Automatic control of hydraulic bulging pressure in barrel

Automatic control of hydraulic bulging pressure in barrel

Winlyons

At the end of the 1980s, our country began to use hydraulic bulging technology to produce barrels. The “three-in-one” barrel forming machine produced by Xi'an Machinery Research Institute is the first hydraulic bulging machine. Now the equipment has undergone several improvements, with a high degree of automation and advanced technology. A programmable mathematical model has been adopted in electrical control. It has functions of addition, subtraction, multiplication, division, logical operation and data conversion. It is controlled by the PLC. After the device is started, each part is automatically and continuously operated, and a series of actions can be completed automatically.

At present, the barrel hull production equipment with hydraulic bulging has become more popular. Although most of the hydraulic bulging machines have high degree of automation and production efficiency, they cannot effectively control the bulging pressure, thereby affecting the quality and yield of products. In the trial production process, we analyzed the causes of waste products and the drawbacks of domestic bulging machines, and proposed ways to improve them.

1, the normal relief valve overflow

In order to overcome the disadvantages of positioning bulging and manual bulging, we have designed the following improvements:

• Install a common relief valve on the bleeder valve block.

• Calculate the maximum bulging pressure (ie, overflow pressure) required for the tube by calculating the bulge pressure.
P=a1·2δbt/D
Where: δb - tensile strength, kg/cm; t - pipe wall thickness, cm; D - internal diameter of the three-way branch, cm; a1 - forming factor.

• Move the common relief valve to the pump seat, calibrate the calculated relief pressure on the normal relief valve, and move it back to the repetitive valve block.
During bulging, when the bulge pressure exceeds the calibrated overflow pressure, the liquid flows into the tank, and the bulge always maintains the calibrated overflow pressure value. This fixed overflow is much better than positioning bulging and manual overflow.

Ordinary relief valve setting overflow also has disadvantages. First, the maximum rated pressure of the relief valve is 25MPa. When the bulge pressure is greater than 25MPa, the overflow valve cannot overflow. Generally, the bulging pressure of the steel plate is greater than 25MPa.

Second, each three-way specification, or every bulging pressure, must be recalibrated. In order to avoid repeated access to the relief valve, we have designed a new automatic overflow control method.

2. The booster self-adjusts the fixed value overflow

There is a 200MPa turbocharger on our hydraulic bulging machine. The area of ​​the rear cavity of the turbocharger is 8 times the area of ​​the exit of the front cavity. Under the action of the initial pressure of 25 MPa, the piston of the supercharger moves forward (forward), and the pressure at the outlet of the supercharger is 200 MPa. This constitutes a 1:8 relationship. Based on this feature of the supercharger, we have designed three improvements.

・Remove the double check valve ball so that the supercharger can move backwards (reversely) by itself, and constitute an 8:1 relationship, that is to convert the 200MPa bulging pressure in the front chamber of the supercharger to 25MPa in the rear chamber. .

• Install a current proportional relief valve on the return line at the end of the booster.

• Proofread the current value of the proportional relief valve and the corresponding current value on the console to obtain a current-pressure reading.

With the above improvement, the supercharger is changed from a single stroke of the original forward movement to a pressure-pressure double stroke of the supercharger that can also move backwards. In bulging, as long as the proportional relief valve is set to a corresponding current value during operation, all the forming process can be completed automatically at one time, achieving the purpose of automatic control. Through the improvement of process technology, product quality and yield have been greatly improved.

3, the conclusion

• There are many factors that affect the bulging quality and yield of the barrel, but the adjustment and control of the bulging pressure is the most important factor, and the positioning forming and manual overflow forming cannot effectively control the bulging pressure. Therefore, it is difficult to guarantee product yield.

・ Through the analysis of the drawbacks of the domestic bulging machine, a control approach for overflow, pressure reduction, and pressure regulation was proposed, and after two process improvements, automatic control of bulging pressure was finally achieved.

• After the bulging pressure is automatically controlled, the bulging pressure parameters of the barrels of different specifications can be input into the programmable mathematical model, so that all the final realizations can be controlled by the PLC to achieve full automation.