Tube assemblies that are fabricated according to the instructions in they are to be installed, provided the operating pressure is greater than 50 psi. Tubing, installed in systems having an operating pressure of less than 50 psi must be proof pressure tested to a minimum of 100 psi. Vent tubes or drain tubes do not require proof pressure testing.

The fluid medium for proof pressure testing of all tube assemblies except oxygen systems should be a liquid medium such as hydraulic fluid, water, or oil. Oxygen tubing should be tested using dry nitrogen and inspected for leaks while the tubing is submerged in water.

CLEANING TUBING AND TUBE ASSEMBLIES 

All tubing and tube assemblies must be cleaned after fabrication to prevent contamination of the system in which they will be installed. Dry-cleaning solvent P-D-680, Type II, is the preferred cleaner, but the alternate cleaning solvents in table 6-7 maybe used.

Table 6-8.Prime and Paint for Tube Assemblies

Oxygen system tube assemblies require special precautions for cleaning. After fabrication, and testing, clean oxygen tube assemblies in accordance with MIL-STD-1359, using trichlorotrifluoroethane (MIL-C-81302) in a spray gun or vapor degreaser. If a vapor degreaser is not used, tube assemblies must remain in the vapor degreaser until the temperature specified in the manufacturing instructions is reached. Tube assemblies must be blown clean and dried with a stream of clean, dry, water-pumped air. 

CAUTION 

Oil-pumped air is not a suitable substitute for water-pumped air because it causes oil to be deposited in the tube assemblies. Oxygen reacts violently with oil and may cause equipment damage and injury to personnel. Oxygen (BB-0-925) or clean, dry, water-pumped nitrogen (BB-N-411) must be used in place of water-pumped air. Only MIL-C-81302 is approved for cleaning oxygen system tubing.