Working Principle and Maintenance Methods of Hard Sealing Butterfly Valve

I. Working Principle

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

1. Structure Composition

Butterfly Plate: A circular disc-shaped closure element that rotates around the fixed axis inside the valve body (0°~90°) to control the flow of the medium.

Valve Body: A cylindrical channel that provides the flow path for the medium, and forms a sealing surface with the butterfly plate.

Valve Rod: Connects the butterfly plate with the driving device, transmitting the rotational power.

Sealing Pair: Uses metal-to-metal sealing (such as stainless steel and graphite composite plates), or replaceable metal sealing rings to ensure sealing performance under high-temperature and high-pressure conditions.

Drive Device: Supports manual, electric, pneumatic or worm gear transmission to achieve remote or automated control.

2. Opening Process

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

Close: The butterfly plate rotates to be perpendicular to the pipeline direction (0°), closely adhering to the valve body sealing surface, and blocking the medium flow through mechanical pressure.

Regulation Function: Some designs support any angle stay between 0° and 90° to achieve flow regulation, but be aware of the risk of seal surface wear.

3. Sealing Mechanism

Three-Dimensional Eccentric Design: The sealing surface of the butterfly plate is an upward-convex cone. When closed, the sealing ring is compressed elastically, achieving a zero-leakage seal that gets tighter as it closes.

Temperature Adaptability: The sealing performance is not affected by temperature changes and is suitable for -196°C (low temperature) to 600°C (high temperature) conditions.

Anti-Clogging Characteristics: There is no phase-clogging phenomenon between the butterfly plate and the sealing ring, and solid particles are not prone to accumulation, ensuring long-term stable operation.

II. Maintenance Methods

The maintenance of hard sealing 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

Daily inspect the appearance of the valve, remove dust, oil, and debris to keep the surface clean.

Regularly lubricate the threaded parts of the drive mechanism (such as worm gears, gears), reducing wear and preventing rust.

• Operation Inspection

Manually operate the valve to confirm that the opening and closing actions are flexible, without sticking or abnormal sounds.

Electric valves need to test the function of the actuator (such as overload protection, limit switches) to ensure the normal electrical system.

• Leakage Observation

When the valve is closed, inspect the pipeline connection points and seal surfaces to ensure no medium leakage.

2. Monthly Maintenance

• Seal Surface Inspection

Disassemble the valve (if necessary), inspect the wear of the seal surface. Minor scratches can be polished with aluminum oxide abrasive (grain size W20); hardened layers that peel off need to replace the sealing ring.

• Valve Rod Maintenance

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

• Actuator Inspection

Tighten the terminal connections of the electric actuator to prevent loosening or poor contact.

3. Quarterly Maintenance

• Internal Cleaning

Disassemble the valve, clean the deposits (such as solid particles in the medium) inside the valve body to avoid damage to the seal surface.

• Component Tightening

Check and tighten the connecting bolts and nuts to prevent vibration from causing loosening.

• Lubrication of Transmission Components

Add lubricating oil to worm gears, gears, etc. of the transmission components to reduce friction and extend lifespan.

4. Semi-Annual Maintenance

• Seal Performance Test

Inject medium at the standard pressure (such as 1.5 times the working pressure) and test the valve's sealing performance. If the leakage exceeds the standard (such as ≥ 0.1 mL/min), analyze the cause and repair.

• Electrical System Inspection

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

5. Annual Maintenance

• Replacement of Wearable Components

Replace the severely worn sealing parts, valve stem bushings, gaskets, etc., and preferentially use original factory parts.

• Comprehensive debugging

After reinstalling the valve, adjust parameters such as stroke, opening and closing speed, to ensure compatibility with the control system.

• Record archiving

Detail the maintenance content (such as replacing parts, test data), and establish equipment archives to trace historical issues.

6. Long-term storage maintenance

• Regular inspection

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

• Storage environment

Block both ends of the ball valve and keep it open; block both ends of the pneumatic valve and close it, and store it in an indoor, ventilated and dry place to avoid outdoor stacking.

III. Important Notes

1. Operating Specifications

• When operating the valves, use handwheels and prohibit the use of levers or other tools to avoid damaging the valves.

• For manual valves, rotate clockwise to close and counterclockwise to open; for electric valves, follow the control logic.

2. Installation Requirements

• Verify the pressure, diameter, etc. parameters of the valves to ensure they match the pipeline system.

• The medium flow direction of the stop valves should be "downward from below the valve disc", and the lift-type check valves should be installed horizontally.

3. Safety Protection

• Before maintenance, cut off the power supply and release the pressure to ensure the valves are in a safe state.

• Use appropriate tools (such as torque wrenches) to disassemble and assemble the parts to avoid violent operations that cause deformation.