Showing posts with label Flowseal. Show all posts
Showing posts with label Flowseal. Show all posts

Wednesday, December 9, 2015

A Close Look at Butterfly Valve Seat

Butterfly valve soft seat cutaway view
Cutaway View of Butterfly Valve With Soft Seat
Courtesy Flowseal - Crane CPE
Butterfly valves are found throughout the fluid based applications in the process control field. They are one of many common and special types of industrial valves used to regulate fluid flow in ways that are compatible with the media being controlled and the degree of precision needed to produce the desired process outcome.

The industrial process control field benefits from a large array of valve manufacturers in pursuit of the favor and business of process operators. Operators continually seek better performance and lower life cycle costs. Manufacturers respond with increasingly improved designs.

A butterfly valve has a disc that is positioned in the fluid flow path. It 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 critical element of a butterfly valve is the seat, where the disc seals to the body in the closed position. Seat design should provide these positive operating attributes:
  • Low friction to reduce valve operating torque
  • Resistance to wear
  • Arrangement that provides for easy replacement
  • Seal or shutoff tightness appropriate for the application
Flowseal, part of the Crane, CPE group of brands, utilizes their specially designed Soft Seat valve sealing arrangement on their resilient sealed butterfly valves. The Soft Seat feature provides beneficial fulfillment of process requirements for the attributes listed above. The valve is available in a range of sizes, with options and variants to meet a wide array of industrial process requirements.

Learn more about the Flowseal Soft Seat butterfly valves by watching the short video below. You can delve deeper with a browsing of the illustrative brochure that is also included below. It provides some detailed illustrations of how the seat functions under differing operating conditions. Contact a product specialist and share your process challenges. Your process knowledge and their product application expertise, when combined, will produce a useful solution.


Monday, September 28, 2015

Triple Offset Valves - Some Advantages and Considerations

Flowseal brand triple offset butterfly valve
Triple Offset Butterfly Valve
Courtesy Flowseal, Crane CPE
Industrial process control often involves the control of fluid flow, ranging from slurries or petroleum to highly refined liquids and gases. The enormous variety of application specifics has given rise to a wide range of valves with performance characteristics to match those requirements. One common valve type is the butterfly valve. In it's simplest form, it is a disc located in the path of fluid flow that is connected to a shaft. The disc rotates through a 90 degree arc to present either its face (valve closed) or its edge (valve open) to the fluid flow path. I wrote about some advantages and disadvantages of butterfly valves a couple months ago under the title "Is a Butterfly Valve Right for Your Application?".

There is a variant of the simple version of the butterfly valve that provides distinct advantages for many applications. Referred to somewhat officially as a triple offset butterfly valve, it can also be more commonly called simply a triple offset valve.

How is a triple offset butterfly valve different from a basic butterfly valve?


The triple offset valve does away with the centric alignment of the shaft and disc, using instead a shaft mounting arrangement that relocates the shaft axis off both the center of the disc and the center of the bore. This shaft positioning, while creating a larger flow obstruction in the fully open position, sets the disc movement path in the proper alignment to take advantage of the third offset, which is the sealing surface. Triple offset valves have a different seals than other butterfly valve variants. There is an angular sealing surface, the angle of which is determined by sectioning an imaginary right angle cone shape that extends along the bore. However, the apex of the cone does not lie on the center of the bore. This inclination of the seal cone constitutes the third offset. You can see an illustration of this description in the document included below.

What advantages might those differences bring to your application?


  • Triple offset valves have discs that do not contact the sealing surface until the valve is closed. This is in contrast to other butterfly valve designs, which have contact between the disc and resilient seals for part or all of the disc travel, along with the associated friction and wear.
  • Elastomer or other similarly resilient materials are not needed to provide a zero-leakage, bubble tight shutoff. Sealing is generally accomplished with metal-to-metal contact.
  • Friction free stroking of the valve disc. Actuator power requirements may be reduced.
  • All metal construction provides elements of corrosion and heat resistance not found in other butterfly valve designs with resilient seals.
  • This valve is torque sealed, not position sealed like other butterfly variants. Actuator torque forces the seal of the machined metal surfaces to produce tight shutoff.
  • No breakaway torque requirement, since the disc is not contacting resilient seals. 
  • Seating arrangement prevents overstroking of the valve, a potential problem with other butterfly valves.
Different manufacturers may have slightly different feature sets, but this should help you consider the benefits of this butterfly valve variant. Though its initial cost may be higher, the expected lower maintenance requirement, longer service life, and better performance may be well worth it. Talk to a valve product specialist about your application. I've written many times that combining your process expertise with the up to date product knowledge of a professional sales engineer will produce a positive outcome.


Thursday, February 26, 2015

High Performance Butterfly Valve Seating Principles - Metal Seats

high performance butterfly valve
High Performance Butterfly Valve
(courtesy of Flowseal)



PRINCIPLE OF METAL SEATING



Metal-to-metal sealing is accomplished by the “line contact” between a spherical surface and conical surface. Figure 1 illustrates a typical globe control valve seat and plug. The plug seating surface is the segment of a sphere; when engaged against the seat ring, a line contact seal is achieved.

In a metal seat design, it is necessary to apply enough force per linear inch to maintain a tight metal-to-metal contact between the seal- ing members; however, high linear thrust can cause a collapse of the seating members (“bearing failure”).




DISC CLOSED, Self-Energized Seal

In Figure 2, the Flowseal disc and seat are engaged, and the process fluid is under low pressure. The spherical edge of the disc, with a larger diameter than the conical seat tongue, imparts a thrust of approximately 600 pounds per linear inch against the seat. The mechanical properties and shape of the Inconel® seat allow it to both flex and maintain a constant thrust against the disc.

This controlled loading prevents the occurrence of bearing failure and reduces the leakage and wear between the components.

Wednesday, February 25, 2015

High Performance Butterfly Valve Seating Principles - Soft Seats

high performance butterfly valve
High Performance Butterfly Valve
(courtesy of Flowseal)

High performance butterfly valves (HPBV) are a standard in many industries including heating, ventilating and air conditioning, power generation, hydrocarbon processing, water and waste water treatment, and marine and commercial shipbuilding.

They are also installed in applications as diverse as food and beverage processing, snowmaking and pulp and paper production. Configurations are available for harsh conditions as well as applications requiring nominal pressure and temperature ratings.

The following describes the soft seating design principles for high performance butterfly valves:

soft seated HPBV valve
DISC OPEN 

In Figure 1, the disc and seat are not engaged. In this position, the shoulders of the seat are forced against the cavity shoulders by the compression of the o-ring.

The seat is recessed inside the seat cavity and acts as a gasket in the anchoring groove area.The seat cavity is sealed from exposure from the process fluid and protects the seat from abrasion and wear. The o-ring, which is completely encapsulated by the seat, is also isolated from exposure to the process fluid.

Thursday, October 9, 2014

High Performance Butterfly Valves for On/Off and Throttling Service

High Performance Butterfly Valves (HPBF) are a standard in many industries including heating, ventilating and air conditioning, power generation, hydrocarbon processing, water and waste water treatment. The key features of HPBV are high performance shutoff and modulating service for standard industrial process lines, materials of construction options include carbon and stainless
steel,  sizes up to 48”, both wafer and lugged body styles available, in pressures classes 150 – 600.

Here is a short video introducing the Flowseal high performance butterfly valve.