Valves and Instruments Blog

Selecting a Flexible Metal Hose is as simple as S.T.A.M.P.E.D.

We want to do our very best to help you make the best possible choices when selecting your stainless steel flexible metal hoses. Taking extra care up front in the selection process can eliminate a lot of heart burn, give you longer service life and increase plant safety.

Here is an easy way to remember everything you need to consider:

S = Size
T = Temperature
A =Application
M = Media
P = Pressure
E = Ends
D = Delivery (Velocity and Flow)

Size: Need to know both diameter and length. Over the years we’ve witnessed a lot of customers installing hoses that are either too long or too short for the installation. A too long hose fails when the customer forces it to fit, compressing it end to end. A too short hose will either not provide the performance expected or will fail when the installer pulls on it length-wise to make it fit. Occasionally we get customers that want a hose with a useable live length of an inch or less, which is as effective as installing a pipe nipple. If you have any questions on your installation, call us and we can review it so you can get the best life possible out of the hose assembly.

Temperature: Need to consider both the temperature of the fluid in the hose and the ambient temperature to select the correct hose and end fittings. Is it a hot application that is exposed to people? We can protect it with Fire Sleeve to prevent burns. Concerned about a potential leak over time? Maybe an armor casing will reduce those concerns.

Application: Hoses are the flexible member of the piping system and are quite often not clearly thought out in the planning process (think afterthought). Hoses must be installed to prevent torquing, movement in more than one plane, compression, extension and over-bending. We need to consider how the hose is moving. What is the angle of movement and how often does it move? Is the hose meant to reduce vibration? What is the frequency and amplitude of the vibration? Is their risk of abrasion inside or outside the hose? The more you consider all aspects of the application up front, the longer your hoses will last.

Media: What is the fluid traveling through the hose? Make sure that the materials of the hose, end fittings and any gaskets you are using are compatible with the fluid.

Pressure: What are the minimum, normal and maximum pressures that the hose will see? Do you have any pressure surges? If so, how high and how fast does the pressure spike. Make sure that when you select a hose you use the derating factors for elevated temperatures and/or dynamic pressure spikes. Note that with metal hose that when pressure increases, so does the minimum bend radius. Selected end fittings typically have a lower pressure rating than the metal hose. Make certain you research the end fittings pressure capabilities as they may be your limiting factor in regards to pressure capability. Take a close look on our web site to all the technical hose information. Call us with any questions.

Ends: There are two ends to each hose (Duh) and we can attached virtually any type of fitting or fittings required to meet your application. Again, be careful in fitting selection to assure that they too meet the Pressure/Temperature/Media needs of your application

Delivery: What is the flow rate? In metal hose, since you don’t have a smooth interior, high velocities can cause a resonant frequency, which results in high vibration and premature failure. For example, maximum velocities for a straight run configuration of your metal hose with braid is 75 ft/second for liquids and 150 ft/second for dry gas. Bent in a 180 degree bend they are 19 ft/second for liquid and 38 ft/second for dry gas. Solutions are using a larger diameter hose or installing a “smooth bore” liner on the ID of the hose.

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