The centric butterfly valve is a quarter-turn valve with a centered stem and disc that provides on/off flow control in industrial piping systems. It is also known as a concentric, center-line, or zero-offset butterfly valve.
Its simple quarter-turn operation is the reason why it is mainly used in water treatment, power generation, and chemical processing industries.
This guide provides information on the design of concentric butterfly valves, their function, types, advantages, and areas where they can be used successfully.
How a Centric Butterfly Valve Works
A centric or concentric valve works with a simple, quarter-turn operation and straightforward design. Knowing this operating principle helps you match the valve to the right service condition.
This zero-offset configuration features three components aligned on a single central axis: the stem, the disc, and the valve body. Because this concentric alignment serves as its defining structural feature, it is classified as a concentric or zero-offset butterfly valve.
The disc mounts on a centered shaft and sits directly in the flow path. Rotating the shaft 90 degrees moves the disc from fully open (parallel to flow) to fully closed (perpendicular to flow).
At the closed position, the disc compresses against a resilient elastomeric seat ring. The seat ring deforms slightly under pressure. This elastic deformation creates a bubble-tight seal that prevents leakage.
This elastic deformation yields a bubble-tight, zero-leakage bi-directional shut-off certified to API 598 testing standards. It is also known as a resilient seated butterfly valve because of this elastomeric seat design.
Types of Centric Butterfly Valves by End Connection
There are three main end connection types that serve different installation and service needs. Choosing the right one affects installation cost, maintenance access, and long-term performance.
Wafer Type Butterfly Valve
The wafer-type butterfly valve fits between two pipe flanges using through-bolts. The valve body has no integral flanges. This keeps the design compact and lightweight.
The wafer type is the most cost-effective option for general service. Standard wafer TYPE butterfly valve Dimensions follow API 609, BS EN 558-1, and ASME B16.10. The size range covers DN 40 to DN 600.
Lug Type Butterfly Valve
The lug-type butterfly valve features threaded inserts cast into the valve body. Each pipe flange bolts to the valve independently. This allows one side of the pipeline to be removed without disturbing the other side.
It suits dead-end service and systems that require periodic removal of downstream piping. Process plants and water distribution networks use this type frequently.
Double Flanged Butterfly Valve
The double-flanged butterfly valve has integral flanges on both ends. It bolts directly to matching pipe flanges. The heavier body suits larger pipe sizes and more demanding service conditions. This is entirely different from a double offset butterfly valve, which will be discussed in the next section.
Water mains, power plant cooling circuits, and large-diameter industrial pipelines use this type. Request the double-flanged butterfly valve catalogue from Xintai Valve for configuration details.
What are the Differences Between a Centric vs. Double Offset Butterfly Valve?
The main difference between a centric and a double offset butterfly valve is in the stem or disc alignment.
Knowing the key differences saves time and prevents costly specification errors.
- Centric or zero-offset butterfly valve: The stem aligns with the disc and body centerlines. The seat is a soft elastomeric material. It handles standard pressure classes: PN 6, PN 10, PN 16, and Class 150. It suits clean or mildly corrosive liquids and gases.
- Double offset butterfly valve: The stem has two offsets from the disc centerline. The seat is metal or PTFE. It handles higher pressures, elevated temperatures, and abrasive media. It costs more but extends service life in demanding conditions.
A centric butterfly valve manual typically covers quarter-turn operation using a hand lever or gearbox. The ISO 5211 mounting pad accommodates electric, pneumatic, and hydraulic actuators.
Design Specifications and Materials
These parameters define the operating envelope of a standard-centric or zero-offset butterfly valve. Use them to verify compatibility with your piping system before specifying.
| Parameter | Value |
| Size Range | DN 40 to DN 600 |
| Pressure Rating | PN 6 / PN 10 / PN 16 / Class 150 |
| Design Standard | API 609 / BS EN 593 / IS: 13095 |
| Face-to-Face Dim. | API 609 / BS EN 558-1 / ASME B16.10 |
| Testing Standard | API 598 / BS EN 12266 Part 1 |
| Actuator Mounting | ISO 5211 |
| Flange Drilling | ASME B16.5 |
Body and disc materials: Cast iron, ductile iron (nylon or epoxy coated), CF8, CF8M.
Seat liner materials: EPDM, NBR, Viton, silicone, PTFE, Hypalon, and Neoprene. Select the seat material based on the media and its chemical properties.
Stem design: Blow-out-proof stem. Prevents stem ejection under pressure. Allows safe valve disassembly.
Seat retention: Centre-lock seat design eliminates seat movement during disc seating and unseating.
What Are the Strengths and Weaknesses of Centric/Concentric Valves?
To help buyers to make informed choices, here is a comparison of the pros and cons of concentric or zero-offset butterfly valves.
| Advantages | Disadvantages |
| Compact, lightweight body. Reduces pipe support requirements and labor during installation. | Soft-seal design limits service to PN 6 through PN 16 / Class 150 pressure classes. |
| Low operating torque. Allows smaller, lower-cost actuators. | Not recommended for high-temperature steam without correct seat material selection. |
| Few moving parts. Reduces maintenance frequency and total lifecycle cost. | The disc remains in the flow path when open. This creates a small but measurable pressure drop. |
| Bi-directional shut-off. Seals in both flow directions. | |
| Wide seat material range. Handles most liquids, gases, and powders. | |
| Line-sized body bore. Maximizes flow and minimizes pressure drop. | |
| Serves both on/off isolation and throttling/flow control duties. |
Where Are Concentric or Centric Valves Used in Industry?
The concentric butterfly valve serves a broad range of industries. Its adaptability to different media, pipe sizes, and actuation methods drives wide adoption.
These valves are mainly used in:
- Water and wastewater treatment: Coagulation, sedimentation, filtration, and disinfection. Handles large flow rates with tight shut-off.
- Power generation: Cooling water systems, condensate pipelines, and auxiliary services.
- Chemical and petrochemical processing: PTFE and Viton seat options resist aggressive chemical media.
- HVAC systems: Chilled water, hot water, and steam distribution in air handling units and ductwork.
- Fire protection: Water hydrant networks, sprinkler systems, and foam suppression systems.
- Mining and mineral processing: Slurry handling with high-chrome or CF8M stainless steel disc and corrosion-resistant seat selection.
How to Select the Right Centric or Center-line Butterfly Valve
Use this guided checklist to help you match the right valve to your system. This will help avoid mismatch errors and prevent costly maintenance or replacements.
- What is the media type? Is it liquid, gas, slurry, or powder?
- What are the operating pressure and temperature? Confirm the required PN rating and seat material compatibility.
- What is the pipeline connection type? Is it wafer, lug, or double-flanged?
- What are the pipe size (DN) and face-to-face dimensions? Always refer to wafer-type butterfly valve dimensions in the product catalogue.
- What is the actuation method? Is it a hand lever, gearbox, electric, pneumatic, or hydraulic actuator?
- Check the chemical compatibility: Make sure to select the seat material based on the media’s chemical properties.
Industry Application: Trusted OEM solution for chemical processing, water treatment, pharmaceutical, and industrial facilities.
Conclusion
The centric, zero-offset, or center-line butterfly valve suits industrial systems due to its simple design, low operating cost, and broad application range. It handles water, gas, chemical, and powder media across the most common pressure classes.
Xintai Valve designs butterfly valves in accordance with API 609, BS EN 593, API 598, ASME B16.10, and ISO 5211 standards. These types of butterfly valves include concentric, double eccentric, and triple eccentric butterfly valves
