Comparing Industrial Butterfly Valves: Rubber Lined, High Performance, and Offset Designs

Butterfly valves play a vital role in industrial fluid control systems, efficiently regulating flow across a wide range of applications. Rubber-Lined (General-Purpose) Butterfly Valves—and High-Performance Butterfly Valves (including Double and Triple Offset designs) stand out due to their unique designs and specific uses. Understanding the differences in valve style, construction, and application is crucial for selecting the most suitable valve for a given industrial need.

Rubber-Lined (General-Purpose) Butterfly Valves feature a straightforward, robust design ideal for low-pressure and low-temperature environments. In these valves, the stem is centered in the middle of the disc and seat, meaning the disc remains in constant contact with the seat throughout its operation. The valves consist of a disc mounted on a rotating shaft within a rubber-lined body, where the rubber lining acts as both the seat and the seal, ensuring tight shut-off when the disc closes. While this design offers simplicity and cost-effectiveness, it can lead to increased wear under higher pressures and temperatures due to the constant contact between the disc and seat. Industries such as HVAC, water treatment, and general manufacturing frequently employ rubber-lined butterfly valves due to their reliability and economical nature, especially in applications involving non-corrosive fluids at low pressures and temperatures.

In contrast, High-Performance Butterfly Valves are engineered for more demanding applications involving higher pressures and temperatures. These valves often incorporate advanced materials like stainless steel or specialized alloys for the disc and seat, enabling them to handle steam, gases, and corrosive chemicals. High-performance designs include Double Offset and Triple Offset Butterfly Valves, each offering enhanced capabilities for specific industrial needs.

Double Offset Butterfly Valves incorporate two distinct offsets: one from the centerline of the pipe and the second from the centerline of the seat cone. This design minimizes rubbing between the disc and seat during operation, reducing wear and enhancing seal longevity. The reduced friction allows these valves to operate effectively in higher pressure and temperature conditions than zero offset valves. Industries requiring reliable performance and extended service life under challenging conditions often utilize double offset designs.

Triple Offset Butterfly Valves add a third offset by designing the sealing components with a conical profile. This feature ensures that the disc contacts the seat only at the final point of closure, virtually eliminating wear and providing a torque-seated, zero-leakage valve. Constructed with metal-to-metal sealing surfaces, triple offset valves can withstand extreme temperatures and pressures. Industries such as petrochemical, power generation, and refining favor these valves for critical applications where safety and reliability are paramount.

Comparing these valves reveals key differences in design and operational capabilities. Rubber-lined valves, with their concentric design and elastomeric lining, offer simplicity and cost-effectiveness for general-purpose use but are limited to lower pressure and temperature applications. High-Performance Butterfly Valves, including double and triple offset designs, enhance performance for moderate to high-pressure systems thanks to their offset stems and improved sealing mechanisms.

Selecting the appropriate butterfly valve hinges on the application's specific requirements, including the type of fluid, pressure, temperature, and the necessity for tight shut-off. Rubber-lined butterfly valves present economical and effective solutions for general-purpose needs involving non-corrosive fluids at low pressures and temperatures. Conversely, High-Performance Butterfly Valves with double and triple offset designs are better suited for challenging environments where reliability and longevity are essential under higher pressures and temperatures.

Understanding the nuances of each valve type ensures optimal performance, safety, and cost-effectiveness in industrial fluid control systems. Engineers and operators can make informed decisions that enhance system efficiency and reliability by carefully considering valve style, construction, and application requirements.

Classic Controls  

+1 863-644-3642  

https://classiccontrols.com

Fluid Processes - When A Butterfly Valve Is The Best Choice

High performance butterfly valve with actuator
Image courtesy ABZ Valve

Industrial process control valves are available in uncountable combinations of materials, types, and configurations. An initial step of the selection procedure for a valve application should be choosing the valve type, thus narrowing the selection field to a more manageable level. Valve "types" can generally be classified by the closing mechanism of the valve.

A butterfly valve has a disc that is positioned in the fluid flow path. In the most common form of butterfly valve, the disc rotates around a central axis, the stem, through a 90 degree arc from a position parallel to the flow direction (open) to perpendicular (closed). A variety of materials are used in the valve body construction, and it is common to line the valve with another material to provide special properties accommodating particular process media.

What attributes might make a butterfly valve a beneficial selection over another valve type?

• The closure arrangement allows for a comparatively small size and weight. This can reduce the cost, space, and support requirements for the valve assembly.
• Generally low torque requirements for valve operation allow for manual operation, or automation with an array of electric, pneumatic, or hydraulic actuators.
• Low pressure drop associated with the closure mechanism. The disc in the flow path is generally thin. In the fully open position, the disc presents its narrow edge to the direction of flow.
• Quarter turn operation allows for fast valve operation.
• Some throttling capability is provided at partially open positions.
• Small parts count, low maintenance requirements.

What may be some reasons to consider alternate valve types?

• Butterfly valve throttling capability is generally limited to low pressure drop applications
• Cavitation can be a concern.
• Some sources mention the possibility of choked flow as a concern under certain conditions.

Butterfly valves, like other valve types, have applications where they outperform. Careful consideration and consultation with a valve expert is a first step toward making a good selection. Combine your process know-how with the product application expertise of a professional sales engineer to produce the best solutions to your process control challenges.

Resilient Seated Butterfly Valves from Classic Controls, Inc.

High Performance Butterfly Valves Meet Special Application Challenges

High Performance
Butterfly Valve
ABZ Valve

Industrial process control applications can present stringent and challenging performance requirements for the physical equipment and components that comprise the process chain. The valves employed in fluid based operations need to be resistant to the impact of extreme fluid conditions, requiring careful design and selection consideration to assure proper performance and safety levels are maintained in a predictable way.

Industrial valves intended for extreme applications are generally referred to as severe service or high performance valves. While there are plenty of published and accepted standards for industrial valves, one does not exist to precisely define what constitutes a severe service valve.

So, how do you know when to focus valve selection activities on severe service or high performance valves, as opposed to those rated for general purpose? There are a number of basic criteria that might point you in that direction:

• Extreme media or environmental temperature or pressure
• High pressure drop operation that may cause cavitation
• Rapid or extreme changes to inlet pressure
• Certain types or amounts of solids contained in the fluid
• Corrosive media

Certainly, any of these criteria might be found in an application serviceable by a general purpose valve, but their presence should be an indicator that a closer assessment of the fluid conditions and commensurate valve requirements is in order. The key element for a process stakeholder is to recognize when conditions are contemplated that can exceed the capabilities of a general purpose valve, leading to premature failure in control performance or catastrophic failure that produces an unsafe condition. Once the possibility of an extreme or challenging condition is identified, a careful analysis of the range of operating conditions will reveal the valve performance requirements.

There are numerous manufacturers of severe service or high performance valves, each with specialized product offerings focusing on a particular performance niche. ABZ Valve manufactures high performance butterfly valves ranging from 2-48 inches and 150-600 psi. The valve design is ideal for manual or automated actuation, installed with a manual hand gear, electric actuator, or a pneumatic actuator. Seats are available as soft, metal, and fire safe, and body types include wafer, double flanged, and butt-welded. Construction materials include carbon steel and 316 stainless steel. A range of options and variants are available to customize the valve build to suit a replacement or new installation.

More information about the ABZ  Valve high performance offering is included below. You can always get more information and discuss your special requirements with a valve specialist. They have application experience and access to technical resources that can help with selecting the right valve components to meet your severe service and high performance applications.

Double Offset High Performance Butterfly Valves from Classic Controls, Inc.