2.1 INTRODUCTION
The term "hydraulic plumbing" refers to process of forming, installing as well as associated repairing/maintenance of the hose, tubing, fittings, and connectors used in the aircraft hydraulic system.
Occasionally it may be necessary to repair or replace damaged aircraft hydraulic plumbing lines. Very often the repair can be made sim ply by replacing the tubing. However, if replacements are not available, the needed parts may have to be fabri-cated. Replacement tubing should be of the same size and material as the original line. All tubing is pressure tested prior to initial installation, and is designed to withstand several times the normal operating pressure to which it will be subjected. If a tube bursts or cracks, it is generally the result of excessive vibration, improper installation, or damage caused by collision with an object. All tubing failures should be carefully studied and the cause of the failure determined.
This week will also highlight plumbing connectors.
2.2 PLUMBING LINES :
Aircraft plumbing lines usually are made of metal tubing and fittings or of flexible hose. Metal tubing is widely used in aircraft for fuel, oil, coolant, oxygen, instrument, and hydraulic lines. Flexible hose is generally used with moving parts or where the hose is subject to considerable vibration.
Generally, aluminum alloy or corrosion-resistant steel tubing have replaced copper tubing. The high fatigue factor of copper tubing is the chief reason for its replacement. It becomes hard and brittle from vibration and finally breaks, however it may be restored to its soft annealed state by heating it red hot and quenching it in cold water. Cooling in air will result in a degree of softness but not equal to that obtained with the cold water quench. This annealing process must be accomplished if copper tubing is removed for any reason. Inspection of copper tubing for cracks, hardness, brittleness and general condition should be accomplished at regular intervals to preclude failure. The work ability, resistance to corrosion, and lightweight of aluminum alloy are major factors in its adoption for aircraft plumbing.
In some special high-pressure(3,000 p.s.i.) hydraulic installations, corrosion resistant steel tubing, either annealed or 1/4 -hard, is used. Corrosion resistant steel tubing does not have to be annealed for flaring or forming; in fact, the flared section is somewhat strengthened by the cold working and strain hardening during the flaring process. Its higher tensile strength permits the use of tubing with thinner walls; consequently the final installation weight is not much greater than that of the thicker-wall aluminum alloy tubing.
The term "hydraulic plumbing" refers to process of forming, installing as well as associated repairing/maintenance of the hose, tubing, fittings, and connectors used in the aircraft hydraulic system.
Occasionally it may be necessary to repair or replace damaged aircraft hydraulic plumbing lines. Very often the repair can be made sim ply by replacing the tubing. However, if replacements are not available, the needed parts may have to be fabri-cated. Replacement tubing should be of the same size and material as the original line. All tubing is pressure tested prior to initial installation, and is designed to withstand several times the normal operating pressure to which it will be subjected. If a tube bursts or cracks, it is generally the result of excessive vibration, improper installation, or damage caused by collision with an object. All tubing failures should be carefully studied and the cause of the failure determined.
This week will also highlight plumbing connectors.
2.2 PLUMBING LINES :
Aircraft plumbing lines usually are made of metal tubing and fittings or of flexible hose. Metal tubing is widely used in aircraft for fuel, oil, coolant, oxygen, instrument, and hydraulic lines. Flexible hose is generally used with moving parts or where the hose is subject to considerable vibration.
Generally, aluminum alloy or corrosion-resistant steel tubing have replaced copper tubing. The high fatigue factor of copper tubing is the chief reason for its replacement. It becomes hard and brittle from vibration and finally breaks, however it may be restored to its soft annealed state by heating it red hot and quenching it in cold water. Cooling in air will result in a degree of softness but not equal to that obtained with the cold water quench. This annealing process must be accomplished if copper tubing is removed for any reason. Inspection of copper tubing for cracks, hardness, brittleness and general condition should be accomplished at regular intervals to preclude failure. The work ability, resistance to corrosion, and lightweight of aluminum alloy are major factors in its adoption for aircraft plumbing.
In some special high-pressure(3,000 p.s.i.) hydraulic installations, corrosion resistant steel tubing, either annealed or 1/4 -hard, is used. Corrosion resistant steel tubing does not have to be annealed for flaring or forming; in fact, the flared section is somewhat strengthened by the cold working and strain hardening during the flaring process. Its higher tensile strength permits the use of tubing with thinner walls; consequently the final installation weight is not much greater than that of the thicker-wall aluminum alloy tubing.
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