What Is The Working Principle Of A Sanitary Sewage Valve?

Explanation of the Working Principle of Sanitary Sewage Valves
Sanitary sewage valves are specially designed to treat sanitary sewage and play a vital role in sewage treatment and pipeline discharge systems. They work based on fluid flow control. Through different structural design and driving methods, while meeting sanitary requirements, the functions of sewage interception, discharge and regulation are realized to prevent sewage leakage and environmental pollution. The following details the working principle of different types of sanitary sewage valves.
Gate Valve Type Sanitary Sewage Valves
Structural Characteristics
Gate valve sanitary sewage valves mainly consists of valve body, gate, valve stem and drive device. The valve body has a media passage, and the gate can move vertically and linearly in the direction of fluid flow to open and close the valve. Depending on the threaded position of the stem, it can be divided into ascending and stem types, and wedge and parallel stem according to the structural characteristics of the gate.
Principles of work
When sewage needs to be discharged, the drive rotates the stem. In an ascending stem gate valve, the valve stem thread is located outside valve cover. As the valve stem rises, the gate moves upward, away from the seat cover, allowing sewage to pass through the valve passage. When the gate is fully raised, fluid can pass through the valve unimpeded, reaching a state of complete opening. When it is necessary to close the valve to cut off sewage flow, the drive is reversed, the stem descends, and the gate moves down, finally pressing against the valve seat sealing surface to prevent sewage from continuing to flow to full closure.
In a non-ascending stem gate valve, the valve stem thread is located in the valve cover. When opened, the valve stem does not rise. Instead, the rotation of the valve stem drives the gate to move linearly, opening and closing the valve. Its working principle is similar to vertical stem, but the overall structure is more compact, suitable for the application of limited installation space.
The seal cover of the wedge gate is formed at a certain angle to the vertical centerline, usually 2-5 degrees, 8°-10°, etc., depending on the temperature of the medium. The higher the working temperature, the greater the sealing angle to reduce the likelihood of wedge formation due to temperature variations. In the closing process, under the action of middle pressure and stem thrust, valve stem gate clings to the seat the valve seat sealing surface to form a reliable seal. The two sealing surfaces of the parallel gate valve are parallel. In parallel gate valves, thrust wedges are the most common, i.e., there is a two-sided thrust wedge between the two gate valves. Some gates also have springs between them that create tension and help seal the gates. Parallel gate valves are suitable for low, medium and small caliber pipelines.
Butterfly Valves Valve
Structural features: Butterfly valve (sanitary sewage valves) consists mainly of valve body, butterfly plate, valve stem and sealing device. The butterfly plate is a disc-shaped opening and closing element mounted on the diameter direction of the pipe and rotates around valve stem. According to the sealing method, it can be divided into elastic seal and metal seal. Flexible butterfly valve seal ring is usually embedded in valve body or attached to the outside of the butterfly plate, good sealing performance, but its sealing is very limited by temperature. Metal sealing butterfly valves can withstand high operating temperatures, but it is difficult to achieve complete sealing.
How it works: When sewage needs to be discharged, the drive rotates valve stem so that the butterfly plate rotates at an angle around its axis, typically 0°-90°. When the butterfly plate rotates parallel to the pipe axis, the valve opens, allowing sewage to flow smoothly through the valve passage. Butterfly valve is characterized by a fast opening and closing speed, from full opening to full closing requires 90 ° rotation, easy remote control. When the valve needs to be closed to cut off sewage flow, the drive will operate in reverse, causing the valve stem to rotate the butterfly plate perpendicular to the pipe axis. The butterfly plate presses the valve seat sealing surface tightly to prevent sewage from passing through and closes the valve.
Butterfly valve has the characteristics of low fluid resistance and good flow control and is suitable for adjusting and cutting off medium flow. Its simple structure, small size, light weight, easy to operate, suitable for manufacturing large diameter valves, widely used in low and mediumpressure pipeline system.
Ball Valves for Sanitary Wastewater Use
Structural characteristics: Ball valves for sanitary wastewater use consists of valve body, ball body, valve stem and sealing device. The ball has a circular opening or passage. By rotating the sphere, the holes in the sphere are aligned or perpendicular to the pipe axis, opening and closing the valve. According to the structure of the sphere, it can be divided into floating ball valves, fixed ball valves and elastic ball valves.
How it works: In a floating ball valve, the ball floats. Under the pressure of the medium, the ball can produce a certain displacement, pressing the the sealing surface of the outlet end, ensuring the seal of the outlet end. When it is necessary to open the valve to discharge wastewater, the drive rotates the stem 90 degrees, aligning the hole in the stem with the pipe axis, allowing wastewater to flow smoothly through the valve channel. When it is necessary to close the valve to cut off sewage flow, the drive operates in reverse, rotating the stem 90 degrees so that the hole in the ball is perpendicular to the pipe axis. Under the pressure of the medium, the ball is pressed on the sealing surface of the outlet end, and the sealing ring of the inlet end is also in tight contact with the ball to achieve a bidirectional seal and prevent sewage from passing through.
Bearing of fixed ball valves is usually mounted on the upper and lower shaft of the ball club, so operating torque is low, suitable for high voltage and large diameter applications. The working principle is similar to that of floating ball valve, but in the process of opening and closing, the ball moves more smoothly and the sealing performance is more reliable. The sphere of the flexible ball valve is elastic and is achieved through an elastic groove at the lower end of the inner wall of the sphere. This valve is suitable for high temperature and high pressure media. When the channel is closed, the wedge head of the valve stem opens the sphere and presses the sphere against valve seat for sealing.
Dirt Check Valves check valve
Structural Characteristics: sanitary drain valve check valve according to its structure can be divided into lift type and swing type. A lift check valve's valve disc moves up and down the vertical centerline, relying on fluid pressure and its own gravity to open and close the valve. The disc of the rotary swing check valve revolves around the pin outside the valve seat. It works in a similar way to lift type, except the discs movement differently.
How it works: When sewage is flowing forward, fluid pressure pushes the lift check valve disc up, opens the valve and allows sewage to flow smoothly through the valve passage. When sewage reverses, the disc drops under gravity and reverse pressure, squeezing the valve seat sealing surface and closing the valve to prevent backflow. When sewage flows forward, the swing check valve rotates around its pin at an angle under fluid pressure, away from the valve seat sealing surface, and opens the valve. When sewage reverses, the disc rotates in reverse under gravity and reverse pressure, squeezing the valve seat sealing surface and closing the valve to prevent backflow.
The main function of the check valve is to prevent dielectric backflow and to protect equipment and components in the pipeline system from damage caused by dielectric backflow. It is a kind of automatic valve that does not require external force to operate, is a reliable valve. However, it is generally suitable for clean media, not suitable for media containing solid particles or high viscosity, otherwise it is easy to cause disc adhesion, affecting the normal operation of the valve.
Special Function Sanitary Sewage Valve
Sleeve-Type Sewage Valve
Structural characteristics: casing drain valve adopts cage labyrinth structure for throttling, with a multi-stage throttling design. valve seat cover is a tapered design, the disc has a balance hole and a piston seal. The packing adopts V-shaped structure and the stuffing box has auxiliary sealing and grease injection structure. This valve allows replacement of fillings and other vulnerable parts under pipeline pressure. A drain hole is provided at the bottom of the valve. O-ring seal on the outer disc circle.
How it works: The process of casing drain valve can be divided into normal closing state, pressure-relief state, throttling state, sewage discharge state and closing state. In normal closure, the hard cover of the disc compacts the valve seat convex to form the first hard seal, while the soft seal embedded in the disc compacts the valve seat end to form the second seal. This double sealing structure ensures ``zero leakage"under high pressure gas medium conditions. When the valve needs to be opened for drainage, the valve enters a decompression state and the disc is sealed on the inner diameter of the cage sleeve to release pressure. As the disc continues to move, it enters throttling drainage. a multi-stage throttling structure, involving the throttling shaft and valve seat nozzles, sleeve window and valve seat channels, core bottoms and valve valve sleeve window, are used to accommodate changes in drainage flow and reduce erosion of valve core seal pairs by media containing moisture and sand particles. An equidistant, synchronous pressure-relieving empty stroke is provided at the point of alignment between the the throttling shaft and the seat nozzle, the sleeve and valve seat cavity, and the core valve core the lower end of the valve seat. This ensures that only after the valve core has moved some distance from the valve seat sealing surface does the media begin to flow, further protecting the sealing surface. During closing, the gap between the gasket and the valve seat channel prevents larger media particles from flowing to the seal. The medium enters the valve seat channel from the slant of the gasket, changes its flow direction, increases the flow resistance coefficient and velocity, and increases the radial force of the medium on the valve seat end. At the same time, due to the change of direction of media flow, the bottom groove of the valve core will generate vortexes, thus preventing impurities from adhering to the hard and soft cover. The valve core is provided with a slag storage slot and a slag discharge slot, and has two O-rings. The O-ring at the lower end of the core moves up and down inside the valve sleeve to automatically store and discharge slag and reduce wear and tear.
The structural characteristics of steam trap, also known as steam trap, steam trap, water return valve or water return valve. According to different principles of steam and condensate identification, steam traps can be divided into mechanical traps, thermostatic traps and thermal traps. Mechanical steam traps take advantage of the density difference between condensed water and steam. Changes in the condensate level cause the float to rise and fall, opening or closing the valve. Thermostatic steam traps take advantage of the temperature difference between steam and condensate. Thermodynamic steam traps is based on the principle of phase change principle of steam and condensate.
How it works: Take the free-float mechanical steam trap, for example, which has only one moving part-a finely ground stainless steel hollow float that is both a float and an on/closing element. It has no breakable parts and a long service life. When the equipment is first started, air is pumped out of the pipe through an automatic venting device. Low-temperature condensate enters the steam trap, causing the condensate level to rise. The float rises, the valve opens, and the condensate is quickly expelled. Steam quickly enters the equipment, causing it to heat up rapidly. Temperature sensing liquid expands and shuts down in an automatic venting device. Then the trap begins to work properly, and the float rises and falls with the condensate level, preventing steam from escaping and draining. The free-floating ball-type steam trap's seat is always lower than the liquid level, forming water seal, preventing steam leakage, thus achieving good energy saving effect. The minimum working pressure is 0.01 MPa, independent of temperature and pressure fluctuations, and fluctuates between 0.01 MPa and maximum working pressure to ensure continuous drainage. It can expel condensate at saturation temperature with a minimum of 0 degree of supercooling, prevent water accumulation in heating equipment and achieve optimal heat transfer efficiency. The backpressure ratio is greater than 85%, which is one of the most ideal steam traps for heating equipment during production.