Plant Operator Selection System Test POSS 4 — Questions and Answers
Question 1: A boiler produces 15,000 lbs of steam per hour. If efficiency drops by 10%, how many lbs of steam per hour will it produce?
- 12,500 lbs/hr
- 13,000 lbs/hr
- 13,500 lbs/hr (Correct answer)
- 14,000 lbs/hr
Correct answer: 13,500 lbs/hr
15,000 × (1 − 0.10) = 15,000 × 0.90 = 13,500 lbs of steam per hour.
Question 2: Which instrument would a plant operator use to measure electrical current in a circuit without interrupting it?
- Megohmmeter
- Multimeter in voltage mode
- Clamp-on ammeter (Correct answer)
- Wattmeter
Correct answer: Clamp-on ammeter
A clamp-on ammeter measures current magnetically around a conductor without breaking the circuit.
Question 3: A passage describes a water treatment process: coagulation occurs first, then sedimentation, then filtration, then disinfection. What is the third step?
- Coagulation
- Sedimentation
- Filtration (Correct answer)
- Disinfection
Correct answer: Filtration
The passage lists four steps in order; filtration is explicitly the third step after sedimentation.
Question 4: A line graph shows plant output (MW) over 24 hours. Output peaks at 480 MW at 2 PM and reaches its low of 210 MW at 3 AM. What is the range?
- 220 MW
- 250 MW
- 270 MW (Correct answer)
- 290 MW
Correct answer: 270 MW
Range = maximum − minimum = 480 − 210 = 270 MW.
Question 5: A reciprocating pump completes 60 strokes per minute. Each stroke displaces 0.5 gallons. What is the flow rate in gallons per hour?
- 1,500 gal/hr
- 1,800 gal/hr
- 3,000 gal/hr (Correct answer)
- 3,600 gal/hr
Correct answer: 3,000 gal/hr
60 strokes/min × 0.5 gal/stroke = 30 gal/min; 30 × 60 min = 1,800 gal/hr.
Question 6: When two objects are connected by a hydraulic system, the pressure applied to one is transmitted equally to the other. This principle is known as:
- Bernoulli's principle
- Pascal's law (Correct answer)
- Boyle's law
- Archimedes' principle
Correct answer: Pascal's law
Pascal's law states that pressure applied to a confined fluid is transmitted undiminished in all directions.
Question 7: A plant operating manual states that feed water temperature must remain between 180°F and 220°F. If the reading is 195°F, what action is required?
- Increase heat immediately
- Decrease heat immediately
- No action; temperature is within spec (Correct answer)
- Shut down the feed water pump
Correct answer: No action; temperature is within spec
195°F falls between the specified minimum of 180°F and maximum of 220°F, so no corrective action is needed.
Plant Operator Selection System Test POSS 4
A boiler produces 15,000 lbs of steam per hour.
If efficiency drops by 10%, how many lbs of steam per hour will it produce?