The HPHT Hydraulic Cubic Press is a high-tech product integrating machinery, electrics, and hydraulics, used primarily for synthesizing superhard materials such as diamond and cubic boron nitride. The hydraulic system's working pressure is 14 MPa.

1. Excessive Hydraulic Pump Operating Noise and Rapid Wear of the Elastic Coupling Rubber Pad

Phenomenon/Cause Analysis The primary cause of the excessive noise from the hydraulic pump and the rapid wear of the elastic coupling rubber pad (with noticeable rubber powder flying out) is the large coaxiality error between the axis lines of the hydraulic pump and the electric motor. This error causes relative high-speed sliding between the coupling and the rubber pad, accelerating the wear.

Solutions

1. During assembly, the pump stand and the electric motor must be installed on the machine base simultaneously.

2. Ensure that the coaxiality error between the electric motor's axis line and the pump stand's locating hole is maintained within 0.05.

3. After installing the pump and the coupling, manually moving the assembly should allow free rotation without jamming.

4. Use a feeler gauge to check that the clearance of the coupling is uniform.

2. Failure of the Hydraulic Pump to Establish Working Pressure

2.1 External and Pump Self-Checks

1. Motor Direction: Check and ensure the rotation direction of the electric motor is consistent with the direction required by the pump.

2. Displacement Setting: Since the machine uses an axial piston type manually variable displacement hydraulic pump, the displacement is manually adjusted. If the displacement indicator plate is at the zero point, the pump's displacement is zero, meaning it is running idle. During commissioning, the setting should be placed at around 6.5.

3. Suction Pipe Sealing: Check the pump's oil suction port and pipe for sealing. If the suction pipe leaks air, the pump cannot draw in enough oil and cannot operate normally.

4. Initial Oil Filling: Before the first start-up, sufficient hydraulic oil must be injected through the pump's cooling oil pipe to form a sealed cavity. Because the suction pipe enters the oil tank from the upper liquid level, without this initial seal, the pump cannot draw oil solely by its self-priming ability.

2.2 Checking the Valve Working Position

1. Overflow Valve (Relief Valve): Check if the overflow valve is in the working position. Rotating the valve handle should be met with resistance, confirming that the spring of the pilot valve is compressed and the overflow valve is active.

2. YA15 Solenoid Valve Check: If pressure still fails to establish, check the YA15 solenoid directional valve. YA15 controls the remote control port of the overflow valve; only when YA15 is active (closing the remote control port) can the overflow valve establish system pressure.

    If the PC (Programmable Controller) output relay for YA15 is not conducting (indicator light off), use the programmer to check if the YA15 program content or input node status matches the requirements.

    Check the wiring continuity between the PC's YA15 output point and the electromagnet, including the neutral line and the 220V power line (including the fuse).

    Check if the YA15 electromagnet is intact.

     If all checks are clear, replace YA15 or the overflow valve to isolate the fault.

2.3 Checking Pump Body or Manifold Issues If replacing the valves is unsuccessful, check the pump itself: connect a transparent plastic tube to the pump output and observe if the output oil is complete, continuous, and free of interruptions or air bubbles.

The presence of interruptions or air bubbles indicates air leakage in the suction system, pointing to the pump body if the piping is sound.

 If pump output is normal, check the first valve plate to see if the inlet and outlet ports are connected (short-circuited).

3. System Pressure Exists Immediately After Startup

Phenomenon/Cause Analysis Pressure immediately upon startup means the pump is working, but a valve or pipeline is malfunctioning, as the system should not have pressure if valves are not actuated. First, check if the YA15 solenoid directional valve has actuated.

Solutions

1. If YA15 has actuated: Check the PC. If the YA15 output relay shows no output (indicator light off), the program is fine, but the fault is likely miswiring (input and output points directly connected). If so, rewire. If measurement shows direct continuity, it might be due to a quality issue where the PC’s output solid-state relay node is "cold-welded" together. Attempts can be made to restore it by repeatedly cycling the activating button; otherwise, the PC must be replaced or repaired.

2. If YA15 has NOT actuated, but the system has pressure: Turn the overflow valve adjusting handle until it is completely disengaged.

     If pressure does not change: The pressure is established by resistance from an obstructed return oil line. Dismantle the return oil pipe from the first valve plate to the oil tank to check flow. This is often due to poor connection between the pipe joint and the steel pipe. If the piping is fine, the first valve plate is faulty.

    ◦If pressure changes with the handle and drops to zero when disengaged: The pressure is established by the overflow valve because its remote control port is closed. Check the YA15 valve itself (e.g., by applying 220V AC power to check passage). If YA15 is fine, check the flow path from YA15's input port to the overflow valve's remote control port, and the return oil line from YA15's output port to the oil tank.

4. Failure of the Hydraulic System to Achieve Ultra-High Pressure

4.1 Working pressure exists, but the booster indicator rod does not move.

1. Check YA2/34DO: Check if the 34DO solenoid valve (YA2 directional valve) is actuated. If not, identify whether the fault lies between the PC and the valve, between the PC and the signal device, or within the PC program or the PC itself.

2. Check YA13 and 34DO Installation: If YA2 is normal, check YA13. Dismantle 34DO, check its installation alignment (P port alignment), and check the valve itself. If realignment fails, and pressure remains, check the connecting steel pipe and passages between the 1st valve plate and the 5th valve plate (V-block) for obstructions. If the 34DO valve itself is faulty, replace or repair it.

4.2 During pressurization, the booster indicator rod moves up, but there is no ultra-high pressure. This indicates that the low-pressure chamber of the booster has oil, but the high-pressure oil is not entering the main working cylinder.

1. Check YA12: Check if the YA12 solenoid directional valve is actuated.

2. Check Six Ultra-High Pressure Hydraulic Control Check Valves: Unscrew the upper plugs of the six check valves individually. If there is no hydraulic oil, the valve is unsealed. Remove the spool and check if the sealing oil line is complete and clear, and free of foreign matter. If the oil line is incomplete, re-lapping is required.

3. Check Two-Position Seven-Way Valve (2/7 Valve): Feel the control oil pipe. If it is very hot, pressure oil is being relieved through the control oil circuit. Check the sealing performance of the 2/7 valve and inspect for damaged or missing seals.

4.3 During pressurization, the booster indicator rod does not move, but system pressure reaches the set working pressure. This suggests that the high-pressure chamber (lower) and ultra-high pressure chamber (upper) have reached a force balance, or the 2/7 valve is in a closed state.

1. Check YA13: Check the YA13 solenoid directional valve (the control valve for the 2/7 valve) and its piping.

2. Check 2/7 Valve: If YA13 is fine, inspect the 2/7 valve itself. Check if the fit between the spool and the valve body is too tight or if there are impurities. If the fit is too tight, re-lapping according to the valve body's actual dimensions is required.

4.4 No ultra-high pressure, and the high-pressure pump pressure gauge reads zero working pressure. This assumes normal function of the pump, overflow valve, and all six working cylinder actions (forward/retraction) in non-ultra-high pressure mode.

1. Check Mechanical Unloading Valve: Check if the mechanical unloading valve is closed. Dismantle it, check for the conical spool, and confirm the contact oil line of the spool is complete and clear. Reinstall and tighten.

2. Check Parallel Hydraulic Control Check Valve: If ultra-high pressure is still absent, check the parallel hydraulic control check valve. Dismantle it, inject oil into the inlet, and observe its sealing performance. If sealing is poor, replacement or repair is needed.

3. Check Valve Plate: If all the above are ruled out, the fault is certainly caused by the valve plate itself.

5. Screeching Sound and Violent Oscillation of the Pressure Gauge Needle During Booster Depressurization

Phenomenon Description When the booster depressurizes and the high-pressure pump pressure gauge reaches the set value, an occasional piercing screech occurs. The ultra-high pressure gauge pointer oscillates violently, and the oil pipe running from the overflow valve's remote control port to the YA15 solenoid directional valve becomes very hot, accompanied by strong, intense vibration.

Cause Analysis This issue was identified by experts as being caused by the excessive volume of the remote pressure regulating capacity of the overflow valve.

Solutions Two methods were proposed to eliminate this fault:

1. Add a damping hole inside the inner diameter of the oil pipe connecting the overflow valve’s remote control port to the YA15 directional valve.

2. Use an oil pipe with a smaller inner diameter to reduce the remote pressure regulating capacity. (In practice, replacing the oil pipe with one of a smaller inner diameter successfully eliminated the screeching and violent oscillation of the pressure gauge needle.)