F-F-351F
procedure, the element shall be visually examined for evidence of damage or failure. If the
element appears satisfactory, it shall be installed in a test case and a filtering ability test made in
accordance with 4.6.5. After completion of the filtering ability test, element shall be dissembled
and examined for evidence of damage to determine conformance to 3.5.6.
4.6.7 End load strength. To determine conformance to 3.5.7, type IV filter elements shall
be tested for resistance to static end loading by installing the element over a center tube of
appropriate diameter, supporting one end of the element on a plain concentric surface of at least
the maximum diameter listed in table X. Pressure shall be applied to the opposite end of the
element by means of a flat surfaced annular ring, 0.06 in. (1.5 mm) in width, within the element-
sealing surface diameters per class as listed in table X. Constant pressure shall be applied for a
period of 30 minutes, after which the element shall be examined for evidence of damage.
TABLE X. Element sealing surface diameters.
Max.diameter1/
Min. diameter 1/
Class
inches (mm)
inches (mm)
1
2.00 (51)
1.00 (25.4)
2
2.50 (63.5)
1.00
3
3.50 (76)
1.63 (41.4)
4
4.00 (102)
3.00 (76.2)
1/ Pressure ring to apply force between limits.
4.6.8 Differential pressure. To determine conformance to 3.5.8, all type IV filter
elements assembled in a filter body (see figure 1) shall be tested for resistance to differential
pressure by means of a test apparatus similar to that employed for the filtering ability test. The
same filter element tested for filtering ability may be used in this test. Otherwise, a new, unused
element which has been subjected to 180°F clean oil at rated flow for a period of 66 hours shall be
selected for test. With the element installed in the appropriate filter body, a viscous oil (see 6.4.6)
shall be circulated through the system at room temperature. The system shall be started with the
pump bypass valve in the open position. The bypass valve shall then be slowly and uniformly
closed, causing the element differential pressure to rise gradually until element failure occurs, or
until 100 psi is observed. The psi differential pressure shall be held for 30 seconds. The bypass
valve shall then be opened, the element shall be removed from the filter body, and a disassembly
inspection shall be made for evidence of damage or failure.
4.6.9 Cover-spring force. To determine conformance to 3.5.9, each hold-down spring of
the four sample type I, class 3 filters shall be tested to determine the force required to compress
each spring to its assembled height.
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