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These 10 free C-273 questions are organized by exam domain, so you can see how each part of the Process Systems 4 - Analytical (C-273) blueprint is tested. Reveal the answer and explanation under each question.
A technician is preparing to replace a chemical-pump discharge fitting. The motor supply is locked out, and the process and reagent connections are isolated. The gauge on the isolated discharge section still reads 250 kPa gauge. What must precede opening the fitting?
Correct answer: A - Use the designated bleed to remove trapped pressure, then verify a safe pressure state before opening.
A calibration record documents an as-found error of +0.27 pH that failed the acceptance check, followed by a passing as-left verification after adjustment. The transmitter supplied several batch records before this check, but the onset of its error is unknown. How should the record be used?
Correct answer: C - Preserve the as-found and as-left results, and assess which earlier batches may have been affected.
Reagent draw from a liquid-jet eductor stops when a downstream valve is partly closed. Pressure at the motive inlet stays at 300 kPa, while outlet pressure rises from 100 to 285 kPa; motive water still flows. Restoring the original valve position immediately restores reagent draw. What mechanism explains this reversible loss of suction?
Correct answer: D - Higher outlet backpressure reducing the pressure differential that creates suction.
At normal suction and discharge conditions, a metering pump lowers a calibration-column reading from 250 mL to 190 mL in 3 minutes. Stroke frequency is set to 60%, and stroke length is fixed. Testing has established proportional delivery versus frequency from 40% through 90%. The required rate is 1.50 L/h. Which frequency setting should be tried before repeating the drawdown test?
Correct answer: D - 75%
Two equal-volume wastewater batches both start at pH 5.00 at 25 °C. Representative samples titrated to the same stable endpoint require markedly different amounts of the same caustic solution. An operator proposes using the same full-batch caustic charge because the starting pH values match. What should govern the dosing estimate?
Correct answer: B - Use each batch’s measured titration demand, scaled to its own volume.
A gel-filled combination pH electrode will be stored for several weeks. Its manufacturer specifies wet storage in 3 M KCl. The technician has cleaned and rinsed the electrode. Which preparation protects both the measuring and reference systems?
Correct answer: A - Fill the cap with 3 M KCl, covering the glass and reference junction; keep the connector dry.
During commissioning, a pH transmitter has the approved range of 4-20 mA = pH 2.00-12.00 and reads 9.50 locally. A verified handheld meter agrees. At the controller input, the measured signal is 16.00 mA, but the controller displays pH 10.50. Which correction is supported by all three readings?
Correct answer: C - Restore the controller scaling to pH 2.00-12.00, then verify the loop across its range.
At 25 °C, an electrode produces +182.0 mV in a reference certified at pH 4.00 and +11.0 mV in one certified at pH 7.00. The ideal slope magnitude is 59.16 mV per pH unit. The service procedure accepts 92-102% slope; offset and independent verification checks have already passed. Which slope assessment belongs on the calibration record?
Correct answer: A - Approximately 96.3%; the slope meets the acceptance requirement.
A batch controller has a nominal target of pH 7.00. Its base-feed relay turns ON at or below 6.70 and OFF at or above 7.30, retaining its previous state between those limits. The pump started at pH 6.50; the rising pH is now 7.08. All dosing permissives remain satisfied. The expected relay behavior is:
Correct answer: B - Remain ON until pH reaches the upper switching threshold of 7.30.
A previously stable proportional-integral pH loop calls for 100% base feed while an empty-tank interlock inhibits the pump. After refill and authorized restart, the controller continues commanding 100% even after verified process pH passes the setpoint. Its output eventually falls. Which controller change most directly addresses this behavior?
Correct answer: C - Enable anti-windup tracking that accounts for the pump’s inhibited output.
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