GLOSSARY OF METAL HOSE TERMS

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BEND RADIUS

     Constant Flexing: The minimum radius of a bend measured to the assembly's centerline to maximize assembly life and to be used in motion calculations.

     Static Bend:The radius of a bend measured to the assembly's centerline to which an assembly may be bent for installation. The assembly should be subjected to no further motion other than vibration.

BRAID

     Tubular sheath of braided wires made to fit snugly over the hose and welded at the ends of the assembly. Braid is the pressure member of the assembly and prevents elongation of the corrugations under pressure.

CONSTRUCTION

     Annular: Convolutions that are a complete circle or ring.

     Helical: Convolutions that are continuous and spiral along the length of the hose.

FAILURES (TYPICAL)

     Abrasion: Failure caused by rubbing.

     Braid Wear: Failure caused by motion between the braid and the corrugations.

     Carbide Precipitation: Corrosion that occurs between dissimilar metals on the less noble of the metals.

     Fatigue: Failure caused by flexing which results in the break down of the metal structure.

     Squirm: Failure caused by excessive internal pressure that causes the corrugations to break out and shoot into an "S" OR "U" shape.

     Torque: Excessive twisting of the assembly causing metal fatigue and failure.

FLOW RATE

      The volume of media being conveyed in a given time period.

FREQUENCY

      The rate of vibration or flexure of an assembly in a given period of time.

HARMONIC RESONANCE

      The sympathetic vibration of convolutions caused by buffeting of the convolutions by a high velocity gas or steam flow.

LENGTH

     Live: The length of the exposed hose and braid excluding weld rings and fittings.

     Overall: The total length of the assembly including end fittings.

MOTION

     Angular Motion: Motion that occurs when one end of an assembly is deflected in a simple bend. In these applications, care must be taken not to unload the braid by expansion.

     Axial Motion: Motion that occurs along the longitudinal axis of the hose so as to compress or expand the length of the assembly. Care should be taken to never use braided assemblies or helical assemblies for this application. Unbraided corrugated assemblies at low pressures and small axial motions are acceptable, alternatively, expansion joints are recommended.

     Offset Motion: Motion that occurs when the ends of an assembly are displaced laterally to each other in a plane perpendicular to the longitudinal axis with the ends remaining parallel. The offset radius should never be greater than 25% of the minimum centerline bend radius.

     Radial Motion: Motion that occurs when the centerline of the assembly is bent in a circular arc.

     Random Motion: Motion that occurs non cyclically as when an assembly is handled manually.

PRESSURE

     Pressure Drop: The amount of pressure lost by the medium as it travels through the hose. In long assemblies pressure loss can be estimated to be three times that of comparably sized pipe.

     Maximum Working Pressure: The maximum operating pressure to which the hose assembly should be subjected to.

     Burst Pressure: The pressure at which the hose assembly can be expected to rupture or the braid fail in tensile. This pressure is determined in a laboratory setting at 70 degrees fahrenheit, and the hose installed in a straight line.

     Deformation Pressure: The pressure at which the hose corrugations will permanently deform regardless of the external braiding.

     Test Pressure The maximum pressure a hose can be tested at before damage will occur. It is not recommended that hydrostatic testing be conducted above 120% of the maximum working pressure, or 150% of the actual operating pressure of the particular application, whichever is less.

     Pulsating Pressure: A rapid change in pressure above and below the normal base pressure.

     Shock Pressure: Also called surge pressure. A sudden increase in pressure which causes a shock wave through the assembly.

     NOTE: For applications that experience pulsating, shock, or surge pressures, the peak pressure should not exceed 50% of the Maximum Working Pressure and the braid must be tight to the hose with no slack after installation.