VALVE MAGAZINE Fall 2023

Meeting these standards has become a mandate for trade with the European Union, as well as JIS standards for Japan and similar requirements elsewhere. Other common specifications for the rating of ball valves include WOG (water/oil/gas), CWP (cold working pressure) and WSP (working steam pressure). These ratings are more limited and are typically established by the individual manu facturer. All of these specifications will establish a pressure/ temperature curve for the valve design, which lowers the pressure rating as the temperature rises. BODY DESIGNS ARE DIVIDED INTO FOUR BASIC CONFIGURATIONS: • Three-Piece Swing Out. The body is designed in three pieces with the ability to easily swing the center body sec tion out of the line for repair without having to remove the entire valve (Figure 3). This is handy when valves are thread ed or welded into a pipeline. • End Entry. This design uses a one-piece or unibody

Figure 5: Split-body design.

Stem

Adjusting Nut Gland Ring Stem Seals

Bonnet

Bonnet Bolting

Body

Spring

Bonnet Gasket

Ball

Seat Ring

Figure 3: Three-piece ball valve design.

Seat

design (Figure 4). All the internal components are assembled into the valve through the end, where an end plug is installed to retain the parts. This design elim inates any form of body or bonnet seal, eliminating a potential leak path. • Split Body. This design (Figure 5) splits the body into two halves and allows for easy assembly and one less seal than the three-piece design. This split body design is

Figure 6: Top-entry design.

THE BALL The flow control element of the ball valve is, of course, the ball. The ball acts against the seat and can stop or control flow through the valve. Balls are designed and manufactured to exacting tolerances for surface finish and spherosity, or roundness. Both the ball and seat are critical to smooth operation, reduced torque and good sealing performance, especially when metal seats and metal-to-metal sealing are required. The ball port configuration can vary from a stan dard straight and through-hole style to a multi-port style for ball valves that offer three- to five-way port designs (Figure 7). While most ball valve designs use a full spherical ball, there are also designs that use a half ball (sector) and those that use cam action to force the ball into the seat. The balls are machined from many materials, including metal, ceramic or plastic. Metal balls can be enhanced with a variety of coatings or surface treatments to provide improved wear resistance, corrosion resistance or high hardness to pre vent galling, which is where the base metal does not hold up. Surface enhancements can include polymers, flame spray, electroless nickel, PVD coatings and diffusion processes such as nitride and boride application. These enhancements are a major reason for the successful application of ball valves in the wide variety of applications they are used.

especially advantageous when the valve is large, making it easier for the assembly of large components.

Figure 4: End-entry design.

• Top Entry. The top entry design (Figure 6) utilizes a one-piece body like the end entry, except that the top of the body is exposed in order to assemble the internal parts. A bonnet is then bolted on the top of the valve, making this design repairable in-line, similar to the three-piece design. The most common top entry designs are unique to ball valve designs, as the ball and seats float and operate in unison and on a taper within the body, unlike the other designs.

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