ΚΕΣΕΝ Μηχανικών cheat sheet
ΚΕΣΕΝ Μηχανικών · Keep the key ideas within reach.
Diesel propulsion mechanisms and supplied performance models
Identify the actual crosshead or trunk-piston arrangement.
Use the correct two-stroke or four-stroke cycle frequency.
Separate indicated power, brake power, heat input and consumption.
Do not turn one symptom into a universal repair or emergency instruction.
Pumps, separation, freshwater, refrigeration and heat exchange
Trace the actual source, pump, consumer and return path.
State pump-law and heat-exchanger assumptions.
Distinguish centrifugal separation, vacuum evaporation and reverse osmosis.
Use the correct refrigeration energy balance without an operational recipe.
Hull form, free surfaces and bounded stability calculations
Define displacement and hull-form quantities precisely.
Positive initial GM is not complete stability compliance.
State the rectangular small-angle free-surface assumptions.
Separate stability, hull strength and controlled drydocking decisions.
Programme scope, watchkeeping and accountable ship systems
Distinguish the Danish programme, Greek upgrade and Egyptian CoC pathways.
STCW knowledge does not replace practical competence assessment.
Maintain critical-equipment, handover and defect evidence.
Use actual vessel safety and environmental requirements, not universal shortcuts.
Electrical circuits, machines and digital logic
For a sinusoid V_rms = V_peak/√2; the stated impedance magnitude is for a series RLC model.
Q_C = P(tan φ₁ − tan φ₂) for power-factor correction
Transformer: V₁/V₂ = N₁/N₂ = I₂/I₁
Induction motor: n = (1 − s)·60f/p
Thévenin voltage is open-circuit voltage; deactivate independent sources to obtain resistance while preserving dependent-source behavior.
Karnaugh: give the minimum sum of products
Measurement, feedback, PLC and automation
Sensitivity = Δoutput/Δinput; resolution = smallest detectable change
Closed-loop error compares reference and measurement; integral action can remove appropriate steady-state error only under suitable stability and operating assumptions.
PLC scan: read inputs → run program → update outputs
4–20 mA live zero: (I − 4)/16 of the span
Repeatability ≠ accuracy, resolution ≠ sensitivity
Robot DOF come from its joints; workspace is the reachable volume
Thermal Physics
Use kelvin in all gas-law and kinetic-theory calculations
Q = mcΔθ for temperature change; Q = mL for change of state
Mixtures: heat lost by hot bodies = heat gained by cold bodies plus calorimeter
pV = nRT and pV = ⅓Nm⟨c²⟩; mean KE = (3/2)kT
For a fixed amount of an ideal gas, internal energy depends only on temperature
First law: ΔU = Q − W with W defined as work done by the gas
Maintenance diagnosis, condition evidence and controlled restoration
Distinguish observed symptoms, hypotheses and established causes.
Use actual condition criteria rather than universal setpoints.
A stopped control display does not establish safe isolation.
Controlled restoration and accurate records complete the reasoning loop.