scope:

- This specification covers hydraulic pressure relief valves for use in type II aircraft hydraulic systems conforming to, and defined by Specification MIL-H-5440.

- Hydraulic pressure relief valves shall be furnished in the sizes and for the rated flows indicated on the applicable MS standard for the class of service as indicated in table I. TABLE I Classes and rated flow pressures

Maximum pressure Rated flow pressure differential between setting (psi) 2/ full flow and reseat Standard Class 1/ pressure (psi) min max ---------------------------------------------------------------------- MS28893 A 500 825 100 B 825 1,400 160 C 1,400 2,300 270 D 2,300 3,850 460 1/ A valve shall be adjustable to deliver rated flow at any pressure within the range of the maximum and minimum rated flow pressure settings listed for its class in table I. Relief valves adjustable to the range of more than one class shall carry in the part number the abbreviated letter designation of the lowest and highest pressure class and shall conform to the applicable envelope, for example: A valve adjustable from l,400 to 3,850 psi would be Part No. MS28893 CD. 2/ The rated flow pressure setting is the pressure differential which results between the inlet and relief ports of the valve at rated flow.

intended Use: