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Questions and Answers
What is the formula to calculate the height of a liquid using hydrostatic pressure?
How does temperature affect the density of a substance?
What characteristic of gauge glasses contributes to their accuracy?
What is the primary function of a differential pressure (D/P) cell?
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Which type of gauge combines safety features for high-pressure service?
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What principle do displacer transmitters primarily rely on for operation?
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Which level measuring method allows for measurement without direct contact with the fluid?
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In terms of level measurement, what does 'ullage' refer to?
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What type of level measurement system is regulated by the Nuclear Regulatory Commission?
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What does the hydrostatic head pressure of 36 inches of water translate to?
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What measurement describes the distance from the zero reference point to the surface of a liquid?
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Which type of level measurement monitors the entire range from empty to full?
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What term refers to the measurement from the surface of a product to the top of a vessel?
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Which of the following best describes ' datum' in level measurement?
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Which property is used in indirect level measurement to infer the level?
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What is the common boundary between two immiscible liquids called?
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How is head pressure calculated?
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What does percent level measurement indicate when it reads 50 percent?
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What is the primary purpose of point level measurement?
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Which term refers to the curved upper surface of a liquid column?
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Study Notes
Level Measurement in Process Industry
- Level is the height or depth of a process material within a piece of process equipment.
- Innage is the measurement from the bottom of the tank to the surface of the product.
- Ullage is the measurement from the surface of the product to the top of the vessel.
- Point level measurement determines high and low level alarm points.
- Continuous level measurement monitors and controls all level points in the tank.
- Direct level measurement determines the process variable directly.
- Indirect level measurement infers the level by measuring another property of the material, e.g., head pressure or weight.
- Datum line is the zero reference point for level measurement.
- Interface level is the boundary between two immiscible liquids.
Temperature and Density
- Temperature influences the density of all matter.
- Increased temperature causes a fixed amount of mass to occupy a larger volume, decreasing density.
- Density is mass per unit of volume.
- Level instruments assume that the characteristics of the process remain constant.
Hydrostatic Head Pressure
- Hydrostatic head pressure is a common indirect level measurement method.
- Head pressure is calculated using the formula: P= ((1 in w.c.) (h) (SG))/ in, where P is the head pressure, h is the level, and SG is the specific gravity.
- Head pressure is commonly expressed in inches of water column (in w.c.) or pounds per square inch (PSI).
Level Sensing Instruments
- Gauge glasses provide a visual indication of the level.
- Tubular sight glasses resemble a U-tube manometer.
- Flat glass level gauges offer variations including reflex, transparent, and welded pad gauges.
- Floats and float gauges use floats to indicate, measure, or track level.
- Tapes and tape gauges consist of a calibrated tape attached to a float, measuring both liquids and solids.
- Differential pressure (D/P) cells connect to the bottom and top of the tank to measure the head pressure.
- Bubblers are used for nonflammable processes to measure head pressure without direct contact with the fluid.
- Displacer and Transmitter utilize buoyancy to measure level changes.
- Distance measuring devices like ultrasonic and radar use electromagnetic waves to measure level.
- Nuclear devices employ gamma radiation sources and detectors to infer level.
- Load cells are indirect level measuring devices that measure the deformation of the tank's support structure.
Check your Understanding
- Ullage is the measurement from the surface of material to the top of a tank.
- Innage is the measurement from the bottom of a tank to the surface of material.
- Indirect level measurement is the measurement of another property of a contained material to determine level.
- Direct level measurement is the measurement of the process variable.
- Interface level is the measurement of the point where two immiscible materials meet.
- The hydrostatic head pressure exerted by 36 in. of water is equal to 36 in w.c.
- If the mass remains constant and the density of a liquid in a tank decreases, the level of the liquid in the tank increases.
- When the volume of a liquid in a tank decreases, the level of the liquid in the tank decreases.
- The oldest type of gauge glass still in use today is the tubular type.
- A bubbler method is used to measure nonflammable processes.
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Description
This quiz explores key concepts related to level measurement in the process industry, including innage, ullage, and various measurement techniques. It covers both direct and indirect measurement methods, along with the importance of temperature and density in these processes.
