Islanded simple-cycle

76 questions this plant already has.

You are not the designer. You audit the drawing, defend the field, and have to be useful at first fire. Start at Plant identity if you do not yet have the three facts that hang every other module.

Primer will not invent this plant’s megawatts, kV, or machine model. Shop-floor physics lives on trades.

1. 06 questions

   Plant identity

   Islanded, behind-the-meter, computing load. Every unusual drawing traces to those three.

   • Islanded, behind-the-meter, off-grid — are those the same?Open
   • Why does an islanded plant's protective relaying differ from a grid-connected plant's?Open
   • A large load step hits an island with many machines at part load. What happens to frequency in the first five seconds?Open
   • Why no HRSG on a simple-cycle plant serving a computing load?Open
   • Who has authority to direct a field change, and what happens when an owner's inspector issues a directive outside a formal change?Open
   • Why many small machines instead of a few large ones on an island?Open

2. 09 questions

   The machine

   Brayton cycle, back-work, derate, Wobbe, SCR on hot exhaust. A turbine is not 'a turbine.'

   • What is compressor back-work in a gas turbine, and why does a small efficiency drop hurt so much?Open
   • Sketch the Brayton cycle. Where do the real-machine losses sit?Open
   • Why does a gas turbine lose output on a 105°F afternoon at 1,800 ft?Open
   • What is Wobbe Index, and what happens if pipeline gas drifts outside the band?Open
   • Why is SCR harder in simple cycle than combined cycle?Open
   • Two dissimilar machines share load on an island. How does that go wrong?Open
   • What is ammonia slip, and why is it a permit issue rather than an efficiency issue?Open
   • Trace fuel gas from the pipeline tap to the combustor. What does each stage do?Open
   • Why isn't 'use the best inlet filter' the answer?Open

3. 09 questions

   The island

   Frequency is shaft speed. Fault current decays. 51V, droop, black start, sync.

   • Why 51V instead of a plain 51 on an island?Open
   • A 30 MW islanded machine, H = 4 s, takes a 6 MW step. What is the initial RoCoF? What changes with twenty machines?Open
   • Explain droop. Why can't two machines both run isochronous on one bus?Open
   • Walk the black-start sequence. What powers each step?Open
   • Read a generator capability curve. What limits you at 0.85 lagging versus 0.95 leading?Open
   • Why a 200% neutral bus?Open
   • Grounding grid versus deep foundations — why do they fight, and what are three resolutions?Open
   • Five synchronizing conditions. What does a 30° out-of-phase close actually do?Open
   • High-resistance versus low-resistance grounding when availability is the plant's job?Open

4. 08 questions

   Piping and BOP

   Pipe class literacy, B31.1, WPS/PQR/WPQ, pickling, nozzle loads, hydro extent.

   • Given a medium-pressure gas line number, what does the pipe class actually specify?Open
   • Why stainless for ammonia, chemical feed, and sample — but carbon steel for fire water?Open
   • A welder has a valid WPQ but the contractor has no PQR for that procedure. What is wrong?Open
   • What is natural-gas pipeline pickling, and which failure does it prevent?Open
   • A 400 ft carbon-steel run goes from ambient to 120°F. About how much does it grow, and how do you let it?Open
   • Why are unreinforced stub-in branches prohibited? What belongs on a 6" branch off a 12" header?Open
   • Two spec sections give different pressure classes for the same fire-water main. What do you do?Open
   • What does a hydrotest log's 'extent of system tested' actually protect against?Open

5. 08 questions

   Civil and foundations

   Expansive clay, drilled piers, hot-weather concrete, PEMB setting-plan loop.

   • Why drilled piers instead of spread footings on expansive clay?Open
   • It's 104°F, 15 mph wind, 20% RH. Can you place concrete? What has to change?Open
   • A structural note imposes a tighter pour window than the spec. Which governs?Open
   • Internal erosion along an old-fill/new-fill interface — why is 'leakage' the wrong word in an RFI?Open
   • What is the delegated-design boundary for a PEMB, and which three coordination failures does it predict?Open
   • A foundation's natural frequency is 58 Hz; the machine runs at 3,600 rpm. Acceptable?Open
   • Thrust restraint is missing from the contract. What is the contractor's exposure?Open
   • Why will a crew chasing density compact expansive clay dry of optimum?Open

6. 08 questions

   Controls and loops

   P&ID as a narrative. Loop check ≠ functional test ≠ logic test. Two overspeeds.

   • Decode every field of a typical process line number.Open
   • Trace fuel gas on a P&ID from the supply to the machine. What closes on high-high pressure?Open
   • Why does a gas turbine have two independent overspeed systems?Open
   • Loop check versus functional test versus logic test. Which catches a reversed thermocouple? Which catches a wrong C&E entry?Open
   • Many machines, two vendors, one island. What is the control architecture, and how does the integration fail?Open
   • Read one row of a cause-and-effect matrix and write the test that proves it.Open
   • Why is instrument air stainless, and how does that connect to the air blow?Open
   • What is a thermowell wake-frequency calculation, and what fails when it is skipped?Open

7. 08 questions

   Construction execution

   IFC versus permit set. RFI as design-intent. Hold versus witness. Diagrammatic drawings.

   • Most of the spec is still at permit status while the field is working to IFC drawings. What is the risk?Open
   • Admin and quality divisions were never issued, but technical sections reference them. What do you do?Open
   • Write an RFI that confirms design intent when a drawing runs a pipe through a beam.Open
   • A hold point appears in an RFI answer that was not in the contract. What is the entitlement argument?Open
   • Nine items converge on one fabrication date in three weeks. What is the recovery logic?Open
   • When does construction LOTO become operational LOTO, and who owns the system at that instant?Open
   • The piping spec says drawings are diagrammatic. What does that obligate, and what does it not?Open
   • Why is a rasterized schedule print worse than useless?Open

8. 08 questions

   Commissioning

   Area to system. Six milestones. Lube-oil flush as schedule risk. Real trips, not simulated.

   • Area-based construction versus system-based commissioning — how does that change a punchlist?Open
   • Name the six completion milestones and the commercial consequence of each.Open
   • Write the pre-commissioning sequence for one gas turbine from mechanical completion to first fire.Open
   • Why is lube-oil flushing a schedule risk, and what actually says it is finished?Open
   • Describe a full load-rejection test on an islanded machine. What are you proving?Open
   • How do you correct a measured performance result to guarantee conditions?Open
   • A system is 90% turned over with one open punch on a live bus. Walk the LOTO.Open
   • Why does simulated trip testing prove less than you think?Open

9. 06 questions

   Operations

   Part-load heat rate versus spinning reserve. Surge. Hours versus starts. Peak demand plus peak ambient.

   • Twelve of many machines are at 70% and one trips. Describe the next thirty seconds.Open
   • Why is minimum load a regulatory constraint, not merely a technical one?Open
   • Explain compressor surge, how you detect it, and what the control system does.Open
   • Hours-based versus starts-based maintenance. Which governs a plant following a variable computing load?Open
   • Many machines at 40% versus fewer at 62%: fuel, emissions, reserve, maintenance, reliability.Open
   • Why is the worst hour the one where peak demand and peak ambient coincide?Open

10. 06 questions

    Codes and permits

    B31.1 versus B31.3. NFPA 56 before gas. PSD/BACT. Aqueous ammonia thresholds. IEEE literacy.

    • Which code governs power-plant piping inside the fence, and how would B31.3 change the requirements?Open
    • What does NFPA 56 require before natural gas piping enters service?Open
    • What triggers PSD review, and what is BACT?Open
    • Besides intrinsic safety, what regulatory threshold drives aqueous ammonia over anhydrous?Open
    • Name three IEEE standards a large plant's electrical spec will cite, and what each governs.Open
    • In a high-wind, low-seismic region, which ASCE 7 load case governs a pipe rack — and why do people assume otherwise?Open