Power Systems Protection and Relaying code numbers

In North America protective relays are generally referred to by standard device numbers. Letters
are sometimes added to specify the application (IEEE Standard C37.2-2008).


Following the ANSI/IEEE Standard Device Numbers (the more commonly used ones are in bold)

1 - Master Element
2 - Time Delay Starting or Closing Relay
3 - Checking or Interlocking Relay
4 - Master Contactor
5 - Stopping Device
6 - Starting Circuit Breaker
7 – Rate of Change Relay
8 - Control Power Disconnecting Device
9 - Reversing Device
10 - Unit Sequence Switch
11 – Multifunction Device
12 - Overspeed Device
13 - Synchronous-speed Device
14 - Underspeed Device
15 - Speed or Frequency-Matching Device
16 – Data Communications Device
20 - Elect. operated valve (solenoid valve)
21 - Distance Relay
23 - Temperature Control Device
24 – Volts per Hertz Relay
25 - Synchronizing or Synchronism-Check Device
26 - Apparatus Thermal Device
27 - Undervoltage Relay
30 - Annunciator Relay
32 - Directional Power Relay
36 - Polarity or Polarizing Voltage Devices
37 - Undercurrent or Underpower Relay
38 - Bearing Protective Device
39 - Mechanical Conduction Monitor
40 –Field (over/under excitation) Relay
41 - Field Circuit Breaker
42 - Running Circuit Breaker
43 - Manual Transfer or Selector Device
46 – Rev. phase or Phase-Bal. Current Relay
47 - Phase-Seq. or Phase-Bal. Voltage Relay
48 - Incomplete-Sequence Relay
49 - Machine or Transformer Thermal Relay
50 - Instantaneous Overcurrent
51 - AC Time Overcurrent Relay
52 - AC Circuit Breaker
53 – Field Excitation Relay
55 - Power Factor Relay
56 - Field Application Relay
59 - Overvoltage Relay
60 - Voltage or Current Balance Relay
62 - Time-Delay Stopping or Opening Relay
63 - Pressure Switch
64 - Ground Detector Relay
65 - Governor
66 – Notching or jogging device
67 - AC Directional Overcurrent Relay
68 - Blocking or “out of step” Relay
69 - Permissive Control Device
74 - Alarm Relay
75 - Position Changing Mechanism
76 - DC Overcurrent Relay
78 - Phase-Angle Measuring Relay
79 - AC-Reclosing Relay
81 - Frequency Relay
83 - Automatic Selective Control or Transfer Relay
84 - Operating Mechanism
85 – Pliot Communications, Carrier or Pilot-Wire Relay
86 - Lockout Relay
87 - Differential Protective Relay
89 - Line Switch
90 - Regulating Device
91 - Voltage Directional Relay
92 - Voltage and Power Directional Relay
94 - Tripping or Trip-Free Relay
B – Bus
F - Field
G – Ground or generator
N – Neutral
T – Transformer

Engine Cycle

a constant mass of gas, the operation of a heat engine is a repeating cycle and its PV diagram will be a closed figure. The idea of an engine cycle is illustrated below for one of the simplest kinds of cycles. If the cycle is operated clockwise on the diagram, the engine uses heat to do net work. If operated counterclockwise, it uses work to transport heat and is therefore acting as are frigerator or a heat pump.



Engine Cycle Analysis

1.

2.


3.

4.

Standard diesel engine cycle


The diesel internal combustion engine differs from the gasoline powered Otto cycle by using a higher compression of the fuel to ignite the fuel rather than using a spark plug ("compression ignition" rather than "spark ignition").
Air standard diesel engine cycle
In the diesel engine, air is compressed adiabatically with a compression ratio typically between 15 and 20. This compression raises the temperature to the ignition temperature of the fuel mixture which is formed by injecting fuel once the air is compressed.
The ideal air-standard cycle is modeled as a reversible adiabatic compression followed by a constant pressure combustion process, then an adiabatic expansion as a power stroke and an iso volumetric exhaust. A new air charge is taken in at the end of the exhaust, as indicated by the processes a-e-a on the diagram.
Since the compression and power strokes of this idealized cycle are adiabatic, the efficiency can be calculated from the constant pressure and constant volume processes. The input and output energies and the efficiency can be calculated from the temperatures and specific heats:
It is convenient to express this efficiency in terms of the compression ratio rC = V1/V2 and the expansion ratio rE = V1/V3. The efficiency can be written
and this can be rearranged to the form

The difference between TBN and TAN

TBN is total base number and TAN is total acid number. TBN is a measure of the reserve alkalinity or reserve acid neutralization remaining in the oil. TAN measure the increase of oil oxidation and build-up of corrosive acidic compounds. Engine manufacturers often recommend utilizing both tests to gain a more in depth understanding of oil condition and engine oil remaining protection. In utilizing both tests, the TBN will decrease over time and TAN will increase over time. The point where the two numbers meet or cross over can be considered the point where the oil can no longer provided adequate corrosive where protection.

TBN In Diesel Engine Oils

TBN is an important property of engine oils. The abstract definition is as follows;

“Total Base Number (TBN) is the quantity of acid, expressed in terms of the equivalent number of milligrams of potassium hydroxide that is required to neutralize all basic constituents present in 1 gram of sample (ASTM Designation D 974)”. But this tells us little about what TBN in an engine oil does, nor how much we need for effective engine oil performance and engine protection.

The detergent additive in an engine oil has two functions
• To control deposits in the hot parts of the engine such as the pistons and turbocharger bearings.
• To neutralize acidic products of combustion from the fuel that can cause corrosive wear.

Engine oil formulators have always matched the amount of TBN to the amount of sulfur in the fuel. Today Chevron manufactures engine oils with 70 TBN which are used in marine engines operating on 5% sulfur fuel. This is very high sulfur content, 50,000 parts per million. Diesel fuel in the US was approximately 2,500 to 3,000 ppm sulfur (the legal maximum for ASTM 2D fuel was 5000 ppm) until 1993, when EPA regulations required a reduction to a maximum limit of 500 ppm for on road use. Today all diesel fuel is limited to 15 ppm sulfur maximum (Ultra Low Sulfur Diesel, or ULSD).

With 3000 ppm sulfur diesel fuel, oil TBN in the range of 10 to 14 was common, with lower priced oils at approximately 8 TBN. Current engine oils for use with ULSD are around 8 to 9+. Clearly the need for high TBN does not exist with today’s ULSD fuels.

How is TBN measured? It is important to note there are several test methods for Total Base Number. The one used in product data sheets is generally ASTM D 2896. This method uses perchloric acid to neutralize the alkalinity in the oil and yields a slightly higher number than the test method used by the oil analysis labs. They generally use ASTM D 4739 and the acid used here is hydrochloric acid. This produces a number approximately 2 mg KOH/g LOWER than ASTM D 2896 for the same oil. Due to chemical interferences, this test method does not recognize all of the alkalinity that ASTM D 2796 sees.

Why are there two test methods? The oil manufacturers have typically used ASTM D 2896 and their labs are set up to handle perchloric acid, which is toxic and hard to handle. In addition ASTM D 2896 can measure both the “hard base” from metallic detergent as well as the “soft base” from organic, non- metallic ingredients. So it is a more accurate method. BUT, the production oil analysis labs prefer to use a safer and easier to use titration acid, namely hydrochloric acid. The tests can be run faster, more cost effectively and more safely.

How much TBN do we need to protect the engine? The old rule was to change the engine oil when 50% of the new oil TBN had been consumed. Because of the virtual absence of fuel sulfur today, much less is needed. Chevron now sets the TBN guidelines for all of its diesel engine oils as follows:

FOR ALL OILS when using ULSD
• Severity 1: 50%-44% of new oil TBN or 3.5 to 4
• Severity 2: 43%-36% of new oil TBN 3 48 to 2.9
• Severity 3: <35% of new oil TBN < 2.8 to 2
• Severity 4: less than 2 <2

Other parameters of engine oil are now more important to engine durability and extended service protection than TBN. These are parameters such as oxidation stability, wear control, effective soot dispersancy. A balanced oil has multiple performance abilities and TBN is only one of the performance measures that are important in today’s high performance engine oil.

Power Plant Generators: What is Excitation?

Electric generators work on the principle of Faraday’s electromagnetic induction. The essential part of this principle is the magnetic field. The magnetic filed is produced from a DC power source from an Exciter that is part of the generator system.


The main requirement for electricity generation as per the basic principle is a magnetic field. The generator while producing electricity also has to produce this at a constant voltage for the electrical system to work properly. Controlling the magnetic field controls the voltage output of the generator.

  • How does one produce and control this magnetic field in a large generator?
  • The rotor or the field coils in a generator produce the magnetic flux that is essential to the production of the electric power. The rotor is a rotating electromagnet that requires a DC ( Direct Current) electric power source to excite the magnetic field. This power comes from an exciter.
  • DC Exciter

    In the past, the exciter was a small DC generator coupled to the same shaft as the rotor. Therefore, when the rotor rotates this exciter produces the power for the electromagnet. Control of the exciter output is done by varying the field current of the exciter. This output from the exiter then controls the magnetic field of the rotor to produce a constant voltage output by the generator. This DC current feeds to the rotor through slip rings.
  • Static Exciter

    In modern generators the exciters are static. The DC power for the electromagnet is from the main generator output itself. A number of high power thyristors rectify the AC current to produce a DC current which feeds to the rotor through slip rings. This eliminates the operation and maintenance problems associated with having another rotating machine. Static exciters offer a better control of the output than an electromechanical control.
    • During start up, when there is no output from the generator, a large battery bank provides the necessary power for excitation.
    • Brushless Exciter

      Another method is the brushless system. In this system the armature of the exciter is on the rotor shaft itself. The DC output of this armature, after rectification by solid-state devices, goes to the rotor coils. Since the armature and rotor are on the same rotating shaft, this eliminates the need for slip rings. Hence it reduces maintenance and operational requirements and thus improving reliability.


Reactive Power

Reactive Power can best be described as the quantity of “unused” power that is developed by reactive components, such as inductors or capacitors in an AC circuit or system. In a DC circuit, the product of “volts x amps” gives the power consumed in watts by the circuit. However, while this formula is also true for purely resistive AC circuits, the situation is slightly more complex in an AC circuits containing reactive components as this volt-amp product can change with frequency.
In an AC circuit, the product of voltage and current is expressed as volt-amperes (VA) or kilo volt-amperes (kVA) and is known as Apparent power, symbol S. In a non-inductive purely resistive circuit such as heaters, irons, kettles and filament bulbs, etc. their reactance is practically zero, and the impedance of the circuit is composed almost entirely of just resistance.
For an AC resistive circuit, the current and voltage are in-phase and the power at any instant can be found by multiplying the voltage by the current at that instant, and because of this “in-phase” relationship, the rms values can be used to find the equivalent DC power or heating effect.
However, if the circuit contains reactive components, the voltage and current waveforms will be “out-of-phase” by some amount determined by the circuits phase angle. If the phase angle between the voltage and the current is at its maximum of 90o, the volt-amp product will have equal positive and negative values.
In other words, the reactive circuit returns as much power to the supply as it consumes resulting in the average power consumed by the circuit being zero, as the same amount of energy keeps flowing alternately from source to the load and back from load to source.
Since we have a voltage and a current but no power dissipated, the expression of P = IV (rms) is no longer valid and it therefore follows that the volt-amp product in an AC circuit does not necessarily give the power consumed. Then in order to determine the “real power”, also called Active power, symbol P consumed by an AC circuit, we need to account for not only the volt-amp product but also the phase angle difference between the voltage and the current waveforms given by the equation:VI.cosΦ.
Then we can write the relationship between the apparent power and active or real power as:
 
active and reactive power equation
 
Note that power factor (PF) is defined as the ratio between the active power in watts and the apparent power in volt-amperes and indicates how effectively electrical power is being used. In a non-inductive resistive AC circuit, the active power will be equal to the apparent power as the fraction of P/S becomes equal to one or unity. A circuits power factor can be expressed either as a decimal value or as a percentage.
But as well as the active and apparent powers in AC circuits, there is also another power component that is present whenever there is a phase angle. This component is called Reactive Power (sometimes referred to as imaginary power) and is expressed in a unit called “volt-amperes reactive”, (VAr), symbol Q and is given by the equation: VI.sinΦ.
Reactive power, or VAr, is not really power at all but represents the product of volts and amperes that are out-of-phase with each other. The amount of reactive power present in an AC circuit will depend upon the phase shift or phase angle between the voltage and the current and just like active power, reactive power is positive when it is “supplied” and negative when it is “consumed”.
The relationship of the three elements of power, active power, (watts) apparent power, (VA) and reactive power, (VAr) in an AC circuit can be represented by the three sides of right-angled triangle. This representation is called a Power Triangle as shown:

Power in an AC Circuit

reactive power triangle
 
From the above power triangle we can see that AC circuits supply or consume two kinds of power: active power and reactive power. Also, active power is never negative, whereas reactive power can be either positive or negative in value so it is always advantageous to reduce reactive power in order to improve system efficiency.
The main advantage of using AC electrical power distribution is that the supply voltage level can be changed using transformers, but transformers and induction motors of household appliances, air conditioners and industrial equipment all consume reactive power which takes up space on the transmission lines since larger conductors and transformers are required to handle the larger currents which you need to pay for.
reactive power analogy
Reactive Power Analogy with Beer
In many ways, reactive power can be thought of like the foam head on a pint or glass of beer. You pay the barman for a full glass of beer but only drink the actual liquid beer which is always less than a full glass.
This is because the head (or froth) of the beer takes up additional wasted space in the glass leaving less room for the real beer that you consume, and the same idea is true for reactive power.
But for many industrial power applications, reactive power is often useful for an electrical circuit to have. While the real or active power is the energy supplied to run a motor, heat a home, or illuminate an electric light bulb, reactive power provides the important function of regulating the voltage thereby helping to move power effectively through the utility grid and transmission lines to where it is required by the load.
While reducing reactive power to help improve the power factor and system efficiency is a good thing, one of the disadvantages of reactive power is that a sufficient quantity of it is required to control the voltage and overcome the losses in a transmission network. This is because if the electrical network voltage is not high enough, active power cannot be supplied. But having too much reactive power flowing around in the network can cause excess heating (I2R losses) and undesirable voltage drops and loss of power along the transmission lines.

Power Factor Correction of Reactive Power


Industrial customers, on the other hand, which use 3-phase supplies have widely different power factors, and for this reason, the electrical utility may have to take the power factors of these industrial customers into account paying a penalty if their power factor drops below a prescribed value because it costs the utility companies more to supply industrial customers since larger conductors, larger transformers, larger switchgear, etc, is required to handle the larger currents.
One way to avoid reactive power charges, is to install power factor correction capacitors. Normally residential customers are charged only for the active power consumed in kilo-watt hours (kWhr) because nearly all residential and single phase power factor values are essentially the same due to power factor correction capacitors being built into most domestic appliances by the manufacturer.
Generally, for a load with a power factor of less than 0.95 more reactive power is required. For a load with a power factor value higher than 0.95 is considered good as the power is being consumed more effectively, and a load with a power factor of 1.0 or unity is considered perfect and does not use any reactive power.
Then we have seen that “apparent power” is a combination of both “reactive power” and “active power”. Active or real power is a result of a circuit containing resistive components only, while reactive power results from a circuit containing either capacitive and inductive components. Almost all AC circuits will contain a combination of these R, L and C components.
Since reactive power takes away from the active power, it must be considered in an electrical system to ensure that the apparent power supplied is sufficient to supply the load. This is a critical aspect of understanding AC power sources because the power source must be capable of supplying the necessary volt-amp (VA) power for any given load.

Harmonics

In an AC circuit, a resistance behaves in exactly the same way as it does in a DC circuit. That is, the current flowing through the resistance is proportional to the voltage across it. This is because a resistor is a linear device and if the voltage applied to it is a sine wave, the current flowing through it is also a sine wave.
Generally when dealing with alternating voltages and currents in electrical circuits it is assumed that they are pure and sinusoidal in shape with only one frequency value, called the “fundamental frequency” being present, but this is not always the case.
In an electrical or electronic device or circuit that has a voltage-current characteristic which is not linear, that is, the current flowing through it is not proportional to the applied voltage. The alternating waveforms associated with the device will be different to a greater or lesser extent to those of an ideal sinusoidal waveform. These types of waveforms are commonly referred to as non-sinusoidal or complex waveforms.
Complex waveforms are generated by common electrical devices such as iron-cored inductors, switching transformers, electronic ballasts in fluorescent lights and other such heavily inductive loads as well as the output voltage and current waveforms of AC alternators, generators and other such electrical machines. The result is that the current waveform may not be sinusoidal even though the voltage waveform is.
Also most electronic power supply switching circuits such as rectifiers, silicon controlled rectifier (SCR’s), power transistors, power converters and other such solid state switches which cut and chop the power supplies sinusoidal waveform to control motor power, or to convert the sinusoidal AC supply to DC. Theses switching circuits tend to draw current only at the peak values of the AC supply and since the switching current waveform is non-sinusoidal the resulting load current is said to contain Harmonics.
Non-sinusoidal complex waveforms are constructed by “adding” together a series of sine wave frequencies known as “Harmonics”. Harmonics is the generalised term used to describe the distortion of a sinusoidal waveform by waveforms of different frequencies.
Then whatever its shape, a complex waveform can be split up mathematically into its individual components called the fundamental frequency and a number of “harmonic frequencies”. But what do we mean by a “fundamental frequency”.

Fundamental Frequency

Fundamental Waveform (or first harmonic) is the sinusoidal waveform that has the supply frequency. The fundamental is the lowest or base frequency, Æ’ on which the complex waveform is built and as such the periodic time, Î¤ of the resulting complex waveform will be equal to the periodic time of the fundamental frequency.
Let’s consider the basic fundamental or 1st harmonic AC waveform as shown.
fundamental waveform
Where: Vmax is the peak value in volts and Æ’ is the waveforms frequency in Hertz (Hz).
We can see that a sinusoidal waveform is an alternating voltage (or current), which varies as a sine function of angle, 2πƒ. The waveforms frequency, Æ’ is determined by the number of cycles per second. In the United Kingdom this fundamental frequency is set at 50Hz while in the United States it is 60Hz.
Harmonics are voltages or currents that operate at a frequency that is an integer (whole-number) multiple of the fundamental frequency. So given a 50Hz fundamental waveform, this means a 2nd harmonic frequency would be 100Hz (2 x 50Hz), a 3rd harmonic would be 150Hz (3 x 50Hz), a 5th at 250Hz, a 7th at 350Hz and so on. Likewise, given a 60Hz fundamental waveform, the 2nd, 3rd, 4th and 5th harmonic frequencies would be at 120Hz, 180Hz, 240Hz and 300Hz respectively.
So in other words, we can say that “harmonics” are multiples of the fundamental frequency and can therefore be expressed as: 2Æ’3Æ’4Æ’, etc. as shown.

Complex Waveforms Due To Harmonics

harmonics and harmonic waveforms
Note that the red waveforms above, are the actual shapes of the waveforms as seen by a load due to the harmonic content being added to the fundamental frequency.
The fundamental waveform can also be called a 1st harmonics waveform. Therefore, a second harmonic has a frequency twice that of the fundamental, the third harmonic has a frequency three times the fundamental and a fourth harmonic has one four times the fundamental as shown in the left hand side column.
The right hand side column shows the complex wave shape generated as a result of the effect between the addition of the fundamental waveform and the harmonic waveforms at different harmonic frequencies. Note that the shape of the resulting complex waveform will depend not only on the number and amplitude of the harmonic frequencies present, but also on the phase relationship between the fundamental or base frequency and the individual harmonic frequencies.
We can see that a complex wave is made up of a fundamental waveform plus harmonics, each with its own peak value and phase angle. For example, if the fundamental frequency is given as;E = Vmax(2πƒt), the values of the harmonics will be given as:
For a second harmonic:
E2 = V2max(2×2πƒt) = V2max(4πƒt), = V2max(2ωt)
For a third harmonic:
E3 = V3max(3×2πƒt) = V3max(6πƒt), = V3max(3ωt)
For a fourth harmonic:
E4 = V4max(4×2πƒt) = V4max(8πƒt), = V4max(4ωt)
and so on.
Then the equation given for the value of a complex waveform will be:
harmonic frequency harmonics equation
Harmonics are generally classified by their name and frequency, for example, a 2nd harmonic of the fundamental frequency at 100 Hz, and also by their sequence. Harmonic sequence refers to the phasor rotation of the harmonic voltages and currents with respect to the fundamental waveform in a balanced, 3-phase 4-wire system.
A positive sequence harmonic ( 4th, 7th, 10th, …) would rotate in the same direction (forward) as the fundamental frequency. Where as a negative sequence harmonic ( 2nd, 5th, 8th, …) rotates in the opposite direction (reverse) of the fundamental frequency.

Negative sequence harmonics on the other hand circulate between the phases creating additional problems with motors as the opposite phasor rotation weakens the rotating magnetic field require by motors, and especially induction motors, causing them to produce less mechanical torque.
Generally, positive sequence harmonics are undesirable because they are responsible for overheating of conductors, power lines and transformers due to the addition of the waveforms.
Another set of special harmonics called “triplens” (multiple of three) have a zero rotational sequence. Triplens are the odd multiples of the third harmonic ( 3rd, 6th, 9th, …), etc, hence their name, and are therefore displaced by zero degrees. Zero sequence harmonics circulate between the phase and neutral or ground.
Unlike the positive and negative sequence harmonic currents that cancel each other out, third order or triplen harmonics do not cancel out. Instead add up arithmetically in the common neutral wire which is subjected to currents from all three phases.
The result is that current amplitude in the neutral wire due to these triplen harmonics could be up to 3 times the amplitude of the phase current at the fundamental frequency causing it to become less efficient and overheat.
Then we can summarise the sequence effects as multiples of the fundamental frequency of 50Hz as:

Harmonic Sequencing

NameFund.2nd3rd4th5th6th7th8th9th
Frequency, Hz50100150200250300350400450
Sequence+0+0+0
Note that the same harmonic sequence also applies to 60Hz fundamental waveforms.
SequenceRotationHarmonic Effect
+ForwardExcessive Heating Effect
ReverseMotor Torque Problems
0NoneAdds Voltages and/or Currents in Neutral Wire causing Heating

Harmonics Summary

Harmonics have only been around in sufficient quantities over the last few decades since the introduction of electronic drives for motors, fans and pumps, power supply switching circuits such as rectifiers, power converters and thyristor power controllers as well as most non-linear electronic phase controlled loads and high frequency (energy saving) fluorescent lights. This is due mainly to the fact that the controlled current drawn by the load does not faithfully follow the sinusoidal supply waveforms as in the case of rectifiers or power semiconductor switching circuits.
Harmonics in the electrical power distribution system combine with the fundamental frequency (50Hz or 60Hz) supply to create distortion of the voltage and/or current waveforms. This distortion creates a complex waveform made up from a number of harmonic frequencies which can have an adverse effect on electrical equipment and power lines.
The amount of waveform distortion present giving a complex waveform its distinctive shape is directly related to the frequencies and magnitudes of the most dominant harmonic components whose harmonic frequency is multiples (whole integers) of the fundamental frequency. The most dominant harmonic components are the low order harmonics from 2nd to the 19th with the triplens being the worst.

Important Checks Before Starting Power Plant Engines

The starting procedure of engines requires several points to be taken into consideration. While it is necessary that none of these points should be missed, there are a few extremely important things that should be done without fail while starting engines. Ten such important points are as follows:

1. Lubrication of Main Engine : Start pre-lubrication of the engine well before starting. For 4-stroke engines at least 15 minutes in advanced.

2. Check All Parameters: After starting the lubrication pump, check lube oil levels and all other running pump parameters such as cooling water pressure, fuel oil temp and pressure, control and starting air pressure etc. to ensure that all are in the accepted range.

3. Open Indicator Cocks and Blow Through: All the indicator cocks of the marine engine must be opened up for blow through of combustion chamber prior starting to avoid hydraulic damage because of water leakage.

4. Rotate the Crankshaft: Rotate the crankshaft of the engine by means of turning gear so that all the parts are thoroughly lubricated before starting.

5. Manual Check Turning Gear: Ensure that the turning gear is properly disengaged by checking it locally even when the remote signal is showing-“disengaged” sign. Some auxiliary engines are provided with tommy bar for rotation, ensure that it is removed from the flywheel before the engine is started.

6. Check Jacket Cooling Water Temperature: The jacket cooling water temperature of the engine should be maintained at at least 60 deg C for the main engine and 40 deg C for the auxiliary engine (it may vary depending upon the KW rating of the engine).

7. Warm up the Engine: The incoming ship generator should be run at no load for at least 5 mins to allow warming up of the system.


8. Put Load Sharing Switch to Manual / Automatically: 1st synchronized the engine with GRID after that slowly slowly increase the load.

Fuel Characteristic Definition as per ISO 8217:2010

ISO specification 8217 stipulates acceptable characteristics of marine fuel oil products. In order to understand the relative importance of each characteristic it is important to understand the definition. The following definitions are deemed useful to users of marine fuels products.

Viscosity A measure of fluid resistance to flow. Viscosity of fuel oil decreases with increasing temperature. The viscosity of the fuel oil at the point of injection into the engine is key to performance. Viscosity is used to classify residual fuel types but is not a key indicator of fuel quality. For example, all other characteristics being equal, a fuel of 360 cSt is of no better or worse quality than a fuel of 400 cSt, it is just less viscous.

Density Mass per unit volume of a product. It is used to convert the volume delivered into the quantity purchased. Density varies with temperature and is an important parameter in the onboard purification of the marine fuel product.

Calculated Carbon Aromaticity Index (CCAI) The most widely accepted empirical formula to estimate the ignition quality of fuel oil. CCAI uses the physical properties of density (d) and viscosity (V) in the following equation: CCAI = d - 81 –141*log [log (V+0.85)]

Sulfur Sulfur is the main inorganic component of fuel. It occurs naturally in crude oils and tends to concentrate in the heavier fractions. Sulfur concentration in fuel oil strongly influences the choice of lubricant. Energy content of fuel oil diminishes with increasing sulfur.

Flash Point Flash point is the minimum temperature at which vapours released from the fuel oil will ignite when exposed to an open flame. The flash point of a blended fuel oil is the same as that of the lightest component in the fuel oil product.

Acid Generally, marine fuel products should not contain inorganic acids, however ISO 8217 allows for minimal acceptable levels.

Sediment Sediment in distillates is composed mainly of rust, general dirt & scale. Marine fuel oil sediment can be both inorganic and organic in nature.

Carbon Residue Carbon residue is a measure of the carbonaceous material left after the volatile components of a fuel have been vaporized in the absence of air. It is used to estimate the potential of a fuel to create deposits in an engine upon combustion.

Pour Point The pour point of a fluid is the lowest temperature at which it ceases to flow. In fuels, the pour point is largely determined by the petroleum wax content in the oil. Pour point determines the minimum temperature required for storage and handling onboard of fuel oil products.

Ash Ash is the carbon free (inorganic) residue remaining after completely burning the fuel in air. It occurs naturally in crude oils and tends to concentrate in the heavier fractions. Ash can contain hard and erosive particles, some of which may also be corrosive.

Vanadium Vanadium is a metal occurring naturally in some crude oils and is concentrated in residual components during refining. In high concentration, it can form high melting point, corrosive deposits. In combination with sodium, it can form lower melting point, oxygen deficient deposits.

Sodium Sodium occurs naturally in crude oils and is concentrated in residual streams during refining. It can be introduced into fuel streams as a scavenger used to control the hydrogen sulfide content of fuel oil, via salt water contamination, or through sodium ingress into a marine diesel engine due to salt water saturated air.

Cat Fines Cat fines contamination in fuel oil is caused by carryover of catalytic material used in the refining process and evidenced by the presence of Alumina and Silica. Cat fines are hard and abrasive.

Used Lubricant (or Lube) Oil Some used lube oil may contain components harmful to an engine, but all used lube oils may not necessarily be unfit for purpose. Some additives used to identify used lube oil such as calcium are naturally occurring in crude oil and hence residual fuel. Test methods are designed to eliminate false positives.

Calcium A soft grey alkaline earth metal, the fifth most abundant element in the earth’s crust. Essential for living organisms, particularly in cell physiology, and is the most common metal in many animals. Calcium occurs naturally in crude oils. It is introduced into the combustion space via cylinder lubrication oil. The alkaline Total Base Number (TBN) additives of cylinder lube oil contain calcium. Calcium is concentrated in the residual part of the refinery process as lighter products are removed.

Compatibility Compatibility of a fuel is a function of the stability of the two individually stable oils used to blend marine fuel oil when they are co-mingled. Heavy marine fuels are complex mixtures of hydrocarbons. Some very large molecules called asphaltenes are held in suspension by maltenes. Mixing fuels can adversely affect this equilibrium.

FUNDAMENTALS OF REFINERY PROCESSING



The basic products from fractional distillation are:

Liquid petroleum gas (LPG) has carbon numbers of 1-5 and a boiling point up to 20 °C. Most of the LPGs are propane and butane, with carbon number 3 and 4 and boiling points -42 °C and -1 °C, respectively. Typical usage is domestic and camping gas, LPG vehicles and petrochemical feedstock.


Naphtha, or full range naphtha, is the fraction with boiling points between 30 °C and 200 °C and molecules generally having carbon numbers 5 to 12. The fraction is typically 15–30% of crude oil by weight. It is used mainly as a feedstock for other processes:
• In the refinery for producing additives for high octane gasoline
• A diluent for transporting very heavy crude
• Feedstock to the petrochemical olefins chain
• Feedstock for many other chemicals
• As a solvent in cleaning


Gasoline has carbon numbers mainly between 4 and 12 and boiling points up to 120 °C. Its main use is as fuel for internal combustion engines. Early on, this fraction could be sold directly as gasoline for cars, but today’s engines require more precisely formulated fuel, so less than 20% of gasoline at the pump is the raw gasoline fraction. Additional sources are needed to meet the demand, and additives are required to control such parameters as octane rating and volatility. Also, other sources such as bioethanol may be added, up to about 5%.


Kerosene has main carbon numbers 10 to 16 (range 6 to 16) boiling between 150 °C and 275 °C. Its main use is as aviation fuel, where the best known blend is Jet A-1. Kerosene is also used for lighting (paraffin lamps) and heating.


Diesel oil, or petrodiesel, is used for diesel engines in cars, trucks, ships, trains and utility machinery. It has a carbon number range of 8 to 21 (mainly 16-20) and is the fraction that boils between 200 °C and 350 °C.


White and black oils: The above products are often called white oils, and the fractions are generally available from the atmospheric distillation column. The remaining fraction below are the black oils, which must be further separated by vacuum distillation due to the temperature restriction of heating raw crude to no more than 370-380 °C. This allows the lighter fractions to boil off at a lower temperatures than with atmospheric distillation, avoiding overheating.


Lubricating oils, or mineral base lubricating oil (as opposed to synthetic lubricants), form the basis for lubricating waxes and polishes. These typically contain 90% raw material with carbon numbers from 20 to 50 and a fraction boiling at 300-600 °C. 10% additives are used to control lubricant properties, such as viscosity.


Fuel oils is a common term encompassing a wide range of fuels that also includes forms of kerosene and diesel, as well as the heavy fuel oil and bunker that is produced at the low end of the column before bitumen and coke residues. Fuel oil is graded on a scale of 1 to 6 where grade 1 and 2 is similar to kerosene and diesel, 3 is rarely used anymore. 4-6 are the heavy
fuels, also called Bunker A, B and C, where B and C are very high viscosity at normal ambient temperatures and requires preheating to about 100 °C and 120 °C respectively, before it flows enough to be used in an engine or burner. Fuel oil grade 4 does not require preheating and is sometimes mixed with off spec products, such as tank residue and interface liquid from multiphase pipelines or with grade 2 fuel oil to achieve low-enough viscosity at ambient temperatures. Fuel oil 6 is the lowest grade, its specification also allows 2% water and 0.5% mineral soil and is consumed almost exclusively by large ships in international waters, where pollutants such as sulfur is less regulated.


Bitumen and other residues like coke and tar has carbon numbers above 70 and boiling points above 525 °C. Low sulfur coke can be used for anodes in the metals industry (aluminum and steel) after processing (calcining). The remainder is a problem fuel, because of high sulfur content and even higher CO2 emissions than coal (typically 15% higher). Bitumen in the form of asphalt boiling above 525 °C is used for roofing and road paving. Asphalt concrete pavement material is commonly composed of 5% asphalt/bitumen and 95% stone, sand, and gravel (aggregates).


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