Maintenance Technology August 2017 - 34

FLUID HANDLING

Select
The Best
Seats for
Your
Butterfly
Valves
BUTTERFLY VALVES OWE much
of their popularity to their economic
cost and efficient designs. Among the
butterfly valves available in today's
marketplace, the resilient-seated type
(the most basic) is the design that's
commonly used in fluid-processing
applications.
According to the fluid-handling
experts at Crane Engineering
(Kimberly, WI, craneengineering.
net), the functionality of a butterfly
valve is greatly dependent on its seat,
which seals between the pipe flanges
and the valve disc. In resilient-seated
designs, the stem is centered in the
middle of the valve disc that, in turn,
is centered in the pipe bore. These
valves typically feature a somewhatflexible seat and rely on the disc for a
high level of contact with the seat to
ensure a proper seal.
Crane Engineering is a distributor
of industrial-grade pumps, valves,
filters, wastewater-treatment
equipment, and other fluid-processing
technology. Services include repair,
corrosion-resistant coatings, and skidsystem design and fabrication. For more
information and instructional videos, visit
craneengineering.net.

34 |

MAINTENANCE TECHNOLOGY

Seat-Type Pros and Cons
Three basic seat styles are available for resilient-seated butterfly valves. A recent post
on the Crane Engineering blog discussed the pros and cons of each, including their specific strengths and weaknesses. (Use Table I for quick reference.)

Table I. Quick Butterfly-Valve-Seat Selection Guide

Feature
Replaceable
Consistent Torque
Ideal for Vacuum Service
Ideal for Dead-End
Service
Deformation Resistant
Flange-Type Independent

Cartridge
Seat

Molded
Seat

Booted
Seat

YES
YES
YES

NO
NO
YES

YES
NO
NO

YES

YES

NO

YES
YES

YES
YES

NO
NO

Booted (dovetail) seats. These seats have a dovetail shape that mates with
the inner-diameter valve bodies. They're easily removable and serviceable
because the fit isn't physically bonded. Unfortunately, they're prone to
movement when mounted between flanges, resulting in deformation that
tends to bulge around the disc-contact points. This sensitivity to mounting conditions
limits the versatility of booted-seat butterfly valves. Molded and cartridge seats were
developed to address such weaknesses.
Molded seats. These seats are bonded to the bodies of valves through an
injection-molding process. While this provides a direct bond, it makes the
seat irreparable. Since the seat is integrated with the valve body, the entire
valve must be replaced if the seat becomes damaged. Still, a molded seat's
permanent bond with a rigid valve body has advantages over a booted
seat. Molded-style seats also resist deformation and dislocation during valve mounting
and are capable of dead-end or vacuum service.
Cartridge seats. These seats are created by compression molding a layer
of elastomer onto a rigid phenolic backing ring, which supports the
elastomer in multiple directions. This process is much more consistent
than the injection molding used to create molded-style seats. It provides
constant pressure to form the seat shape and maintains tight control of its
dimensions. Because of the tight tolerances, cartridge seats offer the best
torque consistency and highest wear resistance. This type of seat also improves upon
the molded style by making the seat replaceable. In highly abrasive applications, i.e.,
where valves need to be replaced on a regular basis, the cartridge seat could simply be
replaced rather than the entire valve.
Cartridge seats offer advantages unmatched by other seat styles. When the valve body
has an integrated retaining lip, a cartridge-seated valve is capable of dead-end service.
Unlike booted or dovetail seats, cartridge seats can more efficiently operate in a system
that requires vacuum service.
Update Your Valve-Speak
To learn more about general valve terminology, download Crane Engineering's  "Ultimate Glossary of Valve Terminology" at info.craneengineering.net/glossary-of-valveterminology. MT
- Jane Alexander, Managing Editor
AUGUST 2017


http://info.craneengineering.net/glossary-of-valve-terminology http://www.craneengineering.net

Table of Contents for the Digital Edition of Maintenance Technology August 2017

Editorial
Uptime
On The Floor
Reliable Security, Reliable Operations
Highly Charged Reliability
Drowning in Data? Look to the 'Stars'
Reliable Pumping Supplement
SAP: Tips and Tricks
Steam-Trap Inspections
Saving Tribal Knowledge
Seats for Butterfly Valves
IIoT
ISO 55000
Understand Lube ID Systems
Tomato Processor Boosts Steam Output, Cuts Emissions
Products
Ad Index
Showcase
Final Thought
Maintenance Technology August 2017 - 1
Maintenance Technology August 2017 - Cover1
Maintenance Technology August 2017 - Cover2
Maintenance Technology August 2017 - 1
Maintenance Technology August 2017 - 2
Maintenance Technology August 2017 - 3
Maintenance Technology August 2017 - Editorial
Maintenance Technology August 2017 - 5
Maintenance Technology August 2017 - Uptime
Maintenance Technology August 2017 - 7
Maintenance Technology August 2017 - On The Floor
Maintenance Technology August 2017 - 9
Maintenance Technology August 2017 - Reliable Security, Reliable Operations
Maintenance Technology August 2017 - 11
Maintenance Technology August 2017 - 12
Maintenance Technology August 2017 - 13
Maintenance Technology August 2017 - 14
Maintenance Technology August 2017 - 15
Maintenance Technology August 2017 - Highly Charged Reliability
Maintenance Technology August 2017 - 17
Maintenance Technology August 2017 - 18
Maintenance Technology August 2017 - Drowning in Data? Look to the 'Stars'
Maintenance Technology August 2017 - 20
Maintenance Technology August 2017 - 21
Maintenance Technology August 2017 - 22
Maintenance Technology August 2017 - Reliable Pumping Supplement
Maintenance Technology August 2017 - 24
Maintenance Technology August 2017 - 25
Maintenance Technology August 2017 - 26
Maintenance Technology August 2017 - 27
Maintenance Technology August 2017 - 28
Maintenance Technology August 2017 - 29
Maintenance Technology August 2017 - 30
Maintenance Technology August 2017 - SAP: Tips and Tricks
Maintenance Technology August 2017 - Steam-Trap Inspections
Maintenance Technology August 2017 - Saving Tribal Knowledge
Maintenance Technology August 2017 - Seats for Butterfly Valves
Maintenance Technology August 2017 - IIoT
Maintenance Technology August 2017 - ISO 55000
Maintenance Technology August 2017 - Understand Lube ID Systems
Maintenance Technology August 2017 - 38
Maintenance Technology August 2017 - 39
Maintenance Technology August 2017 - Tomato Processor Boosts Steam Output, Cuts Emissions
Maintenance Technology August 2017 - 41
Maintenance Technology August 2017 - 42
Maintenance Technology August 2017 - Products
Maintenance Technology August 2017 - 44
Maintenance Technology August 2017 - 45
Maintenance Technology August 2017 - Ad Index
Maintenance Technology August 2017 - Showcase
Maintenance Technology August 2017 - Final Thought
Maintenance Technology August 2017 - Cover3
Maintenance Technology August 2017 - Cover4
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