Improving the stability of a HPHT Hydraulic Cubic Press is crucial for ensuring the efficient and reliable operation of the equipment, especially since the HPHT Hydraulic Cubic Press is a high-tech device for synthesizing artificial diamond, requiring high precision and operational sensitivity. Below is a detailed explanation of how to improve the stability of a HPHT Hydraulic Cubic Press:
1、Improvement of the Valve Plate Return Oil System
Problem Description: When the press is in operation, the system is under high pressure (13-15 Mpa, which can reach 87-89 Mpa after boosting) and high temperature. After synthesis, during depressurization, the 10-liter variable plunger pump needs to be frequently started to achieve depressurization. Due to the high pressure and frequent starting, the press becomes unstable, noisy, and various oil pipes vibrate violently, especially the booster return oil pipe, which frequently breaks, leading to oil spray accidents. Furthermore, the loud noise makes it difficult to hear hammer cracking sounds, shortens the service life of the plunger pump, increases maintenance time and production costs, and raises power consumption.
Improvement Measures: A powerless unloading electromagnetic ball valve was added to the valve plate return oil system. This type of ball valve has good sealing performance, is not affected by hydraulic locking, is less affected by hydraulic forces, requires small thrust for commutation and reset, and is suitable for high pressure. The electromagnetic ball valve is installed at the hydraulic control one-way valve in the valve plate return oil circuit. Through electrical control, the plunger pump is shut off during charging, overpressure, and fast return, and the high-pressure automatic depressurization is controlled by the electromagnetic ball valve. When the pressure is relieved to 3-4 Mpa, the plunger pump automatically starts until depressurization is completed.
Improvement Effects:
Equipment stability has improved. Oil pipe vibration is reduced, return oil pipe joints no longer break, reducing accidents and increasing uptime.
Noise is significantly reduced. This provides favorable conditions for accurately judging abnormal sounds and reduces human-caused hammer breakage and explosion accidents.
The service life of the plunger pump is extended. It can now be used for one year instead of six months, saving costs.
The number of plunger pump starts is reduced, and power consumption is lowered, saving costs.
2、 Transformation of the Pump Group
Problem Description:
The 50-liter vane pump used by the equipment has a large flow rate (50 liters at 1000 rpm, actual up to 73.5 liters/minute), which is a significant difference from the 10-liter axial plunger pump (10 liters at 1000 rpm, actual maximum 14.4 liters/minute). This mismatch leads to frequent equipment failures, higher oil temperature, and easy wear of the axial plunger pump, often resulting in insufficient or slow pressure compensation. This causes the vane pump to intervene too quickly for pressure compensation, leading to equipment instability.
The 50-liter vane pump has a large flow rate, but the valve plate return oil port is small (inner diameter about φ17mm). This results in poor oil return, excessively fast oil flow, which causes the hydraulic oil to heat up easily. High oil temperature can lead to internal and external leaks, frequent pressure compensation, and fast wear of valves, thus causing equipment instability.
The large flow rate of the 50-liter vane pump creates a significant impact on the electromagnetic relief valve (valve core bore φ10mm). The valve core has high usage frequency and wears out quickly, leading to frequent damage, repair, and replacement of the relief valve, resulting in more downtime. This is also a factor contributing to equipment instability and high noise.
Improvement Measures:
The 50-liter vane pump was replaced with a 32-liter adjustable axial plunger pump. This pump controls plunger operation via a swash plate, resulting in lower noise than quantitative vane pumps, easier maintenance and parts replacement. Its flow can be adjusted according to actual use, reducing impact on the relief valve and extending its service life.
The 10-liter axial plunger pump was replaced with a 16-liter variable axial plunger pump. This change resolved the issues of insufficient or slow pressure compensation, improving equipment stability, shortening plunger pump start-up time, and reducing noise.
An additional return oil pipe with an inner diameter of φ14mm was added to the valve plate return oil circuit.
Improvement Effects: The oil temperature significantly decreased, and the return pressure can be better controlled at 3-4 Mpa, which plays a crucial role in improving equipment stability.
3、Optimization of Hydraulic Oil Management
Importance: Hydraulic oil is a key component for improving equipment stability.
Improvement Measures:
The 46# oil used at the initial stage of factory construction was replaced with 68# anti-wear hydraulic oil.
Hydraulic oil is filtered every 4 months to address oil contamination issues.
The hydraulic system employs methods such as suction oil filtration, high-pressure oil filtration, and return oil filtration to ensure the cleanliness of the hydraulic oil.
An oil cooler is used for forced cooling of the hydraulic oil in the oil tank to reduce oil temperature.
Improvement Effects: These measures provide assurance for the reliable operation of the hydraulic system and contribute significantly to ensuring equipment stability.
4、Modification of the Electrical Control System
Improvement Measures: Several programs were added to enhance safety and stability:
"No block loaded" protection to prevent hammer extrusion.
Slow rise of hammer head voltage protection to reduce hammer burning.
"Previous block curve" display added to the screen, facilitating comparison with the previous block by synthesis operators during operation to prevent accidents.
Improvement Effects: Through these improvements, the equipment's stability has significantly increased, and noise has been reduced. This provides a quiet and comfortable working environment for synthesis operators, allowing them to accurately identify abnormal sounds and reduce hammer breakage and explosion accidents.
5、Improvement of Main Machine Installation and Overhaul Accuracy
Importance: The installation and overhaul accuracy of the press's main machine components are another important factor affecting equipment stability.
Problem Description: The press main machine consists of 6 sets of hinge beams connected by 12 pins. There are many fit clearances, and improper selection of dimensional tolerances can cause the pressure cylinder to "bow". During high-pressure operation, the hinge beams expand in six directions. If the fit between a pin and its hole is improper in a certain direction, that direction will expand more, causing the force direction to shift, leading to deformation of the synthesized block and easy occurrence of hammer cracking accidents.
Improvement Measures:
During cylinder removal, key dimensions are measured to select appropriate fit tolerances.
Ensure that the fit tolerance between the pin and the pinhole is within the specified range.
Grinding of damaged pinholes must be carefully managed; large-area grinding must be avoided to ensure the surface roughness of the hole.
The fit between the piston and the working cylinder, and between the piston and the guide sleeve, must strictly adhere to the required tolerances.
Dimensions of all removed workpieces must be measured, and those out of tolerance should be re-selected or replaced.
The outer surface of the workpieces must be polished to prevent damage to sealing components.
Through the comprehensive management and improvement of the HPHT Hydraulic Cubic Press as described above, equipment stability has been significantly enhanced, and uptime has increased, ensuring the completion of production tasks. Concurrently, various costs have been reduced, accidents have decreased, and hard hammer consumption and maintenance costs have been greatly lowered.