Introduction to Threaded Ball Valves
August 4th 2022
What is a Ball Valve?
A ball valve is a type of quarter-turn valve that employs a perforated, hollow, and rotating ball to regulate the flow through it. It opens when the hole of the ball is aligned with the flow and closes when it is revolved 90-degrees by the handle of the valve. When it is opened, the handle has a flat alignment with the flow. And the handle is aligned perpendicularly to the flow when it is closed. This helps to visually check the status of the valve.
Threaded Connection
Threaded valve connection is one of the most commn valve connection types. And it provides a tight seal and streamlined connection between the valve and pipe.Threaded ball valves are generally divided into internal thread ball valves and external thread ball valves. Commonly, valves have female threaded connections to fit over the end of a male threaded pipe. Besides, the threads on both the valve and pipes must adhere to the same standard thread design in order to be compatible.
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| Threaded Ball Valve Specifications |
Product category: Ball Valves
Valve size: It refers to the size of the passage opening. Valve sizes of different valves vary and depend on the manufacturer. It is given in inches or millimeters.
Number of ports: It specifies the number of connections or inlet/outlet ports to the valve.
Flow (Cv): It refers to the valve flow coefficient and is used to forecast the flow rates.
Connection description: Threaded
| Characterisctics of Threaded Ball Valves |
Threaded ball valves are easy to install, maintain and replace, are inexpensive and ideal for smaller applications. Threaded connections are typically preferred in applications that feature ball valves with a diameter less than 4 inch. This is because connections with larger diameters are more difficult to seal and thus prone to leaks through the threads(Even with smaller threaded ball valve connections, pipe tape or sealant between the male and female threads is recommended as a precaution. Both provide extra sealing, and sealant also acts as lubrication and prevents metal-to-metal contact and galling).
Industry Standards for Thread Design
Threaded connection can either be straight or tapered, and the exact specifications are determined by three sets of standards: National Pipe Thread, British Standard Pipe and Metric.
| 1.Straight vs. Tapered
( 1)Straight threaded connection maintains the same diameter along the entire length, and requires a washer or soft O-ring seal to stay leak-tight.Tapered threads, as the name shos, taper in diameter toward the end of the connection. (2)Tapered connections do not require an O-ring seal, but still need pipe tape or sealant to achieve a leak-tight seal. |
2.Industry Standards of Design
| (1) National Pipe Thread (NPT)
National Pipe Thread (NPT) is the standard for piping thread design in most of North America (excluding Mexico). NPT threads are unified and pitched at a 60 degree angle with flat peaks and valleys, and can be either straight (NPS) or tapered. When male and female tapered threads are connected, they pull tight against one another to create a leak-tight seal. NPT specifications are defined by ASME B1.20.1. Sizes are classified by the connection’s major diameter in inches followed by “NPT” (4 NPT). (2) British Standard Pipe Threads (BSP) British Standard Pipe (BSP) threads are accepted in most parts of the world besides the U.S. and Canada. BSP threads are unified and pitched at a 55 degree angle with rounded peaks and valleys; like NPT threads, they can be tapered or straight. Tapered BSP (BSPT) threaded connections require sealant to form a leak-tight seal between the male and female components. Straight or parallel BSP (BSPP) threaded connections do not require thread sealant, since a bonded seal is incorporated into the design. BSP threads are defined by BS EN 10226-1:2004, BS EN 10226-2:2005 and BS EN 10226-3:2005. BSP sizes are specified using the letters R (which stands for rohr, or “pipe” in German) for tapered connections and G (gas) for straight connections, followed by the major diameter in inches (R 2 ½) (3) Metric Thread Standard (M) The ISO metric thread standard, or M, is an international, general purpose screw thread standard. M threads are parallel, pitched at 60 degrees and have flat peaks and valleys. The design is defined by ISO 68-1, which was one of the first standards set by the ISO in 1947. The major difference between M, BSP and NPT threads is that M threads are measured in millimeters. Sizes are specified with M followed by the major diameter and the pitch, separated by a hyphen (M8-1.25). The pitch is the distance in millimeters between the crests of two threads.
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