Adjustable Pressure Relief Valve

The pressure regulating valve is a safety device of the long pressure diversion tunnel hydropower station. Generally, when the pressure diversion pipeline ΣLV / H is greater than 15 to 30, a surge tank should be installed. Due to the large amount of civil engineering works and the long construction period, the use of a pressure regulating valve instead of a pressure regulating well can save investment and shorten the construction period.

The main body of the pressure regulating valve is arranged horizontally, that is, the center lines of the water inlet pipe and the oil cylinder are parallel to the ground, mainly composed of the valve housing, the valve plug, the main oil cylinder, the guide oil cylinder, and the air supplement valve.

The valve housing is welded or cast steel. It is composed of two semi-volute tubes symmetrical left and right. There are three open holes, one end is the water inlet, the other end is the water outlet, and the other end is reserved for connection with the main cylinder. There are fixed guide vanes in the volute tube of the valve housing, so that after the water enters, it forms a circular flow and collides with each other in the valve body to dissipate energy, and then discharges to the tail water, which has good energy dissipation performance. In order to reduce vibration, an air supplement device is provided so that the atmosphere can evenly enter the negative pressure area at the inlet end of the discharge channel of the pressure regulating valve.

The valve plug is made of cast steel with chrome-plated surface to prevent rust. The valve plug is provided with pressure equalizing holes. The purpose is to balance the water pressure on both sides of the valve plug to reduce the operating oil pressure.

The main oil cylinder and the guide oil cylinder are used to operate the switch of the valve plug. The cylinder is made of cast steel and has a piston. The oil source from the governor of the unit is connected to the front and rear chambers of the main oil cylinder piston respectively. When the unit is working normally , The pressure oil passes through the closing cavity, so that the pressure regulating valve is in the closed state; when the unit emergency shutdown or instantaneous load dump exceeds about 15%, the pressure oil will automatically pass through the opening cavity, so that the pressure regulating valve opens to release the set size Water flow to ensure the safety of the unit and pressure tunnel system.

The supplementary air valve is installed on the valve housing, which can make the atmosphere directly enter the negative pressure area at the inlet end of the drain channel of the pressure regulating valve when the pressure regulating valve is draining, so as to reduce the cavitation of the flow channel and reduce the pressure regulating valve. Vibration.

A hard seal is used between the valve plug and the valve housing, that is, a stainless steel water stop ring is fixed on the valve plug, and a removable stainless steel or bronze water stop is used on the valve housing (the stainless steel material with hardness different from the stainless steel on the valve plug is better ), Through fine grinding between the two to achieve close contact, with good water stopping properties. All parts that will move relatively between the cylinder barrel and the piston, between the piston rod and the valve housing are all sealed with a special rubber ring.

In order to realize the control of the pressure regulating valve, it is necessary to install a special main pressure control valve, a throttle valve and an oil pressure check valve for control in the hydraulic system. Among them, the special main pressure regulating valve is installed in the governor of the unit, which is the most reliable form of control with the pressure regulating valve governor. The structure of the special main pressure regulating valve is to add an additional valve disc to control the pressure regulating valve.

The characteristics of the pressure regulating valve are mainly flow characteristics (see the series of design data collection for details).

The function of the pressure regulating valve is to quickly open the pressure regulating valve at the same time when the unit guide vane is quickly closed when the unit is dumping the load, and to discharge the flow that needs to be reduced when the unit is closed from the pressure regulating valve. That is to say, after installing the pressure regulating valve, the flow rate change in the water diversion system can proceed slowly, thereby reducing the water pressure rise value. On the other hand, since the unit is still closed quickly, which ensures that the rate rise value will not be too high, the pressure regulating valve is one of the effective measures to reduce the pressure rise value of the diversion system and the unit rate rise value. The role of surge tank.