HSE 2 Flashcards
Corrosion
Caused by a chemical or electrochemical attack on the surface of the metals.
How to lessen scaling?
*Increase velocity
*Use strainers
*Wash using steam condensate
Factors affecting corrosion
*Purity of metal
*Temperature
*Exposure to moisture and acids
TYPES OF CORROSION:
Galvanic / Fretting
When two electrochemically dissimilar metals are in electrical contact in an electrolytic environment
TYPES OF CORROSION:
Pitting
*Most destructive
*Redox Reaction causing giants pits
*Metal relocates to cathodic metal film
TYPES OF CORROSION:
Crevice
*Localized
*Difference in ion concentrations in two areas of metal
TYPES OF CORROSION:
Intergranular
*Caused by impurities at grain boundaries (crystalities) of solid
TYPES OF CORROSION:
Stress Corrosion Cracking
*Tensile stress + corrosive environment
TYPES OF CORROSION:
Uniform
*Most common form
*Attack across the surface of metal
TYPES OF CORROSION:
Corrosion Fatigue
Repeated application of stress
Erosion
Wear of the pump internal parts by suspended solid particles contained in the fluid being pumped.
Fire Point
Lowest temperature at which oil vapor will BURN after exposure to OPEN FLAME
Smoke Point
Lowest temperature at which oil will produce VISIBLE SMOKE
Flash Point
Lowest temperature at which OIL EVAPORATES to form COMBUSTIBLE GAS CONCENTRATION
Pour Point
Lowest temperature at which the oil will pour
Boiling Point
Temperature at which vapor pressure of a liquid is equal to the pressure of the atmosphere on the liquid
Auto-ignition Temperature
Temperature at which liquid readily ignites at atmospheric pressure
Equipment Cost by Scaling
Six-Tenths Rule
(Big Cost) / (Small Cost) = (Big Size / Small Size)^0.6
DCS vs PLC
DCS
*Regulatory actions
*Alarms
*Used for Basic Process Control System
PLC
*Discrete control
*Alarms
*Used for Safety Instrumented system
WAYS TO DISPOSE:
*Liquids
*Gases
*Liquids
-Drain
-Ground
-Vessel in ground
*Gases
-Atmosphere (Innocent)
-Flare (Combustible)
-Scrubber (Absorbable)
FEEDBACK CONTROL
*What is measured?
-manipulated variable
*When is error adjusted?
-AFTER error is propagated
*Closed or Open Loop?
-closed loop
FEEDFORWARD CONTROL
*What is measured?
-disturbance variable
*When error is adjusted?
-BEFORE error is propagated
*Closed or Open Loop?
-open loop
Ratio Control
*Setpoint determined by another sensor
*Setpoint calculated by equation
Split Range vs Parallel Control
*Split Range Control
-Preference between streams
*Parallel Control
-No preference between streams
Basis for Temperature Rating
- (Fire Point) / (Max Surface Temp)
OR * (Fire Point) / (T rating temp + Max Fluid Temp - Reference Temp)
Hot Dip Galvanization
Dipping steel in molten zinc
Cathodic Protection
Active sites converted to passive sites by providing electrons
Alloying
Mixing of different metals to get the optimal mix of their characteristics
Double Bleed and Block
*2 On-Off Valves
*1 Drain
Vertical vs Horizontal Storage Tanks
Vertical
+ Most used
+ Put in flat solid surface
Horizontal
+ Can be above or below ground
+ Underground serves as insulation (cold climate)
- Corrosion
Safety Factor
Multiplier to equipment capacity to account for safety and uncertainties in processes
Cladding
Covering a metal with another metal as protective layer
CONTROLLER TUNING:
*Cohen-Coon
*Ziegler-Nichols
*Cohen-Coon
-For open loop
*Ziegler-Nichols
-For open and closed loops
Transducer vs Sensor vs Transmitter
*Transducer (sensor + transmitter)
-converts energy to another form of energy
*Sensor
-converts energy to signal
*Transmitter
-transports signal from sensor to computer
Hot burn and Cold Burn Temperatures
*Hot burn
-short exposure: > 60 deg C
-prolonged exposure: > 49 deg C
*Cold burn
< 0 deg C
*Limiting Oxygen Concentration
*Lower and Upper Flammable Limit of Solution
*Limiting Oxygen Concentration
+ O2 = z * LFL
(where z = stoich O2)
*Lower and Upper Flammable Limit of Solution
+ LFL,mix = sum (yi / LFL,i)
+ UFL,mix = sum (yi / UFL,i)
Flash Tank
Vessel to separate gas flashed from liquid from high to lower pressure
Scrubber or Knockout Drum
*Vessel to handle high gas/liquid ratio.
*Liquid entrained as mist
Three Phase Separator
Vessel to separate gas, water and oil
Slug Catcher
Vessel to absorb in-flow of large liquid volumes at irregular intervals.
Total Cost by Lang Factor
Total Cost = C * Purchase Cost
Process hazard
inherent chemical or physical characteristic with the energy potential for damaging people, property, and/or the environment.
Hazard
condition, event, or circumstance that could lead to or contribute to an unplanned or undesirable event.
PHA
*Process Hazard Analysis
*Identify and analyze potential hazards associated with processing or handling of hazardous chemicals.
FMEA
*Failure Modes and Effects Analysis
*Identify potential failure modes and determine the effect of each on system performance.
*Individual failure is independent of other failures
Categories of Inherently Simpler Design
SILA
*Simplification
-Reduce complexity to reduce errors
*Intensification
-Reduce required materials by using more efficient processes and equipment
-Ex: PFR volume < CSTR volume
*Limitation
-Minimize involved equipment and materials
-Less pumps, and piping
*Attenuation
-Use hazardous materials under least hazardous conditions
-Reduce temperatures
-Use atmospheric pressures
Primary vs Secondary Explosion Protection
*Primary
-Prevent explosive atmospheres
*Secondary
-Using the ff:
-Ignition source and Static
-Hot surfaces
-Flameproofing
Flame / Explosion Proofing
Parts that may ignite is surrounded by an enclosure
Work Permits
*Hot work permit
*Cold work permit
*Enclosed work permit
Lockout and Tagout
*Lockout
-To prevent device to be turned on or opened
*Tagout
-Putting tag on locked device
Floating Roof Tank
- Floating roof rises and falls according to oil level
- Higher volumes
Fixed Roof Tank
*Cone
*Dome
*with Internal Floating Roof
*Cone
- Cheapest and most common
*Dome
-High vapor pressure liquids
*with Internal Floating Roof
-Prevent vapor losses and air pollution
Bunded Tank
- Enclosed by one more tank
- Or has surrounding dike
Open Top Tank
- Used when fluid has minimal losses due to evaporation
Single Skin & Double Skin Tanks
- Has one or two layers of plastic or steel
When to use Horizontal or Vertical Vessels?
*Horizontal Vessels
-Three-Phase Separation
- Liquid-Liquid separation
- Foaming Feed
*Vertical Vessels
- Smaller land usage
- High Gas content
- Solid removal
Ways to Prevent BLEVE
Boiling Level Elevation Vapor Explosion
*Overfill protection
*Overpressure protection
*Spill containment
Temperature Rating
Layer of protection to prevent sparks from instruments from igniting a potentially hazardous atmosphere
When to Use (Vessel Heads and Bottoms):
*Hemispherical Head
*Semi-Ellipsoidal Head
*Flat Head
*Hemispherical Head
-High pressure
*Semi-Ellipsoidal Head
-Most common
-High pressures
*Flat Head
-Small diameters
-Low pressures
