A thermal imaging camera is preferred to a spot thermometer when the question is
Answer: C
Scanning a switchboard or a furnace wall reveals the loose joint or the failed insulation without knowing in advance where to look, which is precisely what a spot instrument cannot do. Absolute accuracy is better from a calibrated contact probe.
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Three of the following are found with a thermal imager during an audit. The exception is
Answer: D
Correct answer: the power factor of a feeder
Power factor is an electrical relationship between voltage and current and produces no thermal signature at all; it is read with a power analyser. The other three are all classic thermal imaging finds - a hot joint, a cold or wet patch on lagging, and a trap running at line temperature on its downstream side because it is passing live steam.
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A flue gas analyser measures the oxygen in the flue chiefly in order to determine
Answer: A
Excess air carries heat up the stack for nothing, and the oxygen left over is the direct measure of how much is being admitted. Too little air is worse still, producing carbon monoxide and unburnt fuel, so the analyser reports both.
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Carbon monoxide in the flue gas indicates
Answer: B
Every molecule of carbon monoxide represents carbon that has released only part of its energy, and it is also a hazard. It appears when the air is insufficient or the mixing poor, which is the opposite fault to excess air.
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Stack temperature is measured alongside the flue gas composition because the loss depends on
Answer: C
The heat carried away is the mass of gas multiplied by its specific heat and by the rise above ambient, so both the quantity and the temperature enter. A high stack temperature with correct excess air points at fouled heat transfer surfaces instead.
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An ultrasonic flow meter is valuable in an audit because it
Answer: D
Cutting into a live process line to fit a meter is rarely permitted for an audit, and a clamp-on transducer gives a figure in minutes. It needs the wall thickness and material entered, a clean liquid and a full pipe, and is defeated by heavy scaling.
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A clamp-on ultrasonic flow meter gives an unreliable reading when the pipe is
Answer: A
The technique depends on sound crossing the liquid, and bubbles or a free surface scatter the beam so the transit times cannot be resolved. Insulation is simply removed at the measuring point, and steel is the commonest material it is used on.
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An orifice plate measures flow by
Answer: B
The differential pressure varies as the square of the flow, so the meter is read through a square root and its accuracy suffers at low flow. It is cheap and permanent and imposes a lasting pressure loss, which is itself an energy cost worth noting in an audit.
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A permanent orifice plate in a pipe represents an energy cost because it
Answer: C
The unrecovered pressure loss is pumping or fanning energy spent for measurement alone, and over a year on a large duct it is substantial. A venturi recovers much more of it, and an ultrasonic meter none at all, which is a point in its favour.
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A vane anemometer is used in an audit to measure
Answer: D
Correct answer: air velocity at a grille or duct
A vane anemometer reads the air speed directly from the rotation of its vanes, and multiplying by the free area gives the volume flow - which is what a fan or ventilation audit needs. Static pressure needs a manometer and a pitot tube, humidity a hygrometer, and temperature a thermometer.
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