Question 55 OSE01 - Chief Engineer - OSV

The Correct Answer is A. **Explanation for A (Once per watch while underway):** The lubricating oil system for critical machinery like the main propulsion reduction gear (or main engine, depending on system design) is essential for preventing catastrophic failure. The duplex strainer illustrated (sometimes referred to as a duplex filter or self-cleaning strainer, where rotating the handle 'A' cleans the element) is designed to remove particulate matter continuously from the circulating oil. To ensure the oil flow rate remains adequate, the strainer must be frequently cleaned by rotating the handle. Standard engineering practice, often codified in planned maintenance systems (PMS) and standing orders for offshore vessels, dictates that strainers on critical, continuously operating machinery like the main reduction gear lube oil system must be checked and cleaned (rotated) **at least once per four-hour watch** (i.e., "Once per watch while underway"). This routine action prevents excessive differential pressure across the strainer, ensuring proper lubrication and maximizing the service life of the filter element. **Explanation for Incorrect Options:** * **B) Once per month:** This frequency is far too infrequent for a continuously circulating oil system on critical equipment. Waiting a month would almost certainly lead to a heavily clogged strainer, resulting in high differential pressure, potential oil starvation, and alarm conditions, necessitating a shutdown or changeover to the standby filter under duress. * **C) Once every six months:** This interval is severely inadequate for routine operational cleaning and would be considered negligence. Cleaning every six months is typically associated with major maintenance tasks like oil analysis or changing the oil charge itself, not routine strainer operation. * **D) Once per year:** This is completely impractical for an operational vessel. If the strainer handle were rotated only annually, the system would fail within hours or days of operation due to clogging and restricted flow.