Reciprocating Steam Engine (ES) cheat sheet

Saturated steam temperature and pressure are locked together: at 1 atm abs (0.101 MPa) saturation temperature is 100 °C; at 10 bar abs it is about 179 °C.

Superheated steam has temperature above saturation at the same pressure; degree of superheat = actual temperature minus saturation temperature.

Dryness fraction x = mass of vapor / total mass; enthalpy h = hf + x·hfg, where hfg is latent heat of vaporization.

Specific enthalpy of saturated liquid hf rises with pressure, while hfg falls to zero at the critical point (22.06 MPa, 374 °C).

Ideal Rankine cycle efficiency = (h1 − h2) − (h3 − h4) divided by (h1 − h2), where 1-2 is turbine/engine expansion and 3-4 is feed pump work.

Adiabatic (isentropic) expansion gives maximum work; actual engine work is less, and isentropic efficiency = actual work / isentropic work.

Throttling is isenthalpic: a pressure drop across a partly open valve leaves enthalpy essentially constant and raises entropy.

Steam flow through an engine follows the continuity equation mdot = A·V/v, where v is specific volume at the section considered.

Reciprocating engine types include horizontal/vertical, single- or double-acting, simple or compound (two-stage), and uniflow or counterflow exhaust.

A double-acting cylinder produces work on both piston strokes; effective area differs between head end (full bore) and crank end (bore minus rod area).

In a compound engine, high-pressure exhaust feeds the low-pressure cylinder; receiver pressure sits between the two stages.

Piston rod packing (gland) seals the rod where it leaves the cylinder; a leaking gland shows as steam blow-by at the rod.

Crosshead and guide take the side thrust of the connecting rod so the piston rod stays aligned with the bore.

Indicator diagrams (pressure-volume or pressure-crank angle) reveal valve timing, compression, and power; mean effective pressure = diagram area / stroke length.

Indicated horsepower = PMEP × L × A × N × k / 33,000 (English units), with k accounting for single/double acting and cylinder count.

Cylinder clearance volume is expressed as a percentage of swept volume; it stores compressed steam that re-expands at the start of the next stroke.

Slide valve, piston valve, and Corliss/poppet gears differ in port opening speed; Corliss releases steam quickly for better efficiency at part load.

Valve events in order per stroke: admission (lead), cutoff, release (exhaust opening), compression. Lead admits steam slightly before dead center.

Cutoff fraction controls economy: earlier cutoff at light load reduces throttling loss and improves efficiency.

Stephenson link motion reverses and varies cutoff by shifting the link; the die block position sets valve travel and lead.

Watt centrifugal governor is a speed-sensing device: flyballs rise with speed and reduce steam admission through a throttle or linkage.

Governor droop (speed regulation) = (no-load speed − full-load speed) / full-load speed, expressed as a percentage.

Isochronous governing holds constant speed regardless of load; most mechanical governors have 2–5 % droop for stable parallel operation.

Hunting is governor/engine oscillation from excessive sensitivity or lost motion; it appears as cyclic speed swings with steady load.

Boiler fittings required for safe operation include safety valve, pressure gauge, water-level gauge glass, feed check valve, and low-water cutoff.

Safety valve set pressure must not exceed the boiler maximum allowable working pressure; it lifts and reseats automatically.

Feedwater is treated to control scale, corrosion, and carryover; blowdown removes dissolved solids and sludge.

Steam separators and traps remove moisture and condensate; wet steam lowers engine efficiency and erodes valve faces.

Steam header pressure is held by boiler firing and feed control; a pressure-reducing valve sets engine inlet pressure downstream.

Superheaters raise steam temperature above saturation; attemperators spray water to limit final steam temperature.

Condensate return saves energy and water; a faulty trap passing live steam shows as a hot return line and reduced efficiency.

Air in a steam space causes sluggish heating and corrosion; vents and air-removal devices purge non-condensables at startup.

Before rolling, drain condensate from steam lines and cylinders; water hammer and hydraulic lock can bend rods or crack heads.

Warm the engine slowly with drains open and the cylinder cocks cracked, rotating by barring or slow steam until condensate clears.

Startup sequence: verify lube oil flow and pressure, open drains, admit steam slowly, confirm rotation direction, then close drains as steam clears.

Never admit steam to a cold engine without warming; thermal shock and trapped water are the primary startup hazards.

Shutdown: reduce load, close steam stop valve, open drains, continue lubrication and cooling until the engine stops and cools.

Barring gear or turning the engine after shutdown prevents uneven cooling and shaft bow on large units.

Overspeed trip must be tested before service; a stuck trip is a stop-work condition until proven functional.

Log speed, load, steam pressure/temperature, oil pressure, and bearing temperatures at intervals; trends reveal developing faults.

Cylinder lubrication uses high-temperature steam-cylinder oil fed by a mechanical lubricator; feed rate scales with steam rate and load.

Crankcase and bearing oil is separate from cylinder oil; cross-contamination dilutes bearing oil and destroys its film strength.

Oil viscosity grade is selected for bearing speed and temperature; too light an oil causes metal contact, too heavy causes overheating.

Bearing temperature rise above normal (roughly 10 °C over baseline) signals inadequate oil flow, misalignment, or contamination.

Cooling water to glands, packing, and bearings controls temperature; loss of cooling shows as rising temperature with unchanged load.

Routine checks: oil level and condition, filter differential pressure, gland tightness, coupling alignment, and vibration readings.

Oil analysis (viscosity, water content, wear metals, acidity) schedules changes and detects wear before failure.

Maintenance intervals follow running hours and condition monitoring; record every adjustment so trends can be compared.

Loss of power with normal steam pressure points to valve timing, worn rings, or leaking piston rod packing.

Knocking or pounding in the cylinder usually means water carryover or excessive clearance; stop and drain before continuing.

Uneven bearing heating indicates misalignment or a bent shaft; check with dial indicator and correct shim or alignment.

High exhaust pressure and low power suggest restricted exhaust line, faulty trap, or late release timing.

Governor instability (hunting) traces to lost motion, worn linkage, or excessive sensitivity; tighten linkage and reset droop.

Steam leakage at the gland is corrected by adjusting packing or replacing rings; do not overtighten or the rod scores.

Vibration with rising amplitude suggests imbalance, loose foundation bolts, or worn bearings; measure and correct before running.

After repair, verify clearances against specifications, bar the engine over by hand, and run a no-load trial before returning to service.

Pressure vessels and boilers fall under codes such as ASME Boiler and Pressure Vessel Code; inspection intervals are set by jurisdiction.

Lockout/tagout isolates steam, electrical, and mechanical energy before maintenance; verify zero energy by test.

Confined space entry into boilers or receivers requires atmosphere testing, permit, attendant, and rescue plan.

Hot surfaces and steam lines require insulation and guarding; steam burns are the leading injury in engine rooms.

Relief valves, gauges, and low-water cutoffs must be tested on a defined schedule and records retained.

Environmental compliance covers boiler emissions (NOx, CO, particulates), blowdown discharge limits, and fuel handling.

Noise exposure above 85 dBA requires hearing protection and monitoring under occupational noise rules.

Incident and near-miss reporting feeds corrective action; repeat faults indicate a system problem, not operator error alone.