Stop valve, also known as shut-off valve. During the opening and closing process, the friction between the sealing surfaces is small, relatively durable, with a small opening height, easy manufacturing, and convenient maintenance. It is not only suitable for medium and low pressure, but also for high pressure. Today, let's delve into the matter of the shut-off valve~~

Working principle of shut-off valve

The opening and closing parts of a shut-off valve are plug shaped valve discs, with a flat or conical sealing surface. The valve disc moves in a straight line along the centerline of the fluid.

The closing principle of a shut-off valve is to rely on the pressure of the valve stem to tightly fit the sealing surface of the valve disc and the sealing surface of the valve seat, preventing the flow of medium.

The shut-off valve only allows one-way flow of medium and has directional installation. The structural length of the shut-off valve is larger than that of the gate valve, and the fluid resistance is high. Therefore, the sealing reliability is not strong during long-term operation.

Classification of globe valves

Classification by channel direction

1. Straight through globe valve

The medium inlet and outlet channels are 180 ° in the same direction, and the degree of damage to the flow state is relatively small. The pressure loss through the valve is relatively small.

2. DC stop valve

The valve stem and channel form a certain angle, and the sealing surface of the valve seat and the inlet and outlet channels have a certain angle. The fluid hardly changes the direction of flow, making it the smallest flow resistance in a shut-off valve. Suitable for pipelines with coking and solid particles.

3. Angle globe valve

The medium inlet and outlet channels are not in the same direction and form a 90 ° angle, which will generate a certain pressure drop. The biggest advantage is that they can be installed at the turning point of the pipeline system, which saves bends and facilitates operation.

Classification based on the position of threads on the screw

1. Upper threaded stem globe valve

The valve stem thread is located outside the casing and does not come into direct contact with the working medium. The valve stem thread is not corroded by the medium, making it easy to lubricate and labor-saving to operate.

2. Lower threaded stem globe valve

The valve stem thread is located inside the valve body and in direct contact with the working medium. The valve stem thread is susceptible to medium corrosion and cannot be lubricated. It is often used in situations with smaller nominal diameters and low medium operating temperatures.

Classification by purpose

1. Fluorine lined shut-off valve

Fluorine lined valves, also known as fluorine plastic lined corrosion-resistant valves, are made by placing polytetrafluoroethylene resin (or processed profiles) on the inner wall of steel or iron valve pressure parts (the same method is applicable to the lining of various pressure vessels and pipeline accessories) or the outer surface of valve internals, using its unique performance in resisting strong corrosive media to make various types of valves and pressure vessels.

Fluorine lined globe valve is suitable for various concentrations of aqua regia, sulfuric acid, hydrochloric acid, hydrofluoric acid, and various organic acids, strong acids, and strong oxidizing agents at -50~150 ℃. It is also suitable for use on pipelines with various concentrations of strong alkaline organic solvents and other corrosive gases and liquid media.

2. National standard shut-off valve

The national standard globe valve is the most commonly used product in the globe valve series. The API American standard globe valve follows ANSI and API standards, and the sealing surfaces of the valve disc and valve seat are welded with Stellite cobalt based hard alloy of different hardness. The sealing is reliable, high hardness, wear-resistant, high-temperature resistant, corrosion-resistant, scratch resistant, and has a long service life.

3. Needle valve

Needle valve is a small caliber instrument valve that plays a role in opening and closing and precise flow control in instrument measurement pipeline systems. It mainly includes power station instrument series, oilfield specific series, American standard series, etc.

4. Low temperature shut-off valve

Low temperature globe valves usually refer to valves with operating temperatures below -110 ℃, widely used in liquefied natural gas, liquefied petroleum gas, and other low-temperature industries.

Currently, globe valves with temperatures up to -196 ℃ can be manufactured, and all parts are pre treated with liquid nitrogen at low temperatures to completely avoid sealing deformation and leakage during use.

5. Plunger type globe valve

Plunger valve, also known as plunger stop valve, has a radial sealing structure on its sealing surface. The two elastic sealing rings on the polished plunger are applied to the valve cover through the connecting bolts between the valve body and the valve cover to compress the elastic sealing rings around the plunger to achieve a sealed stop valve.

6. Insulation jacket globe valve

The insulated jacket globe valve adopts an insulated jacket design, which utilizes an external heat source to circulate and heat the valve externally, effectively preventing temperature loss when the medium passes through the valve and ensuring the temperature of the medium.

7. Oxygen dedicated shut-off valve

The oxygen dedicated shut-off valve is made of high-quality silicon brass or stainless steel casting, which has advantages such as high mechanical strength, wear resistance, and good safety.

Used on oxygen pipelines, it has the best explosion-proof and flame-retardant performance, eliminating unsafe factors on oxygen pipelines, and is widely used in pipeline networks for oxygen engineering such as steel, metallurgy, petrochemical, and chemical engineering. In addition to having the functions of ordinary valves, it also has its own characteristics.

Strict oil prohibition measures are adopted during manufacturing, and all parts undergo strict degreasing treatment before installation.

8. Bellows globe valve

The corrugated pipe stop valve adopts a shaped stainless steel corrugated pipe design. The corrugated pipe has undergone 10000 reciprocating tests without any faults, and its sealing performance is reliable. The corrugated pipe stop valve is suitable for industries with flammable, explosive, toxic and harmful media, and can effectively prevent valve leakage.

(Keywords: globe valve, bellows globe valve)