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Common faults of water treatment valve

Valve is the control device of fluid pipeline. Its basic function is to connect or cut off the flow of pipeline medium, change the flow direction of medium, adjust the pressure and flow of medium, and set various valves in the piping system, which is an important guarantee for the normal operation of pipe network and equipment.

Common valves for water treatment

Gate valve

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It is the most commonly used opening and closing valve, which uses the gate (i.e. the opening and closing parts, in the gate valve, the opening and closing parts are called the gate or gate, and the valve seat is called the gate seat or gate seat) to connect (fully open) and cut off (fully close) the medium in the pipeline. It is not allowed to be used as throttling, and the micro opening of the ram shall be avoided in use, because the erosion of the high-speed flowing medium will accelerate the damage of the sealing surface. The gate valve is called gate valve because it moves up and down in the plane perpendicular to the center line of the gate seat channel and cuts off the medium in the pipeline like a gate.

  • 1. Low flow resistance. The medium channel inside the valve body is straight, the medium flows in a straight line and the flow resistance is small.
  • 2. It is labor-saving when opening and closing. Compared with the stop valve, the movement direction of the ram is perpendicular to the medium flow direction whether it is open or closed.
  • 3. High height and long opening and closing time. The opening and closing stroke of the ram is large, and the lowering is carried out through the screw.
  • 4. Water hammer is not easy to occur. The reason is that the shutdown time is long.
  • 5. The medium can flow in any direction on both sides, which is easy to install. Both sides of the gate valve channel are symmetrical.
  • 6. The structural length (the distance between the two connecting end faces of the shell) is small.
  • 7. The sealing surface is easy to wear, affecting the service life. During opening and closing, the two sealing surfaces of the gate and the valve seat rub and slide against each other, which is easy to cause abrasion under the action of medium pressure, affect the sealing performance and shorten the service life.
  • 8. The price is expensive. There are many contact sealing surfaces and the processing is complex, especially the sealing surface on the ram seat is not easy to process, and there are many parts.

Stop valve

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The stop valve is a closed-circuit valve that uses the valve disc (the closing part of the stop valve is called the valve disc) to move along the center line of the valve seat (valve seat) channel to control the opening and closing of the pipeline. The stop valve is generally suitable for conveying liquid and gas media under various pressure and temperature conditions within the specified standard range, but it is not suitable for conveying liquids containing solid precipitation or precipitated crystals. In the low-pressure pipeline, the stop valve can also be used to adjust the flow of medium in the pipeline. Due to structural constraints, the nominal diameter of the stop valve is less than 250mm. If it is on the pipeline with high medium pressure and high flow rate, its sealing surface will wear quickly. Therefore, when it is necessary to adjust the flow, a throttle valve must be used.

  • 1. The wear and scratch of the sealing surface are not serious, so the work is more reliable and the service life is long.
  • 2. The sealing surface area is small and the structure is simple. The man hours required to manufacture the sealing surface and the valuable materials required for the sealing ring are less than those of the gate valve.
  • 3. When opening and closing, the valve disc stroke is small, so the height of the stop valve is small. Easy to operate.
  • 4. The use of thread to move the valve disc will not cause sudden opening and closing, so it is not easy to cause “water hammer”.
  • 5. The opening and closing torque is large, and the opening and closing is laborious. When closing, the movement direction of the valve disc is opposite to the action direction of the medium movement pressure. The force of the medium must be overcome, so the opening and closing torque is large. Therefore, it affects the application of the large diameter stop valve.
  • 6. The flow resistance is large. Among all kinds of block valves, the flow resistance of stop valve is the largest. (the media channel is tortuous)
  • 7. The structure is complex.
  • 8. The medium flow direction is unidirectional. The medium shall flow from bottom to top, so the medium must flow in one direction.

Butterfly valve

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Butterfly valve is a rotary valve that uses disc (also known as butterfly plate) to open and close the channel by rotating the opening and closing parts by 90 ° or about 90 °. The movement of butterfly valve disc is wiping, so most butterfly valves can be used for media with suspended solid particles.
There are two kinds of commonly used butterfly valves: wafer butterfly valve and flange butterfly valve. The wafer butterfly valve connects the valve between two pipe flanges with stud bolts. The flange butterfly valve has flanges on the valve, and the flanges at both ends of the valve are connected to the pipe flanges with bolts.

  • 1. Small overall size, short length, simple structure and light weight.
  • 2. It is easy to operate and open and close quickly. It only needs to rotate the valve disc 90 ° to open and close.
  • 3. Good sealing and adjustment performance. Due to the use of rubber as sealing ring, it has good compression and resilience (i.e. it will not harden), so it has good sealing performance. When the valve disc is opened between 15 ° ~ 70 °, it can carry out sensitive flow control.
  • 4. Small operating torque and fluid resistance. According to measurement, the fluid resistance of butterfly valve is less than that of other types of valves except ball valve.
  • 5. Due to the limitation of sealing material, the service pressure and working temperature range of butterfly valve are small.

Check valve

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Purpose and characteristics
The check valve is a valve used to prevent the backflow of medium in the pipeline. It opens when the medium flows forward and closes automatically when the medium flows backward. It is generally used in the pipeline that does not allow the medium to flow in the opposite direction to prevent the countercurrent medium from damaging the equipment and parts. When the pump stops running, it will not cause the rotary pump to reverse. In the pipeline, the check valve and closed-circuit valve are often used in series. This is because the tightness of the check valve is poor. When the medium pressure is small, a small part of the medium will leak, and a closed-circuit valve is needed to ensure the closure of the pipeline. The bottom valve is also a check valve, which must be submerged and specially installed at the front end of the suction pipe of the water pump that cannot self-priming or has no vacuum pumping water diversion.

Common faults and measures of water treatment valve

After the valve operates in the pipe network for a period of time, there will be various faults. First, it is related to the number of parts constituting the valve. If there are many parts, there are many common faults. Second, it is related to the advantages and disadvantages of valve design, manufacturing, installation, working condition operation and maintenance. The common faults of general non power driven valves are generally divided into four categories:

Transmission failure

Transmission failure is often manifested as stem jamming, inflexible operation or valve failure. The reasons are: the valve is rusted after being closed for a long time; Improper installation and operation damage the valve rod thread or valve rod nut; The ram is stuck in the valve body by foreign matters; The ram is often in the half open and half closed state, and the dislocation, looseness and seizure of stem screw and stem nut wire are caused by hydraulic or other impact force; The packing is pressed too tightly and the valve stem is locked; The valve rod is jacked or jammed by the closing part. Lubricate the transmission parts during maintenance. With the help of a wrench and gently tapping, the phenomenon of jamming and jacking can be eliminated; Stop water supply to repair or replace the valve.

Valve body damaged and cracked

Reasons for damage and fracture of valve body: the corrosion resistance of valve material decreases; Settlement of pipeline foundation; Large changes in pipe network pressure or temperature difference; Water hammer; Improper operation of closing valve, etc. The external causes shall be eliminated in time and the valve parts or valves of the same model shall be replaced.

Valve leakage

Water leakage of the valve is shown as: water leakage of the valve stem core; Gland leakage; The flange rubber gasket leaks. Common causes are: wear, corrosion and peeling of valve stem (valve shaft), pit and falling off of sealing surface; Aging and leakage of seal; Gland bolts and flange connecting bolts are loose. Add and replace sealing media during maintenance; Replace new nuts and readjust the position of fastening bolts.
No matter what kind of fault, if it is not repaired and maintained in time at ordinary times, it may cause a waste of water resources and even paralysis of the whole system. Therefore, valve maintenance personnel must know the causes of valve failure, be able to skillfully and accurately adjust and operate the valve, timely and decisively deal with various emergency failures, and ensure the normal operation of water treatment pipe network.

Poor valve opening and closing

Poor opening and closing of the valve shows that the valve cannot be opened or closed, and the valve cannot operate normally. The reason is: the valve rod is rusted; The ram is stuck or rusted when the ram is closed for a long time; Ram falling off; Foreign matters are stuck in the sealing surface or sealing groove; The transmission part is worn and blocked. Repair and lubricate the transmission parts under the above conditions; Repeatedly open and close the valve and impact foreign matters with water; Replace the valve.

Maintenance of water treatment valves

Valve cleaning

The surface of the valve, the trapezoidal thread on the valve stem and valve stem nut, the sliding parts of the valve stem nut and support, gears, worm gears and other parts are easy to be contaminated with many dirt such as dust, oil and medium residues, which will cause wear and corrosion to the valve. Therefore, keep the outside and moving parts of the valve clean; Protect the integrity of valve paint.

Lubrication of valves

The trapezoidal thread of the valve, the sliding part of the valve stem nut and the support, the bearing part, the meshing part of the gear, worm gear and worm and other cooperative moving parts all need good lubrication conditions to reduce mutual friction and avoid mutual wear. Lubricating parts shall be lubricated regularly according to specific conditions.

Maintenance of valves in operation

All valves in operation shall be complete and intact. Bolts on flanges and supports are indispensable, and threads shall be intact without looseness. If the fastening nut on the hand wheel is found to be loose, it shall be tightened in time to avoid wearing the connection or losing the hand wheel and nameplate. If the hand wheel is lost, it is not allowed to replace it with a monkey wrench, and it shall be equipped in time. The packing gland shall not be skewed or have no pre tightening clearance. The scale on the valve shall be complete, accurate and clear. The lead seal, cap and pneumatic accessories of the valve shall be complete and intact. If it is equipped with electric or pneumatic driving device, it shall be maintained in strict accordance with the corresponding operation manual.

Source: Network Arrangement – China Valve Supplier:

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

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