Rotary valve features and types

Rotary valve features and types:

1, the characteristics of rotary valve:

Valves are usually divided into two categories: straight stroke and rotary. The linear valve allows or cuts the flow through a linear moving part such as a gate. Straight-stroke valves include globe valves, gate valves, and diaphragm valves. Rotary valves allow or cut off the flow through a rotating part. A rotary valve that can rotate 90 degrees in a rotating part is called a 1/4 rotary valve. Sometimes the classification of a 1/4-rotary valve can be extended to a rotary valve with a rotation angle of less than 270 degrees. As can be seen from the definition, a rotary valve is a rotary valve that changes the valve from an open position to a closed position by rotating a rotating member such as a rotating baffle by 90 degrees. Rotary valves generally have the following features.

(1) Wide adjustable range

In the process industry, the adjustable range is the most critical. The adjustable range of the rotary valve is approximately 150:1 (the adjustable range of the VALTEK ball valve can reach 300:1, and the adjustable range of the butterfly valve and the cam deflection valve is 100: 1). The corresponding cut-off valve has an adjustable range of 30:1, which means that the rotary valve can provide a five-fold adjustable range. For example, at a maximum flow rate of 1000 liters per minute, the cut-off valve can effectively reduce the flow to 30 liters/minute, while the rotary valve can adjust the flow to less than 10 liters/minute, the more accurate the control flow for the critical valve in the process The better the medium repeatability, directly reduces the unqualified products in the process industry.

The two features of the eccentric rotary valve increase its adjustable range. The first is its orifice plate design. The eccentricity is an effective 1/4 circle. The eccentric spool is V-shaped. The traditional spool is Park-shaped, when the eccentric rotary valve is closed, its small V-shape allows very precise control at low flow rates. For large flows, it opens the valve almost to the same diameter as the pipe. The second feature is the execution of the stroke of the machine. The actuator of the rotary valve has two types of membrane method and cylinder with a certain stroke. The stroke of the 1" globe valve is approximately 3/4" to 7/8" while the stroke of the rotary valve exceeds 2". For any other size valve. The greater the stroke at the input, the better the control at the working end.

High-adjustable control valves provide precise ratios according to recipe requirements. Regardless of the size of flow in each flow path, conventional linear or regulating valves no longer adapt to such tasks. Rotary valves can increase device performance while reducing control valves. Plant life cycle costs. The wide adjustable range of rotary valves allows the user to increase the strictness of standards and increase the cost/benefit indicators. Metal seats combined with villages made of special materials can extend valve life and improve valve performance. The design of a simple rotating structure can minimize maintenance work. Reduce the owner's production costs.

(2) strictly close

The shaft of the linear valve is the valve stem in and out of the valve body, which brings out the product every cycle. It is difficult to avoid leakage for the straight stroke design. It can bring unwanted products into the production process system, and can produce large Unacceptable factory volatile external leakage. Rotary valve rotary design does not inherently have this problem because it uses a low-hysteresis, high-thrust cylinder actuator that provides more precise and higher stability than other forms of actuators, and can provide long-term tightness Cut off the metal seat.

(3) large circulation capacity

The capacity of the linear valve is the fraction of the pipeline capacity of the installed valve. The method of increasing the capacity is to increase the size of the linear valve, which is usually larger than the pipeline. Rotary valve capacity is about 2 to 3 times that of the same size of linear valve, rotary valve can be used to increase the blending volume without changing the size of the feed line, which can greatly reduce the cost, for this reason, part of the rotary valve has The flanges designed to replace the shut-off valve face the flange surface and are equipped with connecting bolts, which are even cheaper than the shut-off valves they replace.

(4) Anti-cavitation

In the process industry, throttling can cause a lot of cavitation, cavitation can damage the pipeline, produce unacceptable noise levels, and can also cause disturbances in the metering system causing unclear or unreliable readings. The rotary valve has a sturdy design This greatly reduces the failure of the valve due to the water hammer phenomenon. At the same time, the valve core can absorb some of the excess energy, significantly reducing cavitation and related problems.

(5) No external leakage

The standard rotary valve is 100 times more leaky than the standard globe valve design. The stem movement of the stop valve pulls the dust out and forces the sand into the valve, damaging the graphite packing. In the rotary valve, the valve stem does not make any movement in and out, but performs a rotary motion so as not to damage the packing and avoid external leakage.

(6) Maintenance costs and spare parts

Metal seat rotary valves have much less spare parts than stop valves, and maintenance is usually easier.

2, the type of rotary valve:

2.1, according to the type classification

Rotary valves are categorized into three types according to the type: butterfly valve, ball valve and plunger valve.

1). Butterfly valve: The direction of the flow is controlled by rotating the baffle or blade around the rotation axis at a certain angle. The baffles or blades look a bit like a butterfly. The butterfly valve can act as a shut-off or adjustment and is suitable for slurries or fluids with suspended solids.

2). Ball valve: Its valve core is a spherical body with a round hole. When the valve is in the open position, fluid is allowed to flow. The ball is rotated 90 degrees to cut off the flow. The ball valve can play a role in cutting and regulating. It has a small pressure drop and is suitable for viscous and corrosive fluids and slurry cryogenic fluids. Ball valves can also be used for high temperature, high pressure fluids.

3). Plunger valve: Its valve core is a conical or cylindrical plunger with a round hole in the middle. When the plunger hole and the flow direction are the same, the fluid can pass. When the plunger rotates 90 degrees in any direction, the flow path Was cut off. Plunger valves are commonly used for on/off control.

2.2. Classification according to operation mode

Rotary valves are categorized according to the mode of operation as follows: manual valves, automatic valves and regulating valves.

1). Manually rotating valve: Hand operation is performed by manual actuators such as hand levers, gears, hand wheels, etc., including a component that can rotate 90 degrees. The actuator opens and closes the valve by operating the valve stem and the flow control element.

2) Automatic rotary valve: includes an automatic actuator that uses external energy to automatically control or remotely open and close the valve. In general, automatic valves should be used in the following cases: large valves (eg, valves larger than 8”) and valves that are difficult to operate manually. It is not possible to use manually operated valves in toxic or other harsh environments. Valves that close quickly; Valves that fit all flow paths in a batch recipe, etc. The types of automatic actuators include hydraulic, pneumatic, and electric, etc. Most automatic rotary valves can be operated by electric and pneumatic actuators.

3) Rotary regulating valve: It can operate at a specific opening. This type of valve includes an actuator that can generate a corresponding rotation angle according to the size of the electrical signal. Butterfly valves are often used in low-pressure, large-diameter controls that require less stringent leakage. A rotary control valve is a type of control valve. The control valve also includes some straight stroke valves such as stop valves, gate valves, and diaphragm valves. The automatic rotary cut-off valve is not a control valve because it can only be limited to open and closed positions.