Industrial Butterfly Valves

Resilient seated butterfly valve (Pratt)

Industrial process control valves are available in a very wide array of materials, types, and configurations. The first 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, ball, butterfly, globe, and plug for example, are generally defined by the closing mechanism of the valve.

High performance butterfly valve (Pratt)

A butterfly valve uses a  flat disc that is positioned, paddle-like, in the fluid flow path. It rotates around a central axis (the stem) over a 90 degree rotational arc from open (position parallel to the flow direction) to closed (perpendicular to flow). Butterfly valves referred to as resilient seated are generally used in lower pressure, lower temperature applications and create a seal through compressing the disc into some type of elastomer seat. Another type of butterfly valve, used in higher pressure and higher temperature applications, are known as high performance butterfly valves (HPBF). They have highly machined discs and seats which are precisely seated together. Butterfly valve body materials include cast iron, bronze, and stainless steels. It is common to line the butterfly valve with another material to provide special protection from the process media.

Butterfly Valve Advantages:

• Lower cost
• Minimal lay length
• Easy to automate
• Generally lower torque

Butterfly Valve Disadvantages:

• High wear rate - seals are in flow paths
• Not a good choice as a control valve. Has a very nonlinear flow coefficient. 
• Not great for erosive flowing media.

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.

What Is A High Performance Butterfly Valve?

High performance butterfly valve.
(Pratt Industrial)

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

So, how do you know when to focus valve selection activities on high performance butterfly 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 high performance butterfly valves. Pratt Industrial manufactures high-quality resilient-seated, high performance, and triple offset butterfly valves. Construction materials include carbon steel and stainless steel. Their TE Series triple offset valve offers premium, zero-leakage seating capability even in severe service applications.

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.

For more information, contact Process Control Solutions by calling (800) 462-5769 or by visiting https://processcontrolsolutions.com.