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PROCESS SAFETY > Source Models > Flashcards

Source Models Flashcards

1
Q

Most incidents in chemical plants result in spills of?

A

Toxic, Flammable, and explosive materials

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2
Q

Typical incidents might include?

A
  1. Rupture or breakage of a pipeline
  2. A hole in a tank or pipe
  3. Runaway reaction
  4. Fire external to the vessel
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3
Q

Once the incident is known, _______ are selected to describe how the hazardous materials were discharged from the process

A

Source models

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4
Q

Is usually done as part of Quantitative Risk
Analysis (QRA) in the design phase to define the limits of the
design envelope and to ensure that the resulting engineering
design to mitigate or remove the hazard is overdesigned.

A

Source Modelling

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5
Q

Source Modelling is usually done as part of __ in the ____-

A

Quantitative Risk Analysis, Design phase

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6
Q

The resulting engineering design to mitigate or remove the hazard is _____

A

overdesigned

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7
Q

Describes the physical and chemical processes occurring during the release of a material

A

Hazardous material event model

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8
Q

A release could be?

A
  1. Outflow from a vessel
  2. evaporation from a liquid pool
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9
Q

Source models provide?

A

description of the rate of discharge,
total quantity discharged,
total time of discharge and
state of discharge

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10
Q

Characterized by the amount of material released

A

Strength of a source

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11
Q

What governs source strength?

A

Physical state of material
Containment pressure
Temperature

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12
Q

A release may be:

A

Continuous
Instantaneous

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13
Q

Source strength is total mass released (kg)

A

instantaneous

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14
Q

Source strength is rate of mass released (kg/s)

A

Continuous

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15
Q

Constructed from fundamental/empirical equation representing the physiochemical process occurring during release of materials

A

Source models

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16
Q

Only can be applied once the incident has been identified

A

Source models

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17
Q

Technical information needed:

A

Rate of discharge
total quantity discharged
State of discharge

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18
Q

Other Types of Hazardous Material Event Models

A
  1. Dispersion Model
  2. Fire & Explosion Model
  3. Effect Model
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19
Q

To describe how the material is transported downwind and dispersed to some concentration levels

A

Dispersion Model

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20
Q

To convert the source model information into energy hazard potentials

A

Fire & Explosion model

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21
Q

Example of Energy hazard potential

A

Thermal radiation
Explosion overpressure

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22
Q

Evaluate potential loss/damage on people, properties and environment

A

Effect model

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23
Q

Mode of Release (2)

A

Wide aperture release
Limited aperture release

24
Q

Releasing a substantial amount of material in a short time

A

Wide aperture release

25
Q

Large hole developing in process unit

A

Wide aperture Release

26
Q

Examples of WAR

A

Overpressure explosion, explosion of a storage tank

27
Q

Slow release of material that causing non-immediate effect to upstream

A

Limited Aperture Release

28
Q

Examples of LAR

A

Leaks in flanges, valves and pumps
Ruptured Pipes, cracks, relief systems

29
Q

Number of possible release points from a chemical vessel

A

Relief valve
Hole
Crack
Valve
Severed or Rupture Pipe
Pump Seal
Flange
Pipe Connection

30
Q

Types of Release

A

Gas/Vapor Leak
Vapor or Two-Phase Vapor/Liquid Leak
Liquid or Liquid Flashing into Vapor

31
Q

Influences type of release

A

Physical State of a material

32
Q

Source models describing a material release:

A
  1. Flow of Liquid through a hole
  2. Flow of liquid through a hole in a tank
  3. Flow of Liquid through Pipes
  4. Liquids Flashing
  5. Liquid pool evaporation or boiling
  6. Flow of gases/vapor through holes from vessels or pipes
33
Q

A tank that develops a hole. Pressure of the liquid contained in the tank is converted into kinetic energy as it drains from the hole.

A

Liquid flow through a hole (Ambient Conditions)

34
Q

Frictional forces of the liquid draining through the hole convert some of the kinetic energy to thermal energy

A

Liquid flow through a hole (Ambient Conditions)

35
Q

Uses mechanical energy balance for the flow of incompressible liquids through pipes (density is constant)

A

Flow of liquid through pipes

36
Q

Driving force for the movement of liquid across pipes

A

Pressure gradient

37
Q

Friction forces between he liquid and the wall of the pipe convert?

A

Kinetic energy into thermal energy

38
Q

Frictional forces results in a decrease in the liquid ______ and a decrease in the liquid ______

A

velocity and pressure

39
Q

Normally occurs when a liquid stored under pressure above their normal boiling point experiences sudden ambient environment causing the liquid to flash into vapor sometimes explosively

A

Flashing

40
Q

If the tank develops a leak, the liquid will?

A

Partially flash into vapor

41
Q

The process is rapid and is assumed to be adiabatic

A

Partial flashing

42
Q

Rate of evaporation from a pool depends on:

A
  1. liquid’s properties
  2. subsoil’s properties
43
Q

A key note is if liquid is released into a?

A

contained pool or not

44
Q

The pool height = volume spilled/cross sectional area of the containment structure

A

Contained pool

45
Q

Release is not contained then it is called?

A

Freely spreading pool

46
Q

US EPA Offsite Consequence Analysis Guide recommends a pool depth of ? for not contained pools

A

1 cm

47
Q

The vapor above the pool is blown away by prevailing winds as a result of vapor diffusion

A

Evaporation from a pool for Non-boiling liquids

48
Q

The amount of vapor removed through the process of evaporation from a pool (Non-boiling liquids) depends on:

A

Partial vapor pressure of the liquid
Prevailing wind velocity
area of the pool

49
Q

Energy contained within the gas or vapor as a result of its pressure is converted into kinetic energy as the gas escapes and expands through the hole

A

Flow of Vapor though Holes

50
Q

What do change as the gas or vapor exits through the leak?

A

Density, pressure and temperature

51
Q

Is modeled using two special cases

A

Vapor flow through pipes

52
Q

Vapor flow through pipes is modeled using two special cases:

A

Adiabatic and isothermal

53
Q

Corresponds to rapid vapor flow through an insulated pipe

A

adiabatic case

54
Q

Corresponds to flow through an uninsulated pipe maintained at a constant temperature

A

Isothermal case

55
Q

Example of isothermal case

A

Underwater pipeline

56
Q
A

PROCESS SAFETY (3 decks)

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