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PROCESS SAFETY > CHAPTER 4 - SOURCE MODEL > Flashcards

CHAPTER 4 - SOURCE MODEL Flashcards

1
Q

These are selected to describe how materials are discharged from the process

A

Source Models

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2
Q

This pertains when the material is ejected from holes and cracks in tanks and
pipes, leaks in flanges, valves and pumps, and severed or ruptured pipes.

A

Limited aperture release

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2
Q

It is subsequently used to describe how the material is transported downwind and dispersed to some concentration levels.

A

Dispersion Models

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3
Q

This model converts the incident-specific results into effects on people, such as injury or death, and structures.

A

Effects Models

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4
Q

This pertains to large holes developed in the process unit, releasing a substantial
amount of material in a short time.

A

Wide aperture release

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5
Q

This is designed to prevent the overpressuring of tanks and process vessels.

A

Relief Systems

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5
Q

What will happen if the liquid is stored under pressure above its atmospheric
boiling point and the leak is below the liquid level?

A

It will result in a stream of liquid flashing partially into vapor

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6
Q

What will happen if the leak is located in the vapor space above the liquid inside a
tank?

A

It will result in either a vapor stream or a two-phase stream composed of
vapor and liquid, depending on the physical properties of the material.

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7
Q

This force between the moving liquid and the wall of the leak converts some of
the kinetic energy of the liquid into thermal energy, resulting in a reduced
velocity.

A

Frictional Forces

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8
Q

This is the complicated function of Reynolds number of the fluid escaping
through the leak and the diameter of the hole.

A

Discharge Coefficient

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9
Q

Frictional forces between a liquid and the wall of a pipe convert kinetic energy
into

A

Thermal Energy

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10
Q

What is the driving force for the movement of a liquid in the pipe?

A

The pressure difference across the pipe

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11
Q

A type of flow that is characterized by smooth, layered fluid movement is known
as

A

Laminar Flow

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12
Q

The Reynolds number is a dimensionless quantity used to predict the onset of
turbulence. A low Reynolds number indicates:

A

Laminar Flow

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13
Q

Which of the following factors contributes to turbulence in fluid flow?

A

High Reynolds Number

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14
Q

In a pipe system, what happens to the pressure as the pipe diameter decreases?

A

Decreases

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15
Q

What is the primary function of a valve in a piping system?

A

Control fluid flow

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16
Q

A Function of the Reynolds number and the roughness of the pipe ε.

A

Fanning friction factor

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16
Q

A method that defines the excess head loss in terms of two constants (reynolds
number and pipe internal diameter)

A

2-K Method

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16
Q

It is the maximum downstream pressure resulting in maximum flow through a
hole or pipe.

A

Choked pressure

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16
Q

This is characterized by releasing the gas through a small crack with large
frictional losses.

A

Throttling

16
Q

Which of the following statements is valid for downstream pressures less than
𝑃choked ?

A

The velocity of the fluid at the throat of the leak is the velocity of sound at the
prevailing conditions.

16
Q

For sharp-edged orifices with a Reynolds number greater than 30,000 and not choked,
what is the constant discharge coefficient?

A

0.61

17
Q

For choked flows, the discharge coefficient __________ as the downstream pressure
decreases.

A

Increases

18
Q

1.

For this type of discharge, most of the pressure energy is converted into kinetic energy,
source models require only the diameter of the leak

A

Free Expansion

19
Q

In the context of modeling vapor flow through pipes, which of the following best
describes adiabatic flow?

A

Rapid vapor flows through insulated pipes without heat exchange with
surroundings.

20
Q

The phenomenon where a liquid rapidly evaporates due to a leak in a pressurized
container, causing some of the liquid to turn into vapor explosively, is known as?

A

Flashing

21
Q

The type of vapor flow that occurs through an insulated pipe with no heat exchange is
called?

A

Adiabatic Flow

22
Q

What happens to the temperature of a superheated liquid during flashing?

A

It decreases to the new boiling point as vaporization occurs.

23
Q

Why are numerical models required for real vapor flow through pipes?

A

Because no generalized accurately capture the intermediate behavior

24
Q

For flashing liquids composed of multiple miscible substances, the flash calculation
becomes more complex because?

A

The more volatile components flash preferentially.

25
Q

In isothermal flow of gas in a pipe with friction, the gas velocity is assumed to be?

A

Below sonic velocity

26
Q

Which of the following must be considered when a flashing liquid escapes through pipes
or holes?

A

Two-phase flow conditions.

27
Q

What provides the driving force for gas transport in the isothermal flow through the
pipe?

A

Pressure gradient across the pipe

28
Q

Who identified that the expansion factor reaches a maximum 𝑌g in both adiabatic and
isothermal gas flow scenarios?

A

Keith and Crowl

29
Q

In isothermal flow conditions, the temperature of the gas is?

A

Constant across the entire pipe length

30
Q

In the adiabatic choked flow of gas through a pipe, the maximum velocity is typically
reached at?

A

The end of the pipe

31
Q

What is a distinguishing feature of the adiabatic flow case compared to the isothermal
case?

A

There is no heat exchange with the surroundings in adiabatic flow

32
Q

1.

At the end of the pipe in isothermal flow, the pressure is?

A

Equal to the pressure of the surroundings

33
Q

In the modeling of vapor flow through pipes, which two special cases are primarily
considered?

A

Adiabatic and isothermal flow behavior

34
Q

The initial stage of boiling is usually controlled by the heat transfer from _____?

A

Ground

35
Q

The realistic releases represent the incident outcomes with a low probability of
occurring. Worst-case releases are those that assume almost catastrophic failure of the
process.

A

The first statement is true

36
Q

All the models, including consequence models, have uncertainties. These uncertainties
arise because of

A

An incomplete understanding of the geometry of the release, unknown or poorly
characterized physical properties, a poor understanding of the chemical or
release process, and unknown or poorly understood mixture behavior.

37
Q

How is heat transferred to a liquid boiling from a pool?

A

From the ground by conduction and convection, and by radiation from the sun or
other sources

38
Q

1.

Realistic release incident for process pipes smaller than 2 inches.

A

Assume a full bore rupture

39
Q

How are uncertainties treated in consequence modeling?

A

By dispersion modeling to obtain conservative estimates

40
Q

If an internal company study is being completed to determine the actual consequences of
plant releases, then the realistic cases would be selected. However, if a study is being
completed to meet the requirements of the EPA Risk Management Plan, then the worst
case releases must be used.

A

Both statements are true

41
Q

The method for liquid pool evaporation or boiling works adequately for,

A

Liquefied natural gas (LNG) and perhaps for ethane and ethylene

42
Q

For any particular modeling study several receptors might be present that require the
same decisions for conservative design. For example, dispersion modeling based on a
ground-level release will minimize the consequence for the surrounding community but
will not minimize the consequence for plant workers at the top of a process structure.

A

Both statements are false

43
Q

Guidelines for selection process for worst-case incidents, except one;

A

Use calculated total release rate at set pressure; assume all material released is
airborne.

PROCESS SAFETY (13 decks)

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