Working principle and maintenance method of hard sealed butterfly valve

1、 Working principle

The hard sealed butterfly valve achieves the opening, closing, or adjustment of pipeline media by rotating the butterfly plate. Its core structure and working logic are as follows:

1. Structural composition

Butterfly plate: a disc-shaped opening and closing component that rotates around a fixed axis inside the valve body (0 °~90 °) to control the flow of the medium.

Valve body: cylindrical channel, providing a medium flow path, and forming a sealing surface with the butterfly plate inside.

Valve stem: connects the butterfly plate and the driving device to transmit rotational power.

Sealing pair: Metal to metal sealing (such as stainless steel and graphite composite plate) or interchangeable metal sealing rings are used to ensure sealing performance under high temperature and high pressure conditions.

Drive device: supports manual, electric, pneumatic or worm gear transmission, achieving remote or automated control.

2. Opening and closing process

Open: The driving device drives the butterfly plate to rotate parallel to the pipeline (90 °), allowing the medium to pass smoothly. At this point, the thickness of the butterfly plate is the flow resistance of the medium, and the pressure drop is minimal.

Close: Rotate the butterfly plate to the vertical direction of the pipeline (0 °), tightly adhere to the sealing surface of the valve body, and block the flow of the medium through mechanical pressure.

Adjustment function: Some designs support staying at any angle between 0 ° and 90 ° to achieve flow adjustment, but attention should be paid to the risk of sealing surface wear.

3. Sealing mechanism

Three dimensional eccentric design: The sealing surface of the butterfly plate is a conical shape that protrudes upwards. When closed, the sealing ring is elastically compressed, achieving a zero leakage seal that becomes tighter as it closes.

Temperature adaptability: The sealing performance is not affected by temperature changes and is suitable for working conditions from -196 ℃ (low temperature) to 600 ℃ (high temperature).

Anti jamming feature: There is no jamming phenomenon between the butterfly plate and the sealing ring, and solid particles are not easy to accumulate, ensuring long-term stable operation.

2、 Maintenance methods

The maintenance of hard sealed butterfly valves should follow the principle of "prevention first, regular inspection", and the specific maintenance strategies are as follows:

1. Daily maintenance

• Cleaning and lubrication

Check the appearance of the valve daily, remove dust, oil stains, and debris, and keep the surface clean.

Regularly lubricate transmission threads (such as worm gear rods and gears) to reduce wear and prevent rust.

• Operation inspection

Manually operate the valve and confirm that the switch action is flexible, without any jamming or abnormal sound.

Electric valves require testing of actuator functions (such as overload protection and limit switches) to ensure the electrical system is functioning properly.

• Leakage observation

Check the pipeline connection and sealing surface in the closed state to confirm that there is no medium leakage.

2. Monthly maintenance

• Sealing surface inspection

Disassemble the valve (if necessary) and check the wear of the sealing surface. Minor scratches can be repaired by polishing with alumina grinding paste (particle size W20); The hardened layer peeling off requires replacement of the sealing ring.

• Valve stem maintenance

Check for rust or wear on the surface of the valve stem, and if necessary, remove rust and apply lubricating grease (such as molybdenum disulfide).

• Inspection of actuators

Tighten the wiring terminals of the electric actuator to prevent looseness or poor contact.

3. Quarterly maintenance

Internal cleaning

Disassemble the valve and clean the sediment inside the valve body (such as solid particles in the medium) to avoid damage to the sealing surface.

• Component fastening

Check and tighten the connecting bolts and nuts to prevent loosening caused by vibration.

Lubrication of transmission components

Add lubricating oil to transmission components such as worm gears and gears to reduce friction and extend their lifespan.

4. Half year maintenance

Sealing performance test

Inject the medium at standard pressure (such as 1.5 times the working pressure) and test the sealing performance of the valve. If the leakage exceeds the standard (such as ≥ 0.1mL/min), the cause needs to be analyzed and repaired.

Electrical system testing

Detect the performance of the motor, controller, and sensor of the electric actuator to ensure accurate signal transmission (such as stable 4-20mA current signal).

5. Annual maintenance

• Replacement of vulnerable parts

Replace severely worn seals, valve stem bushings, gaskets, etc., and prioritize using original factory accessories.

• Comprehensive debugging

After reinstalling the valve, adjust the stroke, switch speed and other parameters to ensure that they match the control system.

• Record archiving

Detailed records of maintenance content (such as replacement of parts, testing data), establishment of equipment archives to trace historical issues.

6. Long term storage and maintenance

• Regular inspections

Check the valve status every 3 months and remove any dirt from exposed machined surfaces.

• Storage environment

Both ends of the ball valve are blocked and remain open; Both ends of the pneumatic valve channel are blocked and closed, and stored indoors in a ventilated and dry place to avoid outdoor stacking.

3、 Precautions

1. Operating standards

When opening and closing valves, use a handwheel and do not use levers or other tools to prevent damage to valve components.

The manual valve rotates clockwise to close and counterclockwise to open; Electric valves must follow control logic.

2. Installation requirements

Check valve pressure, diameter and other parameters to ensure compatibility with the pipeline system.

The flow direction of the shut-off valve medium should be "upward from below the vertical valve disc", and the lift check valve should be installed horizontally.

3. Security protection

Cut off the power and relieve pressure before maintenance to ensure that the valve is in a safe state.

Use appropriate tools (such as torque wrenches) to disassemble and assemble parts, avoiding deformation caused by violent operation.