Oil and Gas Fundamentals

Gas Conditioning and Processing Instrumentation and Control Learn Oil and Gas Oil and Gas Equipments Oil and Gas Processes Plant Utilities

GENERIC FOR ALL DISCIPLINES

 

Table of Content

 Oil/Gas Industry Basic Knowledge

    1. Hydrocarbon Content
    2. Oil/Gas Usual Units Of Measurement
    3. Hazards Associated With Oil/Gas Industry
    4. Company Description / Organization
  1. Basic Processing Techniques
    1. Gas-Lift
    2. Water Injection
    3. Gas Injection
    4. Liquid / Gas Separation Principle
    5. Glycol Treatment
    6. Liquefaction
  • Basic Chemical / Physical Knowledge
    1. Temperature
    2. Pressure / Vacuum
    3. Level
    4. Flow
    5. Density / Specific Gravity
    6. H.
    7. Calorific Value
    8. Viscosity
    9. Pourpoint
    10. Dew Point
    11. Flash Point
    12. Combustion
    13. Explosivity
    14. Hydrates
    15. Heat Transfer
    16. Radiation
    17. Velocity
    18. Acceleration
    19. Vibration
    20. Luminance
    21. Accoustic Level
    22. Torque
    23. Galvanic Corrosion
    24. Chemical Corrosion
    25. Bacterial Corrosion
    26. H2s Corrosion
    27. Co2 Corrosion
    28. Erosion / Abrasion
  1. Documentation
    1. Piping & Instrument Diagrams (P&ID’s)
    2. Process Flow Diagrams (PFD)
    3. Cause and Effect Charts
    4. Electrical / Equipment Lists
    5. Electrical schematics
    6. Plot Plan / Layout drawings
    7. Wiring Diagrams
    8. Cable lists/schedules
    9. Instruments Hook-Up Diagram
  2. Functional Logic Diagram
  3. Engineering Data
  4. Instrument / Equipment Lists
  5. Isometric Drawings
  6. Loop Diagrams
  7. ESD Diagrams
  8. Office Computer
    1. Network Knowledge
    2. Peripherals And Components Identification
    3. Usual Programs
    4. Start Up/ Backup/ Shutdown

 

Module: Generic for all Disciplines

 

Objectives

At completion of this module, the employee will have an understanding of:

Section 1:                Oil / Gas industry basic knowledge.

Section 2:                Basic processing techniques. Section 3: Basic chemical / physical knowledge. Section 4:         Documentation.

Section 5:                Office computer.

 

Section 1: Oil / Gas Industry Basic Knowledge

 

1.  Hydrocarbon content

Hydrocarbons are substances composed of carbon and hydrogen. Crude oil, natural gas and petroleum products are all hydrocarbons but with different composition of carbon and hydrogen atoms in their molecule. Heavy hydrocarbons have more carbon atoms in their molecule than what light hydrocarbons have.

 

2.  Oil/gas usual units of measurement

Commonly Used Units of measurement

 

Crude Oil Production :      Barrels per Day (bbl / Day) MBD (Thousand Barrel per Day) (1 Barrel = 159 Litres)
Gas Production :      MMSCFD (Million Standard Cubic Feet per Day)

35. 314 SCFD = 1M3/day

Pressure :      PSI (Pounds Per Square Inch)

14. 5 PSI = 1 Bar

Temperature :      Degree Celsius         (°C) Degree Fahrenheit (°F)
Level :      %

Feet (ft) Meters (m)

 

3.  Hazards associated with oil/gas industry

  • Hydrogen Sulphide (H2S)
  • High speed rotating equipment (noise)
  • Ignition (positive and potential)
  • Hydrocarbons Under pressure
  • High temperature Pipe lines
  • Working at heights
  • Lifting
  • Flammable Materials
  • Toxic Chemicals
  • Radiation
  • Heat Stroke
  • Environmental Pollution

 

4.  Company Description / Organization.

 

Insert High Level Organization chart with summary.

 

SECTION 2: BASIC PROCESSING TECHNIQUES

 

1.  Gas-lift

A method for bringing crude oil or water to the surface by injecting gas into the producing well string to lower the hydrostatic pressure of the produced fluid and allows to flow to the surface.

 

2.  Water injection

The injection of water into a reservoir to maintain or increase the reservoir pressure or reduce the rate of decline of the reservoir pressure. The increase of the reservoir pressure will allow for better oil recovery from the original oil in place. This is a secondary recovery system.

 

3.  Gas injection

The injection of the gas into the reservoir is to maintain or increase its pressure or reduces the rate of decline of the reservoir pressure. It also allows for better oil recovery from the original oil in place.

 

4.  Liquid / gas separation principle

Specific gravity of gas is less than the specific gravity of any liquid. In any separator the gas flow to the top while the liquid settles at the bottom. In other words gas is a lighter fluid compared to liquids.

Gas is separated from oil by Pressure reduction and the water by density difference.

In the separators Gas is taken out from top and settled water is removed from bottom.

The water should be separated from the oil as the pipelines and refinery systems specifications require to have less than 0.1 to 0.5 % water in the oil.

Separator:

A mechanical device used for primary separation to remove and collect liquid from gas by gravity and centrifugal force.

 

Two conditions for Separators to function:

  • The fluids to be separated must be insoluble in each other
  • One fluid must be lighter than the

Classification of Separators:

  • By the number of fluids separated

2-Phase: Liquid, Gas

3-Phase:        Oil, Water and Gas

  • By shape

Horizontal, Vertical, Spherical

 

5.  Glycol treatment

It is one of the methods used to remove water vapour (moisture) from Natural Gas and thus dry the gas for safe and economical transfer through pipelines. In this method, a glycol liquid mixes with the wet gas in a tower and the glycol absorbs the water vapour (moisture) so that the gas becomes dry. The glycol is then separated and heated to release the water and recycled again. This process is also called Dehydration of Natural Gas.

6.  Liquefaction

Is a process by which we change mater phase from GAS to LIQUID. It is mainly to remove the light liquids from gas and either sale it as a product such as pentane or injected back to the crude oil.

7.  Amine Sweetening

The gas sweetening process is to remove the acidic gas from the hydrocarbon gases, the process include absorber and stripper, amine solutions is used to remove the acid gases (H2S & CO2) in the absorber and then regenerated in the stripper after applying heat to vaporize the H2S and CO2 from the amine solution.

 

SECTION 3: BASIC CHEMICAL / PHYSICAL KNOWLEDGE

 

1.  Temperature

Temperature is the degree of hotness or coldness, measured on definite scales.

The motion of the molecules in a substance determines how hot or cold it is. When the motion of the molecules slows, the temperature falls

Temperature must be closely monitored because it is difficult to control.

 

Temperature measurement:

Is very important in the oil industry, which use equipment supply, remove and exchange heat energy in various processes. It is also important for protection of the equipment, as uncontrolled high or low temperatures can cause structural deterioration of pipelines and vessels.

 

Temperature Scales: Temperature is expressed in degree scale. Centigrade the Fahrenheit scales are commonly used in Industrial applications.

The centigrade scale: Zero starts at the point of pure water and divided into 100 graduations at the temperature of boiling point of pure water each division is known as a degree centigrade.

The Fahrenheit scale: Zero starts below ice point. It is divided into 10 equal graduations in between pure water ice point and boiling point. The ice point is 32°f and the boiling point is 212°F.

Temperature Measuring Devices:

Conversions of Temperature scales

°C = (°F –32) x 5/9

 

°F = (°C x 9/5) + 32

Example, to convert 212 °F to °C

°C = (°F – 32) x 5/9

= (212 – 32) x 5/9

= 100 °C

And To convert 100 °C to °F

°F = (°C x 9/5) + 32

= (100x 9/5) + 32

= 212 °F

Five types of devices are commonly used to measure or sense temperature: Mercury Thermometer

Filled System Temperature Indicator Bimetallic Thermometer Thermocouple

Resistance Temperature Detector (RTD)

 

Filled Thermometers: Is a metallic assembly that consists of a bulb, capillary and a Bourdon tube assembly. Three types of metal bulb temperatures are in common use and they are categorised according the working fluid, Mercury, Liquid, Gas or Vapour. Filled Thermometers working on the principle of thermal expansion of Mineral substances.

Bimetallic Thermometers: Working on the principle that different metal substances have different thermal expansion coefficient. Bimetallic element made from two metal strips bonded together. Bimetallic element can be formed spiral or helix to increase the amount of motion available for a given temperature change.

Thermocouple “T/C”: Is a temperature-measuring element. Formed from two dissimilar metals joined together at one of both ends (hot junction), if it is exposed to the temperature being measured an emf is produced and measured at their other end (cold junction). Thermocouples are used in measuring wide range of temperatures from 250°C to1400°C. T/C is fast respond to temperature changes.

Types of thermocouples: There are about a dozen commonly used thermocouples, which have been assigned a letter designation. The most common types are type J, type K, type T and type E.

 

2.  Pressure / Vacuum

Pressure is the force acting on unit area. Units of pressure is PSI, Atm, bar, mm Hg, inches water, feet of water etc.

In processing plants the hydrocarbon gases and liquids in pipes and vessels exert pressure on the surface area.

P = F/A (Pressure = Force divided by Area)

 

Atmospheric Pressure:

 

Air, which is a mixture of gases, has weight. That is, the force of gravity attracts the air. At sea level, the standard weight of earth’s atmosphere exerts a pressure of 14.7 PSI.

 

Gauge pressure:

Is the pressure exerted above the atmospheric pressure

 

Absolute pressure:

Absolute pressure is the sum of gauge pressure and atmospheric pressure

 

Vacuum pressure:

Pressure below atmospheric pressure

Vacuum scale starts from atmospheric pressure to a maximum of 29.92 “Hg

 

Zero absolute pressure = perfect vacuum

Absolute Pressure = Pressure above Absolute zero

Gauge Pressure = Absolute Pressure – Atmospheric pressure

Vacuum gauge Pressure = Atmospheric Pressure – Fluid Pressure

 

 

Conversions of Pressure Scale.

 

 

PSIA = PSIG + Atmospheric pressure 1 in Hg Vac = – 0.491 PSIG

 

Example, to convert 2 psig to psia,

 

 

PSIA = PSIG + atmospheric Pr.

= 2 + 14.7 = 16.7 PSIA.

 

 

To convert 20 PSIA to PSIG,

PSIG = PSIA –atmospheric Pr.

= 20 – 14.7 = 5.3 PSIG

 

 

To convert 25 in Hg Vac to PSIG and PSIA

 

 

1 in Hg Vac = – 0.491 PSIG

 

 

PSIG = – 0.491 x 25 = -12.3 PSIG

PSIA = PSIG + atmospheric Pr.

= – 12.3 + 14.7

= 2.4 PSIA

Pressure Scales:

 

Gauge Pressure Scale Absolute Pressure Scale Vacuum Scale

 

Pressure Measuring Devices: There are 4 types of pressure Measuring devices, which are:

Manometer

Bourdon Tube Gauge Diaphragm Gauge Bellows Gauge

 

 

Pressure Gauge:

Is a device sense pressure and provides a visual representation of that pressure.

Pressure Gauge errors:

Zero error (always read high or low by a constant amount), Span error (Has an internal magnification error so the gauge reading will be out by different amounts at each point), and Linearity error (May read correctly at 0 and 100% but will not follow a linear path between these points)

 

3.  Level Measurement:

Defined as the measurement of the position of an interface between two media such as gas and liquid or between two liquids.

 

Level measurement Units:

May be expressed in units of length or percentage level.

 

Level Measurement Principle

Level devices operate under three main different principles:

  1. The position (height) of the liquid surface
  2. The pressure head
  3. The weight of the material

There are two methods used to measure the level of a liquid:

1.    Direct Methods

  1. Indirect Methods

 

Direct Level measurement Methods:

Direct methods are simple to use, reliable, low cost items and generally well suitable to hazardous areas. They measure the height above a zero point. There are four types of direct level measurement devices:

  1. Dip-sticks & Dip-Rods
  2. Weighted gauge tape
  3. Sight Glasses, and

 

Sight Glasses:

The most common types being used are (tubular and magnetic)

 

 

Indirect level measurement Methods:

Uses the changing position of the liquid surface to determine level with reference to a datum line. It can be used for low & high levels where the use of the direct method instruments is impractical.

 

Hydrostatic head pressure:

Is defined as the weight of liquid existing above a reference or datum line. Level measurement involving the principles of hydrostatics including (Diaphragm-box system, Hydrostatic differential-pressure meters, and air-bubble tube or purge system. A depth/height of liquid has a particular static pressure or head expressed as P = rgh

 

The Diaphragm-box System: Operate by giving an indication of the pressure produced by the static head of the liquid that is related to the actual level in the tank.

 

HDP Meters for Open Vessels:

Uses a DP transmitter to provide a signal to a remote indicator or controller. Any differential pressure detected between the HP and LP side is converted to a signal that is directly proportional to the level in the tank.

 


Zero
: Is the bottom scale value of measuring range.

LRV: Is the lower range value

URV: Is the upper range value

Span: The difference between (URV) and (LRV) of the instrument range

 

HDP Meters for Closed Vessels:

The pressure above the liquid will affect the pressure measured at the bottom. These instruments are affected by changes in the process density and should only be used for liquids with fixed specific gravity or where errors due to varying specific gravity are acceptable.

 

Bubble Tube (Purge) Systems:

The bubble tube system continuously bubbles air or an inert purge gas through a tube that extends to nearly bottom of the vessel at low flow rate. The back-pressure in the bubble tube will be a function of the hydrostatic pressure or head of the liquid in the vessel. Constant airflow must be kept through the purge tube.

 

Displacement devices:

It works on the buoyancy principle. Each increment of displacer submersion in the liquid; an equal increment of buoyancy change will result. The height of the liquid is in linear proportional displacer buoyancy change.

Torque tube: In this method a displacer body is connected to a torque tube which twists a specified amount for each increment of buoyancy change.

 

Automatic Tank Gauge (ATG) Level System:

Used to measure the liquid level when the fluid stored at atmospheric pressure or slightly higher. A servo keeps constant tension on a tape attached to a float. The float follows guide wires so that tape is always vertical and the float stays at the surface of the liquid.

Level Troll:

Is a level-measuring device directly connected to the vessel or tank at the same elevation where the Level being measured. Equipped with separate specific gravity adjustment so a transmitter calibrated for water can be used for another liquid by simply changing the SG (specific gravity) adjustment dial, to the SG of the liquid level to be measured.

 

Interface Level:

Is the line of separation formed if two or more immiscible liquids of different specific gravity are flown into a vessel/tank and are allowed sufficient time to settle, the higher SG (specific gravity) liquid settle down at the bottom of the vessel, over that the lower SG, over that the light and so on. Differential pressure transmitters and Level-trolls are equally used for liquid interface measurement.

 

4.  Flow rate

The flow rate is the amount of fluid that passing through vessel or meter or pipeline or a given point per unit time. Two types of flow rates are widely used in process industries.

 

Mass Flow rate

It is the Mass or quantity passing through vessel or  meter or pipeline per unit time.  It is expressed in Kilograms per minute (Kg/Min) or Pounds per second (lb / sec)

 

Volumetric Flow rate

It is the volume  of  fluid  passing  through  vessel  or  meter  or  pipeline  per  unit  time. It is expressed in cubic centimetres per second (cm3 / sec) or cubic meters per second (m3 / sec) or cubic meters per day (m3 / d).

In the oil industry, the flow rate of crude oil is expressed as barrels per day (BPD) and the flow rate of gas is expressed in standard cubic feet per day (SCFD).

 

Mass flow meters:

Flow meters measure mass directly

Differential Pressure Flow meters: Provide the best results where the flow conditions are turbulent. The most common types of differential pressure flow meters are: Orifice, Venture tube, Elbow and Pitot tube

 

Orifice Plates:

Orifice plates are the most widely used primary elements. Consist of a flat piece of metal with a sized hole bored in to it. When fluid through the orifice its velocity increases, resulting a drop in pressure and an increase in turbulence. The flow of liquid through the orifice plate creates a differential pressure across it, in such a way that the faster the flow the larger the pressures drop.

 

Orifice plate holders:

Are used to hold and position the orifice plate concentrically within the flow line. 3 holders are common; orifice flanges, junior orifice fitting and senior orifice fitting.

 

Orifice taps:

Are used to provide the differential pressure created across the orifice. There are 4 common arrangements of pressure taps; Flange taps, Vena Contracta taps, Corner taps and Pipe taps

 

Venturi tube:

Consists of conical entrance, throat, and conical outlet. The differential pressure is measured between the inlet (upstream of the conical entrance) and the throat.

 

Pitot tube: Consists of two parts that senses two pressures; the impact pressure

 

(dynamic) and the static pressure

 

Variable Area Flow meter (Rotameter): Is used for measuring low flows of clean liquids or gases of high temperatures and pressure. The area of the annulus is proportional to the height of the float in the tube. The measured flow is proportional to the annular area around the float.

Vortex shedding flow meters:

Is suitable for measuring liquid flows at high velocity. Vortices are produced from alternate edges of the bluff body at a frequency proportional to the volumetric flow rate

 

Turbine Flow meter:

Is a velocity flow meter, consists of machined housing has free rotating rotor and magnetic pickup. The angular velocity (rotor speed of rotation) is proportional to the volumetric rate of flow.

 

Positive Displacement Flow meters:

It is a very accurate volumetric flow meter. Separates the incoming fluid into a series of known discrete volumes then totalities the number of volumes in a known length of time.

 

Ultrasonic (Transit time) Flow Meters:

Has two transducers mounted diametrically opposite of the pipe, one upstream of the other. Each transducer sends an ultrasonic beam at approximately 1 MHz. The difference in transit time between the two beams is used to determine the average liquid velocity. The beam that travels in the direction of the flow travels faster then the opposite one.

 

Ultrasonic (Doppler Effect) Flow Meters:

Utilizes separated dual transducers mounted on opposite sides of the pipe. Transmitter projects a continuous ultrasonic beam at about 0.5 MHz through the pipe wall into the flowing stream. Particles in the stream reflect the ultrasonic radiation, which is detected by the receiver. The frequency reaching the receiver is shifted in proportion to the stream velocity. The frequency difference is a measure of the flow rate.

 

Major factors affecting Fluids Flow Through Pipes:

Velocity of the fluid, pipe size, friction due to contact with the pipe, viscosity of the fluid, specific gravity of the fluid, fluid Condition and velocity profiles

Three types of flow profile: Laminar or Streamlined, Transition and Turbulent

 

Laminar or Streamlined Laminar or streamlined flow is

described as liquid flowing through a

pipeline, divisible into layers moving parallel to each other.

 

 

Turbulent

Turbulent flow is the most common type of flow pattern found in pipes. Turbulent flow is the flow pattern which has a transverse velocity (swirls, eddy current).

 

Transitional

Transitional flow profile exists which is between the laminar and turbulent flow profiles. Its behaviour is difficult to predict and it may oscillate between the laminar and turbulent flow profiles

 

5.  Density / Specific Gravity

  • Density

Density of a solid or liquid is mass per unit volume. Its unit of measurement is gm/cc.

·        Specific Gravity

For gas, the specific gravity is the ratio of the density of the gas to density of air. For liquid, the specific gravity is the ratio of the density of liquid to the density of water.

Its unit of measurement is pure number.

 

SPECIFIC GRAVITIE OF COMMON LIQUIDS
Gasoline 0.751
Kerosene 0.820
Crude Oil 0.8299 – 0.8473
Pure Water 1.000
Milk 1.02 – 1.05
100% Sulphuric Acid 1.830
Mercury 13.547

6.  PH

 

PH value is a number that indicates concentration of hydrogen ions in solutions. It is used to express the degree of acidity or alkalinity for solutions as follows.

PH < 7 (below 7) for acidic solutions

 

PH = 7 for neutral solutions. Example water. PH > 7 (above 7) for basic solutions

7.  Calorific value

Is the amount of heat produced by burning a given mass of the fuel on complete combustion.

 

8.  Viscosity

The viscosity of a liquid is a measure of the internal friction tending to resist flow. Not all liquids flow or pour as easily as other liquids. The viscosity of a liquid changes with the change in temperature. Crude oil and petroleum products viscosity decrease as their temperature increases, and their viscosity increase as their temperature decreases.

Viscosity is expressed in two ways, namely the “Absolute Viscosity” and “Kinematics viscosity”. The Absolute viscosity and Kinematics viscosity of a fluid can be expressed in Metric or English system terms. The units of viscosity in both systems can be tabulated as follows:

 

System Absolute Viscosity Kinematics viscosity
Metric system Poise = dyne.sec/cm2 Stroke = cm /sec.
English System Pound.sec./ft2 Ft2 /sec.

 

To convert the viscosity from one system to the other, use the following conversion factors:

 

9.  Pour point

1 Poise           = 1*0 centipoises

= 0.00209 lb.sec/ft2 1 Stoke            = 0.001*9 ft2 /sec.

 

The minimum temperature at which a liquid can be poured is called “Pour Point”. The liquid freezes at a temperature lower than the pour point by about 5°F.

10.  Dew point

The temperature at which the first liquid droplet appears when the mixture is cold at constant certain pressure.

11.  Flash point

The flash point of a liquid is the minimum temperature at which sufficient vapours are released of liquid to form combustible mixture which can be ignited by an arc, spark or naked flame.

It is very important factor for safety precautions when handling liquid hydrocarbons.

12.  Combustion

Combustion is firing of a hydrocarbon fuel by burning it with air to produce the energy required for operation.

 

13.  Explosivity

Explosivity is the possibility of causing an explosion during oil and gas operations. The explosion occurs at a certain ratio of hydrocarbon and air mixtures. This ratio lies between two limits:

Lower Explosive Limit (LEL),                    Higher Explosive Limit (HEL)

 

14.  Hydrates

Hydrates are compounds of hydrocarbons, water, and other substances such as hydrogen sulphide and carbon dioxide, which form granular solids, very similar to ice. They are formed in gas pipelines and upstream of control valves at certain conditions of temperature and pressure.

Hydrate formation is usually controlled by either methanol or glycol injection.

 

Preventing Hydrate Formation

The hydrate formation can be prevented by

 

  • Heating the cold unprocessed
  • Inhibitor injections like ammonia, brines, glycol and methanol have been used to lower the freezing point of water
  • Methanol and glycol are the most inhibitors widely

 

15.  Heat Transfer

  • Heating and cooling are vital to the petroleum industry. Modes of heat transfer without mass transfer are conduction, convection, and
  • Evaporation and condensation are important heat transfer phenomena, which involve mass
  • Heat transfer occurs from the high-temperature region to the low- temperature region. Balance is achieved when both the regions temperatures are
  • Heat transfer by conduction occurs when heat travels through a body by the transfer of momentum of individual molecules without
  • When heat flows by actual mixing or physical turbulence, the mechanism (method) is known as convection.
  • Radiation is the transfer of energy through space by means of electromagnetic waves. Most heat transfer is due to combination of conduction and

Heat exchangers and the Furnaces are the commonly used equipment for the heat transfer.

Typical Heat Exchanger

 



  • Radiation

 

Heat energy is transferred in the form of rays sent out by the heated substance as its molecules undergo internal change. Only energy is transferred. The direction of the flow of heat is from the radiating source. The radiant energy is then absorbed by a colder substance or object.

Radiation takes place in any medium (gas, liquid, or solid), or in a vacuum.

 

17.  Velocity

It is the distance covered in unit time. Common units are cm/ sec, ft / sec etc.

 

Velocity = distance / Time

18.  Acceleration.

Change of velocity (either magnitude or direction) per time unit; a vector quantity.

a = v/t

a = acceleration

v = change in velocity. t = change in time.

19.  Vibration

Vibration is the instability of machines or equipment during operation. Several design and operational factors can cause vibration. As an example, misalignment and cavitations can cause pump vibration. Commonly used unit is Micron or mm

 

20.  Luminance

Luminance is the condition or quality of being luminous.

It is measured as the intensity of light per unit area of its source.

 

21.  Acoustic level

Acoustic level relates the sound level. Heavy equipment like, turbine, compressor, engine develop high level of sound during their operation. Acoustic levels are measured in decibel (db). Any acoustic level more than 95 db needs an ear protection to work in that environment. Over exposed to high acoustic level can kill the hearing sensation.

 

22.  Torque

Torque is a turning or twisting force. The moment of a force; the measure of a force’s tendency to produce torsion and rotation about an axis, equal to the vector product of the radius vector from the axis of rotation to the point of application of the force.

 

23.  Galvanic corrosion

Corrosion reactions are a combination of oxidation and reduction reactions. Oxidation is the electrochemical process by which an element or species looses electrons and increases its valence state. A metal transforming to a metal ion with the simultaneous loss of an electron is an example.

M <–> M+ + e

Reduction is the electrochemical process by which an element or species acquires one or more electrons. Thus reducing its valence. The transformation of hydrogen ions to atomic hydrogen is an example.

H+ + e <–> H0

When reactions of these types occur, they never occur in isolation, only in pairs or combination. In fact, the oxidation process, which produces more electrons, depends on the simultaneous consumption of those electrons by a reduction reaction. If no reduction reaction is available, no oxidation occurs. In these cases, the species which undergoes a reduction reaction is called the oxidising agent. The quantitative study of oxidation/reduction reactions has resulted in two useful concepts:

  1. Oxidation – reduction potentials (which apply to elements and compound)
  2. Galvanic series (which applies to alloys in their environments)

 

24.  Chemical corrosion

Corrosion is the natural process of deterioration of metals and alloys in a corrosive environment. This is a very broad definition, but corrosion occurs in a wide variety of forms, both in pure metals and in alloys. This discussion considers primarily the two most frequently occurring forms of corrosion, general corrosion and pitting. General corrosion is the wasting away of a metal or alloy in a corrosive environment, resulting in an actual decrease in the thickness or size of the original metallic structure. This wasting away occurs relatively uniformly over the surface exposed to the corrosive environment. Pitting is a form of localised corrosion in which a small portion of the metallic structure is corroded at a rate much faster than the bulk of the structure.

Metals such as steel and copper and alloys such as brass and stainless steel appear to be fairly rugged and able to withstand a great deal of physical abuse. This is not true when these metals are surrounded by a corrosive environment. They can be quickly reduced to thin, rusty or oxide-encrusted specimens. To put it another way,

 

these metals always have a tendency to return to their naturally occurring forms.

Metallic elements such as iron, copper, zinc and nickel occur naturally in the form of oxides, sulphides and carbonates. In metal making, this natural process is reversed and the metallic element is separated from its oxide. This requires a great deal of energy, as anyone who has seen a blast furnace can tell you. The resulting metal or alloy is in a high-energy state and, under the right conditions; it will attempt to return to its more natural, lower-energy, reacted state. A detailed corrosion study of a piece of metal is the study of how this happens, the rate at which it happens and what causes it to happen. There are several conditions that must be met before these reactions can occur.

  1. The metal, in this case, iron, must be reactive. It must be inherently unstable in the metallic form, thereby tending to
  2. The metal must be in contact with an An electrolyte is a solution, usually aqueous, which can conduct electric current and support ionised species.
  3. The electrolyte must contain dissolved This can be either dissolved gases, such as oxygen or chlorine, or dissolved ions, such as the hydrogen ion, which acts as an oxidising agent.
  4. The kinetics of the situation (the rate at which the corrosion reactions can occur) must be rapid enough to be of practical

 

25.  Bacterial corrosion

Bacteria are single celled micro organisms. There are two types of bacteria, Aerobic and Anaerobic (Non aerobic).

Aerobic bacteria needs free oxygen for their growth. They can be removed by adding chlorine in water. But anaerobic bacteria don’t need oxygen to live. They digest sulphate available in the water resulting in hydrogen sulphide, which in turn combines with iron, and form iron sulphide (scale).

 

26.  H2S corrosion

  • Hydrogen Sulphide (H2S) is extremely
  • Dissolves in water to form corrosive
  • It can react with steel to make it brittle in cracks and
  • If left in fuel gas, it burns to form sulphur dioxide and trioxide, both of which can create

Fe + H2O       FeO    (Ferric Oxide)

FeO + H2S     FeS     (Ferris Sulphide) (Also known as pyrophoric

iron)

  • When Ferris Sulphide is dry, the auto ignition temperature is less than room temperature when it is dry

Precautions when handling pyrophoric

  • Use a water spray to keep any residues (pyrophoric) wet during cleaning and removal.

 

  • Personnel must wear full protective clothing and breathing apparatus, because of possible exposure to H2
  • Both launching and receiving barrels must be purged with an inert gas prior to opening.
  • Fireman with extended fire hose to be stand
  • Fire extinguisher to be on stand

 

27.  CO2 Corrosion

Corrosion caused by water containing carbon dioxide is characterised by clean, uniformly thinned surfaces. The rate of corrosion that take place is dependent upon the carbon dioxide content, oxygen content, temperature and composition of the steel.

Carbon dioxide is present in water as:

  • Carbon dioxide in carbonate
  • That necessary to convert carbonates to
  • That necessary to keep bicarbonates in
  • AGGRESSIVE carbon

This excess aggressive carbon dioxide is the most cursive form

28.  Erosion

The process by which material (as rock or soil) is worn away or removed (as by wind, water or moving fluids).

 

 

SECTION 4: DOCUMENTATION

1.  P&ID is a document that contains information on

Main Equipment Main Pipelines

Instrumentation and Control functions

Explanatory notes at bottom of P&ID gives information on special features of stationary equipment, rotary equipment, complex process control loops, legend page showing symbols and codes used

Different equipment used in process industry are given unique and simple symbols in the P& ID.

Examples are,

 

Control Valve – Takes the controlling signal from a remote controller

 

Spectacle blind in OPEN position

 

P&ID’s / Symbols Understanding

P&ID (Piping and Instrumentation Diagram) is a detailed flow diagram of a process unit, utility unit or complete process module or offsite product storage and loading system or a drawing of a process and instrumentation system which connects different operating facilities

 

2.  Process Flow Diagrams (PFD)

A PFD is a simplified flow diagram of either a single process unit, a utility unit, a complete process module or offsite product storage or loading system. PFD provides a preliminary understanding of the process system indicating only the main items of equipment, the main pipelines and the essential instruments

3.  Cause and Effect Charts

Cause and Effect charts are logic matrices, which list the detectable problems (causes) against the automatic control reactions (effects) taken to safeguard the process and process area. The causes are described by the problem (event), the location or equipment involved (process component) and the device detecting the problem (normally the instrument tag no.). The effects explain the action taken, the location/equipment affected (process component) and which shutdown devices are activated (by tag no.).

4.  Electrical / Equipment Lists

 

List the give inventory of all equipment list and spare parts list. Power and control equipment list are provided in details to aid in reordering as spare parts.

 

5.  Electrical schematics

It is an electrical diagram that represents all of the components of an electrical system in their proper electrical positions. Schematic diagrams show contacts and switch in their de-energized state. Schematic diagrams are generally more detailed than single line diagrams.

 

6.    Plot Plan / Layout drawings

 

One type of architectural diagram is called a plot plan, It show electric distribution to all the plant buildings.

 

7.    Wiring Diagrams

 

The ‘Wiring Diagram’, or ‘Diagram of Connections’, which shows the actual wiring between every terminal in an equipment or group of equipment’s. In some cases it may show details of the type of wire used or its color, and it is possible to distinguish between power and control connections by thickness of line.

The wiring diagram is still necessary for the wire man who is building the equipment

8.    Cable lists/schedules

 

Cable lists to indicate the following data

√         Cable Tag reference

√         Cross section area

√         Length of cable

√         Operating voltage

√         Number of cores

√         From/To Places

√         Drawing details number

 

Example for Cable lists

 

 

9.   Instruments Hook-Up Diagram

Shows how the instruments and their fittings of a loop are assembled to form a working unit. List and identify the material required.

 

10.  Functional Logic Diagram

The Logic Diagram is mainly a summarization of the Shutdown philosophy of a specific equipment or plant in the form of symbols.

 

11.  Engineering Data Sheets.

There are two datasheets in engineering; Equipment datasheet or Instrument datasheets. There objective is to define specifications of the subject item.

Specifications are defined at different stages.

At design stage by the engineer (designer), he specifies requirement features of the equipment or the instrument.

At bidding stage; a bidders specifies the nearest specifications that he could supply. At procurement stage; the procurement team specifies exactly the subject item.

At end of project; the vendor specifies the supplied (agreed upon) specifications.

 

12.  Instrument / Equipment Lists

These are two important lists developed by the engineer during the early phase of the project. It lists main features of each and every equipment / instrument required in the project. Data are extracted from P&IDs. It is used at different project stages.

13.  Isometric Drawings

They are produced during the detailed engineering stage of the project by the engineer. They show a three dimensional presentation of a spool (part of pipe), it is done for all project lines.

Isometric drawings are not to scale, shown dimensions are for fabrication purposes. It also shows specification of all material needed to fabricate this part of a pipe. When isometrics are finalised are checked they are used for construction.

14.  Loop Diagrams

This drawing shows details of a group of instruments for a specific function.

15.  ESD Diagrams

It is a matrix to describe the Emergency Shut Down System.

 

 

SECTION 5: OFFOICE COMPUTER

 

  1. Networking Knowledge

 

  1. Peripherals and Components Identification

 

  1. Usual Programs (e-mails and office programs)

 

  1. Start Up / Backup /