HSE Flashcards
Deadheading
Blockage on discharge side of the pump results in the flow reducing to zero and an increase in the discharge pressure.
Stages of Design
- Possible design
- Feasible design
- Probable design
- Best design
Cavitation
Occurs when the liquid in a pump turns to a vapor at low pressure.
Reverse flow
Manifest into the form of sporadic pipeline vibrations, media contamination or physical damage.
Pumps
Impart pressure and temperature to move fluids from one point to another
Runaway reactions
*Uncontrollable accelerating exothermic reactions
*Increased temperature and pressure
Lower flammability limit
Minimum concentration of fuel vapor in air in a pre-mixed flame that can sustain combustion
Upper flammability limit
Maximum concentration of fuel vapor in air in a pre-mixed flame that can sustain combustion
Importance of UFL and LFL
Flammable atmospheric between UFL and LFL
Stoichiometric ratio
Optimum theoretical mix of fuel and air to achieve complete combustion of that fuel
Explain Fire modeling
analytical process of estimating the behavior of a fire event in terms of the heat flux impinging material near the fire and behavior of those materials as a result of that.
Fire requires presence of:
Fuel
Oxygen
Heat
Visible (light-emitting) part of a fire.
Flame
Buoyant stream of heated air and combustion products rising above a fire
Fire plume
Breakdown of the molecules of a solid material from exposure to heat into gaseous molecules that may combust in the flame.
Pyrolysis
Slow combustion process without visible flames that occurs in a porous solid fuel
Smoldering
Meaning of IDLH
Immediately Detrimental to Life and Health
Meaning of LFL
Lower flammability limit
Barriers that hinder the operator’s hands or fingers from entering the point of action.
Machine Guarding
Safety feature triggered through the movement of either movable machine or perimeter
Interlocks
Flash point
Lowest temperature at which a liquid can gives off vapor to form an ignitable mixture in air near the surface of the liquid.
Boiling point
Temperature at which the pressure exerted by the surroundings upon a liquid is equaled by the pressure exerted by the vapor
Flammable vs Combustible
*Flammable - liquid ignites quickly
*Combustible - vapor ignites quickly
Refers to a material’s resistance to corrosion, rust or stains when it comes in contact with a chemical.
Material Compatibility
Explain BLEVE
Occurs when the pressurized liquid inside a vessel reaches temperatures higher than that liquid’s boiling point. If the vessel can no longer contain the pressure inside of the sealed tank due to the high temperatures, it will mechanically fail, causing the explosion.
Done by connecting two or more conductive objects are connected by means of a conductor so that they are at the same electrical potential.
Bonding
Grounding
Process of bonding one or more conductive objects to the earth so that they are all at zero electrical potential.
Meaning of LFL
Lower flammability limit
Auto-ignition temperature
Lowest temperature at which chemical spontaneously ignite at atmospheric pressure without external heat source
Wind rose
Map diagram that summarizes information about the wind at a particular location over a specified time period.
PIPE COLORS:
Red
Fire Quenching Fluids
PIPE COLORS:
Yellow
Flammable and Oxidizing
PIPE COLORS:
Orange
Toxic and Corrosive
PIPE COLORS:
Green
Water
PIPE COLORS:
Blue
Air
PIPE COLORS:
Brown
Combustible
Flow-Induced Vibrations
Vibrations due to high turbulence and flow velocities
Ways to Reduce Flow Induced Vibrations
*High flowrate
*Increase pipe schedule
*Use dampeners
Erosional Velocity
*v = C / sqrt(density)
*Velocity at which erosion starts in multiphase flow
NPSHa Equation
NPSHa = P,inlet - Vapor pressure
NPSHa Requirement?
*NPSHa > NPSHr + 3ft
*NPSHa > 1.5 * NPSHr
Flow-Induced Vibrations
Due to high flow velocities such as in a piping dead leg of a centrifugal compressor system.
What is in a Control Narrative?
Importance?
- Describes the control philosophy, process variables and control descriptions.
- Makes P&ID instrumentation easier to understand
Control Step-by-Step
- Sense - measure
- Compare - against setpoint
- Affect / Respond - the controlled variable
What is included in your Control Narrative?
*Step-by-step process
*Setpoints and Design Parameters
*Instruments and Codes
*Control Schematics
What is included in your HSE study?
*Simulated HAZOP Noding
*Material Compatibility
*Proper Clearances
*Bonding and Grounding
*Temperature Rating
*Wind Rose
*Emergency Exits
*Effluent Disposal
What NPFA standards did you use?
NPFA 1 - Fire Safety
NFPA 70 - Electrical Safety
NFPA 231 - General Storage Standards
Hazard and Operability Analysis
Structured and systematic technique for system examination and risk management.
Hazard Identification
Procedure used to uncover and identify hazards in the workplace.
Hazard
Any source of potential harm or damage to humans, to property, to the environment or a combination of these.
Risk
Risk = Hazard * Exposure
- Possibility of disaster happening if exposed to a hazard.
- Chance that the person will be harmed or injured, the environment will be affected or the property will be damaged if exposed to the hazard.
What are HAZOP Nodes?
*Way to break up sections where significant changes in the process takes place
*Nodes
*Section / Equipment
*High, Low, etc.
*Parameters (Pressure, Temperature, etc.)
*Cause and Effect
*Mitigation and Prevention
Safeguard
Safety device that either interrupt the chain of events or reduce the severity of a consequence.
MSDS
Material Safety Data Sheet
* Document that contains information on the potential hazards (health, fire, reactivity and environmental) and how to work safely with the chemical product.
Importance of P&ID
*Multidisciplinary document
*Allows generation of other documents, (including piping isometric drawings, the piping model, equipment and instrument lists, cause‐and‐effect diagrams, control philosophy, etc.)
Sparing Philosophy:
1. 1×100%
2. 2×100%
3. 4×33%
- 1×100%
1 Operating, 0 Spare - 2×100%
1 Operating, 1 Spare - 4×33%
3 Operating, 1 Spare
Process Guard Layers
- Basic Process Control System (BPCS)
- Alarm
*High and Low - Safety Instrumented System (SIS)
*High-high and Low-low - Relief
*High structural integrity level
Material Safety Data Sheet
Document that contains information on the potential hazards (health, fire, reactivity and environmental) and how to work safely with the chemical product.
What is a Split Range Control?
Used when a single controller is employed to control two final-control elements (two valves for example).
Cascade control
Consists of combining two feedback loops
Output of one controller (the primary controller) adjusting the set-point of a second controller (the secondary controller)
How to increase NPSHa?
- Raise suction vessel/ liquid level
- Lower fluid temperature (decrease vapor pressure)
- Pressurize suction vessel
- Reduce friction
*Increase suction diameter
*All valves should be open
*Add filter/strainer
Storage Tank Concepts
a. Shapes
*Dome Shaped - for high pressures
*Floating Roof - volatile liquids
Storage Tank Concepts
b. Manway vs Handhole
Manway - When shoulder width (2 ft) can fit in tank
Storage Tank Concepts
c. Recommended Dimensions
Based on National Board Standards
Storage Tank Concepts
d.Breathing
Inflow and outflow of air and vapor through a vessel
Spherical Storage Tank
*Used in gasoline and fuels
Breathing loss
Losses of vapor from tank through vapor expansion and contraction
Siphon Breaker
Prevents siphon effect
Vortex Breaker
Prevents vortices
Vacuum and Pressure Protection
*Vacuum Protection
-Vacuum Breaker / Vacuum Relief Valve
*Pressure Protection
-Pressure Safety Valve
Tank Blanketting
*Introducing inert gas (nitrogen) to tank
*Increase tank pressure
*Eliminate explosive atmosphere inside tank
*Minimize escape of volatile gas
Steam Trap
Automatic valve that filters out condensate (i.e. condensed steam) and non-condensable gases such as air without letting steam escape
Runaway Reaction
Great acceleration of reaction rate that it becomes impossible to control.
Controlled Variable vs Manipulated Variable
*Controlled Variable
-Variable compared to setpoint
*Manipulated Variable
-Variable manipulated by final control element
Differentiate BFD, PFD, and P&ID
*BFD
-simplest diagram
-proper sequence of processes
-mass balances
*PFD
-instrumentation (not detailed)
-equipment and their interconnectivity
*P&ID
-equipment and line sizes
-tagging
-process and design temperatures and pressure
-design pressure and temperature
-control loops and instrumentation
Purge
*Materials that are bled off the process
*Bypass
*Materials that skip through process/es
Why engineers overdesign?
-Provide flexibility in the process
-Minimize upset during procedures
Safety factor
*used by engineers to overdesign
