The lowly welding hose is usually under appreciated and overly abused. Its users are dragging it through every kind of muck and/or using it for pulling equipment around. It’s stepped on, driven on, spilled on, and left on. And yet, you are depending on it for fulfilling an important job – safely delivering flammable gases to the torch. This rubber pipeline is delivering a rich source of oxygen (with pressure) beside a flammable gas.
But because the hose is spending its life on the ground and doing its job, you can easily forget to be respecting its power: it’s a game changer.
There are a number of things the welder must be doing to ensure the safe using of welding hoses: turning and shutting it off; storing it; its working environment; and the handling of the hose. But, this email is going to be about why it matters what type of rubber is in your welding hose.
One of the characteristics of rubber hose is permeation. Which means, any gas being confined in the bore of a rubber hose is going to show a tendency to be passing through the tube wall, through the reinforcement and then into the environment.
Once these permeated gases enter into the environment, your next worry is: are they building are up in an area? If theses gases are allowed to build up than it can lead to explosions or dangers for breathing.
Each rubber hose is going to have a certain resistance to permeation. For the longest time welders have been using acetylene for the fuel gas. Acetylene has been working well; used at a low pressure, it has little effect on the composition or construction of the hose. But acetylene is no longer the dominant fuel gas. New gases are being developed to replace acetylene. With these new gases come changes that affect the welding hose. The new gases are being developed based on specific hydrocarbons or mixture of hydrocarbons. These special compounds are creating a different effect on rubber hose than acetylene. In fact, the precise effect hasn’t been determined. In addition, the new gases are running at much higher pressures. Acetylene will max out at (15psi) but new gases can be running at (40psi). So, the hose being made for acetylene is not designed for the new gases.
There are two grades of welding hose for acetylene. Grade R hose is the most popular and cheapest. Grade R is only for acetylene. The tube and cover are not flame or oil resistance. Grade RM is only for acetylene and its cover is oil and flame resistant. But the tube is not oil or flame resistant. Because of permeation and the higher pressures of new fuel gases, Grade R and RM should not be used. Grade T should be used when the fuel gas isn’t acetylene; but acetylene can be used (which is why some gas equipment manufacturers have put T grade hose in their kits). The benefits of Grade T are the tube and cover is flame and oil resistant. Plus it has a self-extinguishing tube and cover providing external and internal protection against adverse conditions: e.g. such as hot slag, flashbacks.
So, if your fuel gases are not acetylene than you need to be checking what Grade your welding hose is.