Section 6(1)(c) in The Merchant Shipping (Prevention of Pollution by Oil from Ships) Rules, 2010
(c)an intermediate survey within three months before or after the second anniversary date or within three months before or after the third anniversary date of the Certificate which shall take the place of one of the annual surveys specified in clause (d) and the intermediate survey shall be such as to ensure that the equipment and the associated pump and piping systems, including oil discharge monitoring and control systems, crude oil washing systems, oily-water separating equipment and oil filtering "systems, fully comply with the requirements of these rules and are in good working order: