POSS Flashcards

A pump moves 240 gallons of water in 8 minutes. How many gallons does it move in 15 minutes at the same rate?

Answer: 450 gallons

The rate is 240 ÷ 8 = 30 gallons per minute; 30 × 15 = 450 gallons.

Which type of valve is best suited for completely stopping or fully allowing flow, but NOT for throttling?

Answer: Gate valve

Gate valves are designed for fully open or fully closed positions and can be damaged by throttling.

A gauge reads 35 psi. If 1 psi equals 2.31 feet of water head, what is the equivalent water head in feet?

Answer: 80.85 ft

35 psi × 2.31 ft/psi = 80.85 feet of water head.

A reading passage states that a plant must test cooling water pH every four hours. If a shift is 12 hours long, how many tests must be performed per shift?

Answer: 3

12 hours ÷ 4 hours per test = 3 tests per shift.

On a bar graph showing monthly fuel oil consumption, January shows 8,200 barrels and June shows 3,700 barrels. What is the difference?

Answer: 4,500 barrels

8,200 − 3,700 = 4,500 barrels difference between January and June.

Two gears mesh together. Gear A has 20 teeth and rotates at 300 RPM. Gear B has 60 teeth. At what speed does Gear B rotate?

Answer: 100 RPM

Speed ratio is inverse to tooth ratio: 300 × (20/60) = 100 RPM for Gear B.

A safety data sheet (SDS) lists a chemical's flash point as 100°F. What does this mean for plant handling?

Answer: The chemical can ignite from a spark at 100°F

Flash point is the lowest temperature at which a substance can produce ignitable vapors when exposed to an ignition source.

A log table shows turbine vibration readings for Monday through Friday: 2.1, 2.4, 2.0, 2.8, 3.1 mils. What is the average vibration for the week?

Answer: 2.48 mils

(2.1 + 2.4 + 2.0 + 2.8 + 3.1) ÷ 5 = 12.4 ÷ 5 = 2.48 mils.

Which mechanical principle explains why a longer wrench handle makes it easier to loosen a bolt?

Answer: Mechanical advantage through leverage

A longer handle increases the moment arm, providing greater torque (leverage) with the same applied force.

A plant procedure states: 'Isolate the equipment, verify zero energy state, then apply lockout/tagout.' Which step comes second?

Answer: Verify zero energy state

The passage specifies the order: isolate first, verify zero energy second, then apply lockout/tagout.

A pipe carries steam at 150 psi. The pipe diameter is reduced by half. What happens to the steam velocity?

Answer: It quadruples

Halving the diameter reduces cross-sectional area by 75% (area ∝ r²), so velocity increases 4× to maintain flow continuity.

A chart shows that Motor 3 consumes 18 kW at full load and 6 kW at no load. What percentage of full-load power is the no-load consumption?

Answer: 33%

6 kW ÷ 18 kW = 0.333 = 33.3%, so no-load is approximately 33% of full-load power.

If a belt connecting two pulleys is too loose, what is the most likely result?

Answer: Slippage and loss of power transfer

A loose belt slips on the pulley face, causing inefficient power transfer, heat, and premature belt wear.

A temperature conversion table shows 0°C = 32°F and 100°C = 212°F. What is 25°C in Fahrenheit?

Answer: 77°F

Using F = (C × 9/5) + 32: (25 × 1.8) + 32 = 45 + 32 = 77°F.

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?

Answer: 13,500 lbs/hr

15,000 × (1 − 0.10) = 15,000 × 0.90 = 13,500 lbs of steam per hour.

Which instrument would a plant operator use to measure electrical current in a circuit without interrupting it?

Answer: Clamp-on ammeter

A clamp-on ammeter measures current magnetically around a conductor without breaking the circuit.

A passage describes a water treatment process: coagulation occurs first, then sedimentation, then filtration, then disinfection. What is the third step?

Answer: Filtration

The passage lists four steps in order; filtration is explicitly the third step after sedimentation.

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?

Answer: 270 MW

Range = maximum − minimum = 480 − 210 = 270 MW.

A reciprocating pump completes 60 strokes per minute. Each stroke displaces 0.5 gallons. What is the flow rate in gallons per hour?

Answer: 3,000 gal/hr

60 strokes/min × 0.5 gal/stroke = 30 gal/min; 30 × 60 min = 1,800 gal/hr.

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:

Answer: Pascal's law

Pascal's law states that pressure applied to a confined fluid is transmitted undiminished in all directions.