Week 2+4 Flashcards
What are the PID limitations?
Doesn’t show how straight the process lines are.
The proximity of items isn’t clear.
The actual size of equipment.
What is the function of steam trap?
separates condensate from steam.
What are the abreviations for:
Valves / Relief Valve / Bursting disc / Control valve / Sample point
V / RV / BD / CV / SP
What are the two main types of control loops?
Feedback - control system measures changes in a process output and then adjusts variable to return output at desired setpoint.
Feed Forward - Control system measures disturbance and adjusts variable to compensate for it so that controlles output is not affected.
Describe what ratio control and cascade control are.
Ratio - One stream is controlled in ratio to another control stream.
Cascade control - Primary controller is used to adjust the set point of a second controller.
what is the function of a HAZID
Identifies hazards / Finds interactions between parts of the plants and surroundings which could cause a major accident.
What is the function of a HAZOP
Identifies hazards and operability problems.
Provides action and solutions to deal with them.
what is the function of a HAZAN?
Calculates how likely a hazard is of occuring.
Quantifies with probability.
What is the function of LOPA.
Defence systems against the disasters (checks the alarms/trips and whether they are sufficient enough).
What is the difference between upper flammability and lower flammability?
Upper - the concentration in air above which a flame cannot exist.
Lower - the concentration in air below which a flame cannot exist.
What are the following points in terms of flammability:
Flash point
Autoignition temperature
Minimum oxygen concentration
Flash point - Liquid temperature above which vapour produces ignitable mixture in air.
Augnition temperature - enviromnent temperature above which energy from enviromnent provides ignition.
MOC - Oxygen concentration below which combustion is not possible.
What information is required to plot the flammability diagram.
Lower flammability limit
Upper flammability limit
Stoichiometric composition
Minimum oxidant for combustion
what is the difference between a flashfire and a poolfire?
Flashfire: Occurs when a vapour cloud burns.
Main hazard is contact with flame.
Pool fire: Starts with the release of flammable material.
what are some fire responses?
have multiple layers of protection.
Management of source ignition.
Response plan.
what is a BLEVE?
Boiling liquid expanding vapour explosion.
Short duration.
what are factors which affect dust cloud explosions?
Vessel volume
Degree of turbulence
Dust concentration
Particle size
Composition of sample.
In terms of electrostatics what different atmospheres are there?
Very sensitive atmospheres : MIE < 0.02MJ
Sensitive atmospheres: MIE < 1 MJ
What is the purpose of process control?
Stable process operation
Keeping plant under safe operating conditions
MInimizing damage to the equipment
Ensure operating meets specification
Minmize impact of external disturbance
What are valve failure positions?
Valve fails to open
Valve fails to close
Valve is locked in current position
Failure mode is indertminate
How does an increase in pressure affect UFL, LFL, AIT.
Raises UFL
Reduces LFL (negligible)
Reduces AIT
What does AIT depend on?
Vapour concentration
Shape and size of vessel
Catalytic material
Pressure
Oxygen content
Ignition delay
Describe a jet fire
Running liquid fire from a contained/stored liquid.
What are passive protection systems for a fire.
Spacing and layout
Fireproofing
Containment and drainage
Fire walls
Electrical classification
Why are dust explosions dangerous?
They have a high surface area thus could cause a flash fire. If they occur in confined spaces they cn damage both euipments and buildings.
What are the factors which affect dust cloud flammability?
particle size
Moisture content
Concentration of particles
Solvent content
Temperature and contaminants
What methods are put in place to avoid dust explosions?
Ventilation.
Moisturize the content.
Hazard area analysis to know where explosions zones are more prone of occuring.
