulic system, along with research and curve analysis.
3. The test to determine the stiffness of the hydraulic system and the recording of curve data.
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