How Many Types Of Valve End Connection Are There

author: ATHENA GROUP

2023-05-05

There are three common methods of connecting valves to the pipelines and fittings: flanged, threaded and welded end connection.

Butt Welded Connection(BW): Butt-weld connection is made by welding the beveled ends of the pipe and straight end of the valve together. Weld along a seam that is butted edge to edge. Beveled ends(BE) indicate that the ends of the pipe lengths of the valve are not cut square, but rather are cut or ground to have a tapered edge. The butt-weld ends in standard valves are machined in accordance with ASME B16.25. Wall thickness should be clearly specified by customers.

Socket Welded Connection(SW): For a socket-weld connection valve, the pipe is inserted into the socket of the valve before welding, unlike a butt-weld connection that has the pipe and valve straight end placed end-to-end. Inside the socket-weld end is a collar that prevents the pipe from being inserted too deeply into the valve. Compared with butt-weld connections, socket-weld connections are more cost-effective since they are just simple fillet welds which require less X-ray inspection and less labor work.

Screwed Connection(NPT): Screwed connections are typically used in valves sized 4" and smaller. With tapered grooves cut into the ends of a run of pipe, screwed pipes and screwed valve ends can be easily assembled. NPT is the most common thread type tapered in accordance with ASME B1.20.1.

According to the flanged ends either formed together or separately with the valve body, there are three flanged connection types of valves: Raised Face(RF), Ring Type Joint(RTJ) and Flat Face(FF). The mating surface of the flanged valve connection is called the face. The face is usually machined to create a smooth surface which will help assure a leak-proof seal when two flanges are bolted together with a gasket sandwiched between.

Once the valve has been sized, but before it can be selected, the end connections of the valve must be specified.
End connection type for specific valve should be selected with consideration of pressure/temperature ratings, materials, assembling and disassembling frequency. Additionally the end connections on valves must match piping design and specifications, piping forces that will act on the valve body must be taken into account. Purpose of the end connections is to assure rigid and leak free pipe to valve connections.
For general service, valve end connection selection is a simple question of whether the selected end connection type is available for the required type of valve. But when considering for demanding services, all of the above factors and some other specific for certain applications must be taken into consideration. This can mean considering factors as erosion, corrosion, toxicity, contamination, fire hazard, human health hazard etc. Such requirements can come due to specific operating requirements for the certain valve application and thus can rise the valve price significantly.

End connections on valves are usually specified by the piping design engineer and it is preferable to match the piping design specifications. However, the piping designer does not determine the forces generated in the piping by valve action and must be informed of these by the valve engineer. Proper valve end connections can then be selected according to the strength required to maintain gasket sealing stress under all operating conditions and the degree of gasket seal tightness considering.

End connection types are determined by local and international codes and standards. Generally mostly are used US and EU standards. For more information about end connection types and dimensions for certain connection type and size, one should refer to the following standards:

- ASME B1 6.34 Valves-flanged, threaded, and welding end

- ASME B16.5 - Pipe flanges and flanged fittings

- EN 1092 Flanges and their joints — Circular flanges for pipes, valves, fittings and accessories, PN designated

American standard

American standards is dedicated to providing dependable valves and it helps in plumbing the highest valves standards. For more than 100 years the American valve has represented innovative products and research. It is built with quality and confidence and it is known for high quality valves that are used in HVAC, plumbing and in industrial applications.

GB standards
GB standards are the national standards and it is issued by SAC standardization administration. It is one of the IEC and ISO that is the national committee.

German standard
In German, the German standard is actually called hochdeutsch. It reflects the fact that its phonetics are of those of the High German spoken in the different parts of areas. Like in France the standard language in the area in which German language is spoken. It is not governed by the legitimized body. The regulatory authorities do not actually exist such as the minister conference of cultural and educational issues.

Difference between the American standard, the GB standard and the German standard
GB is the national standard, American standard is called ANSI and German standard is called DIN. These can be differentiated from the model. The valve model of the national standard is known according to the valve category pinyin letter. The safety valve is called A, butterfly valve as D, diaphragm valve as G, check valve as H, globe valve as J, throttle valve as L, drain valve as P, ball valve as Q, trap valve as S and so on.

There is no such difference between the American standard, the GB standard and the German standard. The difference is nothing but about pressure levels and production standards. The material of the valve body internal parts are easy to say. It is more than cast iron, stainless steel and cast steel. The rough the difference between the American standard, the GB standard and the German standard are as follows:
1. The flanges standards of these are different from each other.
2. The structural length of these are different from each other.
3. The inspection requirements of these are different from each other.

Standard ranges of the American standard, the GB standard and the German standard
The pressure level of the American standard ranges from 125 LB to 2500 LB. The main American standards include API, ANSI. They are mostly referred to as API and ANSI American standard valves.

German standard pressure usually is from PN 10 to PN 320. DIN standards valves are flanges and flange standards are adopted. The world’s main valves are the American standard petroleum institute API, the American national standard ANSI, DIM the German standard, JIS the Japanese standard, GB the national standard, the European standard EN and BS the British standard. While both of the standards rely on the same physical/mechanical properties to determine allowable pressure/temperature ratings for different sizes and materials of connections some of the differences between the ASME and EN codes is in designation of the PT ratings. While EU standards use Nominal Pressure designation (PN), ASME uses Class designation.

While all terminal connections perform the same general functions — helping valves perform their basic functions, keeping high pressure contained and maintaining workplace safety — choosing the wrong valve connection types can affect your productivity and, more importantly, put your team in danger.

It’s noteworthy to know which connection types best fit your application to maximize efficiency and safety in oilfield upstream and downstream operations. Finding the best fit(s) can be based on several factors, including:

Pressure Rating
Leakage Prevention
Ease of Installation and Removal for Repair/Replacement
Valve Integrity and Durability
Weight and Size
Cost

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