Section 202(16)(b) in The Naval Ceremonial, Conditions Of Service And Miscellaneous Regulations, 1964
(b)If, however, the absence on temporary duty exceeds or is expected to exceed three months and a replacement is considered necessary, steps' may be taken to authorise an appointment for the duty, with a rank commensurate with its responsibilities. Acting promotion shall then be admissible in place of the absentee from the date the new appointment is created.