Division 4.2.2.2.3 Flexible fuel lines

The length of the flexible part of the flexible fuel line with its fittings attached, to be used in the following test shall be calculated as follows:

L = 4,142R + 3,57D

where:

The flexible fuel line shall be bent in the manner depicted in Figure 4.2.2. and attached to a fixture in that position by the fittings with which it shall be approved. One end of the flexible fuel line shall be attached to a reciprocating manifold and the other end shall be attached to a stationary manifold connected to a hydraulic supply. The flexible fuel line shall be pressurised quickly by means of a quick opening solenoid valve, such that one cycle consists of holding the pressure at 1,25 times the nominal working pressure for 10 ± 1 seconds (except for flexible fuel lines with a required material temperature of 120 °C where the hold pressure shall be 1,37 times nominal working pressure) and then reducing it to less than 0,1 times the nominal working pressure for 5 ± 0,5 seconds. The total number of test cycles shall be equal to 2,0 times the number of filling cycles or duty cycles as appropriate to the use of the flexible fuel line in accordance with section 2.7.6. or 2.7.7. As appropriate 50 per cent of the test cycles shall be performed at the minimum and the remaining 50 per cent at the maximum material temperature in accordance with section 2.7.5.1.

Superimposed on the hydraulic pressure cycles is a flexing cycle. The flexing rate shall be 6 ± 2 per cent of the hydraulic pressure cycling rate. This assures that the flexible fuel line is in a different configuration on each succeeding pressure cycle impulse. The test fixture is shown in Figure 4.2.2. with the distance A calculated as:

A = 1,75R + D

The flexible fuel line shall not show any visible signs of damage.