Types of valve control end connections

In this article, we examine the types of common valve control end connections:

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String connections

String connections are very common. They create a compact and efficient connection between the valve and the pipe.

This valve usually has a female threaded end fitting into which the male threaded pipe fits.

There are also valves with male threaded connections and even valves with one female end and one male end.

These threaded connections must follow a standard to be useful in industry.

There are several different standards. Both the valve and the pipe must be created using the same standard in order to make a proper connection.

There are standards for straight threads and some for tapers. Tapered threads provide a tight seal without the use of soft seals such as o-rings or flat washers.

Straight threads require a soft seal that compresses between the valve and the pipe, hose or fitting to which it is attached.

NPT taper fittings

NPT is a US standard for tapered threads used in threaded pipe and fittings.

Unlike straight threads such as those found on a screw, conical fittings tighten, resulting in a tight seal against the fluid.

Pipe tape or pipe compound should be used on the threads to ensure a fluid seal.

This NPT standard is defined by the ANSI/ASME B1.20.1 standard.

Sizes range from 1/16″ to 24″ but valves over 4″ usually use flanged rather than threaded fittings.

NPT threads are identified by using the size in inches followed by “NPT”.

Example: 2″ NPT

اتصالات مخروطی NPT

NPT taper fittings

BSPT – British Standard Pipe Tapered Threads

This standard is similar to NPT where the threaded parts of the connection are tapered. The only difference is in the angle of the connecting sides.

The angle from root to crown on BSPT threads is 55 degrees versus 60 degrees for NPT.

BSPT threads are defined by ISO 7 and EN10226-1 BS21.

BSPT threads are identified by using the letter “R” followed by the size in inches. R stands for “rohr” which means pipe in German.

Example: R 2 ½”

3-BSPT - رزوه های مخروطی لوله استاندارد بریتانیا — BSPT – British Standard Pipe Tapered Threads

welded joints

This valve simply has a socket with an inside diameter that is slightly larger than the outside diameter of the pipe.

The pipe is inserted into the socket and welded around the edge as shown here.

These butt-weld or socket-weld fittings are typically used for smaller sizes, typically 2 inches and under.

They are permanent connections that are reliably leak-free

Note: Welding connections must be done by a trained professional. You must be careful not to damage the seat of valves and their sealing due to high heat.

Butt weld connection

The end of the valve and the end of the pipe have equal diameters. The outer edge of each is chamfered to create a “valley” to be filled with welding material.

These two pieces are welded around the rims as shown in the picture.

Butt weld joints are usually used for smaller sizes, usually 2 inches and under.

welded joints

Glue socket fittings are also referred to as FIP, slip, friction fit, pipe end or spigot fittings.

They are very simple. The inner diameter of the glue socket connection is slightly larger than the outer diameter of the pipe that simply fits into the socket.

PVC cement (before setting) is used to join PVC or CPVC valves to PVC or CPVC pipes.

It is recommended to turn the tube a quarter turn during insertion.

The cement actually fuses the pieces together and makes them permanent. These connections cannot be deleted.

Flanged Connections:

Most flanged end fittings conform to industry standards.

These standards define specific criteria that must be met to facilitate the use of products from different manufacturers.

ANSI is the American National Standards Institute.

Together with the American Society of Mechanical Engineers (ASME), they have developed and published a standard for flanged joints.

This is the ASME/ANSI B16.5 standard.

There is also a European standard that is similar, but not identical. This standard is DIN, which stands for the German translation of “German Institute for Standardization”. The specific standard for pipe flanges is DN EN 1092-1.

This standard is also recognized by ISO under the ISO 7005 standard.

SAE is the Society of Automotive Engineers. They have also developed a standard for flange-type fittings, where the flange is separate from the components it holds together.

In this standard, it is SAEj518. This standard is also recognized by ISO under the ISO 6162 standard.

تصالات فلنج دار(Flanged Connections):

Flanged Connections

ANSI flanges

This valve has flanges with screw holes that are used to connect it to the corresponding flanges on the pipe.

Flanged connections make removal and replacement easy. Flanged fittings are common on larger valve sizes.

Gaskets should be used in the places where these flanges are paired.

Flange ANSI (Lugged Style)

This type of flanged connection is similar to wafer with two minor differences.

1) The strap holes are threaded and there is one for each screw hole on the flanges.

2) Each threaded hole accepts 2 screws, one from each flange on the opposite side.

This type of connection can be used for dead-end services, where there is only one flange on one side of the valve and the other side is open, provided the valve seat/holder is bolted in place.

فلنج ANSI (Wafer Style)

Flange ANSI (Wafer Style)

Wafer-style flange connections are usually reserved for butterfly valves due to their narrow bodies.

However, they can also be found in some manufacturers’ ball valves.

This type of connection simply squeezes the valve between 2 flanges using long robots or threaded end rods.

There are holes on the valve for bolts and nuts that are not threaded and are large enough to allow play.

There are not always holes for each screw hole on the flanges.

They are simply used to help hold the valve in place until all the other screws are in.

In high performance butterfly valves, raised face flanges are used with gaskets to form a tight fluid seal.

Tri-Clamp fittings

These fittings use a hinged clamp that secures around the flange ends and compresses them together with a gasket in between.

The pressing force is created through the wedge-shaped flanges, which are inserted deeper into the wedge-shaped groove in the clamp.

There are several types of clamps, including the two-piece single hinge (shown here), the three-piece two-piece hinge, and the two-bolt high pressure.

Push fit

Compression fittings are mainly used in residential and commercial plumbing.

These connections, which are originally made for connections such as tees, elbows and couplings, can also be used at the control end of valves.

This innovative type of fitting allows quick and easy connection of the pipe(s) to the valve.

There is an O-ring inside the valve which is slightly smaller than the outside diameter of the pipe to be connected.

When the pipe is pushed in, the O-ring is stretched around the pipe and compressed between the valve body and the pipe.

There is a retaining ring with teeth that sinks into the tube and prevents it from being removed. The tube can be easily removed by pressing the release ring that engages the teeth of the retaining ring.