Select the Right Hose – Stripwound Metal Hose

Care should be taken when specifying a stripwound hose assembly. Each of the components can have a dramatic effect on the assembly’s performance. In addition to carefully selecting components, the way they are assembled is also very important. Hose Master has developed fabrication techniques that help maximize the assembly’s performance. Two of these techniques are square cutting the hose ends and welding on the inside of the fittings.

stripwound-hose-0

The stripwound profile is helical. When it is cut by traditional methods, the hose end will also be helical. This creates a gap between the fitting and the end of the hose. This gap can cause the fittings to separate from the hose during use. Square cutting ensures that the hose end and the fitting are flush, leaving no gaps.

If the fittings are welded on the hose, welding the inside provides for a smooth transition between hose and fittings, preventing product from becoming damaged.


Specifying a Stripwound Hose Assembly:

Designing a stripwound hose assembly requires the determination of five factors:

  1. Hose (type, alloy, and size)
  2. End fittings (type, alloy, and size for each end)
  3. Assembly length
  4. Fabrication options
  5. Accessories

If these factors have been determined, a fabricator will be able to make the assembly. If not, these questions may be answered by proceeding to the next section.


Analyzing an Application:

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. If you do not provide this information it will be assumed that the temperatures are 70 deg F.
  3. Application – This refers to the configuration in which the assembly is installed. This includes the dimensions into which the assembly must fit as well as the details of any movement that the assembly will experience. This is required since you cannot determine the proper length or proper hose type without it.
  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. If no media is given, it will be assumed that both the media and 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. Stripwound metal hose, by the nature of its construction, is not pressure tight. However, pressure and media infiltration through the stripwound wall can be minimized by the insertion of one of a variety of packings into the wall during hose manufacturing. If no pressure is given it will be assumed that there is no pressure.
  6. End Fittings – Identify the necessary 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. Extremely high flow or abrasive media can cause premature failure. If no velocity is given, it will be assumed that the velocity is not fast enough to affect the assembly’s performance.

Stripwound metal hose is a rugged product made from a strip of steel that is profiled and continuouslywound around a mandrel to form a hose. Hose Master’s proprietary manufacturing process yields anextremely consistent and balanced profile that maximizes strength and flexibility. Stripwound hose isused as a guard, exhaust hose, and for the transfer of dry bulk materials.

Types of Stripwound Metal Hose Products

  • Roughbore Interlocked

    The strip is formed with legs that interlock to form a hose that is flexible and ideally suited forconveying dry bulk materials, gas exhaust, or used as a protective cover.

    interflex

  • Smoothbore Interlocked

    Designed to reduce damage to delicate materials, another steel strip is added inside aroughbore hose to provide a smooth interior surface. Smoothbore hose is also flexible and used for dry bulk conveying.

    ultraflex-unpacked

  • Packed Interlocked

    Packing may be added to interlocked hose to minimize leakage through the hose profile.The most effective packings are made from resilient materials such as elastomers and, to a lesser extent, cotton. Harder materials (stainless steel and copper) are also available if requested.

    Roughbore
    interflex-packed

    Smoothbore
    ultraflex-packed

  • Torque-Resistant Interlocked

    Designed for torque resistance and enhanced sealability, this product resists twisting, unwinding, and strip flare-up after cutting. Torque-resistant hose is manufactured in eitherroughbore or smoothbore constructions.

    Roughbore
    trex

    Smoothbore
    trex-sb

  • Floppy Interlocked

    Designed to offer flexibility, strength, and crush-resistance, this product is used for casingor armor of small diameter hose and electrical cables.

    floppyguard

  • Floppy Squarelocked

    The strip is formed into square shapes that are locked together. Squarelocked is flexibleand is primarily used as a protective covering for wires, fiber optic cables, and otherhoses.

    floppyguard-sq

Now that you know more about the options, browse our online selection of stripwound metal hoses.

End Fittings:

Selecting the proper fittings for an application is largely determined by the mating fittings to which the hose assembly will be attached. Once the mating fittings have been identified, the hose fittings should complement the mating fittings in type, size and alloy. Even though the selection of hose fittings is determined by the mating fittings, it is a good idea to confirm that the fittings used in the application are appropriate for the application and any necessary changes made. Ensure that the fittings are chemically compatible with and are able to withstand the conditions in which the hose is installed and in which it will be used.

The following show commonly used fittings for stripwound metal hose assemblies. Please contact Hose Master’s Customer Service Department for end connections that are not listed.

male-pipe-nipple Male Pipe Nipple

  • Alloys – T304 and T316 Stainless Steel, Carbon Steel, Aluminum
  • Sizes – 1 1/2″ thru 8″
  • Schedules – 40, 80
grooved-end-fitting Grooved-End Fitting

  • Alloys – T304 and T316 Stainless Steel, Carbon Steel
  • Sizes – 1 1/2″ thru 8″

 

slip-on-flange Slip-on Flange

  • Alloys – T304 and T316 Stainless Steel, Carbon Steel
  • Sizes – 1 1/2″ thru 12″
  • Class – 150#, 300#
plate-flange Plate Flange

  • Alloys – T304 and T316 Stainless Steel, Carbon Steel
  • Sizes – 1 1/2″ thru 14″
  • Class – 150#

 

c-stub-floating-flange C Stub with Floating Flange

  • Alloys – T304 and T316 Stainless Steel
  • Sizes – 1 1/2″ thru 10″
  • Schedule – 10
part-a-and-part-d Part A and Part D (Cam-Lock)

  • Alloys – T316 Stainless Steel, Carbon Steel, Aluminum
  • Sizes – 1 1/2″ thru 8″

 

tube-end Tube End

  • Alloys – T304 and T316 Stainless Steel, Carbon Steel
  • Sizes – 1 1/2″ thru 8″
  • Wall Thickness – Various
reducer Reducer

  • Alloys – T304 and T316 Stainless Steel, Carbon Steel
  • Sizes – 1 1/2″ thru 6″
  • Schedule – 10, 40 (Carbon Steel)

 

beveled-pipe-end Beveled Pipe End

  • Alloys – T304 and T316 Stainless Steel, Carbon Steel, Aluminum
  • Sizes – 1 1/2″ thru 8″
  • Schedules – Various
npsm-female-or-male NPSM Female or Male

  • Alloy – T304 Stainless Steel
  • Sizes – 4″ thru 6″

 

t-and-a-male-and-female Tar and Asphalt Male and Female

  • Alloys – Malleable Iron
  • Sizes – 1 1/2″ thru 4″
compensator Compensator

  • Alloys – Urethane
  • Sizes – 3″ thru 6″

Various States of Hose Length

Interlocked metal hose can be Compressed (Figure 1) and Extended (Figure 3), and it is this ability that allows the hose to bend. The Relaxed Length (R) is defined as the average between the Extended Length (E) and the Compressed Length (C) of the hose (Figure 2), and is calculated as R=1/2 (C+E). When interlocked hose is bent as far as it can go, the outside surface of the hose is in the Extended state, while the inside surface is in the Compressed state.

length

Measuring Various Hose States

The Relaxation Factor is defined as Extended Length (E) divided by Relaxed Length (R) and is used to facilitate ordering interlocked hose. Hose Master can provide the Relaxation Factor for each of our interlocked hose products. Interlocked metal hose is generally priced and defined in its extended state. Frequently, the hose designer thinks in terms of the relaxed state. This is especially true when using smoothbore hose, packed hose, and calculating assembly length. In these cases, the purchaser must define the state (relaxed) when placing an order, OR multiply the desired (relaxed) length by its Relaxation Factor to order it as an extended length.

Example: For a hose with a relaxation factor of 1.12

To obtain a 20-foot relaxed length of hose, it can be ordered as 22.4 feet of extended product (20’ x 1.12). Additionally, if this extended length of hose weighs 3 lbs. per foot, and costs $4.00 per foot, then in the relaxed state it will weigh 3.36 lbs. per foot (3 lbs. per foot x 1.12) and it will cost $4.48 per foot ($4.00 per foot x 1.12).

Fabrication Options

Interlocked metal hose is used in a variety of applications. Just as the hose, fittings, and other assembly parts must be tailored to suit the demands of the service, so must the methods of joining these components. Hose Master has developed specialized fabrication procedures to assure the integrity and serviceability of metal hose assemblies in even the most extreme applications.

The following page identifies each of these methods and gives a brief explanation under what circumstances each should be considered.

Epoxy Epoxy

Fittings may be attached to interlocked hose using a 2-part epoxy. An epoxied fitting-to-hose connection, made with properly prepared fittings, can be as strong or stronger than the hose itself at service temperatures up to 200°F. Epoxy is recommended for packed interlocked hose to avoid damaging the packing material. Epoxy also affords a convenient method for field attachment of a variety of fittings to interlocked hose.

 

Weld Welding/Brazing

Welding provides the strongest possible connection between the hose and fittings. Whenever possible, the weld is made on the interior, or I.D., hose-to-fitting joint in order to provide a smooth surface over which the media flows. Welding is generally not recommended for packed interlocked hose, as the packing may be damaged by the high welding temperature.

 

ID-OD-Weld I.D./O.D.

If the fittings are welded to the hose, welding the I.D. provides for a smooth transition between hose and fittings, preventing product from becoming damaged. Also, welding the O.D. of the fitting prevents exterior contamination from entering the crevice while providing additional strength.

 

Mech-Attachment Mechanical Attachment

Certain high temperature applications requiring interlock hose, particularly Tar and Asphalt service, require a fitting that actually threads and locks onto the hose corrugations. A high temperature packing is used to seal against leakage. These fittings are leak tight up to 400°F and are easily field attached.

Accessories

index

Stripwound hose assemblies often require special accessories or components. Accessories may be used to improve performance or to make the assembly easier to use.

The following pages list some common accessories along with a brief explanation of the benefits each accessory offers. This is not an exhaustive list of all possible accessories. Please contact Hose Master’s Customer Service Department if you would like an accessory not listed.

lay-line Lay Line

A straight, painted line can be applied to interlocked hose along its entire length. This lay line serves to give clear warning to the user if the hose is being potentially damaged from torque or twisting in service. Monitoring torsion or twisting of the assembly can significantly increase the service life of the hose..

 

flow-arrows Flow Arrows

Smoothbore interlocked hose is unidirectional in that the overlapping liner strip affords a smooth surface in one direction. Media flow in the opposite direction can easily cause damage to both the hose and to abrasion sensitive media, such as plastic pellets. Flow arrows are painted on all smoothbore hose to indicate the correct flow direction. In specific high-velocity applications, the flow direction can also become a factor in roughbore interlock hose. Flow arrows can be provided on roughbore hose upon customer request.

 

square-cutting Square Cutting

If the hose service requires a smooth transition from the hose to the fittings, the end of the hose must fit flush against the fitting shoulder. The only way to provide this kind of fit between hose and fitting is to square cut the end of the hose.

braid Braid

For higher than normal working pressures, or for critical safety situations, a stainless steel braid can be installed and welded over a stripwound hose assembly. The braid serves to prevent the hose from overextending and damaging the hose wall.

 

tagging 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 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.

 

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.