High Performance Butterfly Valve Seating Principles - Metal Seats

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.

High Performance Butterfly Valve Seating Principles - Soft Seats

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:

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.

Applying Cooling Towers

Delta Cooling Tower

Here is a presentation that explains how to apply cooling towers, including the basic cooling tower principles, design considerations, and construction issues.

The original presentation given in 2009 by Steve Lowe, PE to the Hampton Roads, VA Chapter of ASHRAE.

For more information on any cooling tower issue in Colorado, New Mexico, Wyoming, Montana, Utah, Nevada, Idaho, or the western Dakotas, contact:

Mountain States Engineering and Controls
1520 Iris Street
Lakewood, CO 80215
303.232.4100 Phone
303.232.4900 Fax
Email: info@mnteng.com

www.mnteng.com

Description of a Process Control Enclosure in a Hazardous, or Explosion Proof Location

This is a short video that explains what an explosion-proof enclosure looks like, how it works, and why it is safe to use in explosive or combustible atmospheres.

The definition of "explosion-proof" doesn't mean the enclosure can withstand the forces of an external explosion, but rather that it will cool any escaping hot gases (caused by an internal spark or arcing contacts) sufficiently enough as to not to allow the ignition of combustible gases or dusts in the surrounding area.

For more detailed information on electrical equipment enclosures in hazardous areas, visit this page.