Plant Operator Selection System Test Plant Operator Selection System Tables and Graphs Interpretation 5 — Questions and Answers
Question 1: A table shows safety incident rates per 100 employees over four quarters: Q1=3.2, Q2=2.8, Q3=3.0, Q4=2.4. What is the average quarterly incident rate?
- 2.85 (Correct answer)
- 2.80
- 3.00
- 2.70
Correct answer: 2.85
Average = (3.2 + 2.8 + 3.0 + 2.4) / 4 = 11.4 / 4 = 2.85 incidents per 100 employees.
Question 2: A calibration table for a level transmitter shows: 4 mA = 0% level, 12 mA = 50% level, 20 mA = 100% level. If the transmitter reads 16 mA, what is the tank level?
- 75% (Correct answer)
- 80%
- 70%
- 60%
Correct answer: 75%
16 mA is 12 mA above the 4 mA baseline; 12/16 × 100 = 75% of the full 16 mA span.
Question 3: A comparison table shows cooling tower performance at different ambient temperatures. At 90°F ambient, the cooling capacity drops by 15% versus the rated capacity of 800 tons. What is the derated capacity?
- 680 tons (Correct answer)
- 700 tons
- 720 tons
- 660 tons
Correct answer: 680 tons
15% of 800 = 120 tons; derated capacity = 800 − 120 = 680 tons.
Question 4: A graph shows two process variables over time. Variable X reaches its peak 30 minutes before Variable Y reaches its peak. This time offset is called:
- Lag (Correct answer)
- Feedback
- Dead band
- Offset
Correct answer: Lag
A time delay between cause and effect in process variables is known as lag (or process lag).
Question 5: A production yield table shows: Batch 1=94.2%, Batch 2=91.8%, Batch 3=95.5%, Batch 4=93.1%, Batch 5=90.4%. The plant target is 93%. How many batches met or exceeded the target?
- 3 (Correct answer)
- 2
- 4
- 1
Correct answer: 3
Batches 1 (94.2%), 3 (95.5%), and 4 (93.1%) all meet or exceed the 93% target — that is 3 batches.
Question 6: A graph plots pump efficiency (%) vs. flow rate (gpm). Efficiency peaks at 350 gpm and declines on either side. Operating a pump significantly below this peak flow is called operating in the:
- Left of best efficiency point (Correct answer)
- Cavitation zone
- Runout region
- Shutoff zone
Correct answer: Left of best efficiency point
Operating at flows below the Best Efficiency Point (BEP) on the pump curve is referred to as operating to the left of the BEP.
Question 7: A table shows pipe friction loss (ft per 100 ft of pipe) at different flow velocities: 2 fps=0.5 ft, 4 fps=1.8 ft, 6 fps=3.9 ft, 8 fps=6.8 ft. As velocity doubles from 2 to 4 fps, friction loss increases by approximately what factor?
- 3.6× (Correct answer)
- 2×
- 4×
- 1.5×
Correct answer: 3.6×
Friction loss goes from 0.5 to 1.8 ft when velocity doubles; 1.8 / 0.5 = 3.6, consistent with the square-law relationship.
Plant Operator Selection System Test Plant Operator Selection System Tables and Graphs Interpretation 5
A table shows safety incident rates per 100 employees over four quarters: Q1=3.2, Q2=2.8, Q3=3.0, Q4=2.4.
What is the average quarterly incident rate?