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What is the difference between A, B and C welding hoses?

Doug Perry

When looking to understand the difference between welding hoses, one of the most important things to consider is hose size. Generally, there are three common sizes of hoses - "A", "B" and "C". Each hose connection has a matching connecting nut, hose stem and ferrule.

Hose connection diagram

Oxy-fuel applications require left hand nut threads for fuel and right hand threads for oxygen. There is also a "B" size for inert gases; however, the left hand thread configuration of both "B" and "C" sizes are not very common. Whether the standard coupling nut has external or internal threads determines intended gas use. Generally, internal threads are for oxy-fuel applications and external threads are for inert gases, water or industrial air.

Hose Fittings - Sizes and Types:

Size Nut Thread
Gas Use CGA
Coupling Nut Thread
Internal External
A 3/8" - 24 Left Fuel Gas 021 X  
A 3/8" - 24 Right Oxygen 020 X  
B 9/16" - 18 Left Fuel Gas 023 X  
B 9/16" - 18 Right Oxygen 022 X  
B "Inert" 5/8" - 18 Right "Inert" Gas 032   X
5/8" - 18 Left Water/Ind. Air 033   X
C 7/8" - 14 Left Fuel Gas 025 X  
C 7/8" - 14 Right Oxygen 024 X  
C 7/8" - 14 Right "Inert" Gas 034   X

Where Used:
When selecting the connection size, the primary consideration should be the gas volume required and if it is a light, standard or heavy-duty application:

Gas hose fittings

  • Light Duty:  Size "A" are typically used for light gas volume work such as HVAC, arts and crafts, etc.
  • Standard Duty:  "B" size fittings are by far the most common in our industry and probably comprise 95% or more of the market. They are primarily used for oxy-fuel applications that require standard or medium gas volumes. There are also "B" ("Inert") size fittings used for many inert gas applications including MIG and TIG welding.
  • Heavy Duty:  Size "C" is for heavy-duty applications such as heavy duty cutting (≥ 30”) and scarfing. These larger size hose connections are required to ensure the high volumes needed for these types of applications. Harris manufactures gas supply equipment, regulators and manifolds, as well as torches that require "C"size connections because they are necessary on certain equipment for high gas volume applications, but limited to a 200 PSIG maximum working pressure.

Pressure Limitation:
All sizes ("A", "B" and "C") using the standard connections discussed have a maximum working pressure of 200 PSIG per CGA E-1 2009.

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Doug Perry

Doug Perry is a Technical Sales and Marketing Support Representative at Harris Products Group. With over 30 years of experience at Harris, Doug is passionate about teaching people about Harris products - how to use them, how to sell them and new cost-effective applications for them.