Level Measurement in Process Industry

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Questions and Answers

What is the formula to calculate the height of a liquid using hydrostatic pressure?

H = P + SG

H = P - SG

H = P * SG

H = P/SG (correct)

How does temperature affect the density of a substance?

Fixed mass occupies a larger volume, decreasing density. (correct)

Temperature has no effect on volume.

Density remains unchanged with temperature.

Higher temperatures generally increase density.

What characteristic of gauge glasses contributes to their accuracy?

They serve as a window into the process. (correct)

They operate under high pressure conditions.

They are built with fragile components.

They are designed to be cumbersome.

What is the primary function of a differential pressure (D/P) cell?

To measure total pressure and head pressure combined. Signup and view all the answers

Which type of gauge combines safety features for high-pressure service?

Flat glass level gauges Signup and view all the answers

What principle do displacer transmitters primarily rely on for operation?

Archimedes' Principle of buoyancy Signup and view all the answers

Which level measuring method allows for measurement without direct contact with the fluid?

Ultrasonic devices Signup and view all the answers

In terms of level measurement, what does 'ullage' refer to?

Measurement from the surface of a liquid to the top of the tank Signup and view all the answers

What type of level measurement system is regulated by the Nuclear Regulatory Commission?

Nuclear devices Signup and view all the answers

What does the hydrostatic head pressure of 36 inches of water translate to?

36 in w.c. Signup and view all the answers

What measurement describes the distance from the zero reference point to the surface of a liquid?

Innage Signup and view all the answers

Which type of level measurement monitors the entire range from empty to full?

Continuous level measurement Signup and view all the answers

What term refers to the measurement from the surface of a product to the top of a vessel?

Ullage Signup and view all the answers

Which of the following best describes ' datum' in level measurement?

The zero reference point for level measurement Signup and view all the answers

Which property is used in indirect level measurement to infer the level?

Weight Signup and view all the answers

What is the common boundary between two immiscible liquids called?

Interface level Signup and view all the answers

How is head pressure calculated?

P = (1 in w.c.) * (h) * (SG) Signup and view all the answers

What does percent level measurement indicate when it reads 50 percent?

The tank is half full Signup and view all the answers

What is the primary purpose of point level measurement?

To establish high and low level alarms Signup and view all the answers

Which term refers to the curved upper surface of a liquid column?

Meniscus Signup and view all the answers

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.