Tuesday, January 23, 2018

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Globe Valves - Single-Port Valve Bodies

  • Single port is the most common valve body style and is simple in construction.
  • Single-port valves are available in various forms, such as globe, angle, bar stock, forged, and split constructions.
  • Generally single-port valves are specified for applications with stringent shutoff requirements. They use metal-to-metal seating surfaces or soft-seating with PTFE or other composition materials forming the seal. Single-port valves can handle most service requirements.

Figure 3-1. Single-Ported Globe-Style Valve Body

Figure 3-1. Single-Ported Globe-Style Valve Body


  • Because high-pressure fluid is normally loading the entire area of the port, the unbalance force created must be considered in selecting actuators for single-port control valve bodies.
  • Although most popular in the smaller sizes, single-port valves can often be used in 4-inch to 8-inch sizes with high-thrust actuators.
  • Many modern single-seated valve bodies use cage or retainer-style construction to retain the seat-ring cage, provide valve-plug guiding, and provide a means for establishing particular valve flow characteristics. Retainer-style trim also offers ease of maintenance with flow characteristics altered by changing the plug.
  • Cage or retainer-style single-seated valve bodies can also be easily modified by change of trim parts to provide reduced-capacity flow, noise attenuation, or reduction or elimination of cavitation.

 

Figure 3-1 shows two of the more popular styles of single-ported or single-seated globe-type control valve bodies. They are widely used in process control applications, particularly in sizes from 1-inch through 4-inch.

 

Figure 3-2. Flanged Angle-Style Control Valve Body

Figure 3-2. Flanged Angle-Style Control Valve Body

 

Normal flow direction is most often up through the seat ring.

Angle valves are nearly always single ported (figure 3-2). They are commonly used in boiler feedwater and heater drain service and in piping schemes where space is at a premium and the valve can also serve as an elbow. The valve shown has cage-style construction. Others might have screwed-in seat rings, expanded outlet connections, restricted trim, and outlet liners for reduction of erosion damage.

Bar-stock valve bodies are often specified for corrosive applications in the chemical industry (figure 3-3). They can be machined from any metallic bar-stock material and from some plastics. When exotic metal alloys are required for corrosion resistance, a bar-stock valve body is normally less expensive than a valve body produced from a casting.

High-pressure single-ported globe valves are often used in production of gas and oil (figure 3-4). Variations available include cage-guided trim, bolted body-to-bonnet connection, and self-draining angle versions.

Figure 3-3. Bar Stock Valve Bodies

Figure 3-3. Bar Stock Valve Bodies

Figure 3-4. High Pressure Globe-Style Control Valve Body

Figure 3-4. High Pressure Globe-Style Control Valve Body

Flanged versions are available with ratings to Class 2500.


Go to the next page, Valve and Actuator Types - Control Valves - Globe Valves - Balanced-Plug Cage-Style Valve Bodies

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Go to the Control Valve Handbook - Table of Contents page


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