PC controlled closed steel drum hydraulic testing machine

PC-Controlled Hydraulic Testing Machine for Closed Steel Drums

Yi Menglin

Abstract: This paper presents a hydraulic testing machine designed for 200-liter closed steel drums, controlled by a programmable logic controller (PLC). The system's working principle and the role of PLC in automation are explained. The machine is user-friendly, flexible, and efficient, meeting the hydrostatic test requirements for 200-liter closed steel drums as per GB325 standards. It can also be adapted for pressure tests on similar closed containers.

Keywords: PLC control, hydraulic testing

According to the "200-Liter Closed Steel Drum Inspection Rules" issued by the National Packaging Quality Supervision and Inspection Center, 200-liter closed steel drums must undergo a hydrostatic test at a pressure of 13.729 × 10⁴ Pa (1.4 kgf/cm²) as specified in GB325. For maritime transport, the pressure should be increased to 24.500 × 10⁴ Pa (2.5 kgf/cm²), according to the International Maritime Dangerous Goods Regulations. The test procedure involves securing the drum, sealing it, and pressurizing it with water using a pump. Once the required pressure is reached and stabilized, a 5-minute hold is conducted. If no leakage occurs, the test is considered successful.

To meet these requirements, we have developed a PLC-controlled hydraulic testing machine. It allows easy adjustment of test pressure and holding time, and features automatic water injection and pumping. The system ensures compliance with safety standards during storage and transportation of petroleum products. It is suitable not only for hydrostatic testing of 200-liter closed steel drums but also for pressure tests on similar non-corrosive liquid containers. Figure 1 shows the working principle of the testing machine.

1 - Water injection/pumping control valve; 2 - Water pump; 3 - Pressure regulating valve; 4 - Water injection and pressure control valve; 5 - Pressure relay; 6 - Accumulator; 7 - Quick change joint; 8 - Exhaust/inflation control valve; 9 - Test steel drum. Figure 1

The testing machine supports both manual and automatic operation modes. During commissioning, operators can manually run specific processes via button switches or interrupt and switch processes as needed. In automatic mode, the PC program controls the entire cycle. Table 1 outlines the operating status of switches, motor contactors, and valve solenoids for each test stage.

Table 1

Note: KT is the emergency stop button used when a fault occurs.

During the test, after the drum is clamped and ready, pressing the 1QA button closes the contactor JC, starting the pump. At this point, 1DT, 2DT, and 3DT are de-energized, allowing the pump to inject water and expel air through valve 6. When the tank is filled, the PC energizes 3DT, closing the drain and increasing pressure. When the set pressure is achieved, the pressure relay YJ activates 2DT, cutting off the pump and starting the pressure-hold phase. The accumulator compensates for any leaks, stabilizing the pressure. If no leakage occurs within 5 minutes, the system automatically proceeds to the next step. The PC then powers JC and 1DT while de-energizing 2DT and 3DT, releasing the pressure. After a short period, the pump stops automatically, and the operator removes the drum, drains the remaining water, and prepares for the next test.

It’s important to note that all timing parameters—water injection, pressure hold, and pumping—are programmed into the PLC. Users can adjust these settings through the PC programmer based on specific needs. If a failure occurs or if the drum leaks during the process, manual intervention can immediately terminate the test.

The system uses a Mitsubishi F1-30MR PLC, featuring 16 input points and 14 output points, offering room for future expansion. The wiring diagram of the PLC input and output terminals is shown in Figure 2.

Figure 2

Thanks to PLC control, the system efficiently performs hydraulic pressure tests for closed steel drums. Compared to traditional relay-based control systems, it simplifies the circuit, eliminates multiple time and intermediate relays, and offers customizable logic through programming. This flexibility enhances the machine’s functionality and adaptability. Practical applications have proven that the PLC-controlled hydraulic testing machine is reliable, easy to adjust, user-friendly, and simple to maintain.

References

[1] Inspection rules for 200-liter closed steel drum. National Packaging Quality Supervision and Inspection Center (Guangzhou), 1988

[2] Yan Wenxue, Hua Rong. Principle, use and application examples of microcomputer programmable controller. Electronic Industry Press, 1992

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