Tuesday, December 2, 2014
Cover Perforation of Hydraulic Hose
Cover perforation of rubber covered hydraulic hose is required when air or other gases exist in a hydraulic or high pressure hose system. Without perforating, cover blisters or bubbles destroy protective capacity of the rubber cover and result in the deterioration of the reinforcement. Perforation is not required on textile covered hose because the porous textile cover allows gas to escape. If the system has low or medium pressure requirements, C5-type textile-wire-textile hose is an excellent recommendation. If air or other chemically acceptable gases are present in a fluid system and rubber covered hose is not perforated, gas migrates through the tube and reinforcement. It gathers beneath the cover, overcomes adhesion between reinforcement and cover and creates blisters or bubbles. Neither the rubber tube, cover, nor reinforcement suffers chemical ill effects from this action. But, blisters are cavities where moisture can collect and cause rusting or other deterioration of reinforcement. When wire reinforcements are sufficiently weakened by rust, hose fails when pressurized. If blisters are broken, cavity can collect additional dirt and moisture-collecting residue, making the corrosion problem worse. Correctly perforating rubber cover allows gas to escape without creating blisters or destroying protection provided by the cover. Perforation is achieved by pin-pricking small holes in the cover at close intervals along the total length of the hose assembly and around its circumference. Only the cover is perforated, not the tube or reinforcement. Rubber covered hydraulic hose can be ordered factory-perforated or Gates Power Line Perforators (7482-6565 or 7482-6566) are available. Remember, any gas of fluid conveyed in hydraulic hose must be compatible with the hose tube and cover. Always refer to the chemical resistance table if there are questions as to compatibility.