Types of Valve End Connections

Threaded connections are very common. They provide a compact and streamlined connection between the valve and pipe.

The valve typically has female threaded end connections, into which the male threaded pipe fits. There are valves with male threaded connections as well, and even valves with one female end and one male end. Threaded connections must adhere to a standard in order to be useful in industry. There are a few different standards that exist. The valve and pipe must both be created using the same standard in order for them to make a proper connection.

There are standards for straight threads and some for tapered. Tapered threads provide a fluid tight seal without the use of a soft seal like an o-ring or flat washer. Straight threads do require a soft seal that gets compressed between the valve and pipe, hose, or fitting that they are being connected to.

Male vs. Female

Straight vs. Tapered

Anatomy of Threads

The valve simply has a socket with an inner diameter that is ever so slightly larger than the pipe's outer diameter. The pipe is inserted into the socket, and is welded around the rim as shown here. Socket weld connections are usually reserved for smaller sizes, typically 2" and below. They are permanent connections that are reliably leak-free. This example includes "heat sink" fins which help dissipate heat to protect the seals during welding. Valves with this feature are often referred to as "weld-in-place."

Note: These welds should be performed by a trained .professional.Care must be taken to avoid damaging the seats and seals with excessive heat.

This is the most common connection type in residential plumbing systems. This connection type is very similar to socket weld. The pipe fits snuggly into a smooth bore on the valve, then the connection is soldered by heating the valve bore and touching the seam with solder which melts and gets drawn in and around the entire circumference of the pipe/valve seam.

While there are situations where soldering a connection may be dangerous, difficult, or even impossible, they do provide a very rugged and reliable connection that can withstand shock such as water-hammer, temperature fluxtuations, and flexing.

Glue socket connections are also referred to as FIP, slip-fit, friction fit, pipe end, or spigot connections. They are very simple. The inner diameter of a glue socket connection is ever so slightly larger than the outer diameter of the pipe, which simply inserts into the socket. PVC cement is used (prior to inserting) to attach PVC or CPVC valves to PVC or CPVC pipes. It is recommended to twist the pipe 1/4 turn as it is inserted. The cement actually melts the pieces together making them permanent. These connections cannot be un-done.

Most flanged end connections adhere to an industry standard. These standards define certain criteria that must be met in order to facilitate the use of products from various manufacturers.

ANSI is the American National Standards Institute. Together with the ASME (American Society of Mechanical Engineers), they have developed and published a standard for flange connections. That standard is ASME/ANSI B16.5.

There is also a European standard that is similar, but NOT THE SAME. That standard is DIN, which is an acronym for the german translation of "German Institute for Standardization." The specific standard for pipe flanges is DIN EN 1092-1. This standard is also recognized by ISO (International Standards Organization) under ISO 7005.

SAE is the Society for Automotive Engineers. They have also developed a standard for flange type connections where the flange is separate from the components that it holds together. That standard is SAE J518. This standard is also recognized by ISO under ISO 6162.

Lugged style flange connections are similar to wafer with 2 minor differences. 1) The lug holes ARE threaded and there is a lug hole for every bolt hole on the flanges. 2) each threaded hole accepts 2 bolts, one from each flange on opposing sides. This type of connection can be used for dead-end service, where there is only a flange on one side of the valve and the other is open to atmosphere, provided that the seat/retainer is bolted in place.

Wafer style flange connections are typically reserved for butterfly valves due to there slim profile. They can, however, also be found on ball valves from some manufacturers. This connection type simply sqeezes the valve between 2 flanges using long bots or threaded end rods. There are holes on the valve for the bolts to pass through, which are NOT threaded, and are oversized, allowing for some play. There is NOT always a hole for every bolt hole on the flanges. They are simply used to help hold the valve in place until all of the other bolts are in. On resilient seated butterfly valves, the resilent seat is also used as the seal between the valve and flat-faced flange on each side. On high performance butterfly valves, raised face flanges are used along with gaskets to form a fluid tight seal. This type of connection is NOT suitable for dead end service.

This type of connection is typically found on water lines in residential plumbing. They do not require heat like soldered or welded connections making them perfect for installation in places where the use of such would be difficult or dangerous. The connection uses 2 pieces in addition to the valve and pipe. They are the ferrule (sometimes called an olive or sleeve) and a compression nut. The Compression nut is slid onto the pipe with the threads facing where the valve will be. Then the ferrule is slid onto the pipe. If the ferrule is not symmetrical, the longer side should be toward the valve. Next the pipe is inserted into the valve and the compression nut is tightened. Tightening this nut forces the ferrule into the valve stub which is tapered on the inside. Since the ferrule is made of a softer metal than the nut and valve, it gets compressed around the pipe. It also gets compresed between the valve and compression nut, forming a fluid tight seal.

Manifold-mount valve connections incorporate a flat face with recessed o-rings around the ports. Bolts are used to hold the valve in place on the mating surface of the component upon which it is being mounted. The ports on the valves align with ports on the component. When the bolts are tightened, they press the 2 faces together, and compress the o-rings to form a seal between the matching ports. A common example of this type of connection is a NAMUR solenoid valve which are commonly used to attach solenoid valves to pneumatic actuators.