The correct selection method of the valve
Valves play an increasingly important role in today's industrial construction. This is due to the diversity of valve types and functions, but the valves used in different applications are different. Today, Xinhong valve manufacturer will tell you about different valves. The difference has been characterized.
The gate valve is used as a cut-off medium. When fully open, the entire flow is straight, and the pressure loss of the medium is minimal at this time. Gate valves are usually suitable for conditions that do not require frequent opening and closing, and keep the gate fully open or fully closed. Not intended for use as regulation or throttling. For high-speed flowing media, the gate can cause vibration of the gate when it is partially opened, and the vibration may damage the sealing surface of the gate and the valve seat, and the throttling will cause the gate to be eroded by the medium.
From the structural form, the main difference is the form of the sealing element used. According to the form of the sealing element, the gate valve is often divided into several different types, such as wedge gate valve, parallel gate valve, parallel double gate gate valve, wedge double gate gate, etc. The most common forms are the wedge gate valve and the parallel gate valve.
The stem axis of the globe valve is perpendicular to the sealing surface of the valve seat, the opening or closing stroke of the valve stem is relatively short, and it has a very reliable cutting action, which makes this valve very suitable for medium cutting or adjustment and throttling. Once the disc of the globe valve is in the open state, the contact between its valve seat and the sealing surface of the disc is no longer in contact, and has a very reliable cut-off action, so this valve is very suitable for medium cut-off or adjustment and control. stream usage. Once the globe valve is in the open state, there is no longer any contact between its seat and the sealing surface of the disc, so the mechanical wear of its sealing surface is small, because the seat and disc of most globe valves are relatively easy to repair or replace. It is not necessary to disassemble the whole valve from the pipeline when sealing the element, which is very suitable for the occasion where the valve and pipeline are welded into one. The flow direction of the medium changes when passing through this type of valve, so the flow resistance of the globe valve is higher than that of other valves.
Shut-off valve
Commonly used globe valves are as follows:
1. Angle type globe valve; In the angle type globe valve, the fluid only needs to change direction once, so that the pressure drop through the valve is smaller than that of the conventional structure globe valve.
2. DC globe valve; in the DC or Y-shaped globe valve, the flow channel of the valve body and the main channel form a diagonal line, so that the degree of damage to the flow state is smaller than that of the conventional globe valve, so the pressure loss through the valve is also corresponding. 's small.
3. Plunger globe valve: This form of globe valve is a variation of the conventional globe valve. In this valve, the disc and seat are usually designed based on the plunger principle. The valve disc is polished so that the plunger is connected with the valve stem, and the sealing is realized by two elastic sealing rings sleeved on the plunger. The two elastomeric seals are separated by a collar and compress the seal around the plunger by the load applied to the bonnet by the bonnet nut. Elastomeric seals are replaceable and can be made of a variety of materials, the valve is mainly used for "open" or "closed", but is available with special forms of plungers or special collars and can also be used to regulate flow .
Butterfly valve
The butterfly plate of the butterfly valve is installed in the diameter direction of the pipeline. In the cylindrical channel of the butterfly valve body, the disc-shaped butterfly plate rotates around the axis, and the rotation angle is between 0° and 90°. When it rotates to 90°, the valve is fully open. The butterfly valve is simple in structure, small in size and light in weight, and only consists of a few parts. And it only needs to rotate 90° to open and close quickly, the operation is simple, and the valve has good fluid control characteristics. When the butterfly valve is in the fully open position, the thickness of the butterfly plate is the ultimate resistance when the medium flows through the valve body, so the pressure drop generated by the valve is very small, so it has better flow control characteristics. Butterfly valves have two types of seals: elastic seal and metal seal. Elastic sealing valve, the sealing ring can be inlaid on the valve body or attached to the periphery of the disc. Valves with metal seals generally have a longer life than those with elastic seals, but it is difficult to achieve complete sealing. Metal seals can adapt to higher operating temperatures, while elastomeric seals have the disadvantage of being limited by temperature. If the butterfly valve is required to be used as flow control, the main thing is to correctly select the size and type of the valve. The structure principle of the butterfly valve is especially suitable for making large-diameter valves.
Butterfly valves are not only widely used in general industries such as petroleum, gas, chemical, and water treatment, but also in cooling water systems in thermal power plants. Commonly used butterfly valves are wafer type butterfly valve and flange type butterfly valve. The wafer type butterfly valve uses studs to connect the valve between the two pipeline flanges. The flange type butterfly valve has a flange on the valve, and the flanges at both ends of the valve are connected to the pipeline flange with bolts.
The ball valve is evolved from the plug valve. It has the same lifting action of rotating 90 degrees, the difference is that the cock body is a sphere with a circular through hole or channel through its axis. The ratio of the spherical surface to the channel opening should be such that when the ball rotates 90 degrees, all spherical surfaces should be present at the inlet and outlet, thereby truncating the flow. The ball valve can be closed tightly with only a 90-degree rotation operation and a small torque. The completely equal valve body cavity provides a low resistance, straight-through flow path for the medium. It is generally believed that ball valves are most suitable for direct opening and closing, but recent developments have designed ball valves so that they can be used for throttling and flow control. The main feature of the ball valve is its compact structure, easy operation and maintenance, suitable for general working media such as water, solvent, acid and natural gas, and also suitable for media with harsh working conditions, such as oxygen, hydrogen peroxide, methane and ethylene.
The ball valve body can be integral or combined. The valve is selected according to preventing the backflow of the medium. The function of this type of valve is to only allow the medium to flow in one direction and prevent the flow in one direction. Usually this kind of valve works automatically. Under the action of fluid pressure flowing in one direction, the valve flap opens; when the fluid flows in the opposite direction, the fluid pressure and the self-coincident valve flap of the valve flap act on the valve seat, thereby cutting off the flow. Among them, the check valve belongs to this type of valve, which includes swing check valve and lift check valve. Swing check valves have a hinge mechanism and a door-like disc that rests freely on the sloping seat surface. In order to ensure that the valve disc can reach the proper position of the valve seat surface every time, the valve disc is designed in the hinge mechanism, so that the valve disc has enough swing space and makes the valve disc truly and comprehensively contact the valve seat. The disc can be made entirely of metal, or inlaid with leather, rubber, or synthetic overlays, depending on the performance requirements. In the fully open condition of the swing check valve, the fluid pressure is almost unimpeded, so the pressure drop across the valve is relatively small. The disc of the lift check valve is seated on the sealing surface of the valve seat on the valve body.
Except that the valve disc can rise and fall freely, the rest of the valve is like a globe valve. The fluid pressure lifts the valve disc from the sealing surface of the valve seat, and the backflow of the medium causes the valve disc to fall back to the valve seat and cut off the flow. According to the conditions of use, the disc can be of all-metal structure, or it can be in the form of a rubber pad or rubber ring embedded on the disc holder. Like the globe valve, the passage of fluid through the lift check valve is also narrow, so the pressure drop through the lift check valve is larger than that of the swing check valve, and the flow of the swing check valve is limited rare. Valves are selected according to the parameters of the adjusted medium In the production process, in order to make the parameters such as pressure and flow of the medium meet the requirements of the technological process, it is necessary to install an adjusting mechanism to adjust the above parameters. The main working principle of the adjustment mechanism is to adjust the above parameters by changing the flow area between the valve disc and the valve disc and the valve seat.
Valves belonging to this category are collectively referred to as control valves, Xinhong Valve is a professional valve manufacturer in China, specialized in various kinds of valve wholesale and manufacturer for more than 20 years, welcome to get info!
Comments
Post a Comment