HCD.6:5.1 - Pump Explanation and a Pressure Change

The stipulated demonstration begins with a pump delivering 100 m³/h at 400 kPa and 20 kW. After a controller change, measured flow remains 100 m³/h and power becomes 22.4 kW, while comparable pressure data are absent. The worked explanation calculates the 12% rise in energy per volume and keeps resistance, regulation efficiency, and measurement error as rivals.

The task supplies the domain comparison: at the same flow and previous efficiency, increased pressure requires greater power; reduced regulation efficiency can also increase electrical demand. A pressure value near 448 kPa would support increased resistance under those conditions, while a value near 400 kPa would direct attention toward regulation efficiency. Neither value establishes a unique cause by itself.

The controller log and four specialist-hours are available. The supplied complete measurement contributions cost one hour for independent power, one and a half for flow, and one and a half for pressure; they include safe preparation, measurement and result return. A day-long shutdown is outside the allowed arrangement. The learner has ninety minutes to justify the observations and next decision, including explanation and comparison. For the selected pressure branch, changing the receiving engineer’s next diagnostic question warrants the remaining specialist contribution and the learner’s effort, including displaced work. Selection does not supply a pressure result.

The first attempt receives independent measurements of 22.3 kW and 99.5 m³/h, with uncertainties of 0.2 kW and 1 m³/h respectively. Ask the person to compare like quantities and use both uncertainty bounds. Even the lowest new ratio, 22.1/100.5, exceeds the stipulated baseline 20/100; this weakens the measurement-error explanation under the supplied conditions. After the power and flow contributions, one and a half specialist-hours remain for pressure. The learner can select that observation and explain how its possible values change the resistance/efficiency comparison while keeping the cause unresolved.

The target action is conditional explanation and a present response suited to the available basis, not arithmetic alone. In a later variant without a worthwhile obtainable observation, the learner can finish the qualified explanation with its live rivals and return that account while leaving a resistance-specific remedy unselected. A unique cause remains unproved. A renamed machine with the same numbers would add no useful variation; neither does a generic request to collect more data.