Things About Metal Hoses and When to Use Them
Hoses come in different materials, and you're probably wondering which type of hose you should use. Hose types include plastic, fabric, composite, rubber, PTFE, and metal. The type of metal hose to use depends on your piping situation. Normally, a metal hose is used in situations when the non-metallic hoses can't work - it's the last resort. A metal hose is perfect for misalignment correction, absorbing vibration, piping systems' thermal contraction and expansion, and to protect equipment from excess motion.
The following factors should alert you that it's time to use metal hoses...
1. Extreme temperatures
Is the surrounding atmospheric temperature or that of the media passing through the hose extremely cold or hot? Metal hose is your only option as it's the only material that can withstand extreme temperatures.
2. Aggressive chemicals
If you're working with aggressive chemicals, consider using a metal hose. Non-metallic hoses can't handle aggressive chemicals. Stainless steel has good resistance to several common chemicals. Additionally, special alloys may be added to increase corrosion resistance.
Please note that if the hose is exposed to aggressive chemicals (either internally or externally), special care should be taken to make sure that every assembly component is resistant to chemical attack.
3. Possibility of a catastrophic failure
Common metal hose failures include small holes and cracks. However, other types of hose tend to come apart completely or develop huge cracks. If a sudden failure can lead to catastrophic effects, having a metal hose helps to mitigate the effects by leaking a product at a much slower rate.
4. Permeation concerns
Are there permeation concerns? Metal hose is the best option. Unlike other hoses that are susceptible to having gases exiting through the hose wall and into the atmosphere, metal hose doesn’t allow permeation.
5. Fire safety
Unlike other non-metallic hoses, metal hoses maintain their integrity even in extreme temperatures (up to 1200º F). Typically, flexible corrugated hoses are all-metal, which makes them fire-resistant (unless non-metallic seals are used). Fire resistance and low permeation make flexible corrugated hoses the perfect option for barge loading and unloading applications, or any application where the hose may be exposed to open fire. Check out the flexible metal hose from Aero Flex if you're concerned about fire safety.
6. Achieving full vacuum
A metal hose will maintain its shape under a full vacuum while other hose types may collapse. The corrugations in metal hoses give them great hoop strength, which enables them to handle full vacuum. Other hose types have to use helix wires to enhance their vacuum rating, but they can still collapse.
7. Fitting configuration flexibility
Virtually every fitting can be attached to a metal hose, while other hose types need special collars and shanks. This makes metal hoses more versatile.
Tips for Choosing the Right Metal Hose for Your Application
All metal hoses look the same. However, there are several factors to consider to optimize the hose for your specific application. To select the perfect hose for your application, here are the factors you should consider.
Size - To provide a proper fit, you should have the diameter of the connections where the assembly will be installed.
Temperature - High temperatures (internal and external) affect the effectiveness of the assembly’s components. When selecting a hose, there are two temperatures you need to identify - the temperature of the product passing through the hose and the ambient temperature (the temperature that exists outside the hose). Extreme ambient temperatures may have a negative effect on the reinforcement materials and the cover of the hose, leading to reduced service life. The temperature of the product going through the hose can have an even greater effect on the service life of the hose.
Application - It refers to the configuration where the assembly is installed. It includes any movement that the assembly will experience, as well as the dimensions where it has to fit. This is necessary since you can't know the right hose type or the proper length without it. In some cases, specific applications need specific hose types.
Media - The media that the hose will be conveying matters. In some instances, applications require the use of specialized chemicals and oils. It is, therefore, necessary that the hose you select is compatible with the media going through it. Please note that compatibility isn't just about the inner tube; it should also cover the hose fittings, the cover, and O-rings.
Pressure - You should also consider pressure when selecting a hose for your application. What's the maximum pressure that the assembly will be exposed to? The maximum system pressure must be below the recommended maximum working pressure of the hose.
Hose Maintenance Tips
Proper hose selection and installation are important, but without proper maintenance, the service life of the hose is greatly reduced. A hose maintenance program should include the following actions:
Visually inspecting the hose and the fitting
The hose assembly should be inspected regularly. If you notice any of the following signs, the machine should be switched off instantly and replace the hose assembly.
- A cracked or damaged cover
- Fitting spillage on a hose
- A heat-cracked, stiff, or charred hose
- Leaks
- Flattened, kinked, or twisted hose
- Degraded, loose, or blistered cover
Functional test
A functional test involves operating the system at maximum pressure to see if there are any malfunctions or leaks.
Replacement intervals
Seals and hose assemblies used on adapters and hose fittings will harden, wear, and deteriorate with time. They should be inspected and replaced at specific replacement intervals depending on previous service life or industry recommendation.
Are you dealing with hydraulic hoses?
There's a risk of environmental damage since hydraulic hoses are exposed. Places such as scrap yards, construction sites, and such other places are hazardous to hydraulic hoses. In such places, hoses can collide with steel, concrete, jagged rocks or rebar, and get crushed, become abraded, or be severed.
What should you do?
You should be highly cautious during regular inspections not to miss any external cuts and wear. Replace the hoses immediately if there's any sign of damage to prevent more serious problems.