Reform of automatic hydrostatic test system for th

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Transformation of automatic hydrostatic test system for welded steel pipes

water injection and pressure maintaining test is a necessary inspection link for welded steel pipes and an important means to inspect the compactness of welded pipes and ensure the quality of welded pipes. 1. The welded pipe water injection pressure test system sends the repaired welded pipe to the hydrostatic test site by the conveying roller. As shown in Figure 1, 9dt is charged, the system establishes pressure, and then drops to the designated station through pipe drawing and pipe jacking. 2DT is electrified, the vent valve is 8 open, 3DT is electrified, the clamping cylinder clamps the test welded pipe, 5DT is electrified, the sealing cylinder enters, both ends of the test welded pipe are sealed, the water filling pump fills water through the water filling valve 5, and the air is discharged by the vent valve 8. After the air is exhausted, the water filling pump unloads, 1dt is electrified, the vent valve is closed, the pressure water is sealed, 7dt is electrified, the supercharger acts, and the pen recorder starts to record the test pressure. When the test pressure reaches the rated water pressure, The electric contact pressure gauge is connected, 7dt loses power, and the system enters the water sealing and pressure maintaining test phase. When the required pressure maintaining time is up, 2DT is charged, the vent valve 8 is unloaded, 6DT is charged, the sealing cylinder is retracted, 8dt is charged, the booster cylinder is reset, 4dt is charged, the clamping cylinder is loosened, the pipe is jacked up, and the test pipe is welded to the next process. 1 ~ the case is under further review. 9dt loses power, the oil pump is unloaded, and the next round of work cycle is entered. 1. booster cylinder 2 Booster cylinder 3 Water make-up check valve 4, 10 Sealing seat forward and backward cylinder 5 Water filling check valves 6 and 9 Sealing seat 7 Welded pipe 8 Vent valve (also used as pressure relief valve) A2, b2 Fig. 1 Schematic diagram of welded pipe hydrostatic test system in the above-mentioned old test system, due to many intermediate leakage links, the effect of water sealing and pressure maintaining test is not ideal, and there are also the following problems:

(1) using electric contact pressure gauge for pressure control, the accuracy is low, and the test error is large

(2) the recording system composed of pressure transmitter and pen recorder is adopted, so the data is not intuitive and easy to save. A large number of test curves are saved in the form of paper tape, which brings great inconvenience to management and reference

(3) the degree of automation is not high. Due to human factors, the passive frame is adjusted to the horizontal position through the wire adjusting device on the boom, which requires high quality of workers and high labor intensity

in view of the above situation, the factory and the University jointly proposed a technical transformation scheme with the computer control system as the core. 2 automatic hydrostatic test system scheme (1) sealing scheme

the original pressurized water cylinder is used to improve the sealing performance of the hydrostatic test system to maintain the system pressure. This scheme needs to transform the green circulating valve system and all sealing links of the original future plastic industry. Moreover, it is not easy to maintain the good sealing performance of the system for a long time because the test site environment is relatively bad and there are many impurities in the circulating water of the hydrostatic test. Therefore, this scheme is not adopted

(2) supercharger scheme

the original test system uses a supercharging cylinder. When the test pressure reaches the process pressure, the supercharging cylinder stops, and the pressure is maintained by the sealing of the system. The supercharging cylinder cannot continuously supplement water and maintain pressure due to its limited travel. This scheme adopts two travel switches and a one-way valve bridge, and the booster cylinder becomes a supercharger (see Figure 2). Fig. 2 Schematic diagram of supercharger scheme (3) computer controlled water replenishment scheme

the computer controlled water replenishment system for hydrostatic test of welded pipe is shown in Fig. 3. The system uses a pressure sensor to monitor the test water pressure in real time. The pressure signal is input into the industrial control computer system through the pre amplification circuit. The industrial control computer processes the input signal, and the control signal is output to the control water replenishment system through the output interface to make real-time compensation for the water pressure leakage of the welded pipe hydrostatic test, so as to maintain the requirements of the constant pressure process of the hydrostatic test. At the same time, the industrial control computer is connected with the original electric control system through the output interface. In this way, the new and old systems are in parallel, which increases the reliability of the system, saves the funds for technical transformation and reduces the construction difficulty. Fig. 3 block diagram of computer control system for welded pipe hydrostatic test on the basis of the above hardware system, an application software based on VB is developed. The human-computer interface of the software is very friendly. The system can easily set the pressure holding values of different test workpieces and various required test parameters, Real time display and storage of P-T curve and relevant data (test time, steel pipe material, steel pipe specification, test workpiece number, operator, inspector, operation shift, etc.) during the test, so as to easily view the original records of the hydrostatic test of welded pipes. The application effect of the system is good. 3 conclusion through the joint research of Chongqing University and Panzhihua Iron and Steel Group Beihai Steel Pipe Co., Ltd., the computer integrated control system for welded pipe hydrostatic test has been successfully developed. The actual operation shows (as shown in Figure 4): (a) the test pressure curve without water replenishment mechanism (b) the test pressure curve with water replenishment mechanism

Figure 4 the test record results of computer control system (1) the scheme of real-time pressurized water replenishment is successful, The real-time water replenishment can prevent the decrease of water pressure caused by leakage, so as to meet the process requirements of water pressure for welded pipe test

(2) the computer integrated control system composed of industrial computer, sensor and water replenishment actuator has the characteristics of visualization, intuition and accuracy in its structure, which can effectively improve the accuracy and efficiency of water injection and pressure maintaining test of welded pipe

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