Hose Handling Guide
Installation recommendations and handling precautions
To preserve hose life, the following recommendations for metal hose handling should be adhered to and routine inspections should be administered to monitor for common causes of hose or assembly failure.
Installation Recommendations
Avoid Torque
Do not twist the hose assembly during installation when aligning the bolt holes in a flange or in making up pipe threads. The utilization of lap joint flanges or pipe unions will minimize this condition. It is recommended that two wrenches be used in making the union connection; one to prevent the hose from twisting and the other to tighten the coupling.
In-Plane Lateral Offset Installation
Prevent out-of-plane flexing in an installation. Always install the hose so that the flexing takes place in only one plane. This plane must be the plane in which the bending occurs.
In the image at right, the configuration on bottom left shows a correct installation demonstrating in-plane flexing. The image on bottom right, however, shows an incorrect installation demonstrating out of plane flexing.
Similarly, if an assembly is installed in a loop, flexing can only take place in one plane and no more.
Avoid Over Bending
The repetitive bending of a hose to a radius smaller than the radius listed in the specification tables for corrugated hose will result in premature hose failure. Always provide sufficient length to prevent over bending and to eliminate strain on the hose and install flexible connectors so that the bend is as close to the center of the connector as possible.
Avoid Sharp Bends
Utilize sound geometric configurations that avoid sharp bends, especially near the end fittings of the assembly.
Provide Support
When installing the assembly in a horizontal loop, provide support for the arms to prevent the hose from sagging.
Do Not Extend or Compress Axially
A piping system which utilizes metal hose to absorb movement must be properly anchored and/or guided. Always support the piping to prevent excessive weight from compressing the hose and relaxing the braid tension.
Handle With Care
Avoid careless hose handling. Don’t “pre-flex” a hose to limber it up as overbending could cause damage and result in leakage. Don’t apply a wrench to a hose, collar or assembly. Only wrench on the fitting hex flats and don’t try to stretch or compress a hose to fit an installation. This could affect the pressure carry capability of the hose.
Always lift or carry metal hose to prevent abrasion damage particularly to braided corrugated hose. Store metal hose assemblies away from areas where it can be subjected to spillage, corrosive fumes or sprays, weld splatter, etc.
Common Causes of Hose and Assembly Failure
Extreme Overbending
When hoses are bent beyond the recommended Minimum Bend Radius, the hose beneath the braid can be damaged, fatigue cracks may appear in the hose, potential for leak failures increases and there is a higher likelihood for braid bagging.
Damage to the hose and fatigue cracks can significantly decrease hose life. As a general rule, do not bend hose 90 degrees at fitting. Instead, use 45- or 90-degree elbows where tight bends are required.
Hose Stacking
Stacking hose on top of hose can create damage under the braid to the hose tube that cannot be seen. As mentioned above with regard to extreme overbending, damage to the hose can shorten its life.
In addition to ushering in premature hose failure, hose stacking contributes to braid bulging and braid wire damage. Avoid stacking hoses wherever possible.
Braid Bulging
All metal hose, as well as most hoses, grow longitudinally under pressure then contract when pressure is released. It is important to not restrict this movement so that the hose can function optimally.
Hose stacking can restrict the natural expansion or contraction of the hose with the common result being braid bulging. Try to avoid stacking hoses wherever possible.
Braid Wear
Braid wear can occur by dragging the assembly, improper or undersized lifting support or snagging the braid on another object. Since the braid is the “pressure carrier,” damage to it reduces working pressures and can result in premature failures. Braid bulging is an example of braid wear.
Prevent dragging exposed braid over concrete, railings or other exposed hoses and consider using hose buns instead of undersized lifting straps.
Too Tight Protective Covering
Using protective covers does provide protection from braid wear. However, overtightening the clamps that hold the cover restricts the natural movement of the hose and braid. As the hose elongates under pressure, the braid stretches. If the clamps are too tight, when pressure is released, the hose will shrink but the braid will not be able to contract. This causes braids to bulge, reducing the efficacy of the assembly as a pressure carrier.
Clamps should never be put directly on the braided portion of the hose assembly. We recommend moving clamp to position past fitting attachment weld and onto pipe section, per the drawing below.
Hose Assembly Field Inspection Checklist
Periodically inspect hose assemblies in order to recognize features which lead to failure in order to schedule replacement before actual failures occur. If any of these items are observed, replacements should be considered.
- Loose, broken, bulged, frayed or worn braid
- Deformation of the hose, including braid wear, twisting, kinking, denting, flat spots
- Coupling slippage, cracks, severe dents or excess corrosion
- Traces of media on or around the assembly
- Loose or damaged guard or covers
- Indications of corrosion of the hose or braid
- Loose fitting attachments
- Hose assembly rubbing or making contact with adjacent machinery or piping
- Unreadable or missing identification or tag if this information is required
Please contact us if further information is needed.
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