Absolute Pressure: It is the sum of gage pressure plus standard barometric pressure which is typically 14.7 psia. Please note that the numeric value of standrad barometric pressure is based on the sea level. At the site under consideration, the barometric pressure may be lower (when the site is above the sea level or higher when the site is below the sea level (such as New Orleans, LA). For pressure vessels, it does not matter if you use 14.7 as the standard barometric pressure. But for sizing breather vents for atmospheric tanks, the numeric value of standard barometric pressure is important. Please see Prof. Ron Darby’s “Chemical Engineering Fluid Mechanics”, 2nd edition, page 91 about how to calculate it. A simpler equation is: Pa = 14.696 [1 -(0.0065xh)/288]^5.26433, where Pa = Absolute pressure at height h meter above sea level. If the site is below the sea level, then use h as a negative value. Alternatively, if you are using SuperChems(TM) for simulatioin, it takes care of the pressure at the site when you specify the SITE object.
Absorption:Unit operation which involves dissolving gas in a solvent liquid.
Acceptable daily intake dose: It is the number of miligrams of a chemical per kilogram of body weight taken daily during an entire lifetime appears to be be risk-free based on known facts available at that time.
Accumulation: It is the pressure rise above the MAWP of the equipment. See Overpressure and note the difference between the two.
Acid rain: Rain water containing dissolved oxides of sulfur, carbon, and nitrogen.
Acoustically induced vibration: Vibration of a piping component caused by high velocity. Acoustic insulation and pipe-support help.
Activated sludge: It is formed in the biological treatment of waste water which is then mixed with bacteria in an aeration basin. A part of this sludge is incinerated and part recycled.
Activation energy: Energy needed to enable molecules to jump the energy barrier for reaction. In the Arrhenius model, the specific reaction rate k is denoted by k = Ae^(-E/RT), where E is the activation energy J/mol, R = gas constant 8.314 J/mol, T = temperature Kelvin, A = frequency factor or Pre-exponential factor. The factor e^(-E/RT) represents the fraction of the total colliding molecules jumping the energy barrier. The specific reaction rate k for the nth order of reaction is shjown as follows:
k = [(time)^-1][(concentration)^(1-n)].
Agitator: A mechanical device for mixing. Consider EKATO products for agitator.
AI : Artificial Intelligience [See Acronyms for more elaboration.]
Air pollution: A byproduct of civilization wherby humans defecate in their own nests.
ACGIH(American Conference of Governmental Industrial Hygienists)
ALOHA: Area Location Of Hazardous Atmosphere (EPA)
API: American Petroleum Institute (Many Standards for guiding emergency relief system design). See Acronyms.
APTAC: Automatic Pressure-Tracking Adiabatic Calorimeter. Calorimeter to detect onset decomposition temperature and develop kinetic data.
ARC: Acclerating Rate Calorimeter: Same function as APTAC, but has high thermal inertia and requires correction for the Phi-factor.
Arrhenius:He was a Swedish Physicist and Physical chemist who won the Nobel prize in 1903 in Chemisty. The equation of the specific reaction rate is after his name.
ARSST: Advanced Reactive Systems Screening Tool: a simple and inexpensive calorimeter to for sizing relief devices in the contingecy of runaway reaction.
ASME: American Society of Mechanical Engineers. It has many codes for ERS design; see ACRONYM.
ANSI: American National Standard Institute.
Autocatalytic reaction: A reaction in which one of the products act as the catalyst.
Azeotropic distillation: A distillation technique by which the components of an azeotropic (constant boiling) mixture are separated.
Backpressure: The pressure at the outlet nozzle of a relief device.
BOD: Biolchemical Oxygen Demand. It is used in the analysis of an organic waste water to measure the organic content of the waste.
Biot Number (Indicative of heat-transfer between process and surrounding)
BLEVE: Boiling Liquid Expanding Vapor Explosion. A phenomenon of rapid vaporization accompanied by noise that happens when a liquid, such as LNG, is stored under pressure above its boiling point and is discharged to atmosphere due to the opening of the relief device.
Blowdown: It is used to mean two different phenomena in two different contexts. (1) The reseating pressure of a PRV after relieving the pressure below its set point is called blowdown. Thus, when a PRV opens at its set pressure 100 psig and reseats after the pressure in the protected equipemt goes down below the set pressure, the valve reseats at 92 psig. This lowerng of 8% of set pressure after reseating is known as the blowdown pressure. (2) The test using a VSP apparatus done to determine the two-phase behavior of a fluid as to whether it is Churn-Turbulent, Bubbly, or homogeneous is called blowdown test.
Bubbly flow: It is one of the three two-phase behaviors of a fluid. It requres moderate relief area.
Buckling pin: It is a device fitted with a pin that buckles at the prescribed set pressure, Unlike a rupture disk, it can be replaced inplace without shutting a process operation.
CAFT: Calculated Adiabatic Flame Temperature.
Capitalized cost: It is the sum of the initial cost of a project plus the sum of the present worths of the annual costs of a project for its life span. It is used to compare the costs of different options for the same contingency for risk analysis .
Category D: It is qualifier meaning a harmless, non-toxic, non-flammable fluid such as water used at pressure less than150 psig.
Category M: Toxic fluid qualifier.
COD: Chemical Oxygen Demand
Chocked flow: When the downstram pressure of a restriction is lowered, flow of a compressible fluid increases up to a certain point; it does not increase after that. Flow under such limiting condition is called the chocked flow. The ratio of the upstream pressure to downstream pressure in absolute can be computed based on the fluid specific heat ratio (Cp/Cv).
Churn-turbulent Flow: It is a two-phase behavior characterization. It requirs the least relief flow area compared with Bubbly and Homogeneous flow models.
CFR: Code of Federal Regulations involving environments
COP: Coefficient Of Performance. It measures the efficiency of refrigeration system by the ratio of refrigeration duty/ work of compression.
Consciousness: Consciosness is beyond and above awareness and sentience. Consciousness is immanent in the universe, but transcends universe beyond scientific perception especially AI.
CSTR: Completely Mixed Stirred Tank Reactor. A reactor with ideal mixing condition.
Conservation vent: Also known as the breather vent used in low pressure tanks for controlling volatile organic emission.
Containment: Method of retaining contents of a pressure vessel without bursting but with possibly permanent deformation. It also means blowdown tank for secondary containment.
Coupling equation: It is the fundamental equation of DIERS Technology showing the mass balance between (the vapor generated by the heat reaching the vent, vapor generated but trapped in the liquid) with the vapor flow through the vent cross section area.
Corrosion: A physico-chemical phenomenon whereby the material of construction loses material. There are eight forms of corrosion: (1) Uniform (2) Galvanic or bimetal (3) Crevice (4) Pitting or formation of sudden holes (5) Intergrannular (happens at the grain-boundary of metals (6) Selective leaching (one of the components of an alloy is selectively taken away) (7) Erosion (caused by high velocity) (8) Stress
Critical flow: The maximum flow attained by lowering downstream pressure. See chocked flow.
Cryogenic Temperature: Typically below -120 degree C. Cryogenics are gases like He, H, N, O etc., which have boiling points below 120 K. Materials of construction for cryogenic applications must not be brittle.
DAS: Deflagration Arrester System.
DDT: Deflagration to Detonation Transition
Deflagration:Propagation of a combustion zone at a speed less than the speed of sound in the unreacted medium.
Detonation: Propagation of a combustion zone at a speed equal to or greater than the speed of sound in the unreacted medium.
DOT: Department of Transportation
DIERS: Design Institute for Emergency Relief System
Dispersion: Mixing of a toxicant in air
Drift-flux model: The original model of DIERS technology. This model considers mixture as a whole rather than separate phases and ignores the drift between the phases thereby simplifying the estimation of the physical property of the mixture.
Drowning System: Also known as Quench system, it is a system where the potentially runaway mixture is flooded with an unreacting medium to stop reaction.
Dust explosion pentagon: The five necessay combination comprising fuel, oxidizer, sufficient quantity of the fuel to sustain reaction, ignition source, and suspension is known as the Dust explosion pentagon.
Dynamic load factor: A factor (varying from 1 to 2) which is multiplied with a static load when the load is applied quickly.
End-of-line flame arresters: Used at the end of a vent line to prevent air flow back into the system.
EPA: Enviromental Protection Agency
Equilibrium flash:It is an unit operation whereby a fluid (vapor, liquid, or a mixture of the two), is throtttled into vessel, whereby the fluid flashes and reaches an equilibrium between two phases.
Excess flow valve: It is a ball check valve placed in reverse order between a rupture disk and relief valve combination on a tee-line so that any minute leakage between the disk and the relief valve is freely vented thereby preventing a build-up of pressure between the disk and the relief valve.
EPSR: An acronym meaning Explosion Pressure Shock Resistance used in the mechanical design of dust collectors after consideration of the ratio of unvented deflagration pressure to the initial maximum pressure, the ultimate stresss, yield stress, and allowable stress of the material of construction of the dust collector per ASME VIII. It is required by NFPA 69
ERPG (Emergency Response Planning Guidelines)
Eutectic Mixture: A mixture of compunds which behaves like a single compound with regard to melting and boiling. Thus, Dowtherm A is an eutectic mixture of 73.5% diphenyl oxide and 26.5% of diphenyl by weight, and is used as a heat transfer agent.
Explosion venting: It involves sizing explosion panel area for dust-handling equipemt such as dust collector using experimental data.
Extensive property: A property that depends on mass. Volume of a system is an extensive property.
FMECA: Failure Mode, Effects, and Criticality Analysis. It is a systematic method used to identify potential failure in a system, assess their effects and priortize them in terms of severity and probability.
Falling Film Evaporator: A vertical shell-and-tube evaporator where liquid is distributed on the inside of the tubes through a specially designed distributor, so that the liquid falls from the top to down in the form of a film, without filling up the tubes. A part of the concentrated liquid may be recycled with the fresh feed. There is an equation to figure out the minimum wetting rate dependent on viscosity, specific gravity, surface tension, tube loading, and perimeter of the tubes. Actual tube loading must be above this minimum wetting rate to avoid dry spot which deprives liquid film heat transfer area and promotes corrosion.
Fanning Friction Factor: This is used to determine pressure loss due to fluid friction as a function of the Reynolds number, roughness factor to diameter ratio of the pipe for three distinct regions: laminar, laminar-to-transition, and turbulent regions. Note that the Fanning friction factor is NOT the same as Moody-Darcy friction factor; the Fanning friction factor is one-fourth of the Moody-Darcy friction factor.
Fault Tree Analysis:The analysis used to identify combinations of equipment failures and human errors that can result in an accident through a deductive technique. Results are qualitative.
Fauske: A corporation, Fauske Associates, Inc., is famous for experimental data development in the area of process hazard involving reactivity and dust explosion. As one of the founding fathers of DIERS technology, Dr. Hans Fauske was famous for the Einsteinian simplicity in his mathematical formulation in relief sizing using experimental data.
Fenske equation: An equation used for determining the minimum numbers of theoretical plates for the separation of ideal mixtures in a distillation column using constant relative volatility with specified distillate and bottoms composition.
Fire heat: Heat generated by fire usec as a contigency.
FRP: Fibreglass Reinforced Plastics
Fire codes: Codes such as NFPA, API that set rules to handle fire contingency.
Fire heat: Mathematical formulations to quantify heat load due to fire.
Fire pentagon: Five conditions necessary to start explosion with dust: (1) fuel (dust), (2) oxygen or oxidant, (3) ignition source, (4) Confinement, (5) Suspension of fuel.
Fire tetrahedron: Four conditions necessary to start and sustain fire: (1) fuel, (2) oxygen or oxidant, (3) Ignition source, (4) Sufficient quantity of fuel to sustain fire.
Fire Triangle: Three conditions necessary to ignite fire: (1) fuel, (2) oxygen or oxidant, (3) ignition source.
Flame arrester: A device that does not allow passage of flame to the protected equipment by quenching it.
Flame height: Height of flame as prescibed by various codes and standards.
Flash point: The minimum temperature at which a liquid gives sufficient vapor to ignite in presence of air.
Fluidized bed reactor: A reactor where a heterogeneous mixture of solids and gases is mixed and suspended to promote mass transfer and reaction.
Fouling factor: It is a factor that accounts for the resistance to heat transfer due to the buildup of deposits or scale from the fluid a heat exchanger handles. It is an unsteady phenomenon, and the factor is added in the design to avoid premature performace issue. Its unit is the reciprocal of heat transfer: h.ft^2.F/Btu. It is added to inside and outside of the tube.
Fourier’s law: Mathematically, it displays heat transfer by three-dimensional vector notation in terms of the product of thermal conductivity and temperature gradient along three dimensions.
Frank-Kamanetskii model: This model deals in the mathematics of heat transfer between the poorly mixed contents in a large vessel with the surrounding.
Frequency factor: It is also known as the pre-exponential factor, A: a factor in the popular Arrhenius model correlating the specific reaction rate, k, with the frequency factor and temperature, T :
k = A. e^(E/RT)
Friction factor: A factor used in the calculation of pressure loss in piping. There are three models all correlating the Reynolds number: Fanning, Churchill, and Moody-Darcy
Fugacity: Fugacity is the thermodynamic counterpart of pressure and accounts for the non-ideal behavior of a gas when used in the Equation Of State (EOS). The fugacity of a pure component in a mixture is defined by: dGi = RTd(lnfi), where G = Gibbs Energy, R = Universal Gas constant, T = temperature, and fi = fugacity of component i. In the limit pressure approaches zero, properties of a non-ideal gas approaches those of an ideal gas.
Galvanic corrosion: A corrosion which happens when two dissimilar metals in a corrosive medium are in contact with each other.
gel effect : The gel effect or the Tromsdorff-Norrish effect is a phenomenon of autocatylitic free radical bulk polymerization which exhibits an increase in polymerization rate due to chain- entanglement in the increasing viscous solution which hinders the termination step more than the initiation step. An example is the polymerization of methyl methacrylate. The phenomenon may lead to runaway reaction scenario.
Gibbs Energy: It is a thermodynamic function correlating enthalpy H, temperature T, and entropy S: G = H – TS; TS is the lost energy.
HAZOP: HAZard and OPerability study.
HEM: Homogeneous Equilibrium Model
HNE: Homogeneous Non Equilibrium model
Homogeneous: Two or more phases mixed uniformly offering simplicity in the computation of transport propertiess.
Hooper K-factor: A factor, named after the developer, for fittings such as Tee, Elbow, pipe entrance, pipe exit, to calculate the erreversible frictional loss in pipe fittings.
Hydrodynamic entry length: The length of straight piping from the entrance necessary to establish the parabolic velocity profile.
Hydrotest: Test using water as the fluid to verifiy the integrity of equipment such as vessel and piping or both together.
Ideal nozzle: Relief device cnceptualized as an ideal nozzle with Kd = 1 for minimum flow area calculation.
Induction time: Also known as Reaction induction time (RIT), it is an exprimentally determined value (ASTM E2046-99). A test specimen and an inert reference are placed in the apparatus. Both are heated to detect the onset temperature and heat flow. The time taken by the specimen from the beginning to the onset is called the induction time.
ICRMS (International Chemical Regulatory Monitoring Systems)
IDLH: Immediately dangerous to Life and Health
Inherently Safe: Robust design, fail-safe design.
IVAN : Illicit Virtual Asset Notification – an organization with an objective of preventing AI crimes.
JRC (Joint Research Center)
Kd: Discharge coefficient of a relief device to determine the capacity.
Knockout drum: Effluent handling vessel to separate vopor and liquid.
Lethal Concentration and Lethal Dose: The lethal concentration, generally expressed as LC50, refers to the concentration of a chemical in air or water which, when given all at once, causes death of 50% of the test animals. Typically, toxicologists use rats or mice as the test animals. Similar definition applies to Lethal Dose LD50, but refers to an amount of the toxicant.
Lockhart-Martinelli correlation: Named after the authors, it is a method of computing the two-phase flow pressure loss.
MAWP: Maximum Allowable Working Pressure, defined by ASME and stamped on the equipment name plate with the coincident design temperature.
MESG: Maximum Experimental Safe Gap in Flame Arresters.It is the maximum clearence between the two parallel plates through which explosion cannot propagate.
MIE: Minimum Ignition Energy is the energy, expressed in milli Joules, needed to start the combustion of a fuel.
Monin-Obukhov Length: The height at which turbulence is generated by buoyancy rather than by wind shear in dispersion analysis
NAS: National Academy of Science
NBBI: National Board of Boiler and Pressure Vessel Inspectors. The board has procedures to test burst pressure of rupture disks and their Kr values.
NFPA: National Fire Protection Association
NIOSH: National Institute of Occupational Safety and Health
NRC: National Research Council
Noise: Measured in decibel, it is governed by OSHA 1910.95, to control it in wroking environment.
Non-Newtonian fluid: A fluid which exhibits a non-linear relationship between shear stress and shear rate.
Omega: The parameter omega consists of two terms: (1) the first term accounts for the compressibility of the mixture due to void-fraction in the mixture, (2) the second term reflects the compressibility due to phase change or flashing,
OSHA: Occupational Safety and Health Administration
Omega Method: A method of sizing relief devices developed by Dr. Joseph Leung for two-phase flow.
Overpressure: Overpressure is the pressure rise above the setpressure of the relief device. When the relief device is set at MAWP, overpressure and accummulation are synonymous.
Peng-Robinson EOS: An equation of State used for non-ideal gases. Used in SuperChems(TM) simulation.
POPRV: Pilot Operated Pressure Relief Valve
PHA: Process Hazard Analysis
pH: pH is defined as the logarithm to the base 10 of the reciprocal of hydrogen ion concentration in a liquid at 25 degree Celsius. This reference temperature is important.
PTB:Physikalish Technische Bundesanstalt – German standard.
PTC:Performance Test Codes – an ASME Standard PTC – 2023 for testing performance of pressure relief device.
PEL: Permissible Exposure Limit
Polymerization: Unit process of creating macromolecules by reacting one or more molecules which may be same or different.
Process Safety: Deals with the safety aspects of process with regard to life of personnel, equipment, and environment.
Rankine-Hugoniot Condition (it describes the relationship between both sides of a shock wave in dispersion analysis).
RBI Risk Based Inspection. See API 580 RBI for further details, in ACRONYM.
Reactivity: Chemistry of reaction
RSST: Reactive Systems Screening Tool – A simple, ingenious apparatus developed by FAUSKE, Associates.
RKEOS: Redlich-Kwong Equation of State
Relief System Design: Design of a system that covers the overpressure protection of equipment by relieving the pressure-causing fluid to a safe location.
Reynolds Number: It is dimensionless number comprising the diameter of a pipe, fluid velocity, density, and viscosity.
Rollover: It involves stratification of a liquid in a vessel due to temperature difference or compositional difference, and unequal heat transfer between the layers and the outside environment of the storage vessel, leading to instability, pressure rise, and explosion. LNG storage is an example.
Runaway reaction: An uncontrolled reaction.
Rupture Disk: A non-reclosing device to protect an equipment from overpressure.
SADT: Self-Accelerating Decomposition Temperature
Safety Culture: It is an abstract concept comprising attitude, belief, perception collectively used by the leadership of a company to convinvce the employees to follow for the greater goodness of the society in which the corporation exists. In general, the safety cuture has lapses in developing countries. Some US corporations take advantage of these lapses, and have environmentally dangerous intermediate materials manufactured in developing countriess, and bring them to US to produce the finished products. The Bhopal incident in India in 1984 is a classic example.
Safety Relief Valve: Relief Valve in gas application
Set Pressure: Pressure at which a device activate.
Slip: It is the higher velocity of a lighter phase over the heavier phase in contact.
Slurry flow: Flow involving solids and liquids, generally behaving as Non-Newtonian.
Stagnation pressure: It is the pressure of a fluid attained when the fluid is decelerated reversibly and diabatically (i.e., isentropically) to zero velocity with no elevation change. Typically, it is measured by a Pitot tube. It is expressed as the sum of static pressure and the velocity head.
Thermal Inertia: Also known as the Phi-factor, thermal inertia of a calorimetric apparatus such as ARSST, VSP, or ARC is defined by the (measured heat generated by the sample + heat absorbed by the cell itself)/(measured heat generated interms of sample). This factor is greater than 1. The more the cell weighs, the higher the Phi-factor. The observed onset decomposition temperature detected by an apparatus is, therefore, penalized by subtracting an arbitrary number, such as 50 degree C for an ARC.
TLV: Threshold Limit Value
Twophase Homogeneous: It is an oxymoronic term used by the puritam DIERS technologists to mix two phases uniformly for the computation of transport properties. A phase is a physically distinct mechanically separable homogeneous portion of matter. So, two phases cannot be homogenized.
Universal Gas Constant: It is the constant R in the ideal gas law equation: PV = nRT
User-friendliness: It implies the ease with which a person can navigate a software for simulation. Some softwre are so complicated that even a regular use find it difficult to navigate it. Not so, for example, CHEMCAD, ASPEN, etc.
Vapor deflagration: It is the propagation of vapor combustion zone at a speed less than the speed of sound in the unreacted medium.
Vari-Phi: A calorimetric apparatus which has built-in Phi-factor correction.
VSP: A calorimetric apparatus known as Vent Sizing Package, developed by Fauske Associates, Inc.
von Mises Stress: This stress considers the simultaneous application of several stresses such as shear, tension, compression, and torsion on an equipment. It requires Finite Element Analysis (FEA).
Water-hammer: It is the physical sonic manifestation of trapped hydraulic shock when the flow of a liquid-filled system is suddendly stopped. It typically manifests in a sudden rise of pressure of 54 psi for stopping a fluid moving with velocity of 1 ft/s. This pressure rise due to sudden stoppage can be linearly extrapolated for a higher velocity. Water- hammer can be prevented by slowly closing the manual valve or using a modulating control valve or using a restriction orifice at the vent-side of the solenoid valve of the ON-OFF control valve.
Weapon of Math Destruction (WMD): It is a technical satire used by the author to signify the potential danger of misapplication of a mathematical model, deriving a mathematical model wrong way, or applying a model beyond the range for which it was developed.