Preformed hose assemblies

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Procedures

Aviation Structural Mechanic

Proof Pressure Testing

PREFORMED HOSE ASSEMBLIES. Medium-pressure Teflon hose assemblies are sometimes preformed to clear obstructions and to make connections using the shortest possible hose length. Since preforming permits tighter bends that eliminate the need for special elbows, preformed hose assemblies save space and weight. Preformed hose assemblies must be procured from a qualified commercial source (source code P series). When preformed hose assemblies are unavailable and could

Figure 5-14.Nipple assembly adjustment.

Figure 5-15.Firesleeve.

cause a work stoppage, fabrication by depot and intermediate maintenance is authorized.

PROTECTIVE FIRESLEEVES. Some hose assemblies are located in areas where temperatures exceed the capabilities of the hose material. Protec-tive firesleeves should be installed (fig. 5-15) over these hose assemblies. Fire sleeves do not increase the service temperature of hoses, but protect the hose from direct fire long enough to allow the appropriate action to be taken. The sleeve is composed of fiber-glass. It is impregnated and overlaid with a flame-resistant silicone rubber.

Cleaning

Fabricated hose assemblies should be cleaned and visually inspected for foreign material before and after proof testing. Cleaning should be done with cleaning fluid or a detergent solution. In cleaning hose or hose assemblies, the cleaning procedures used depend upon the cleaning material selected for cleaning. See table 5-3. The preferred cleaning method is one that also uses the preferred cleaning material, P-D-680, type II. Note the CAUTION before reading the steps used in the cleaning process.

CAUTION

Oxygen hose assemblies must be cleaned and tested by qualified aviation equipment personnel in accordance with NAVAIR 13-1-6-4 before installation in weapons systems. P-D-680, type II solvent is flammable and its vapors are toxic. Keep P-D-680 solvents away from open flames, and use only in a well-ventilated area. Avoid solvent contact with skin.

Immerse or flush the hose or hose assembly using P-D-680, type II, solvent or equivalent. Brush the exterior of the hose or hose assembly with a nylon or similar synthetic bristle brush that has a corrosion-resistant core. Brush the core and at least the first inch of hose with a brush that has a diameter of at least 1/16 inch larger than the fitting bore. Flush the hose or hose assembly with P-D-680, type II, or equivalent. Drain the cleaning fluid and blow-dry with dry, filtered, oil-free air or nitrogen. Install the protective closures if the hose or hose assembly is not to be cleaned further or proof tested immediately.