Select the Right Corrugated Metal Hose

Industry Standard

This method will be used unless another method is specified
Standard fabrication of an assembly generally consists of:

• Cutting the hose and braid through a hose corrugation valley.
• Installation of a braid collar over each end of the hose.
• Trimming of any excess braid.
• “Cap” welding the hose, braid, and braid collar together.
• Cleaning the cap weld surface.
• Placement and alignment of a fitting on the cap weld.
• “Attachment” welding the fitting to the cap weld.
• Silver brazing is also available. Consult factory.

Half-Corrugation

Standard fabrication sometimes leaves a portion of the cut corrugation, or corrugation “lip”, just under the base of the fitting. In specialized applications this residual lip may not be desirable. To prevent any exposed corrugation edges from causing damage, the hose can be specially prepared for welding by cutting the corrugation on the crest, rather than in the valley, thereby removing the lip.

Smooth Transition Weld

For applications in which corrosion is a concern, all crevices and fissures must be minimized. Specialized hose and fitting preparation, in conjunction with proprietary welding techniques, is available to provide a full penetration hose-to-fitting weld that is smooth and crevice free.

Braid-Over Construction

Assemblies operating at the upper limits of their rated working pressure or in severe service may benefit from a braid-over construction. The fitting is first welded to the unbraided hose. Then a special metal reinforcing ring is installed over the fitting and next to the weld. Finally the braid is drawn over the end of the hose and the ring, and welded to the side of the fitting. This technique reduces the amount of heat introduced into the braid wires, nearly eliminates the heat effected zones of the cap and attachment welds, and maximizes the wire strength. Braid-over construction may also be used for specific high cycle applications.

Standard Leak Testing

Every corrugated hose assembly is leak tested prior to shipment. Standard testing consists of pressurizing the assembly with air and then submerging the entire assembly under water. This method is reliable and sufficient for the majority of applications.

Hydrostatic Testing

While the standard test is designed to detect leaks, hydrostatic testing is designed to test the assembly’s strength. Testing of an assembly to its full permissible test pressure can be economically and accurately accomplished by filling the assembly with liquid while concurrently evacuating all air. The assembly is then hydrostatically pressurized using high pressure pumps. The test pressure is maintained for a predetermined period of time.

High Pressure Gas

Testing with air under water, at pressures of up to 2500 psi, is available for specialized applications. For a more sensitive test, the use of gases such as nitrogen or helium can be requested.

Dye Penetrant

Dye penetrant testing is available for both leak and for weld bead inspection, in accordance with Hose Master procedures or to customer specified standards.

Helium Mass Spectrometer

This is the most sensitive leak detection method generally available. The standard test method is to attach the assembly to a mass spectrometer and generate a very high vacuum in the assembly. The exterior of the assembly is then flooded with helium. The relatively tiny helium atoms penetrate even very small openings and are drawn into the mass spectrometer where they are detected and the leak size quantified. Helium Mass Spectrometer testing can be modified to satisfy customer or regulatory agency requirements.

The hydroforming method of corrugated hose manufacturing inherently yields a very clean product. However, specialized cleaning for specific applications is available upon request. Contact Hose Master’s Customer Service Department for details.

All assemblies are shipped with protectors over sealing surfaces such as threads and flange faces. Spacer bars are installed on all shorter double-flanged assemblies to prevent compression of the assembly during shipping and handling. Special packaging is available to suit customer requirements, including crating, plastic bagging, labeling, and custom fitting protectors.

Spring Guard

When there is potential for damaging an assembly in service, a guard can be easily installed during fabrication. This type of guard consists of a metal spring that is attached behind the fitting. The style of guard can be tailored to meet the application and the type of hose.

Protective Cover

If the potential for impact or high temperature damage is not severe, or if the additional weight and bulk of a full metal guard is unacceptable, rubber or plastic scuff guards can be installed to protect the corrugated hose and braid.

Insulating Jackets

If the corrugated hose is to convey hot media, and there is a potential for skin contact, an insulated, protective jacket is available. The jacket consists of a tubular banded fiberglass insulation, covered and impregnated with silicone rubber. The jacket is installed over the corrugated hose and metal banded in place. The jacket can also be used to insulate the corrugated assembly and either prevent ambient heat from being conveyed to the media or to reduce heat loss.

Tagging

A variety of tags and identifications can be affixed to assemblies. These include cardboard, plastic, and metal tags. Serial numbers, application information, assembly performance capabilities, and other customer specific information can be provided either on tags or permanently engraved onto one or both braid collars.

Certifications

Standard written certifications for materials or inspections can be supplied for corrugated hose or assemblies. Certifications of conformance to specific customer requirements such as military certifications are also available.

Liners

An interlocked hose or liner is often installed inside a corrugated hose assembly. The liner commonly serves two additional purposes, while still maintaining the full working pressure of the corrugated hose. The first is to protect the hose corrugations from excessive media velocities. Media speeds can induce resonant vibrations in the corrugations causing rapid fatigue and subsequent fracturing of the hose wall. The liner provides a relatively smooth surface for the media and, by avoiding the media impacting on the corrugation valleys, reduces the chances of harmonic resonance. The second purpose for a liner is for abrasion resistance. Even slightly abrasive media flowing at medium to high speeds can cause premature wear of the corrugated hose interior surfaces. The liner provides a smooth flow path as well as a relatively thick layer of abrasion resistant metal between the media and the corrugated hose. The liner will also help reduce pressure loss due to friction between the media and corrugated hose. Proper fit between the hoses is essential for good performance. Because Hose Master makes both the corrugated hose and liners, perfect fit is assured. See the Velocity in Metal Hose chart for more information.

Armor Guard / Bend Restricter

Applications in which the corrugated hose is subject to external abrasion, molten material splash, or impact damage may require a protective armor or guard along all or a portion of its length. A guard is typically made from interlocked or squarelocked metal hose and is welded to the assembly. Note that the bend restricter has a bend diameter equal to or greater than the corrugated hose it is protecting.

Jacketed Assemblies

A jacketed assembly consists of a “hose within a hose.” An inner or primary media conveying hose is enclosed or jacketed by a larger diameter hose. The hoses are joined at each end by specially designed fittings so that there is no media pathway between the two hoses. Jacketed assemblies are often specified when the primary media must be kept at either an elevated or cryogenic temperature. Steam is often circulated through the jacket hose to keep a viscous material in the inner hose hot and easily conveyed. A vacuum can also be pulled on the jacket hose to insulate cryogenic liquids being conveyed in the inner hose.

Tracers

Traced assemblies are similar in concept to jacketed assemblies in that there is an inner, smaller diameter hose encased by a single larger diameter hose. Where jacketed assemblies surround the media with heat or cold, traced assemblies have the media surround the hose containing the heating or cooling element. The tracer, or inner hose, may also be installed in a long “U” shaped loop within the outer hose, with the steam inlet and outlet at the same end of the assembly.

Hose Master places emphasis on continual improvements within our manufacturing processes, product offering and services. Hose Master reserves the right to make changes without further notice to any products contained herein.