SAChE Explosion Hazards

For most flammable gases, an MIE of___ is commonly used.

0.25 MJ

How is Pmax established fro a vessel?

20 liter sphere test for the chemical to be used in the vessel

An explosion always consists of what components?

A blast wave & an energy release

In a physical explosion, when a vessel under pressure bursts, the sudden expansion of a compressed gas generates a __ that propagates outward from the source.

Blast wave

Which European standard focuses on dust explosion venting protective systems?

CEN EN 14491

In addition to techniques prescribed by NFPA, design of deflagration vents can be done using:

Computational Fluid Dynamics (CFD) or Testing of vents in service

VCEs usually occur due to the loss of:

Containment

What was the flammable material used in the process at Flixborough?

Cyclohexane

The center for chemical process safety (CCPS) defines ___ as "construction of equipment (or a building) with weak sections to limit the damage to the equipment (building)"

Damage-limiting construction

The combustion of dust in air is most commonly a ___.

Deflagration

What is the term used to describe a combustion or decomposition reaction that propagates by heat and mass transfer through the unreacted medium at a velocity less than the speed of sound?

Deflagration

Which of the following is a commonly used combustible liquid that is used as an aerosol to produce explosions inside equipment?

Diesel

Byproducts of a fire at a process facility can present a toxic hazard to :

Emergency responders, community members, employees, site visitors, contractors

True or false: Flammability limits (LFL & UFL) are always defined with respect to fuel mixtured with air, not other oxidant.

FALSE

True or false: Spring actuated relief valves are well-suited for deflagration venting bc they respond quickly enough to effectively relieve the pressure from a deflagration.

FALSE

True or false: The TNT equivalency method has been historically used for VCE blast modeling bc of its accuracy estimating blast energy for these types of explosions.

FALSE

True or false: burning velocity decreased as turbulence increases.

FALSE

True or false: test data suggests that only aerosols in a confined cloud have the potential to explode.

FALSE

True or False: Failure of Pressure relief devices was the major cause of the incident at the BP Texas city Refinery.

False

True or False: Toxic releases due to an explosion are almost always consumed by fire & therefor communities surrounding process facilities are not considered to be at risk of exposures to tocivs If the toxics were released as a result of an explosion.

False

True or false: The 6 spherical storage tanks and 48 smaller horizontal cylindrical tanks exploded instantaneously at Mexico City LPG terminal.

False

True or false: The hazard zone for fires is typically defined as the region occupied by the fire itself.

False

Which incident discussed was a cornerstone event that prompted the need to address process safety around the world?

Flixborough

Of the hydrocarbons, which would you expect to have the lowest AIT?

Hydrogen

Facilities are much more aware of dust explosion hazards as a result of which case discussed in this unit?

Imperial Sugar company

Burning velocity ___ with turbulence.

Increases

The AIT of a mixture generally ___ as mixtures become either rich or lean.

Increases

The ignition of a flammable material may result in which type(s) of fire?

Jet fire, pool fire, flash fire, fireball

What is belived to be the cause of the disaster that occurred at the Mexico City LPG terminal?

Leak caused flammable vapor cloud to form & ignite

A dust explosion requires a suspended cloud of combustible particles at a concentration above the ___.

MEC

Failure in which 2 risk based process safety (RBPS) elements contributed to the Flixborough incident?

MOC & Hazard Identification and Risk Assessment

The expansion of gas that occurs during an explosion takes place in___.

Microseconds

Which of the following resources is best for understanding explosion vent sizing and design criteria?

NEPA 68

Among other sources, the source of energy for a pressure vessel burst resulting in a physical explosion can be:

Overfilling Phase change Combustion Chemical reaction

In a shock wave, the max pressure over ambient conditions ins called the:

Peak overpressure

Combustible dusts, mists and aerosols, VCEs, and condensed phase explosions are examples of___.

Propagating reactions

True or false: It is generally considered impractical to eliminate all possible ignition sources in a process facility.

TRUE

True or false: a cold fuel released and mized with hot air or contracting a hot surface can autoignite.

TRUE

True or false: spark discharges between 2 objects, such as a fixed vessel and a portable tank, can be prevented by eliminating the air gap between them through bonding.

TRUE

True or false: the 20 liter sphere test can be conducted with dust mixtures

TRUE

True or false: the fudamental burning velocity is the highest achievable value that is obtained in a quiescent environment.

TRUE

True or false: the minimum ignition energy of a material is difficult to characterize and is highly dependent on the experimental configuration.

TRUE

In the Flixborough case, what accounted for a majority of the fatalities?

The collapse of the control room roof as a result of the VCE

A boiling liquid expanding vapor explosion (BLEVE) has the potential for projecting missiles great distances because of:

The large amount of energy released during these incidents fa

Flux multiplied by exposure time is know as:

Thermal dose

True or False: The initial change in the gas density, pressure and velocity of air that occurs with a blast can be either discontinuous or gradual.

True

True or false: Byproducts of a fire can be toxic

True

True or false: Combustible liquid aerosols can lead to deflagrations.

True

True or false: The higher the impulse associated with the blast wave, the greater potential for damage.

True

True or false: When flammable vapor is confined within a vessel and that vapor is ignited, the resulting deflagration could cause a pressure vessel burst.

True

Scaling curves have been developed for:

VCEs, Condesned phase explosives, pressure vessel bursts (PVBs)

In the West TX Fertilizer company case, the majority of the fatalities were___.

Volunteer firefighters

Which case discussed involved improper storage of a large quantity of explosible material near combustible material?

West Tx Fertilizer Company

How can toxic materials in a process subjected to an explosion be released?

When debris from an explosion penetrates a vessel, pipe or other process equipment

Elbows, bens & internal obstacles may increase turbulence ___ run-up distance.

and reduce

As the temp increases, the min ignition energy:

decreases

The AIT of a mixture generally ___ as the test volume increases.

decreases

Thermal oxidixers & boilers generally present which type of ignition sources?

open flame

In which ways can ignition be achieved in the 20 liter sphere test?

spark, chemical igniter, exploding fuse wire, hot wire