Metal Hose

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When to use Metal Hose:

There are many different types of hose available on the market. They include metal, rubber, composite, PTFE and fabric. The decision of which hose type to buy depends on the application for which the hose is being used. Generally, there are eight factors that should alert you to consider using metal hose:

1. Temperature Extremes - If either the temperature of the media going through the hose or the surrounding atmospheric temperature is very cold or hot, metal may be the only material that can withstand the temperature extremes.
2. Chemical Compatibility - Metal hose can handle a wider variety of chemicals than most of the other hose types. If the hose will be exposed to aggressive chemicals (either internally or externally), metal hose should be considered.
3. Permeation Concerns - Non-metal hose is susceptible to having gases permeate through the hose wall and into the atmosphere. Metal hose, on the other hand, does not allow permeation. If containing the gases inside the hose is important, metal hose may be required.
4. Potential for Catastrophic Failure - When a metal hose fails, it usually develops small holes or cracks. Other hose types tend to develop larger cracks or come apart completely. If a sudden failure of the hose can be catastrophic, a metal hose may help minimize the effects of a failure by leaking product at a slower rate.
5. Abrasion and Overbending Concerns - To prevent abrasion and overbending, a metal hose can be used as a protective cover over wires or even other hoses.
6. Fire Safety - Other hose types will melt when exposed to fire while metal hose maintains its integrity up to 1200° F.
7. Achieving Full Vacuum - Under full vacuum, metal hose maintains its shape while other hose types may collapse.
8. Flexibility in Fitting Configuration - Virtually any type of fitting can be attached to metal hose while other hose types require special shanks and collars.

Types of Metal Hose:

1. Corrugated Metal Hose Corrugated metal hose can handle high pressures and is gas tight. It is excellent for gas and liquid transfers.
2. Stripwound Metal Hose Stripwound metal hose, although not gas tight, is rugged, making it excellent for use as a guard, an open-ended exhaust hose, and for the transfer of dry bulk materials.

Corrugated Metal Hose (Designing an Assembly)

There are many components in a metal hose assembly and care should be taken when selecting each of them. Moreover, the components have their own unique technical limitations so it is important to make sure each of the components is compatible with your application. In much the same way as a “chain is as strong as its weakest link”, a metal hose assembly will only perform to the limits of its weakest component. Once the components have been selected, the quality and skill of the fabricator assembling the components becomes important. The procedures and care used when fabricating assemblies also has a dramatic effect on the assembly’s overall performance. Hose Master has invested a considerable amount of resources researching metal hose fabrication and developing a state-of-the-art fabricating center. In addition, we share the welding technology we have developed with our fabricating distributors. All of this is done to promote quality and consistency in fabricating metal hose assemblies.

S.T.A.M.P.E.D.

To properly design a metal hose assembly for a particular application, the following design parameters must be determined. To help remember them, they have been arranged to form the acronym “S.T.A.M.P.E.D.”

1. Size – The diameter of the connections in which the assembly will be installed is needed to provide a proper fit. This information is required.
2. Temperature – As the temperature to which the assembly is exposed (internally and externally) increases, the strength of the assembly's components decreases. Also, the coldest temperature to which the hose will be exposed can affect the assembly procedure and/or fitting materials. If you do not provide this information it will be assumed that the temperatures are 70°F.
3. Application – This refers to the configuration in which the assembly is installed. This includes both the dimensions of the assembly as well as the details of any movement that the assembly will experience. This information is necessary to calculate assembly length and required flexibility.
4. Media – Identify all chemicals to which the assembly will be exposed, both internally and externally. This is important since you must be sure that the assembly’s components are chemically compatible with the media going through the hose as well as the environment in which the hose is installed. If no media is given, it will be assumed that both the media and the external environment are compatible with all of the available materials for each component.
5. Pressure – Identify the internal pressure to which the assembly will be exposed. Also, determine if the pressure is constant or if there are cycles or spikes. This information is important to determine if the assembly is strong enough for the application. If no pressure is given it will be assumed that the pressure is low and there are no pressure surges or spikes.
6. End Fittings – Identify the necessary end fittings. This is required since fittings for the assembly must be chosen to properly fit the mating connections.
7. Dynamics – Identify the velocity at which the media will flow through the assembly. Since corrugated metal hose does not have a smooth interior, rapid media flow can set up a resonant frequency that will cause the hose to vibrate and prematurely fail. If no velocity is given, it will be assumed that the velocity is not fast enough to affect the assembly’s performance.

Corrugated Strip Process (Extraflex/Hydraflex):

In addition to our line of annular, corrugated hose, Hose Master offers two helical hoses specially designed to maximize performance without the drawbacks of traditional, mechanically-formed, helical hose. Rather than welding a tube and mechanically forming the corrugation, these products are made from stainless steel strip that is formed before welding. Because it is not mechanically formed from a tube, it is extremely flexible and does not contain all the residual stresses like traditional mechanically-formed helical hose.

Both Extraflex and Hydraflex are made by pre-forming the stainless steel strip, overlapping the material, and then continuously resistance welding the seam together. While Extraflex is made with one ply of stainless steel, Hydraflex is made with two plies for higher pressure ratings.

Braiding Process:

To give corrugated hose the ability to withstand pressure, stainless steel wire is braided over the hose. Hose may be single braided (one layer of braid) or double braided (two layers of braid) to achieve even greater working pressures. Braided braid is used on large diameter hose. Designing the proper braid for each type of corrugated hose requires sophisticated engineering to maintain the proper balance between the braid strength and the hose flexibility.

Hose Master’s braid packages offer several advantages:

1. High Percentage Braid Coverage – Hose Master has a high percentage of braid coverage yielding better cycle life and protection against damage to the hose.
2. Machine Braided Hose – Hose Master weaves the braid directly onto the hose ensuring that the braid fits tightly against the hose, preventing potential hose deformation or squirm.