Power Eng 1st Class flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Critical path

The longest-duration sequence of dependent activities through a project network. It determines the minimum project completion time, and any delay on it delays the whole project.

Earned value cost performance index

CPI equals earned value divided by actual cost. A value below one means the project has spent more than the work performed is worth, indicating a cost overrun.

ASME Section I scope

The section of the ASME Boiler and Pressure Vessel Code that sets rules for construction of power boilers, including materials, design, fabrication, inspection, and stamping requirements.

Hydrostatic test pressure

Under Section I, the completed boiler is tested at one and one-half times the maximum allowable working pressure, held for inspection, with no permanent deformation accepted.

Rankine cycle efficiency

Net work output divided by heat added in the boiler. Efficiency rises with higher throttle temperature and pressure and with lower condenser pressure.

Isentropic turbine efficiency

The ratio of actual enthalpy drop across a turbine to the enthalpy drop that would occur in an ideal isentropic expansion between the same inlet and outlet pressures.

Log mean temperature difference

The effective driving temperature difference for a heat exchanger, computed as the difference of the terminal differences divided by the natural log of their ratio.

Net positive suction head available

The absolute pressure at the pump suction, less vapor pressure, expressed as head. It must exceed the pump's required value to prevent cavitation.

Creep in boiler tubing

Time-dependent deformation under sustained stress at elevated temperature. It limits design above roughly 400 degrees Celsius for carbon steel and drives alloy selection.

Fitness-for-service assessment

A structured engineering evaluation of an existing flaw against remaining strength and future loading, allowing continued operation without immediate repair when acceptance criteria are met.

Three-element drum level control

A feedwater control scheme using steam flow as a feedforward signal and drum level plus feedwater flow as feedback, compensating for swell and shrinkage during load changes.

Furnace purge requirement

Before ignition, the furnace and gas passages must be ventilated with air at a defined flow for a defined number of volume changes to remove combustible gases.

Selective catalytic reduction

A post-combustion NOx control that injects ammonia or urea into flue gas over a catalyst, converting nitrogen oxides to nitrogen and water within a narrow temperature window.

Excess air and stack loss

Air supplied beyond stoichiometric requirement. Too little causes incomplete combustion and carbon monoxide; too much raises flue gas volume and stack heat loss.

Governor droop

The percentage speed or frequency change a turbine governor permits as load moves from no load to full load, enabling parallel generator load sharing.

Generator synchronization

Closing the generator breaker only after matching voltage magnitude, frequency, phase sequence, and phase angle to the running system, avoiding damaging current surges.

Pump affinity laws

For a centrifugal pump at constant impeller diameter, flow varies with speed, head with speed squared, and power with speed cubed, making variable speed control efficient.

Compressor surge

A damaging instability in which flow reverses through a compressor when the pressure ratio is too high for the flow, prevented by anti-surge recycle control.

Safety instrumented system

An independent protective system, separate from normal process control, designed to bring the plant to a safe state when a hazardous condition is detected.

Two-out-of-three voting

A redundancy scheme in which three sensors are installed and a trip requires agreement of two, reducing spurious trips while still detecting a single failed sensor.

Motor locked-rotor current

The current drawn by an induction motor at standstill, typically five to seven times full-load current for direct-on-line starting, affecting voltage dip calculations.

High-resistance grounding

A grounding method that limits ground fault current to a few amperes, reducing damage and touch potential while allowing continued operation during a ground fault.

Cation conductivity

A measurement in which sample water passes through a cation exchange resin, converting salts to acids and making the reading far more sensitive to chloride and sulfate ingress.

Coordinated phosphate treatment

A boiler water chemistry program that maintains phosphate and pH in a range preventing caustic concentration and minimizing scale, used for drum boilers.

HAZOP study

A systematic team review applying guide words to process parameters to identify deviations, their causes, consequences, and existing safeguards in a facility design or modification.

Lockout tagout

An energy isolation procedure requiring each worker to apply a personal lock and tag, verify zero energy, and remove isolation only under controlled conditions.

Availability

The fraction of time a unit is capable of service, computed as mean time between failures divided by the sum of mean time between failures and mean time to repair.

Maximum allowable working pressure

The highest internal pressure permitted by code at the design temperature, computed from the shell thickness formula using allowable stress and joint efficiency.

Steam moisture at exhaust

The liquid fraction in low-pressure turbine exhaust. Above roughly twelve percent, droplets erode last-stage blades and reduce stage efficiency.

Darcy-Weisbach equation

Head loss in a pipe equals the friction factor times length over diameter times velocity head, with friction factor depending on Reynolds number and roughness.

Master fuel trip

A protective action that rapidly closes all fuel supply valves to the furnace on a critical trip condition such as loss of flame or loss of forced draft.

Low-NOx burner

A burner design that stages fuel and air to lower peak flame temperature and oxygen availability, suppressing thermal and fuel-bound nitrogen oxide formation.