Butterfly valves - Operation, maintenance and installation

What is a butterfly valve?

• A butterfly valve is a valve that controls the flow of fluids, gases, and other similar substances by using a disk-shaped element that rotates around an axis. The disk varies in size, and its shape can take on many forms, including concave, flat, and convex.

Butterfly Valve Specifications:

The following specifications should be considered when selecting a butterfly valve:

Specification	Description
Size	Determine the valve size based on the pipe diameter.
Pressure rating	The maximum pressure the valve can withstand before failure.
Temperature range	The range of temperature that the valve can be exposed to before it fails.
Materials	The materials used for the valve body, disk, and seat. This determines the suitability of the valve for a specific application.
Actuator type	The type of actuator used to operate the valve, such as manual, pneumatic, or electric.
Torque	The amount of force required to operate the valve.

Types of butterfly valves:

There are two main types of butterfly valves: concentric and eccentric.

• Concentric butterfly valves: The stem is centered in the middle of the valve and the disk is positioned in the center of the pipe. These valves are suitable for low-pressure applications and offer low torque.
• Eccentric butterfly valves: The stem is offset from the center of the valve and the disk is positioned to one side of the pipe. These valves are suitable for high-pressure applications and provide a tight seal.

Butterfly valves are further categorized based on the type of disk position. The most common types are:

• Wafer style: The valve is placed between two flanges.
• Lug style: The valve has threaded inserts in the valve body that allows fastening to the pipeline.
• Double flanged style: The valve has flanges on both sides of the valve and can be easily removed from the pipeline without affecting other components.

Working Principle of Butterfly Valves:

• Butterfly valves are designed to regulate and control fluid flow in a piping system. They are quarter-turn valves that can be opened or closed with a 90-degree turn of the disc. The butterfly valve derives its name from the shape of its disc, which resembles the wings of a butterfly.

• The butterfly valve disc is located in the center of the valve body. It is connected to a stem that passes through the top of the valve body and is operated by a handle or actuator. When the handle is turned, the stem rotates the disc to either open or close the valve.

• The butterfly valve disc is mounted on a shaft that sits perpendicular to the flow of fluid. When the valve is open, the disc is parallel to the flow of fluid, providing minimal obstruction to the flow. When the valve is closed, the disc is turned perpendicular to the flow of fluid, blocking it completely.

• The working principle behind butterfly valves is simple. When the valve is open, the disc is in the path of the fluid and directs it through the valve body. As a result, the valve offers minimal resistance to the flow of fluid, and the pressure drop across the valve is low. When the valve is closed, the disc seals against the valve seat, blocking the flow of fluid and preventing it from passing through the valve.

• The compact design and simple operation of butterfly valves make them ideal for a wide range of applications in various industries. They are commonly used in HVAC, food and beverage, pharmaceuticals, and chemical processing industries due to their excellent flow control characteristics.

Butterfly valve selection criteria:

When selecting the right butterfly valve for your application, consider the following criteria:

Criteria	Explanation
Media type and compatibility	Butterfly valves are designed to handle specific media types, so it's important to choose a valve that is compatible with the media flowing through your pipeline.
Valve Size	Choose the right valve size based on your pipeline size and flow rate requirements.
Operating Temperature and Pressure	Ensure that the valve you choose is rated to handle the maximum temperature and pressure of your application.
Valve Material	Butterfly valves are made of different materials, including stainless steel, cast iron, and plastic. The choice of material depends on your application requirements.
Valve Operation Method	Butterfly valves can be operated manually, pneumatically, or electrically. Choose the operation method that best suits your application needs.
Budget	Consider your budget when selecting a butterfly valve. While it's important to choose a high-quality valve, it's also essential to find a valve that fits within your budget.

Butterfly valve installation:

The following steps are essential for installing butterfly valves:

1. Inspect the valve: Before installing the valve, inspect it for any visible damage that may have occurred during shipping, handling, or storage.
2. Prepare the piping system: Ensure that the piping system is free of dirt, debris, and other contaminants that may damage the valve.
3. Position the valve: Properly position the valve in the pipeline, aligning it with the flanges and gaskets.
4. Secure the valve: Tighten the bolts to ensure firm and stable connections between the valve and the pipes.
5. Test the valve: After installation, test the valve for proper operation before putting it into service.

It's important to follow these steps carefully to ensure your butterfly valve is installed safely and correctly.

Maintenance and Operation of Butterfly Valves:

1). Butterfly Valve Maintenance:

To keep butterfly valves functioning optimally, regular maintenance is crucial. Here are some crucial guidelines to remember:

• Regularly inspect the valve for any signs of wear and tear, corrosion, or leakage.
• Lubricate the valve and its components according to the manufacturer's instructions.
• Check the torque of the valve's bolts and retighten if necessary.
• Avoid using harsh chemicals or abrasive materials during cleaning.

Proper maintenance will not only increase the lifespan of your butterfly valves but also ensure their overall efficiency and performance.

2). Butterfly Valve Operation:

Understanding the proper operation of butterfly valves is crucial to avoid any potential damage or malfunction. Here are some crucial guidelines to remember:

• Always operate the valve within its specified pressure and temperature range.
• Avoid using the valve to throttle flow, as this can lead to premature wear and tear on the valve's components.
• Use only compatible materials for the media flowing through the valve.
• Ensure that the valve is fully open or fully closed to avoid any potential damage to the valve or the pipeline.

Troubleshooting Of Butterfly Valve:

1). Leakages:

• If you notice any leakages in your butterfly valve, check the valve seat and the sealing element. Ensure that the valve is tightly closed by checking the bolts and nuts. If the leakage persists, it may be time to replace the valve seat or the sealing element.

2). Difficult to Open or Close Valve:

• When a butterfly valve becomes difficult to open or close, it could be due to a damaged stem or disc. Check if there is any obstruction causing the difficulty, such as dirt or debris. If not, inspect the stem or disc for any damage and replace them if necessary.

3). Noise or Vibration:

• If your butterfly valve produces noise or vibration, it could be due to high fluid velocity or cavitation. To reduce the effects of cavitation, ensure the valve is properly sized for the intended flow rate. If the noise or vibration persists, replace the valve disc with a noise-reducing design.

4). Inconsistent Flow Rate:

• If you notice an inconsistent flow rate, check the valve disc for any damage or obstruction that could be affecting flow. Ensure that the valve is properly installed and that the flow direction is correct. If the problem persists, you may need to replace the valve disc or adjust the valve's position.

Advantages of butterfly valves:

• Low cost.
• Compact design.
• Simple operation.
• Low pressure drop.
• Quick open/close action.
• Good flow control characteristics.

Disadvantages of butterfly valves:

• May not be suitable for high-pressure applications.
• Not recommended for situations requiring exact flow control.

• Not suitable for applications that require high-temperature or abrasive materials.
• Potential for water hammer in certain applications.

Applications of butterfly valves:

The versatility of butterfly valves means that they can be used in a variety of applications. Some common applications include:

• Water treatment plants
• Power generation plants
• Oil and gas refineries
• Chemical processing plants
• Food and beverage production facilities
• HVAC systems