Bunker lines are required to be tested to 1.5 times their allowable operating pressure by placing them under a constant hydrostatic load for a prescribed period of time (usually 5-10 minutes is sufficient). This is best achieved by using the FO transfer pump (s) to fill bunker lines up to the manifolds (with fuel oil), purge the lines via manifold valves, then build pressure in the lines until 1.5 times the normal operating pressure is reached (operating parameters should be available in the bunker plan, or the vessel may be guided by pipeline material pressure ratings).
If the FO transfer pump is a positive-displacement type, it may be stopped when the required test pressure is reached as it should not permit backflow. If a centrifugal type of pump is employed, constant running will be required to ensure the necessary pressure is maintained during the test. In addition to log entries in Deck Logbook and Oil Record Book (ORB), the deck bunker lines are also required to be stenciled with the date of last pressure test together with the pressure maintained (in kg/cm2, psi or bar).