How many kinds of fire valves are there? Fire valve is used to control fluid flow, pressure and direction of the device referred to as valve. The controlled fluid can be liquid, gas, gas-liquid mixture or solid-liquid mixture. The valve is usually composed of valve body, valve cover, valve seat, opening and closing parts (disc, plug body, gate, butterfly plate, diaphragm, etc.), driving mechanism (stem and valve driving device driving it), sealing parts (packing, gasket, etc.) and fasteners, etc. The control function of the valve depends on the driving mechanism or fluid to drive the lifting, sliding, swinging or rotary movement of the hoist to change the size of the flow channel area.

Common fire valves include gate valve, globe valve, throttle valve, instrument valve, plunger valve, ball valve, butterfly valve, check valve, remote control ball valve, solenoid valve, pressure reducing valve, filter, wet alarm valve, etc. The working principles of common valves are as follows:

（1） Gate valveGate valve is one of the most common on-off valves, which uses the gate (i.e. the on-off parts, in which the on-off parts are called the gate or gate, and the gate seat is called the gate seat) to connect (fully open) or cut off (fully close) the medium in the pipeline. It is not allowed to be used for closure, and it should be avoided to slightly open the gate in use, because the erosion of high-speed flowing medium will accelerate the damage of the sealing surface. Shuangde gate in the vertical gate seat channel center line as a lifting movement, like the gate cut off the medium in the pipeline, so it is called gate valve.

According to the sealing surface configuration, gate valves can be divided into wedge gate valve and parallel gate valve. Wedge gate valve can be divided into single gate pole type, double gate plate type and elastic gate type. Parallel gate valve can be divided into single gate plate type and double gate plate type. According to the thread position of the stem, it can be divided into two types: rising stem gate valve and Non rising stem gate valve.

（2） Stop valve

The opening and closing parts of globe valve are plug-shaped disc. The sealing surface is flat or conical. The disc moves linearly along the center line of the valve seat. The movement form of stem, (common name: Non rising stem), there are also lifting rotary stem, (common name: rising stem) stop valve refers to the valve whose closing part (disc) moves along the center line of valve seat. According to the movement of the disc, the change of the valve seat opening is proportional to the disc stroke. Because the opening or closing stroke of the valve stem is relatively short, and it has a very reliable cut-off function, and because the change of the valve seat opening is directly proportional to the stroke of the valve disc, it is very suitable for regulating the flow. Therefore, this type of shut-off valve is very suitable for cut-off or regulation and throttling.

(3) throttle valve

Throttle valve is a valve that controls fluid flow by changing throttle section or throttle length. If the throttle valve and the check valve are connected in parallel, the one-way throttle valve can be formed. The throttle valve and one-way throttle valve are simple flow control valves. In the hydraulic system of quantitative pump, the throttle valve and overflow valve can be combined to form three kinds of throttle speed regulating systems, namely, the inlet throttle speed regulating system, the return throttle speed regulating system and the bypass throttle speed regulating system. Throttle valve has no flow negative feedback function, which can not compensate the speed instability caused by load change. It is generally only used in the situation of little load change or low speed stability requirements.

（4） Butterfly valve

Butterfly valve, also known as flap valve, is a simple structure control valve, which can also be used for low-pressure pipeline medium switch control. Butterfly valve in work refers to a kind of valve whose closing piece (valve disc or butterfly plate) is a disc and rotates around the valve shaft to open and close. It mainly plays the role of cutting off and throttling in the pipeline. The opening and closing part of butterfly valve is a disc-shaped butterfly plate, which rotates around its own axis in the valve body, so as to achieve the purpose of opening and closing or adjustment.

（5） Ball valve

The opening and closing part (ball) is driven by the valve stem and rotates around the axis of the valve stem. It can also be used for fluid regulation and control. There is a strong shear force between the V-type ball core and the metal valve seat of hardfacing cemented carbide. It is especially suitable for media containing fibers and small solid particles.

（6） Pressure reducing valve

The ressure reducing valve is a kind of valve that reduces the inlet pressure to a certain required outlet pressure by regulation and keeps the outlet pressure stable automatically by relying on the energy of the medium itself.

（7） Check valve

Check valve, also known as one-way valve or check valve, its function is to prevent the medium in the pipeline from backflow. The bottom valve of pump suction valve also belongs to check valve. Open and close by the medium flow and force to open or close, in order to prevent the medium backflow of the valve called check valve. Check valve is an automatic valve, which is mainly used in the pipeline with one-way flow of medium. It only allows the medium to flow in one direction to prevent accidents.

Check valve is a kind of automatic valve, its main function is to prevent medium backflow, prevent pump and drive motor reverse, as well as container medium discharge. The check valve can also be used to supply the auxiliary system whose pressure may rise above the system pressure.