Air and gas hoses are designed to transfer compressed air and gases from one point to another in industrial, medical, construction and agricultural applications. These hoses are generally made of materials such as NBR (Nitrile Rubber), PVC (Polyvinyl Chloride), EPDM (Ethylene Propylene Diene Monomer), PTFE (Polytetrafluoroethylene), silicon and so on. In these hoses to ensure safety and longevity. They must also comply with various ISO, EU and US air and gas safety standards. Figure 1 is an example of an air and gas hose with an inner and outer NBR layer.
Figure 1: NBR Air and Gas Hoses Air and gas hoses can typically be distinguished from low pressure hoses and high pressure hoses. Low pressure hoses are used for gases such as acetylene, oxygen, butane / propane mixture, natural gas, neutral gas and so on.
How air and gas hoses work
As the name implies, air and gas hoses are used to transport gases such as compressed air, propylene acetylene and others. When choosing a hose material and specifications, it is important to know and understand your type of media to ensure proper performance.
Air pipes are used to transfer compressed air to pneumatic systems. These air hoses must have a high resistance to withstand high pressures to prevent leakage and damage. In addition, oil lubricants are sometimes added to compressed air to make equipment run smoothly. Therefore, these air hoses must also be oil resistant. To control high pressure lubricants and oil, rubber is the most common material for air hoses. However, in large compressors, air molecules often collide with each other to generate heat. This can cause the hoses to overheat and damage the rubber hoses, which reduces the useful life of the hoses and raises safety concerns. Therefore, for high temperature applications, corrugated metal hose should be used. These corrugated metal hoses dissipate excess heat quickly and help cool the environment.
In industrial installations, the transferred gases may be toxic or flammable. Such programs should pay special attention to choosing the right type of hose and their connections. Gas hoses must be leak-proof and break-resistant. Incorrect judgments about hose materials, pressure and fittings can lead to hose failure, which can be very dangerous in such installations.
A variety of materials are available when choosing the right air or gas hose for your application. Some of the most common hose materials used are discussed below:
Rubber is the most common material and is an inexpensive choice (compared to other materials) for air and gas hoses. These hoses are strong, flexible, durable and can withstand various changes in temperature and heat. Rubber compounds such as EPDM and NBR are also a great choice for air and gas hoses. EPDM rubber offers excellent resistance to heat, temperature and ozone. Similarly, NBR is resistant to oils and chemicals. However, rubber can not provide zero permeability and can not be used for applications that require high purity. High purity gas has a small amount of other gases that improves their quality. Permeable materials may compromise the quality of such gases by collecting contaminants.
PVC is a widely used material for general use of air and gas hoses. PVC hoses are cheap, durable and light. They weigh very little, so they can be used outdoors or at higher altitudes. However, PVC hoses are not recommended for use in cold temperatures because they are prone to twisting or cracking at such temperatures.
Polytetrafluoroethylene or PTFE hoses are suitable for high pressure industrial applications. They are durable, flexible and affordable. For applications that require high purity, PTFE can be subjected to a “post-curing” process. During this process, PTFE is processed again at a controlled temperature and pressure. This helps to increase the number of molecular bonds, increase the strength and thickness of the hose wall, and thus reduce diffusion. Dispersion occurs when gas molecules easily escape through the hose holes due to their smaller molecular weight.
Corrugated metal hoses
All corrugated metal hoses are commonly used with gases such as hydrogen and helium. These gases have a risk of emission. All metal hoses have a metal corrugated inner core. They have zero permeability, so they are not exposed to gaseous emissions. However, they are more expensive than other hoses and much less flexible.
Silicone hoses are known for their flexibility and strength. They can operate in a wide range of temperatures, making them ideal for heating, cooling and charging air applications. Figure 2 is an example of a silicone hose.
Figure 2: Silicone hose
Different hose materials have their own characteristics, so it is important to understand the properties of the material for application and media. The following requirements are key to the safe operation of these air and gas hoses in different conditions.
In general, hose materials such as rubber and PTFE are somewhat permeable. This means that gas molecules can enter or leave through the holes in the hose. When gas molecules escape through the pores, it leads to a pressure drop, which leads to excessive energy consumption and poor system performance. This external emission of gas is especially dangerous when flammable gases are part of the application. Likewise, other gases may enter the hoses leading to contamination. In general, all-metal corrugated hoses are recommended to eliminate the risk of gas emissions. PTFE hoses are also a great alternative to metal hoses after firing.
Air and gas hoses can be exposed to different types of gases. The hose material must be able to withstand the chemical properties. Therefore, it is necessary to choose the hose material directly from the requirements of your program, because the hose material may work for certain media and not for other media.
Hose materials such as rubber and PVC are not resistant to environmental factors such as UV and severe weather. When choosing a hose for your application, you must consider the external environment. EPDM, silicon, ETFE and PTFE are better options for UV-prone and extreme temperature applications.
Air and gas hoses are used in a wide range of industrial applications. Divers use these hoses connected to the oxygen tank for breathing purposes. Laboratories and industries also use these hoses to carry a variety of gases or for applications such as welding. Some of the most common applications are discussed below: Welding Gas hoses are used for various welding applications such as assembly, soldering, cutting, fabrication, preheating, post-heating, soldering and so on. The gases used for welding usually include acetylene, hydrogen, helium, natural gas, propane, propylene, oxygen, and so on.
Air hoses are used in medical and recreational applications to provide breathing air. Standard rubber hoses cannot be used for such cases as toxic hydrocarbons may enter the respiratory system. In general, a food grade polymer is used to prevent such potential health hazards. Figure 3 is an example of air hose breathing.
Figure 3: Breathing air hose
Additional hose components
The choice of additional components for the hoses should be as important as the choice of hose. Specifications such as hose pressure, material type, hose diameter, etc. play an important role in selecting these additional components to prevent accidents.
Hose pulleys are designed to protect the hoses. Modern hose reels are retractable and provide a complete housing for the hose. These hose pulleys also help eliminate loose, non-screw hoses on the shop floor and reduce the risk of accidental damage to the hose.
Figure 4: Automatic hose ring for compressed air
Air and gas hose connections must be able to withstand the pressure required to run smoothly and safely. Generally, brass stainless steel of 304/316 or coated steel is used as the material for the joints. Fittings must be resistant to the corrosion effect of the gas. Figure 5 is an example of a brass hose connection.
Figure 5: Hose connection fittings
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