Structure and design of hydraulic drive device for fast closing butterfly valve

1 Overview

The extraction steam turbine unit can realize cogeneration of heat and power and is widely used in the heating system of thermal power plants. In order to prevent the steam from the steam extraction pipeline from flowing back and the condensate from flowing backward, causing the overspeed accident of the steam turbine, an electric cut-off is made on the steam extraction pipeline of the steam turbine.butterfly valveandcheck valveneed to be installed betweenQuick closing butterfly valve, to protect the safety of the steam turbine by cutting off the pipeline instantly.Due to the fast closing speed (< 1s) and large output force (> 100kN) of the quick-closing butterfly valve, a hydraulic drive device must be used. In order to adapt to various types ofvalveSerialized design of quick-closing butterfly valve hydraulic drive device.

2 structures

The quick-closing butterfly valve hydraulic drive device consists of 5 parts, including hydraulic pump station, control valve group, accumulator, fast oil cylinder, and electrical control box (Figure 1), which can complete the slow opening, slow closing, fast closing, and activities of the butterfly valve. action.

Figure 1 The appearance of the quick-closing butterfly valve hydraulic drive device (1. Electrical control box 2. Accumulator 3. Hydraulic pump station 4. Control valve group 5. Fast oil cylinder)

2.1 Hydraulic control part

According to the requirements and calculation of the quick-closing butterfly valve, the basic parameters of the hydraulic drive device are determined as “Table 1”.

The hydraulic pump station is composed of motor, coupling, hydraulic pump, oil inlet filter, high pressure filter, oil tank and other components. Its main function is to supply the pressure oil required by the system and provide flow and pressure for the accumulator. When designing The imported high-pressure and low-noise gear pump is adopted. The pump device adopts a vertical installation and a high-pressure filter with an inverted structure.Control valveCan act normally. In order to meet the needs of different quick-closing butterfly valves, it is divided into two series for design.

Figure 2 Hydraulic control valve group (1. Solenoid valve DT3 2. Solenoid valve DT2 3. Stop valve AV1 4. Stop valve AV3 5. Stop valve AV2 6. Relief valve RV 7. Pressure measuring joint MP 8. Stop valve AV4 9 .Pressure switch KP2 10. Pressure switch KP1 11. Solenoid valve DT1)

The control valve group (Figure 2) is mainly composed of valve block, relief valve, check valve, throttle valve,Shut-off valve, solenoid valve, pressure relay and pressure gauge, etc. The function of the relief valve RV is to set the safety pressure of the system, the function of the cut-off valve AV1 is to release the pressure oil in the system and return it to the oil tank, and the function of the throttle valve AV3 is to adjust the closing speed of the system , the function of throttle valve AV2 is to adjust the opening speed of the system, the function of pressure relay KP2 is to set the upper limit point of system oil pressure control, the function of pressure relay KP1 is to set the lower limit point of system oil pressure control, and the function of pressure gauge is to display For the system oil pressure, in order to reduce the internal leakage of the system and the number of starts of the oil pump, save energy, and facilitate maintenance and installation, imported threaded cartridge valves and high-quality two-way cartridge valves are selected. In order to meet the needs of different quick-closing butterfly valves, the valve block is divided into three parts: the left valve block, the middle valve block and the right valve block, and different combinations can be used to meet different requirements.

The accumulator provides energy for slow opening, slow closing, fast closing and activities of the butterfly valve. The selection of accumulator specifications has been strictly calculated, and each system is different to meet the requirements of system pressure maintenance and butterfly valve fast closing. The nitrogen used in the accumulator can be regarded as an ideal gas, and the rapid expansion and compression process can be regarded as an adiabatic state change. The formula for calculating the total volume of the accumulator is:

In the formula:
V0——ideal total volume of accumulator, m3
ΔV——the effective oil displacement required by the accumulator, m3
P0——accumulator charging pressure (absolute pressure), Pa
P1——The lower working pressure of the system (absolute pressure), Pa
P2——Maximum working pressure of the system (absolute pressure), Pa
K——gas variability index (nitrogen variability index K=1.4)

Figure 3 Fast oil cylinder

The fast oil cylinder (Fig. 3) is the actuator that pushes the butterfly valve through the rack and pinion. In order to ensure its reliable operation, the oil cylinder is sealed with an imported sealing ring, and a hydraulic buffer device is installed to protect the butterfly valve. A throttling device is designed. According to the system It is required to control and drive the external load and install it directly on the rack and pinion transmission. In order to better connect with the fast-closing butterfly valve, the fast cylinder has also been designed in series, see “Table 2”.

2.2 Electrical control part

According to the requirements of the hydraulic control part, determine the parameters of the electrical control system, see “Table 3”.

The electronic control system of the quick-closing butterfly valve hydraulic drive device adopts a self-designed special integrated printed circuit board, which has been proved to be easy to adjust, stable in performance and reliable in quality through rigorous testing. The electric control box is composed of switching power supply, AC contactor, thermal relay, circuit breaker, circuit board and terminal blocks. Electrical control is divided into two types: ordinary relay control box and PLC type electric control box.

3 model compilation

The model of the electro-hydraulic control driving device is composed of 9 units, which are used to indicate the code of the device, the nominal diameter of the valve, the nominal pressure of the valve, the energy storage form, the quick closing action form, with manual action, with oil source system, electrical options and Product version number. The 9 units of the device model are arranged in the following order:

① Product code——HGKG, electro-hydraulic control fast shut-off butterfly valve electro-hydraulic control drive device;

② Nominal diameter of valve——DN200, DN250, DN300, DN350, DN400, DN450, DN500, DN550, DN600, DN650, DN700, DN750, DN800, DN900, DN1000, DN1.00, DN1200, DN1300, DN1400, DN1500, DN1600 , DN1800, DN2000;

③ Nominal pressure of the valve——PN6, PN10, PN16, PN20, PN25, PN40, PN50, PN63.3;

④ Energy storage form – X is accumulator type (default option), T is spring type;

⑤ Quick closing action form——E is the energized action type (default option), D is the de-energized action type;

⑥ With manual action – S (for accumulator type);

⑦ With oil source system——P (for spring type);

⑧ Electrical options——PT is a common relay control type (default option), XD is a PLC control type;

⑨ Product version number – 2X, 3X;

Example: HGKG① – 450②/06③ -X④ -E⑤ -S⑥/P⑦ -PT⑧ – 2X⑨

4 Epilogue

The electro-hydraulic control driving device of the quick-closing butterfly valve can realize both remote control and local control box operation panel control after several optimized designs. Through the selection of imported high-pressure and low-noise gear pumps, high-pressure and high-flow logic valves, compact screw-in cartridge valves and dedicated control circuit boards, the fast closing speed can reach 0.3s, and the operation is stable and reliable.