CHAPTER 7 - CONCEPTS TO PREVENT FIRES AND EXPLOSIONS Flashcards
Capacitance is defined as
The ability to store electrical charge
What is the recommended residence time in an enlarged section of pipe to reduce charge buildup during liquid transfer?
Half the relaxation time.
To reduce charge buildup during the transfer of a liquid into a vessel, it is recommended to
Install a dip pipe
The primary purpose of bonding and grounding in electrostatic hazard prevention is to
Reduce the potential difference between objects
When handling flammable powders, what is the most effective way to prevent electrostatic ignitions?
Inerting the atmosphere.
To prevent lightning-like discharges in a vessel, it is recommended to
Reduce the vessel volume
An effective way to increase the conductivity of a nonconducting organic liquid is to
Introduce a polar solvent
The “twice the relaxation time” rule provides a safety factor of
Four
What is the purpose of a dip pipe in a liquid transfer system?
To prevent siphoning
Which of the following is NOT a special design feature to prevent electrostatic ignitions?
D. Relaxation
What is the primary purpose of an inert atmosphere when handling solids with flammable vapors?
To prevent the ignition of flammable vapors
Which type of containers are recommended for solids containing flammable solvents?
Conductive and grounded containers
What is the primary function of explosion-proof housings for electrical equipment in XP areas?
To withstand an internal explosion and prevent the spread of combustion
Which of the following is not a class designation for flammable materials in the National Electrical Code (NEC)?
Class IV
What is the purpose of ventilation in preventing fires and explosions in chemical plants?
To dilute explosive vapors with air to prevent ignition
Which type of ventilation system is recommended for open-air plants?
Natural ventilation
What is the primary function of sprinkler systems in fire prevention?
To suppress fires by applying water
What is the primary purpose of deluge systems in vessel protection?
To keep the vessel walls cool and prevent metal failure
What is the main purpose of monitors in chemical plants?
To provide a water source for firefighting
Which of the following is not a design technique for preventing fires and explosions in chemical plants?
Increase in process temperature
In Spark Discharge, the electrons migrate to leave the charged object at a single point and enter the second object at a single point because both are
Conductive
What charge is created when electrons flow over a material interface
Positive or Negative
The number of charge accumulation processes exist in a chemical facility that are relevant to hazardous electrostatic discharges?
Four
The maximum charge density that the surface can reach is
2.7 × 10^(-5) C/m^2
What is formed between two conductors when their distance is small compared to their diameter and the electric field intensity is around 3 MV/m.
Spark
The most elusive of ignition sources.
Static Electricity
A discharge that does not occur in vessels with capacity less than 60 m^3 or silos with diameters less than 3 m.
Lightning-like discharge
What quantity of fines are necessary for coarse particles to create an explosive atmosphere in conical pile discharge so that the dust can ignite?
Small
The flow of electricity produced by transmitting electrons from one surface to another through a flowing fluid or solid
Streaming Current
What occurs when the distance between two conductors exceeds their radius of curvature
Brush Discharge
What is the primary purpose of inerting a vessel?
To reduce the concentration of oxygen in the vessel.
Which purging method is most suitable for large storage tanks?
Sweep-through purging
During vacuum purging, what remains constant throughout the process?
The initial oxidant concentration within the vessel.
What is the primary advantage of pressure purging over vacuum purging?
Shorter cycle times
What is the primary disadvantage of sweep-through purging?
High consumption of inert gas.
What is the role of the flammability diagram in inerting processes?
To identify potential flammable mixtures.
Which of the following is NOT a common inert gas used in inerting processes?
Oxygen
What is the typical limiting oxygen concentration (LOC) for gases?
10%
During pressure purging, what happens to the number of moles of oxygen as the vessel is pressurized?
It remains constant.
What is the primary goal of siphon purging?
To reduce the consumption of inert gas.
