USCG OIM cheat sheet

Diesel engine indicated power: IP = (Pmi × L × A × N × n) / 60 for a two-stroke, where Pmi is mean indicated pressure, L stroke, A bore area, N rpm, n number of cylinders.

Brake mean effective pressure relates to brake power by BMEP = (P_b × 60) / (L × A × N × n); mechanical efficiency is BMEP divided by IMEP.

Specific fuel consumption (g/kWh) = fuel mass flow (g/h) divided by brake power (kW); a rising trend signals fouling, injector wear, or air restriction.

Turbocharger surging on rapid load change is countered by gradual load application and verifying air cooler and scavenge space cleanliness.

Main engine lube oil pressure low alarm typically trips the engine; standby pump auto-start is set above the trip setpoint to prevent nuisance shutdowns.

Two-stroke crosshead engines use separate cylinder oil (total-loss) and system oil; four-stroke trunk engines share one sump oil for pistons and bearings.

Watchkeeping handover must include machinery status, ongoing maintenance, abnormal readings, and standing orders; never hand over during a critical manoeuvre without the chief engineer's approval.

Auxiliary boiler low-water trip and flame failure trip must be tested before lighting off; purge the furnace before ignition to clear unburnt fuel.

Three-phase power P = √3 × V_line × I_line × power factor; reactive power Q = √3 × V × I × sin φ and apparent power S = √3 × V × I.

Generator paralleling requires matching voltage, frequency, phase sequence and phase angle; kW load shares via governor droop, kVAr via excitation (voltage droop).

Droop setting determines load sharing: a generator with lower droop takes a larger share of kW load for the same frequency deviation.

Insulation resistance minimum for a 440 V system is typically 1 MΩ at 500 V DC test; readings below 1 MΩ/kV require investigation before energising.

Preferential (interlock) trip: non-essential loads (HVAC, galley, some pumps) shed automatically on generator overload or loss of one generator.

Battery capacity: Ah rating at a stated discharge rate; charging voltage for lead-acid float is about 2.25 V/cell, equalising about 2.4 V/cell.

A PLC analogue input 4-20 mA loop reads 4 mA at zero and 20 mA at full scale; a live-zero signal allows broken-wire detection (0 mA = fault).

Earth fault on an insulated (IT) distribution system is detected by an insulation monitoring device; a single earth fault does not trip but must be located and cleared promptly.

Planned maintenance system intervals are set by running hours, calendar time, or condition (vibration, oil analysis); deferral requires chief engineer authorisation and record.

Crankcase oil analysis trends: iron (wear), chromium (rings/liners), sodium (coolant ingress), water, viscosity and TBN (base number depletion).

Vibration severity is judged against ISO 10816 zones; a rising trend or zone C/D reading requires investigation before continued running.

Hot work permit requires gas-free certificate, fire watch, removal of combustibles, and a check of adjacent spaces; enclosed space entry requires atmosphere test (O2 20.9%, LEL < 1%, H2S/CO within limits) and a standby man.

Torque tightening follows the manual's sequence and values; use a calibrated torque wrench and record the calibration date.

Lockout/tagout: isolate, prove dead, apply lock and tag, and test the isolation before work; the person working applies their own lock.

Pressure testing of piping uses 1.5× design pressure (hydrostatic) unless the code specifies otherwise; relief valves are set and sealed to design pressure.

Bearing clearance is measured by bridge gauge or lead wire; compare against the maker's wear limit before deciding to renew.

MARPOL Annex I: oil discharge overboard is prohibited except through 15 ppm oily water separator with monitoring; the oil record book must record all transfers and disposals.

MARPOL Annex VI: sulphur limit 0.50% m/m globally and 0.10% in ECAs; NOx Tier limits apply to engines over 130 kW built after the applicable date; a Bunker Delivery Note must be retained 3 years.

An oil record book entry is made without delay; falsification is a criminal offence and the OIM/chief engineer is accountable.

Emergency generator must start and take load automatically within 45 seconds of a blackout (SOLAS); emergency fire pump and steering gear have defined independence requirements.

STCW watchkeeping: a watch is not left unattended; the engineer on watch must be fit for duty and the relief must be competent and briefed before takeover.

Fire triangle: fuel, oxygen, heat; fixed CO2 systems require space evacuation, boundary closing and head count before release.

Enclosed space entry requires a permit, atmosphere test, ventilation, standby man at the entrance, and rescue equipment; never enter to rescue without breathing apparatus.

Garbage record book (MARPOL Annex V) records discharges and incinerations; plastics must never be discharged to sea.