There are three key variables in selecting a metal hose: pressure-carrying capability, flexibility, and chemical compatibility.
Once you've determined your application requires a metal hose, the next step is selecting a metal hose to ensure the assembly will safely meet the rigors of each application.
When selecting a hose, physical specifications (length measurements, hose and fitting sizes, etc.) are always important, but you must also consider these three variables: pressure-carrying capability, flexibility, and chemical compatibility. Let’s take a closer look at each of these variables.
1. Pressure-Carrying Capability
The metal hose must be strong enough to handle the pressures to which it will be exposed. To determine hose pressure capability, consult the manufacturer’s catalog or website for the “Maximum Working Pressure” stated for the hose.
Here is an example.
But we’re not ready to move on yet! The Maximum Working Pressure must be reduced for each of the following circumstances:
• Temperature. As temperature increases, hose working pressure decreases.
After you have determined the proper alloy (see “Chemical Compatibility” below) go to a Derating Factor table and match the alloy of the hose and braid with the highest temperature to which they will be exposed (either internally or externally) to obtain the proper derating factors.
Then multiply the hose’s Maximum Working Pressure by the most-limiting temperature derating factor.
• Dynamic Pressure. Pulsating, surge, or shock pressures, like those encountered with the quick opening or closing of valves, can inflict severe damage on a metal hose. If your application entails pulsating pressures, the working pressure should be derated by 1/2. If your application entails shock pressures, derate the stated working pressure to 1/6 of its value.
2. Flexibility
Step two in selecting a metal hose is confirming that the hose’s minimum bend radius (see this example) is less than the bend radius required for the application.
Increasing the installed radius of the hose will reduce fatigue on the corrugations. And this is important because it will help to increase the life of the hose assembly.
Care should also be taken for applications with vibration. If excessive vibration is present, we recommend contacting the manufacturer’s Inside Sales team. They can help you to navigate this challenge.
3. Chemical Compatibility
Thirdly, you must choose a material for the hose and braid that is compatible with the media being conveyed through the hose, as well as the environment in which the hose is to be installed.
This second aspect is often overlooked, but remember the external environment can be just as harsh to the hose as the media running through it.
When determining chemical compatibility, it is important to know the temperature and concentration of the chemical(s). Although there are many resources to confirm chemical compatibility, two of the industry standards that you may use are the National Association of Corrosion Engineers (NACE) and the Compass Corrosion Guides.
Read More from Hose Master >> When to Use Metal Hose: 8 Factors to Consider
About Hose Master LLC
Hose Master is a leading manufacturer of metal hoses and metal bellows expansion joints. We understand the criticality of the three variables discussed above, and we are happy to leverage our application expertise to make product recommendations that best satisfy our customers’ specific requirements.
For more information or application assistance, contact our Inside Sales team at 800-221-2319 or InsideSales@hosemaster.com, or check out our website at www.hosemaster.com.
