Centerline (Concentric) Butterfly Valves

The Centerline Butterfly Valve (also known as a Concentric Butterfly Valve) is a foundational component in piping systems, primarily used for on/off service and throttling (flow control). It is characterized by its simple design where the valve stem axis, the disc center, and the valve body center are all positioned on the same axis.

While traditional Centerline valves use soft materials like rubber or PTFE for sealing and are often limited in high-temperature, high-pressure, corrosive, and abrasive environments, modern designs incorporate advanced features to enhance performance and service life.

Core Design Philosophy

Concentric Design: The primary characteristic where the stem, disc, and body centers are co-axial.
Sealing: Primarily utilizes a Soft Seat design (resilient seated) for achieving permanently tight closure.
Simplicity & Reliability: Features no pins connection between the disc and the shaft, resulting in only two parts in contact with the medium (disc and seat), which maximizes corrosion resistance.
Maintenance: Available as a maintenance-free version and featuring a replaceable cartridge seat design with a solid backup ring to minimize lifetime costs and allow for the best fit, even for vacuum applications.

central symmetry from several angles of centerline butterfly valve

Key Design Features

Feature Highlight	Benefit
Minimal Wetted Parts	Only the disc and seat contact the medium, with no exposed metal-to-metal contact points, ensuring maximum corrosion resistance.
Self-Centering Disc	The smooth finish and spherical edge of the disc reduce wear and resist corrosion and abrasion.
Vacuum Performance	The replaceable cartridge seat and solid backup ring design ensures optimum operation under vacuum conditions.
Actuator Adaption	Features a standardized top flange for direct mounting of pneumatic, electric, or manual actuators without the need for additional brackets.
Safety	Includes a blow-out proof shaft for enhanced operator safety.
Flow Control	Usable as a quick-closing valve and provides excellent fluid characteristics.
Structural Integrity	Short face-to-face dimension (compact design).

Technical Specifications

Parameter	Specification
Size Range (DN/Imperial)	DN 40 up to DN 1400 / $1\frac{1}{2}''$ up to $56''$
Pressure Ratings	PN10, PN16, ASME Class 150
Temperature Range	$-30^\circ\text{C}$ ( $-22^\circ\text{F}$ ) up to $200^\circ\text{C}$ ( $392^\circ\text{F}$ ) (dependent on material/seat selection)
Sealing Type	Soft Seat (Resilient Seated)
Connection Types	Wafer type, Lug type, Wafer type with centering lugs, Double flanged
Body Lining	Replaceable body lining with firm back-up ring

Connection Methods

Centerline Butterfly Valves are classified by how they connect to the pipeline:

Wafer Butterfly Valve: Clamped between two flanges in the piping system.
Lug-Type Butterfly Valve: Features threaded bolt holes (lugs) around the perimeter, allowing it to be securely bolted to both flanges and used as an end-of-line valve (at reduced pressure).
Flanged Butterfly Valve (Double Flanged): Features integral flanges on the valve body for direct bolting to corresponding pipe flanges.

Special Options

Trunnion Bearing: An additional bearing available for high cycling applications to handle increased lateral forces and reduce friction.
Shaft Extensions: Used when the valve needs to be operated remotely or below insulation.

Centerline butterfly valves are widely applied across various fields, including Petroleum, Chemical, Metallurgy, and Hydropower, providing an efficient, reliable, and cost-effective solution for fluid control.