Essential Butterfly Valve Parts: Expert Guide to Components and Functions

Butterfly valves control massive industrial flows with a quarter turn of 90 degrees. These impressive valves and their butterfly valve parts control flow systems. They can handle pressures of up to 740 psi. The temperatures can reach 300°F in these systems.

The valve's components are the foundation of these versatile flow control devices. The valve body connects to pipe flanges. The disk mechanism controls the flow precisely. Each component serves a specific purpose. 

A complete butterfly valve parts diagram includes key components:

• Stem

• Body

• Sealing arrangement

• Bearings

• Bonnet

• Actuator

• Seat

• Disk

These valves come in sizes up to 200 inches. Chemical plants value them for their simple design and easy upkeep.

This piece looks at how each part functions. It helps you see how these parts work together to create an efficient flow control system. You will discover selection criteria, maintenance needs, and troubleshooting tips. These will help your valve perform at its best.

Butterfly valves deliver excellent performance through simple core components that work together. These quarter-turn valves need four main parts to work reliably and efficiently.

Valve Body: Wafer vs. Lug Designs

The valve body is the base that connects to pipe flanges. It also holds internal parts. Two designs lead the market: wafer and lug styles. Wafer-style bodies fit between pipe flanges. Long bolts run through the whole body. This design is affordable. It keeps seals tight against pressure from both directions. It also prevents backflow in systems made for one-way flow. In stark comparison to this, lug-style valves have threaded inserts (lugs) on both sides of the body. You can install them with two sets of bolts without nuts. This setup lets you disconnect one side of the piping system. The other side stays untouched, which is great for dead-end service applications. Lug-style valves have a lower pressure rating in dead-end service. It drops to 520 kPa, while it is 1,000 kPa when installed between two flanges.

Disk: The Flow Control Mechanism

The disk sits in the pipe's center and controls the flow. It connects to an actuator via the stem. Rotating it parallel or perpendicular to the flow opens or closes the valve. Unlike other valve types, the disk stays in the flow even when fully open, which causes some pressure drop. Different disk designs exist—zero-offset, high-performance double offset, and triple offset configurations. Zero-offset designs use rubber flexibility and have lower pressure ratings. Triple offset butterfly valves reduce sliding contact between the disk and seat. This feature makes them ideal for high-pressure systems.

Stem: Connection and Operation

The stem links the disk to the external actuator. Two main designs exist: one-piece shafts or two-piece (split-stem) configurations. Resilient seated designs protect the stem from media contact, allowing cheaper material choices. High-performance designs must have stems that can handle the media. They must also be strong enough for seating and unseating tasks. Stems can be "wetted," which means they touch the media. They can also be "non-wetted," meaning they are kept safe from it. The choice of material depends on what is compatible.

Seat: Sealing and Material Options

The seat seals between the disk edge and the valve body.

Seat materials change depending on the application. They include:

• EPDM

• Nitrile rubber (NBR)

• Polytetrafluoroethylene (PTFE)

• Metal hard-seal materials.

EPDM stands up to aging, sun, heat, and moisture. It works well in temperatures from -40°C to 130°C. NBR is excellent with oil, heat, abrasion, and water. This makes it ideal for petroleum pipelines. PTFE resists acids, alkalis, and many organic solvents. It can work in temperatures up to 260°C, but can reach a maximum of 290-320°C. Metal seats can withstand higher temperatures and pressures. However, they do not seal as effectively as soft-seat materials.

AWWA C504 Butterfly Valve

Selecting the right butterfly valve parts requires a thorough look at your system's needs. Choosing wisely boosts performance and extends service life. It also reduces maintenance costs.

Temperature and Pressure Considerations

Your system's operating conditions will determine which butterfly valve materials work best. High-performance butterfly valves work in temperatures from -28°C to 500°C (-18°F to 932°F). General service models operate between -28°C and 98°C (-18°F to 208°F). High-performance valves can handle 51 bar (740 psi). General service versions manage about 14 bar (200 psi).

Here are some specialized options to think about:

• The PM and P1M Series have 316L SST seats. They offer Class V shutoff for high-temperature use.

• PH and P1H Series have Inconel 625 seats and Stellite disks. They perform well at very high temperatures.

• Metal seats allow operation in temperatures of up to 1,000°F (538°C).

Media Compatibility with Valve Materials

We determined your material selection based on fluid properties. Ductile iron valves are great for municipal water systems. Yet, they can corrode in saltwater or areas with high chloride levels. For corrosive applications, use 316 or 316L stainless steel. The added molybdenum helps guard against pitting from chloride.

Here's what works best for specific media types:

• Chemical processing: PTFE or RTFE seats provide excellent chemical resistance.

• Plastic butterfly valves made of UPVC, CPVC, PP, or PVDF resist acidic and alkaline solutions well.

• Oil and petroleum: NBR seats deliver excellent oil resistance and abrasion resistance.

Space and Weight Constraints

Butterfly valves stand out because of their compact design. This is a big deal as it means that they need less space and weigh less than ball, check, globe, or gate valves. You'll find them perfect for tight spaces or weight-restricted installations.

Large applications over DN300 need help when using light materials, such as aluminum alloy (ADC12). This is especially true under pressures over 10 kg/cm². Cast steel (WCB) valves are strong and heavy. Aluminum alloy valves offer a lightweight option for low-pressure systems.

WCB (CARBON STEEL) VALVES

Butterfly valves are great devices. They control flow with a simple design. Their performance is exceptional in many industrial uses. Every part is key for reliable flow control. This includes the strong valve body and the precision disc.

A valve works best when you choose the right design and materials. Consider wafer or lug designs, and find the right materials for discs, stems, and seats.

The valve's optimal performance relies on proper maintenance. System failures can be costly. Check wear points regularly. Use the right methods for seat replacement. Take care of stem seals properly. This can help prevent issues. This knowledge helps operators make smart choices. They can fix or replace parts, which extends the valve's life and lowers operational costs.

FAQs

Q1. What are the main components of a butterfly valve? 

The main components of a butterfly valve include the valve body, disk, stem, and seat. The valve body attaches to pipe flanges. The disk controls the flow. The stem connects the disk to the actuator. The seat seals the disk edge against the valve body.

Q2. How do butterfly valves compare to other valve types' space requirements? 

Butterfly valves are more compact and lightweight compared to ball, check, globe, or gate valves. This makes them ideal for installations with tight spatial limitations or weight restrictions.

Q3. What types of actuators are commonly used with butterfly valves?

Common actuators for butterfly valves include manual handles and gearboxes, pneumatic actuators (single and double-acting), and electric actuators (part-turn and multi-turn). The choice depends on factors like valve size, required precision, and operational environment.

Q4. How often should butterfly valve parts be maintained?

Regular maintenance is crucial for optimal performance. The frequency depends on factors like usage, media type, and operating conditions. Common maintenance tasks include inspecting wear points, replacing seats, and maintaining stem seals to prevent failures and system downtime.

Q5. What are the temperature and pressure capabilities of butterfly valves? 

High-performance butterfly valves work well in temperatures from -28°C to 500°C (-18°F to 932°F). They can also handle pressures up to 51 bar (740 psi). General service models typically function from -28°C to 98°C (-18°F to 208°F) and handle pressures of around 14 bar (200 psi).