How does it work: Ball Valves

08 September 2015

By Tashika Varma, Marketing Coordinator - Cameron Valves & Measurement

A ball valve is a device with a spherical closure unit that provides on/off control of flow. The sphere has a port, also known as a bore, through the center. When the valve is positioned such that the bore is aligned in the same direction as the pipeline, it is in open position and fluid can flow through it. When rotated 90 degrees, the bore becomes perpendicular to the flow path, meaning the valve is closed and the fluid cannot pass through.

The ball valve, along with butterfly and plug valves, is part of the quarter-turn valve family. Ball valves are known for reliable, bubble-tight sealing. Thus, they are a great choice for gas applications where tight shutoff is necessary. Due to the potential of constant wearing on the seats, ball valves are not ideal for throttling applications. The body of a ball valve usually is made of steel and can be made more durable with nickel plating.

The most common ball valves are considered to be two-way, which allows flow to travel linearly from the inlet to the exit. Furthermore, the three-way and four-way ball valves allow for flow to travel in multiple directions, including 90-degree angles.

There are four general body styles of ball valves: fully welded, three-piece body (also called side or end-entry), split-body, and top-entry. The difference is based on how the pieces of the valve are manufactured and assembled, but the valve operation is the same in each type. Each design has its benefits.

Types of Ball Valves – Ball Movement

Trunnion Mounted Ball Valve A trunnion mounted ball valve has additional mechanical anchoring at the top and bottom on the ball. This special mounting is suitable for larger and higher pressure valves. Moreover, this design allows for reduction in valve torque as the ball is supported in two places. The trunnion mounted stem absorbs the thrust from the line pressure, preventing excess friction between the ball and seats, so even at full rated working pressure operating torque remains low.

Floating Ball Valve A floating ball valve is not held in place by a trunnion, and instead is attached only to the stem. This sometimes causes the ball to float slightly downstream. However, when this happens, the ball presses against the seat, creating a positive seal.

Rising Stem Ball Valve A rising stem ball valve incorporates tilt-and-turn operation, eliminating seal rubbing which is one of the primary causes of valve failure. When the valve is closed, the core is wedged against the seat, ensuring positive shutoff. When the valve is open, the core tilts away from the seal and the flow passes uniformly around the core face. Additionally, the valve is able to eliminate localized high- velocity flow that typically creates uneven seat wear exhibited by ordinary ball, gate, and plug valves.

Additionally, there are three basic types of bores for ball valves: full port, reduced port (also known as standard port), and v-port. These four types have different constructions and purposes.

Full-Port Ball Valve – A full-port, also known as a full-bore, ball valve has a bore internal diameter (ID) approximately equal to the pipeline ID. This allows for reduced friction and pressure loss across the valve. With a full-port ball valve there is no restriction to the flow of fluid, but the valve can be more expensive. This type of bore is ideal for situations where pigging may be necessary. 

Reduced-Port Ball Valve – A reduced-port, also known as a reduced-bore, ball valve is a valve in which the bore is reduced to one or two nominal sizes lower. This provides a more restricted flow path, generally resulting in higher energy losses. 

V-Port Ball Valve – A v-port ball valve has either a “v” shaped ball or a “v” shaped seat. This type of valve also is known as a control valve in which the flow velocities need to be controlled as required per the application.

Applications

Ball valves can be used in a variety of applications and markets, such as transmission and storage, gas processing, industrial, and many more. Jeffrey Joseph, product manager for the CAMERON ball valves, explains that ball valves provide reliable leak protection which is especially beneficial in gas applications. Ball valves have low pressure drop and can open and close quickly.

A variety of construction materials, trim options and designs make these valves extremely versatile. Ball valves (such as Cameron’s RING-O® subsea ball valves) are commonly utilized in subsea applications on manifolds that require long service life at high pressures. Ball valves are also used in cryogenic applications where compressed gas must be kept at a stable temperature in order to be moved efficiently.

Printer friendly Printer friendly
Tip editor Tip editor

Back to the news archive...

top
  bottom
KCI Publishing Copyright © 2017 - Disclaimer
 
YouTube Twitter LinkedIn Facebook KCI World Webshop