pneumatic gate valve – ZECO Valve

How do Gate Valves Work?

Jerry — Wed, 29 Dec 2021 07:10:15 +0000

All valves are designed to stop, allow, or throttle the flow of a process fluid. Gate valves—one of the original valve designs—are ideally suited for on-off, primarily liquid, service. A gate valve functions by lifting a rectangular or circular gate out of the path of the fluid. When the valve is fully open, gate valves are full bore, meaning there is nothing to obstruct the flow because the gate and pipeline diameter have the same opening. This bore diameter also determines the valve size. An advantage of this full bore design is very low friction loss, which saves energy and reduces the total cost of ownership.

What Is a Gate Valve?

The gate valve is a member of the linear industrial valve family designed to stop or allow media flow. This valve is bi-directional with a wedge-like disc that can cut through media with thicker particles such as the slurry. The shutoff action is provided by moving the wedge upwards to open or downwards to close the valve.

As with most shut-off valves, the gate valve is not recommended to use for throttling although it has the capacity to do so, albeit limited. Its wedge gate is highly prone to damage caused by the vibration of the moving media.

How do Gate Valves Work?

The opening and closing part of a gate valve is the gate, the movement direction of the gate is perpendicular to the direction of the fluid, gate valve can only be fully open and fully closed, and can not be adjusted and throttled.

The gate has two sealing surfaces. The two sealing surfaces of the most commonly used gate valves form a wedge shape. The wedge angle varies with the valve parameters, usually 5 °, and 2 ° 52 ‘when the medium temperature is not high. The gate of the wedge gate valve can be made into a whole, called a rigid gate; it can also be made into a gate that can produce a small amount of deformation to improve its processability and make up for the deviation of the sealing surface angle during processing. The plate is called a spring gate.

When the gate valve is closed, the sealing surface can be sealed only by the pressure of the medium, that is, the sealing surface of the gate is pressed against the valve seat on the other side to ensure the sealing of the sealing surface, which is self-sealing.

Most gate valves are forcedly sealed, that is, when the valve is closed, the gate is forced to be pressed against the valve seat by an external force to ensure the tightness of the sealing surface. The gate of the gate valve moves linearly with the valve stem, which is called a lift lever gate valve, also known as an open lever gate valve. Usually, there is a trapezoidal thread on the lifting rod. The nut at the top of the valve and the guide groove on the valve body change the rotary motion into a linear motion, that is, the operating torque is changed to the operating thrust. When the valve is opened, when the lift height of the gate is equal to 1: 1 of the valve diameter of the valve, the fluid channel is completely unblocked, but this position cannot be monitored during operation. In actual use, the apex of the valve stem is used as a mark, that is, the position that cannot be opened, as its fully open position. In order to consider the lock-up phenomenon due to temperature changes, it is usually opened to the top position, and then back to 1/2-1 turn, as the position of the fully open valve. Therefore, the fully open position of the valve is determined by the position of the shutter, that is, the stroke. In some gate valves, the stem nut is set on the gate plate. The hand wheel rotates to drive the valve stem to rotate, and the gate plate is lifted. This kind of valve is called a rotary lever gate valve, or a dark lever gate valve.

Gate valve Operation

A gate valve operates similar to other valves. To open the valve, turn the handwheel (A), which moves the gate (G) up or down on the stem (B) via the threads. A gate valve requires more than one 360° turn to open or close the valve fully. When the gate is lifted up, it opens the inlet to the outlet allowing an unobstructed passageway for the media to flow. When the gate is lowered, it closes and blocks the media flow.

The relationship between the gate’s vertical travel and the flow rate is nonlinear for a gate valve, with the greatest changes occurring near-complete closure. When used to regulate flow, the relatively high velocity of the flow at partial opening results in gate and seat wear, which along with possible vibrations of the gate, shortens the valve’s service life. Therefore, a gate valve should only be used for on/off control.

Gate valve Actuation Method

There are three main types of gate valve actuation methods:

Manual gate valve: A manual gate valve has a manually spun handwheel to open or close the valve, as shown in Figure 3. This requires a user on-site to spin the wheel. A manual gate valve is the most economical, especially since the usage of gate valves once installed is typically low.

Pneumatic gate valve: A pneumatic gate valve uses a pneumatic actuator instead of a handwheel. By utilizing compressed air, the actuator can spin the stem to raise or lower the gate. This allows it to be operated remotely with no user on-site but requires a pneumatic system on site.

Electric gate valve: An electric gate valve uses an electric motor instead of a handwheel. By utilizing electrical power, the actuator spins the stem to raise or lower the gate. This allows it to be operated remotely with no user on-site but requires electrical power on-site. These are also referred to as motorized gate valve

Gate Valve Movement

When the gate valve is closed, the sealing surface can be sealed only by the medium pressure, that is, only by the pressure of the medium z41h flange wedge gate valve. . Most gate valves are forcibly sealed, that is, when the valve is closed, the gate is forced to be pressed against the valve seat by external force to ensure the tightness of the sealing surface. Movement mode: The gate of the gate valve moves linearly with the valve stem, also known as the open-rod gate valve. There is usually a trapezoidal thread on the lifting rod. The nut at the top of the valve [] and the guide groove on the valve body change the rotary motion into linear motion, that is, the operating torque is changed to the operating thrust. When the valve is opened, when the lift height of the gate is equal to 1: 1 of the valve diameter, the fluid channel is completely clear, but this position cannot be monitored during operation. In order to consider the lock-up phenomenon due to temperature changes, it is usually opened to the top position, and then back to 1/2-1 turn, as the position of the fully open valve. Therefore, the fully open position of the valve is determined according to the position of the gate (ie, the stroke>. Some gate valve stem nuts are located on the gate, and the handwheel rotates to drive the valve stem to rotate, and the gate is lifted. It is called a rotary lever gate valve or a dark lever gate valve.

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Pneumatic Valve Accessories – Pneumatic Actuator Accessories

Jerry — Wed, 29 Dec 2021 05:16:55 +0000

Valves are used to control pressure and flow in a pneumatic system, but they require the use of additional accessories to provide smooth and efficient operation. Accessories including gauges, operators, switches, foot pedals, and mounting brackets are used for the installation and operation of pneumatic control valves. It is important to choose accessories that are compatible with your pneumatic valves to ensure safety and accuracy, and to increase efficiency and productivity.

Pneumatic control valve accessories help ensure optimal performance and are an essential component in a pressure control system. Electric switches help bridge the communication gap between a valve operator and control system, helping to control accuracy. Various styles of operators allow for manual and pneumatic actuation of control valves and mounting brackets are used to mount directional control valves to machinery.

Purpose of Pneumatic Valve Accessories

There are five basic reasons that accessories are added to a control valve:

Improve process control
Improve safety for the process or personnel
Improve valve performance or speed of response
Monitor or verify the valve responsiveness
Diagnose potential valve issues

Pneumatic Accessories For Pneumatic Actuator

Electro-pneumatic valve positioner:

The valve positioner is the main accessory of the pneumatic actuator. It is used in conjunction with the pneumatic actuator to improve the position accuracy of the valve, overcome the influence of the friction force of the valve stem and the unbalanced force of the medium, so as to ensure that the valve is realized in accordance with the signal from the regulator position it correctly.

Under the following circumstances, a positioner is required:

When the medium pressure is high and the pressure difference is large;
When the caliber of the regulating valve is large (DN>100);
High temperature or low-temperature control valve;
When it is necessary to increase the operating speed of the regulating valve;
When using standard signals to operate non-standard spring actuators (the spring range is outside of 20～100KPa);
When used for split-range control;
When the valve realizes the reverse action (the air-to-close type and the air-to-open type are interchanged);
When the flow characteristics of the valve need to be changed (the positioner cam can be changed);
When there is no spring actuator or piston actuator, it is necessary to achieve proportional action;
When using electrical signals to operate pneumatic actuators, power must be distributed to the pneumatic valve positioner.

Solenoid valve:

When the system needs to achieve program control or two-position control, it needs to be equipped with a solenoid valve. When the solenoid valve is selected, in addition to considering the AC and DC power supply, voltage, and frequency, the relationship between the solenoid valve and the regulating valve must be paid attention to. It can be used as “Normally open” or “normally closed”. If you need to increase the capacity of the solenoid valve to shorten the action time, you can use two solenoid valves in parallel or use the solenoid valve as a pilot valve in combination with a large-capacity pneumatic relay.

Air filter pressure reducing valve:

The air filter pressure reducing valve is an accessory in the industrial automation instrument. Its main function is to filter and purify the compressed air from the air compressor and stabilize the pressure at the required value. It can be used for various pneumatic instruments, solenoid valves, Air supply, and voltage stabilizing devices for cylinders, spraying equipment, and small pneumatic tools.

Travel switch (responder):

The travel switch reflects the two extreme positions of the valve switch and sends out an indication signal at the same time. Based on this signal, the control room can betray the switch state of the valve in order to take corresponding measures.

ZECO Valve is a professional pneumatic ball valve manufacturer, if any inquiries, please be free to contact us,

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