F-F-351F
4.6.6.2 Filter body calibration. A flow rate calibration of the modified filter assembly
(without element) shall be determined when circulating new, straight mineral oil at 145°F (63°C)
(see 4.5.5)
4.6.6.3 Flow rate test procedure. Install a filter element in the modified filter body and
circulate new, straight mineral oil at 145°F throughout the filter assembly at a flow rate of
10 gallons per minute (gal/min) (37.8 L/min), or a pressure drop of 30 psi, whichever is attained
first. Record pressure drop of 10 gal/min flow, or flow in gal/min at 30 psi pressure drop.
(NOTE: The pressure drop across the element is equal to the pressure drop across the filter body
and element, minus the pressure drop across the body (see 4.6.6.2) at the same flow rate.) This
data will be required to evaluate the test in 4.6.6.6.
4.6.6.4 Element mounting. The same sample type II, class 3 element, for which the
flow rate has been determined (see 4.6.6.3) shall be installed over a 0.563 in. (14 mm) diameter
center tube and secured in place by a lower stop and upper spring similar in construction to that
specified for the cover and center tube (see 3.4.1.2.1.1 and 3.4.1.3).
4.6.6.5 Shock test procedure. The center tube, with filter element assembled thereon,
shall be rigidly mounted at each end to a support. The contractor's Government approved
inspection test plan will include the shock test configuration and procedures to establish
meeting these requirements. Sufficient shock is established to equal striking the center tube
support, with filter element assembled thereon, an equivalent of 20 blows at 10 second intervals,
alternating the blows on the front and back of the element support. Each blow shall have an
acceleration value of 20 gravity units (g), or approximately 300 ft-lb (406.8 N⋅m.).
4.6.6.6 After-shock flow rate. After completing shock test procedure, to determine
conformance to 3.5.6, the elements shall be examined for any evidence of surface failure or other
injury, then reassembled in the modified filter body (see 4.6.6.1) and the flow rate through the
element determined at the pressure drop obtained in 4.6.6.3. The flow rate, after shock, shall be
reported as percent of the original flow rate.
4.6.6.7 Type IV filter elements. Each filter element for the shock test shall be one used in
the media migration test, or one that has been subjected to 180°F clean oil flow for not less than
eight hours and allowed to drain for not less than one hour. The contractor's Government
approved inspection test plan will include the shock test configuration and procedures to establish
meeting these requirements. The element shall be installed over a center tube of appropriate
diameter and length and secured in place by a lower stop and upper spring and spring bearing
plate to simulate installation in a test filter body. The center tube shall then be rigidly mounted in
a vertical position and subjected to shock testing. Sufficient shock is established to equal striking
the center tube support, with filter element assembled thereon, an equivalent of 20 blows at
10 second intervals, alternating the blows on the front and back of the element support. Each
blow shall have an acceleration value of 20 g, or approximately 300 ft-lb. After completing shock
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