for a broad range of pressures and temperatures . The self-lubricating nature of these rings , along with a high-hardness valve stem , provide ease of movement . The live-loaded , high-compression packing maintains extremely low levels of packing emissions over many valve cycles , and the packing compression can be adjusted to further extend valve life .
Valve body design
While the valve seat and packing designs are critical , a design with installation and maintenance in mind is also important . The valve should come with standard face-to -face valve dimensions , provide an extended stem to allow the packing to be adjusted even when the valve is insulated , and provide an integral , standard actuator mounting base that accepts most actuators without requiring coupling or additional brackets ( see Figure 2 ). Another key feature is a stem / disc design that maximizes flow capacity . Many highperformance butterfly valves have a thick shaft that passes through the flow path , obstructing flow and increasing pressure drop . Better designs reduce the profile of the disc / shaft combination , allowing a valve of equal size to pass more flow with less pressure drop .
Maintenance friendly
While a top-tier high performance butterfly valve will last for years , at some point seat and packing wear are inevitable , so it is important that the valve be designed to easily replace and repair these components . Therefore , the valve should be specifically engineered to allow replacement of both the seat and packing materials without disassembling the valve stem and disc ( see Figure 3 ). Though repairs should be infrequent and maintenance costs low , lifecycle costs will be further reduced if the packing and seats can be easily and quickly replaced .
Key take aways
The small form factor , low cost , and superior sealing capability of highperformance butterfly valves make them an excellent solution for equipment isolation and on / off applications . However , a wise user will carefully evaluate the details of high-performance valve designs . Features such as double offset sealing , advanced disc seat designs , and low emission packing can extend valve life significantly . Advanced sealing techniques operate independent of process pressure
BUTTERFLY VALVES
and maintain zero leakage in bidirectional and even dead-end pipe applications . When maintenance is eventually required , top tier valves are designed to facilitate easy and quick repairs with minimum disassembly . If a project requires reliable and zero leakage isolation , consider the advantages of well-designed high-performance butterfly valves . The initial savings can be significant when compared to plug or ball valve equivalents , and the extended life and ease of maintenance provide longterm lifecycle cost savings as well .
About the author Karin Pharr is the global product manager for high performance butterfly valves at Emerson . She is responsible for portfolio management , pricing , marketing , and strategic program execution across the Keystone™ High Performance Butterfly Valve portfolio . Before product management , Pharr held multiple positions across engineering , information technology , and business process . She holds a Bachelor of Science degree in Nuclear Engineering from Texas A & M University .