P. 472

2.17 Vibration - Vibration can reduce hose service life. If necessary, conduct tests to evaluate the effects of frequency and amplitude of system vibration on a hose assembly. Clamps of other devices may be used to reduce the effects of vibration.
3. After selection of proper hose, the following factors must be considered by the installer:
3.1 Pre-installation Inspection – Prior to installation, a careful examination of the hose must be performed.
All components must be checked for correct style, size and length. In addition, the hose assembly, and each of the individual components comprising the assembly, must be examined for cleanliness, I.D. obstructions, blisters, loose cover, or any other visible defects.
3.2 Follow Manufacturer’s Assembly Instructions.
3.3 Minimum Bend Radius – Installation at less than minimum bend radius may significantly reduce hose life. Particular attention must be given to preclude sharp bending at the hose/fittings juncture which may result in leaking, hose rupturing, or the hose assembly blowing apart.
3.4 Lengths: Unnecessarily long hose can increase pressure drop and affect system performance. When pressurised, hose that is too short may pull loose from its fittings, or stress the hose fitting connections, causing premature metallic or seal failures.
3.5 Twist Angle and Orientation – Hose installations must be such that relative motion of machine components produces bending of the hose rather than twisting.
3.6 Securement – In many applications, it may be necessary to restrain, or guide, the hose to protect it from damage by unnecessary flexing, pressure surges, and contact with other mechanical components. Care must be taken to ensure such restraints do not introduce additional stress or wear points.
3.7 Proper Connection of Ports – Proper physical installation of the hose requires a correctly installed port connection while ensuring that no twist or torque is transferred to the hose.
3.8 Avoid External Damage – Proper installation is not complete without ensuring that all tensile loads, side loads, kinking, flattening, potential abrasion, thread damage, or damage to sealing surfaces are corrected or eliminated.
3.9 System Check out – After completing the installation, all entrapped air must be eliminated, then the system must be pressurised to the maximum system pressure and checked for proper function, and for freedom from leaks.
4. Even with proper selection and installation, hose life may be significantly reduced without a continuing maintenance program. Maintenance and Inspection frequency should be determined by the severity of the application and risk potential. A maintenance program should include the following as a minimum.
4.1 Hose Storage – Hose products in storage can be adversely affected by temperatures, humidity, ozone, sunlight,
oils, solvents, corrosive liquids and fumes, insects, rodents, radioactive materials, sharp edges and abrasive surfaces, electric or strong magnetic fields, mould and fungi. Storage areas should be relatively cool and dark and free of dust, dirt, dampness and mildew. Store hose in a manner that facilitates age control and first-in, first-out usage based on manufacturing date on hose or hose assembly.
4.2 Visual Inspection – Any of the following conditions require immediate system shut down and replacement of the hose assembly:
a) Leaks at fittings or in hose. (Leaking fluid is a fire hazard.)
b) Damaged, cut, or abraded cover. (Any reinforcement exposed.) c) Kinked, crushed, flattened, or twisted hose.
d) Hard, stiff, heat cracked, or charred hose.
e) Blistered, soft, degraded, or loose cover.
f) Cracked, damaged, or badly corroded fittings.
g) Slippage or movement of fittings on the hose.
4.3 Visual Inspection – The following items must be tightened, repaired or replaced as required. a) Leaking port conditions.
b) Clamps, guards, shields.
c) Remove excessive dirt build-up.
d) System fluid level, fluid type, and any air entrapment.
4.4 Functional Test – Operate the system at maximum operating pressure and check for possible malfunctions and freedom from leaks.
4.5 Replacement Intervals – Specific replacement intervals must be considered based on previous service life, government or industry recommendations, or when failures could result in unacceptable down time, damage, or injury risk.

   470   471   472   473   474