Question 4 3AE02 - Third Assistant Engineer (Alt)

The Correct Answer is D **Why option D ("With the compressor in the off mode incapable of starting.") is correct:** The oil level in a reciprocating air compressor, like most mechanical equipment fitted with a static dipstick, must be checked when the unit is completely static (not running) and all oil has had time to drain back into the sump. Checking the level while the machine is running (A or B) would give a false, typically low, reading because oil is being actively circulated throughout the crankcase, rods, and cylinders. Furthermore, checking the oil when the compressor is completely turned off and locked out (incapable of starting) ensures safety for the technician performing the check, preventing accidental movement of internal components or unexpected startup. **Why the other options are incorrect:** * **A) With the compressor running at speed and loaded:** This is incorrect because the dynamic movement of the oil being splashed, pumped, and circulated will give an inaccurate (low) reading, and checking the oil while the machine is running is dangerous. * **B) With the compressor running at speed and unloaded:** Similar to option A, running the compressor will circulate the oil, leading to an inaccurate reading. Safety precautions also dictate that checks should only be performed when the machine is stopped. * **C) With the compressor in the auto mode and currently not running:** While the compressor is stopped, checking the oil in 'Auto' mode is unsafe. The compressor could automatically cycle on at any moment if the pressure drops, posing a severe risk to the technician. The machine must be positively disabled (Off/Locked Out) before maintenance or checks are performed.