A-A-50632A(SH)
3.3.2 Strainer element construction. Strainer element shall be screen type construction, consisting of a supporting framework (strength member) with a wire screen as the straining medium. The supporting framework (strength member) shall be plate construction. The strainer element shall be made of corrosion-resistant steel. Wire screen edges and seams shall be folded back upon themselves and welded or brazed to preclude fraying. All seam welds shall be continuous. The strainer element shall be held securely in place when the strainer is assembled.
3.3.2.1 Element support. The element support shall be designed to facilitate easy removal/installation of the straining element and element support as an assembly. The element support must satisfy the flow area requirements of section
3.4.
3.3.2.2 Straining element. Unless otherwise specified (see 7.1), the straining element shall be attached to the element support in such a manner that it can easily be removed from the element support and replaced. The free flow area through the assembly of the strainer element and element support shall be not less than 2 times the cross-sectional area of the strainer discharge connection. The element micron rating shall be specified by 2.1. Unless otherwise specified (see
7.1), the minimum beta ratio shall be 75.
3.3.2.2.1 Straining element compression test. A differential pressure (outside- inside) shall be applied across the support/straining element assembly equal to
100 percent of the specified strainer design pressure. This differential may be accomplished by installing a strippable film on the straining element exterior. Then increasing the pressure to the maximum pressure drop and held for 20 minutes. Alternate methods of obtaining differential pressure will be considered by the command or agency concerned. Supporting or straining elements which distort, stretch or exhibit other weakness shall be rejected.
3.3.2.2.2 Straining element expansion test. A differential pressure (inside- outside) shall be applied across the straining element assembly equal to 100 percent of the specified strainer design pressure. This may by accomplished by installing a strippable film on the straining element interior. Then increasing the pressure to the maximum pressure drop and held for 5 minutes. Alternate methods of obtaining differential pressure will be considered by the command or agency concerned. Straining elements which distort, stretch or exhibit other weaknesses shall be rejected.
3.3.3 Self-cleaning mechanism. The self-cleaning action of each unit shall be operated by a hydraulic motor included as a part of the strainer. Each hydraulic motor shall use strained system fluid as its sole source of power. The fluid consumption of the motor(s) shall not exceed 4 percent of the total flow through the strainer assembly.
3.3.3.1 Backflush structure. The backflush structure shall periodically clean the entire strainer element by backflushing system fluid through the straining element. The structure shall clean the strainer element in segments, so as not to disrupt the system flow through the strainer at any time. All impurities
separated shall be deposited within a sludge compartment isolated from the strained liquid.
3.3.4 Sludge compartment. Unless otherwise specified (see 7.1), the sludge compartment shall have a volume of not less than 320 cubic inches for each unit. Sludge compartment shall be equipped with a removable cover for manual cleanout.
3.3.5 Material. Unless otherwise specified (see 7.1), materials shall be as specified in table II.
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