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

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:

SizeNut Thread
Pattern
Thread
Direction
Gas UseCGA
Designation
Coupling Nut Thread
InternalExternal
A3/8″ – 24LeftFuel Gas021X 
A3/8″ – 24RightOxygen020X 
B9/16″ – 18LeftFuel Gas023X 
B9/16″ – 18RightOxygen022X 
B “Inert”5/8″ – 18Right“Inert” Gas032 X
5/8″ – 18LeftWater/Ind. Air033 X
C7/8″ – 14LeftFuel Gas025X 
C7/8″ – 14RightOxygen024X 
C7/8″ – 14Right“Inert” Gas034 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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