How to identify the body size of ISO A and ISO B quick coupling?

indentify iso a and iso b quick coupling

ISO A and ISO B quick couplings are standardized types of couplings used for quickly connecting and disconnecting lines in various applications, primarily involving fluids like hydraulic oils, chemicals, and water. ISO A and ISO B are two series of quick couplings listed in the ISO 7241 standard. They are all ball-lock structures.

What are ISO A Quick Couplings?

ISO A quick couplings are a standardized type of quick-connect coupling designed for easy and efficient connection and disconnection of fluid lines. They conform to the specifications outlined in ISO 7241-1 series A for dimensional and functional compatibility across different manufacturers. The ISO 7241 standard not only specifies the connection dimensions requirements but also the flow rate, working pressure, burst pressure, fluid loss during disconnecting and connecting, etc., depending on the performance of the carbon steel material body. 

What are ISO B Quick Couplings?

ISO B quick couplings are another standardized type of quick-connect coupling, also conforming to the ISO 7241-1 standard, but the Series B.

Differences on Applications

  • ISO A: Mainly used in Europe and preferred for forestry and agricultural equipment due to their good performance in dusty environments.
  • ISO B: Predominantly used in the chemical industry and North America, often for general-purpose fluid transfer.

What is the quick coupling body size?

The body size designation corresponds to the nominal size of the hose recommended for use with the coupling. In the ISO 4397 standard, the nominal size of the hose is specified. This unifies the hose standard worldwide. The body size of the quick coupling corresponds to the hose standard, which specifies the corresponding connection size. As an example, in the hose size standard listed in ISO 4397, we can find a hose size of 10mm, which translates into inches of 3/8″. The recommended body size for this hose corresponds to the body size of the quick coupling is 10mm or 3/8″. Then, in the ISO 7241 A series, the corresponding connection size requirements are given for this body size.

Key Dimensions help us identify the ISO A and ISO B

We know that the ISO7241 standard gives the corresponding hose size to the body size of the quick coupling connection size requirements. Then we can determine its body size by an obvious dimension.

The male coupler’s size of the quick-release coupling is easier to be measured than the female coupler’s. We usually measure the outside diameter of the male coupler to identify the body size of the quick-release coupling.

Differences on ISO A and ISO B quick couplings
Body Size ISO A Diameter(mm) ISO B Diameter (mm)
5(1/8″) 10,8-10,9
6.3 (1/4″) 11,73-11,86 14,1-14,2
10(3/8″) 17,2-17,3 19-19,1
12.5(1/2″) 20,48-20,56 23,44-23,55
19(3/4″) 29-29,1 31,34-31,45
25(1″) 34,21-34,34 37,69-37,8
31.5(1-1/4″) 44,9-45
38(1-1/2″) 54,9-55 44,4-44,5
51(2″) 65-65,1 63,14-63,27

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