How to connect valves and pipes


Ball valves with threaded connections are easy to insta […]

Ball valves with threaded connections are easy to install, maintain and replace, and are inexpensive and ideal for small applications. In applications with ball valves smaller than 4 inches in diameter, threaded connections are often preferred. This is because larger diameter connections are more difficult to seal and therefore tend to leak through the threads. Even with smaller threaded ball valve connections, it is recommended to use pipe tape or sealant between male and female threads as a precaution. Both provide additional sealing, and the sealant also acts as a lubricant, preventing metal-to-metal contact and wear. As we mentioned above, there are some industry standards that govern thread design.


Threaded connections can be straight or tapered, the exact size is determined by three sets of standards: National Pipe Threads, British Standard Pipe and Metric Straight Threaded connections maintain the same diameter throughout their length and require gaskets or soft O-rings ring to maintain a seal. As the name suggests, the diameter of the tapered thread tapers towards the end of the connection. Tapered connections do not require an O-ring seal, but still require tubing or sealant for a leak-proof seal. National Pipe Thread (NPT) is the design standard for pipe threads in most of North America (excluding Mexico).


NPT threads are uniform, have a 60-degree pitch, have flat crests and troughs, and can be straight (NPS) or tapered. When connecting male and female tapered threads, they pull against each other to form a leak-proof seal. Valve connections can be welded into the piping system to prevent the possibility of leaks. Welded valve connections are often used in high temperature and high pressure systems, such as chemical processing, where there is zero room for error due to leaks. This is usually considered a permanent installation because the valve needs to be desoldered to be removed from the pipe. Flanges are solid sheet metal with bolt holes around the edge of the valve connection.


When a flanged Pipe Fittings is installed in a piping system, the plate can be bolted to another flange on the pipe, creating a solid connection. Flanged connections are commonly found in valves larger than 4 inches in diameter and are common in industrial applications. Flanges are easy to install and remove for daily cleaning. Slip a threaded nut and a soft metal sleeve called a ferrule over the end of the pipe, then tighten the nut until the ferrule is pressed into the seat. The ferrule is compressed between the valve and the compression nut, creating a leak-proof seal. Traditional compression connections are often found in residential plumbing.