Structural Characteristics of Electrically Controlled Gate Valves

The structural design of electrically controlled gate valves is closely related to their functional characteristics and applicable working conditions. The core is to achieve the on or off and adjustment of the medium through the lifting and lowering of the gate, while combining with electric actuators to achieve automation control. Its structural characteristics can be analyzed from the aspects of core components, sealing design, drive system, and special working condition adaptation.

1.  Core Components and Overall Structure

The electrically controlled gate valve consists of five core parts: valve body, gate plate, valve stem, valve seat, and electric actuator. It has a "vertical lifting" structure as a whole, and its specific characteristics are as follows.

Valve body: As the main frame of the valve, it is usually manufactured using casting (gray cast iron, ductile iron) or forging (carbon steel, stainless steel) processes, with internal flow channels (matching the diameter of the pipeline) and gate chambers. Large caliber valve bodies (DN500 and above) are often designed as split type (left and right valve bodies are connected by flanges) for easy processing and installation. Small caliber valve bodies (below DN200) are integral, with a more compact structure and stronger pressure resistance.

Gate Valves: As a key component for controlling the opening and closing of the medium, it is flat or wedge-shaped and rises and falls vertically along the axis of the valve stem. According to sealing requirements, it can be divided into the following types.

1. Parallel gate valves: The sealing surfaces on both sides are parallel, which are suitable for low-pressure soft sealing (such as PTFE sealing), and sealing is achieved by the flat fit between the gate and the valve seat.

2. Wedge gate valves: The sealing surface has a certain angle (usually 3 ° -5 °), and it is suitable for high-pressure hard sealing (metal to metal), relying on the "self tightening force" of the wedge structure to enhance the sealing effect, and it is more reliable under high temperature and high pressure.

Valve stem: a transmission component that connects the gate and actuator, using trapezoidal thread or ball screw structure to convert the rotational motion of the actuator into the linear lifting of the gate. To prevent medium leakage, a packing box (with built-in flexible packing such as graphite or PTFE) or bellows sealing structure is installed between the valve stem and the valve body.

Valve seat: it is fixed on the inner wall of the valve body, forming a sealing pair with the gate plate. The material is selected according to the characteristics of the medium (such as hard alloy welding for hard seals and rubber/PTFE for soft seals). Some models are designed with "replaceable valve seats" to facilitate the replacement of worn parts during later maintenance.

Electric actuator: it is installed on the top of the valve body, consisting of a motor (servo motor/ordinary asynchronous motor), reduction gearbox, position sensor, and control module, providing power for gate lifting and achieving precise control of opening (supporting 0-100% stepless adjustment).

2.Characteristics of the Design of the Sealing Structure 

Sealing performance is the core advantage of gate valves, and their structural design directly affects the leakage rate. The main features include the following points.

Internal seal valves (gate and valve seat):

Hard seal valves: The sealing surface of the gate and valve seat is welded with hard alloy (such as Stellite 6) or sprayed with ceramic coating, with a surface roughness of ≤ Ra0.8 μ m and a flatness of ≤ 0.01mm/m. We achieve metal to metal sealing through precision grinding, and it is suitable for high temperature (≤ 600 ℃), high pressure (≥ 10MPa), and particulate media (such as steam and slurry).

Soft seal valves: The valve seat is embedded with elastic materials such as PTFE and EPDM, and the gate plate adopts a smooth metal surface. By relying on the deformation compensation of the elastic material to seal the gap, zero leakage can be achieved (in accordance with ISO 15848-1 Class A), which is suitable for low pressure (≤ 1.6MPa) and clean media (such as tap water and food grade fluids).

Combination seal valves: Some models adopt a "hard seal+soft seal" composite structure (such as soft seals on both sides of the gate and hard seals at the bottom), which balances low-pressure sealing and high-pressure reliability.

External seal valves (valve stem and valve body):

Conventional design: using V-shaped composite packing (graphite+ PTFE), sealing is achieved through pre tightening force of the gland. It's suitable for general working conditions, and the gland needs to be tightened regularly to compensate for packing wear.

Bellows sealing valves: For toxic, flammable and explosive media (such as chlorine gas, natural gas), metal bellows (stainless steel material) are welded to the valve stem to achieve "zero leakage", with a service life of ≥ 100,000 opening and closing cycles and no need for frequent maintenance.

3.Characteristics of Drive and Transmission Structure

The transmission design of electric actuators and valve stems determines the control accuracy and response speed, with the following characteristics.

Deceleration transmission: The output speed of the motor is reduced by a gearbox (spur gear/worm gear), increasing the output torque (torque range from tens of N · m to tens of thousands of N · m), matching the opening and closing requirements of different caliber valves (large-diameter valves require greater torque to overcome medium pressure).

Position feedback: The actuator is equipped with an encoder or potentiometer, which monitors the displacement of the valve stem in real time and feeds back the opening signal (4-20mA or digital signal) to the control system to ensure adjustment accuracy (error ≤± 1%).

Manual emergency mechanism: The actuator integrates a handwheel or handle, which switches to manual mode through a clutch. In the event of a power outage or motor failure, the handwheel is manually rotated to drive the gate to rise and fall, ensuring operational feasibility in emergency situations.

4. Structural Characteristics Adapt to Special Working Conditions

To adapt to extreme or complex working conditions, electrically controlled gate valves will undergo targeted structural optimization.

Anti-blocking design: For media containing particles and high viscosity (such as sludge and syrup), a "knife shaped gate" (with sharp edges) is used to cut off fiber impurities in the medium.  The flow channel is designed as a "straight through type" to reduce dead corners and avoid the accumulation of impurities.

Low temperature/high temperature adaptation: Long neck valve covers are used for low temperature conditions (such as LNG transportation, -162 ℃) to avoid the transfer of valve body cooling to the actuator, which may cause icing. Under high temperature conditions (such as steam pipelines, 540 ℃), a heat sink structure is used to reduce the working environment temperature of the actuator, while the valve stem is made of high-temperature resistant alloy (such as Cr12MoV) to prevent creep.

High pressure adaptation: High pressure gate valve (PN160 or above), the valve body adopts forging technology, and the wall thickness is increased by 30% to 50% compared to conventional models. The gate and valve seat adopt a "pressure self-sealing" structure (the higher the medium pressure, the tighter the sealing surface adheres) to avoid leakage under high pressure.

Anti-corrosion design: For strong corrosive media such as acid and alkali, the valve body is made of fully lined fluorine (PTFE) or duplex stainless steel (2205) material, the valve stem is made of Hastelloy alloy, and all metal parts are passivated to enhance corrosion resistance.

The product features "vertical lifting transmission, high-precision sealing pair, and integrated electric drive", which not only retains the advantages of traditional gate valves such as "low flow resistance and strong sealing", but also achieves automation control through electric actuators. 

Structural optimization under different working conditions (such as sealing materials, valve body strength, transmission mode) enables it to adapt to a wide range of scenarios from low pressure and room temperature to high pressure and high temperature, from clean fluids to strongly corrosive media, and is one of the core equipment for industrial fluid control.