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Types of Valve End Connections

Lesson 3: The Various Types of Valve End Connections

So many materials, which to choose and why:

There are quite a few different types of connections used to install valves and other process components in piping of process systems. While they all perform the same function of connecting the valve into the piping system and allowing it to perform its function, each connection type has its own pros and cons. The selection of the best valve connection type for your application is based on many factors:

Factors for Selecting a Connection Type

  • Pressure rating/system pressure
  • Leakage prevention
  • Ease of installation
  • Permanence of valve
  • Ease of removal for repair or replacement
  • Inventory simplification
  • Adherence to industry and/or plant standards
  • Weight and size
  • Cost

Categories of Valve Connection Types
There are 5 general categories that all connection types fall into.

They are:

BSPT - British Standard Pipe Taper Threads

This standard is similar to NPT, where the threaded portions of the connection are tapered. The only difference is the angle of the thread flanks. The angle from root to crest on BSPT threads is 55° as opposed to 60° for NPT. It is possible for a male NPT to fit into a female BSPT, but due to the difference of the thread angle a fluid tight seal will not be made.

BSPT threads are defined by ISO 7 and/or EN 10226-1, BS 21.

BSPT threads are specified using the letter "R" followed by the size in inches. R stands for "rohr" which is german for pipe.
example: R 2 1/2"

BSPT Threaded Valve Connection
BSPT Pipe to Valve Connection

BSPP - British Standard Parallel Pipe Threads

This type of thread does NOT form a fluid tight seal like the tapered threads do. The use of a soft seal is required to do so. These threads will pull the 2 mating parts together, and compress the soft seal between flat surfaces on each component.

BSPP threads are defined by ISO 228-1:2000 (Dimensions, tolerances, and designation) and ISO 228-2:1987.

BSPP threads are specified using the letter "G" followed by the size in inches. G stands for "gas".
example: G 1/2"

BSPP Threaded Valve Connection
BSPT Pipe to Valve Connection

Butt Weld

The valve end and the pipe end are of equal diameters. The outer edge of each is chamfered to create a "valley" to be filled with welding material. The two pieces are welded around the rims as shown in the illustration. Butt weld connections are usually reserved for smaller sizes, typically 2" and below. The example shown here also includes the heat sink fins.

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

Socket Weld Valve Connection

Butt Weld Pipe to Valve Connection

Flanged Connections

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.
ANSI and SAE Flange Patterns


This standard is based on using multiple bolt holes evenly distributed around a "bolt circle". There are 7 classes from 150# to 2500# with the pressure increasing as the class does. The standard includes flanges for pipe sizes from 1/2" to 24." There are a few different types of flanges

Class 150: 1/4" to 24"
Class 300: 1/4" to 24"
Class 400: 1/4" to 24"
Class 600: 1/4" to 24"
Class 900: 1/2" to 24"
Class 1500: 1/2" to 24"
Class 2500: 1/2" to 12"

[ ASME/ANSI B16.5 Flange Class Dimensions and Pressure/Temperature Charts ]

These classes are referred to as "Class 150," or "150#" interchangeably.

DIN 1092-1/ISO 7005

This standard is very similar to ANSI. These flanges are referred to with a "DN" (for Diameter Nominal) followed by size in mm, followed by "PN" (for Pressure Nominal) followed by presure rating in bar. There are 19 sizes from 10 to 2000 and XX pressure classes from 2.5 to 100 bar

example: DN 100 PN 16

[ DIN 1092-1/ISO 7005 ]

Round Flange Types

Both of the standards just mentioned have many different types within them. These types include different mating face styles. The most commonly used on valves are RF for "raised face" where there is a slightly raised inner ring arounf the valves port. Flat faces, counter-bore, o-ring groove, and other styles are available but uncommon in most industries.

There are also various styles that attach to pipes differently. That has no affect on the valve ends. The flanges on the valve are usually part of the valve body itself. They mate up with a matching flange that must be attached to the pipe. That is usually accomplished with welding, and less common with threading.

SAE J518

This standard is based on using 4 bolt holes located on the corners of a rectangle. There are 2 classes, Code 61 and Code 62. The flanges can be split into 2 halves known as "split flanges", or as a single piece which is called "captive."

SAE J518-1 Code 61 (ISO 6162-1): 3000 psi, 1/4" to 24"
SAE J518-2 Code 62 (ISO 6162-2): 6000 psi, 1/4" to 24"

[ SAE J518 Flange Dimensions ]

ANSI Flanges

The valve has a flanges with bolt holes used to bolt it to matching flanges on the pipe. Flanged connections make removal and replacement easy. Flanged connections are common on larger valve sizes. Gaskets must be used where these flanges mate.

ANSI Flange Valve Connection

NPT Pipe to Valve Connection


Also referred to as Tri-Clover, T-clamp, or Sanitary Clamp. These connections use a hinged clamp that tightens around the flanged ends and squeezes them together with a gasket in between. The squeezing force is created by the wedge shape of the flanges being forced deeper and deeper into the wedge shaped groove in the clamp. There are various different clamp styles including two-segment single hinge (shown here), three-segment double hinge, and two-bolt high pressure.

Socket Weld Valve Connection
Tri-clamp sanitary Valve Connection

SAE 4-bolt Flanges

SAE (Society of Automotive Engineers) defines a standard of 4-bolt flanges called SAE J518. They are available as split flanges (two halves as shown here), or captive where the it is a sigle piece. Split flange connections are used in high pressure applications such as hydraulic systems. The flange halves are placed around the valve's end connection which has a lip around the edge. This lip has a flat face with a channel in which an o-ring is placed. The bolts are tightened, causing the face of the valve's lip to be drawn up against the flat face of the mating surface, usually a manifold. When installation is complete, there is metal to metal contact between the valve connection and manifold and the o-ring is trapped and compressed, forming a fluid tight seal.

There are 2 classes of these 4-bolt flange standards:
Code 61: 3000 psi, from 1/2" to 5"
Code 62: 6000 psi, from 1/2" to 2"*
* there are industry standards up to 3" that are not part of the SAE standard

Socket Weld Valve Connection
Tri-clamp sanitary Valve Connection


Push-to-connect connections are mainly used in residential and commercial plumbing. Originally developed for fittings such as tees, elbows, and couplings, these connections can also be found on valve ends. These innovative connection types allow quick and easy connection of the pipe(s) to the valve. There is an o-ring inside the valve port that is slightly smaller than the outer diameter of the pipe to be connected. When the pipe is pushed in, the o-ring gets stretched around the pipe and compressed between the valve body and the pipe. There is a grab-ring with teeth that dig into the pipe and prevent it from being removed. The pipe can be easily removed by pressing the release ring in which retracts the teeth of the grab-ring.

Shark Bite Valve Connection photo

ANSI Flange Lugged Valve Connection drawing

Barbed Hose Connections

Barbed hose connections are a simple and fairly primitive way of connecting soft hose ends to a valve. They are commonly found on low presure systems including air lines for an aquarium. The valves have long end connections that have barbs on them. The hose gets stretched over them when inserted and due to their shape go on far more easily than they come off. In many case this is a sufficient connection as-is, however, a hose clamp can be used to strengthen the connection if needed.

Barbed Hose Valve Connection photo

Hose Barb Valve Connection

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