Guidelines For 3600 Heavy Fuel Oil (HFO) Engines{1000} Caterpillar

Engine:

3606 (S/N: 8RB1-UP)

3608 (S/N: 6MC1-UP)

3612 (S/N: 9RC1-UP; 9FR1-UP)

3616 (S/N: 1PD1-UP; 1FN1-UP)

Introduction

This Special Instruction provides the information required to apply the 3606, 3608, 3612, and 3616 Engines in a heavy fuel oil (HFO) application.

This document replaces the following publications that regard heavy fuel oil (HFO) applications: 3600 Marine and EPG Engines Application and Installation Guide and the Operation and Maintenance Manual.

Do not perform any procedure in this Special Instruction until you have read this information and you have understood this information.

Standard Conditions And Ratings

This Special Instruction provides the information required to apply the 3606, 3608, 3612, and 3616 Engines in a heavy fuel oil (HFO) application. The following standard conditions relate to the ratings:

• Ambient air temperature 35 °C (95 °F)

• Aftercooler water temperature 32 °C (90 °F)

• Altitude (at sea level) 200 m (656 ft)

The following derates for engine power are standard for heavy fuel oil (HFO) applications:

• 1.25% / °C ambient air above 35° C

• 1.40% / 100 m above an altitude of 200 m

• 0.6% / °C for aftercooler water that is above 38° C

A request for a rating is required for all heavy fuel applications. The factory can determine the optimum rating for the specific application and for the conditions at the site.

Fuel Specifications

The acceptable specifications for the fuel are similar to IF380. Refer to Table 12. Fuels with higher viscosity up to "The International Council On Combustion Engines" CIMAC K55 or "International Standard Organization" ISO8217 RMK 55 will be considered and reviewed by the factory. The new temperature limit for the fuel to the engine may affect the allowable bunkered viscosity to a fuel viscosity lower than K55.

Fuels with vanadium concentrations that are greater than 200 parts per million (ppm) will be reviewed by the factory. This process ensures an acceptable life for the exhaust valve. Engine ratings for fuels that contain high levels of vanadium may be modified in order to ensure low exhaust port temperatures. The installation must ensure that the restrictions for both the exhaust back pressure and the inlet air temperature are met. Both items affect exhaust port temperatures. If the vanadium level is greater than 300 ppm, consult with the factory. The factory will verify if the requested rating is capable of exhaust port temperatures below 400 °C (752 °F).

A fuel specification and the results of the analysis should be included in all contracts of sale. This information ensures that the proper type of fuel is used to determine the size and the rating of the equipment. If a specification is not available, ISO8217 RMG35 or CIMAC G35 (similar to IF380) must be inserted into the contract (Refer to table 6). The actual specification of the fuel should replace the inserted ISO8217 RMG35 or CIMAC G35 when the fuel becomes available. The appropriate size of equipment should be confirmed for the actual fuel that is supplied.

Note: Refer to section ""Fuel Specification" " for additional information on fuel specifications.

Fuel Properties

Viscosity

Viscosity is the measure of a liquid's resistance to flow. The viscosity of an oil must be associated with the temperature. The viscosity of the oil increases when the oil is cooled. The viscosity of the oil decreases when the oil is heated. The oil flows more easily when the oil is heated and the oil is lower in viscosity. The viscosity sets the limits on the system that is used to treat the fuel. Higher amounts of carbon residue and asphaltenes are generally contained in fuels with a higher viscosity. Viscosity is not a measure of the quality of the fuel. Table 1 may be used as a guide for estimating the viscosity at some temperatures when the viscosity at 100 °C is known. Illustration 1 may be used as a guideline for determining the viscosity of common fuels at a wider range of temperatures. Illustration 2 may be used as a reference in order to convert between centistokes and other scales of viscosity. When you convert from one of the other scales of viscosity to centistokes or vice versa, the result that is obtained is valid only at that one temperature. When the viscosity at a given temperature is converted to a viscosity at another temperature, a diagram must be used. An example of such a diagram is illustration 1 or Table 1.

Table 1

Estimated Viscosities At Temperatures Other Than 100 °C (212 °F)
Kinematic Viscosity (cSt) (1)
Measured At 100 °C (212 °F)	Approximate Viscosity At
	40 °C (104 °F)	50 °C (122 °F)	60 °C (140 °F)	130 °C (266°F)
10	80	50	17	6
15	170	100	28	8
25	425	225	50	11
35	780	390	75	14
45	1240	585	105	18
55	1790	810	130	20

( 1 )

1 cSt = 1 mm2/s

Illustration 1	g00548722
Fuel Oil Viscosity - Temperature Diagram

Illustration 2	g00551512
Viscosity Conversion Diagram

Density

Specific gravity is defined as the density of a material in comparison to the density of water. The specific gravity of the fuel is determined at a temperature of 15.5 °C, and the water is at the same temperature. The specific gravity is the ratio of the weight at a given volume to water. Specific gravity is measured when a hydrometer is placed in the fuel. Note the point that the level intersects the scale. Corrections must then be made in accordance with the temperature of the sample at the time of the test. The specific gravity of a material increases with the density. High-density fuels are produced through cracking processes. The main concern with fuels of high density is separation. Separators with a proper flow rate may remove water and solid particles in fuels. The density of the fuel oil may not exceed 991 kg/m³ at 15 °C (59 °F) if a conventional separator is used. Some separators may clean fuel with densities up to 1010 kg/m³. The density of the fuel oil must be discussed with the manufacturer of the separator. This discussion will ensure the delivery of the correct type of separator.

Note: Poor separation will lead to plugging of the filters. Poor separation will also lead to engine wear. These problems are due to particles and water in the fuel.

Sulfur

Sulfur is always present in heavy fuel oils. Heavy fuels with high viscosity are more likely to have higher contents of sulfur. The sulfur in heavy fuel is converted to sulfur oxides during combustion. Sulfur trioxide and water form sulfuric acid. If the temperatures in the combustion chamber are below the dew point of sulfuric acid, the acid will condense. The acid may cause cold corrosion and corrosive wear to the engine components. Sulfur may cause deposits in the exhaust system. The sulfur may also combine with vanadium and sodium in order to form these deposits. The following components may be attacked by sulfur: cylinder liners, piston ring grooves and the guides of the inlet valve. High sulfur content may be neutralized with engine lubricating oil of sufficient alkalinity. This oil has a high total base number.

Over-treatment for sulfur may have a negative effect. The treatment may leave an excess of alkaline material that can form hard deposits during combustion. For this reason, analysis of the lube oil is required to verify the acid to the alkaline balance.

Ash

The amount of ash in the fuel is a measure of the metallic content and the solid contamination that is not combustible. The following materials are usually in the ash: aluminum, calcium, iron, magnesium, nickel, sodium, silicon and vanadium. These materials compose about 0.015% to 0.05% of the total content of the ash. Some of the iron could be removed by separating the fuel oil. However, the vanadium and nickel will remain in the fuel oil even after the fuel leaves the separator. A high content of ash causes abrasive wear on the following components: piston rings, fuel injection nozzles and exhaust valves. A high content of ash may also cause the following problems: deposits in the piston groove, liner wear, erosion of the turbocharger turbine and high temperature corrosion. It is important to keep the temperatures of the components of the exhaust system low. The temperature of the valves should also be checked.

You may try the following changes and precautions when you run the engine on fuels with a high content of ash:

• Regular cleaning of the turbocharger or turbochargers (water or dry)

• Control the quality of the stored fuel. Stay within the limits of the Caterpillar 3600 engine.

• Efficiently separate the fuel. If a fuel that is high in sodium is used, washing with water may be considered. Special equipment is required in order to perform this task.

Aluminum And Silicon

Aluminum and silicon oxides are used as catalysts in the refining process. Some catalytic fines may enter the fuel by the malfunction of the cracker and the regenerator. These aluminum fines (catalytic fines) may cause abrasive wear in the following components: fuel injectors, nozzles, cylinder liners and piston rings. The limits in the following tables are intended to limit catalytic fines to a level that will ensure the minimum risk of abrasive wear to those components: Table 6, Table 13 and Table 14. The following practices may reduce the aluminum and silicon levels up to 65%: good treatment of the fuel, separation and filtration.

Vanadium And Sodium

If a fuel analysis reveals that the fuel has more than 200 ppm of vanadium and/or 30 ppm of sodium, the customer is encouraged to consult the Cat Engine factory. Analysis can ensure that the engine has the proper configuration and equipment for the fuel.

In addition to the limits on vanadium and sodium in ppm, limits are established for the comparative concentrations of these elements. Compounds of vanadium and sodium are especially corrosive when the concentration of sodium is more than 20 percent of the concentration of vanadium. Table 2 shows examples for calculating the percentage of sodium to vanadium.

Table 2

Examples for Calculating the Percentage of Sodium (Na) to Vanadium (V)
	50 ppm Na	=	0.083	×	100	=	8.3% (1)
	600 ppm V
	50 ppm Na	=	0.25	×	100	=	25% (2)
	200 ppm V

( 1 )	The concentration of sodium is less than 20 percent of the vanadium. This is an acceptable percentage.
( 2 )	The concentration of sodium is more than 20 percent of the vanadium. This percentage is NOT acceptable.

The concentration of vanadium and sodium can also be expressed as a ratio. A ratio of vanadium to sodium that is five or more is acceptable. Table 3 shows examples for calculating the ratio of vanadium to sodium.

Table 3

Examples for Calculating the Ratio of Vanadium (V) to Sodium (Na)
	600 ppm V	=	12 (1)
	50 ppm Na
	200 ppm V	=	4 (2)
	50 ppm Na

( 1 )	The result of the calculation is more than five. This ratio is acceptable.
( 2 )	The result of the calculation is less than five. This ratio is NOT acceptable.

Carbon Residue

The Conradson Carbon Residue (CCR) and the Microcarbon Residue (MCR) are measures of the tendency of the fuel to form carbon deposits during combustion. MCR is the preferred test method. These measures also indicate the tendency of a heavy fuel to form coke. When the carbon residue in the fuel is too high, carbon deposits may begin to form on the following components: the injector nozzle tip, the piston ring zone and the turbocharger nozzle ring. Carbon residue is the percentage of material that remains after a sample of fuel oil has been exposed to high temperatures. Carbon rich fuels are more difficult to burn. These types of fuels have poor characteristics of combustion which lead to the formation of soot and carbon deposits. For this reason, the value of the carbon residue is very important when you analyze the fuel parameters.

Asphaltenes

Asphaltenes are aromatic, complex compounds that are high molecular weight polymers. The asphaltenes are normally composed of the following materials: sulfur, nitrogen, oxygen, vanadium, nickel and iron. A high asphaltene level in the fuel may cause an increased ignition delay. This high level may also cause slow burning of the fuel. A high content of asphaltenes may also contribute to deposit formation in the combustion chamber and the exhaust system at low loads. When fuel has a high value of aromaticity, asphaltenes may precipitate from the fuel and either block filters or cause deposits in the fuel system or both. Precipitating asphaltenes may also cause excessive sludge in the centrifuge.

Flash Point

The flash point is the minimum temperature which may support momentary combustion of a fuel when a source of ignition is present near the surface of the fuel. Care must be taken when fuel is at the flash point or when fuel is above the flash point. Avoid sources of ignition.

Show/hide table

NOTICE
Residual fuel oil may have the potential to produce a flammable atmosphere in the tank headspace even when stored at a temperature below the measured flash point.

Pour Point

The pour point is the temperature of fuel that will barely flow under normal conditions. The pour point is about 2.8 °C above the temperature when the fuel becomes a solid. Pour point is unrelated to the quality of the fuel oil. The paraffin fraction of the fuel oil contains components of wax. For this reason, the pour point and viscosity of the fuel also need to be considered when you pump the fuel. If the temperature of the fuel drops, the wax begins to crystallize. When the wax crystallizes below the pour point, the fuel will no longer pour. In this state, the fuel may block a strainer or a screen.

Check the amount of wax in the fuel and check the pour point of the fuel before delivery. If the amount of wax is high or the pour point is low, the wax may crystallize. The minimum temperature of the stored fuel must be at least 10°C greater than the pour point. Solidified fuel oil may cause serious problems with the fuel system. Storage temperatures should be around 10 - 15 °C above the pour point.

Water

Water may get into the fuel during one of the following processes: refining, shipping and through condensation during storage. Therefore, the separator must function correctly.

Water tends to collect with the salt and with the metals that exist in the heavier fuels. Water contamination may also cause a decrease in the temperatures inside the combustion chamber. If the water in the fuel is well emulsified, the content of the energy in the fuel decreases as the content of the water increases. This decrease in the content of the energy will lead to an increase in the consumption of fuel.

Contamination by salt water may cause more problems than uncontaminated water. The chlorine in the salt will cause corrosion of the system that is used to handle the fuel and the fuel injection system. This corrosion will especially affect the high temperature areas of the engine. Centrifuging the heavy fuel is a good way to remove water and other deposits in the fuel oil. Salt water may cause a formation of sludge during the separation of the emulsified mixture.

One of the main concerns of contamination of the water is the reaction between the fuel oil and these compounds: sodium, water and vanadium compounds. These reactions occur during the process of combustion. This contamination may cause hot corrosion on the cylinder liner and the exhaust valves.

Calculated Carbon Aromaticity Index (CCAI)

The Calculated Carbon Aromaticity Index (CCAI) may be used as an indication of ignition delay. CCAI is calculated from the viscosity and density of the fuel. Another test of ignition quality is the Calculated Ignition Index (CII). Both equations are shown.

• CCAI = þ − 81 − 141{log₁₀[log₁₀(λ + 0.85)]} − 483 {log ₁₀[(T + 273)/(323)]}

• CII = (270.795 + 0.1038*T) − (0.254565*þ) + 23.708{log₁₀[log₁₀(λ + 0.7)]}

• þ = Density (kg/m³ at 15 °C (59 °F))

• λ = Kinematic viscosity in cSt

• T = Temperature (°C) at which the kinematic viscosity is determined.

Illustration 3 is a nomogram which may be used to determine the CCAI or CII value of a particular fuel based on the viscosity and density. Hold a straight edge so that the edge intersects the nomogram at the correct viscosity and density. The straight edge will intersect the CII and CCAI scales at the corresponding values.

Illustration 3	g00552137
Nomogram For Deriving CCAI And CII

Note: An increased CCAI value indicates decreased ignition quality. A decreased CII value indicates decreased ignition quality.

The Shell CCAI formula is used to predict the ignition quality based on the ratio of the density to the viscosity. Fuels that have high density in relation to viscosity have low ignition quality. Very high ratios of density to viscosity occasionally exist in some bunkered heavy fuel oil. Aromatics are used to adjust the viscosity of thermal cracked residues in order to get a stable blend. Aromatics have low ignition quality. Values of density and viscosity are used to determine the ignition quality of heavy fuel oils.

Fuel Standards And Quality Recommendations

There are published CIMAC recommendations regarding the requirements of heavy fuels for diesel engines (1990). There are also ISO grades of fuel (1996). Formulas and nomograms are included in order to determine the ignition quality. These standards cover the grades of fuel with sufficient scope for very high CCAI numbers. Refer to Table 4 for these values.

Table 4

CCAI Values (1)
BS	CIMAC	ISO	Viscosity (cSt at 50° C)	Density (kg/m3)	CCAI
M8	H45	RMH45	500	991	850
	K45		500	1010	869
M9	H55	RMH45	700	991	846
	K55		700	1010	865
M7	H35	RMH35	380	991	852
	K35		380	1010	871
M6	F25	RMF25	180	991	861
M5	D15	RMD15	80	991	871
M4	B10	RMB10	40	991	881
	A10	RMA10	40	975	865

( 1 )

The CCAI value has been calculated based on the maximum viscosity and the maximum density for each grade of fuel. Consider, for example, an M5, D15, RMD15 fuel that is delivered with maximum density and a lower viscosity of 50 cSt at 50° C instead of the maximum 80 cSt at 50° C. The CCAI value would raise from 871 as shown in Table 4 to 878.

Limits For Acceptable Ignition Quality

CCAI levels above 830 should be avoided on engines that are not preheated before start-up. CCAI levels above 830 should be avoided on engines with cooling systems which lack an increase in temperature at low loads. If CCAI levels exceed this limit, misfiring and rough operation may occur. These problems will occur if either the air intake temperature is low or if the raw water temperature is low. These problems will also occur if both of these conditions are present. The operational difficulties will occur at start-up and these problems will occur when the engine idles. Engines may operate satisfactorily on fuels with CCAI values up to 850 if the engines are efficiently preheated. The engines must also have a temperature control system that is dependent on the load.

The CCAI value of a fuel has an effect on the ignition delay. The effect is higher at very low loads and the effect is less at higher loads. Fuel with a higher CCAI value will generally cause higher maximum pressures of combustion, especially when the engine operates at partial loads. Reduced engine speed does not reduce the ignition delay.

Fuels with low ignition quality cause very large mechanical loads and thermal loads on the engine. Fuels with average ignition quality cause smaller mechanical loads and thermal loads on the engine. Fuels that have poor ignition quality are potentially damaging to the engine.

Fuels with a CCAI value of 850 or higher may cause starting problems. These problems may be overcome by the increased preheating of the engine.

Lubrication Oil

A lubricant encounters very high temperatures in the piston. The average lube oil temperature is about 85 °C as the lube oil enters the pistons. The average lube oil temperature may be up to 120 °C as the lube oil exits the pistons. The average temperature depends on the load of the engine. Temperatures above 350 °C have been measured in the hottest part of the piston crown, which is on the combustion side. The thermal stability and the oxidation stability of the lube oil is very important. If the lube oil is not stable, deposits on the underside of the crown form on the hot surface. Unstable lube oil could also influence the heat transfer. This influence may cause hot corrosion of the top of the piston, which may cause the piston crown to crack. If the deposits are thick enough, these deposits could cause seizure of the piston. The cooling effect of the oil in the piston is better at low viscosities. The flow of the lube oil is better in this case. Thicker oil films are formed if the lube oil has a higher viscosity. This thick oil film will perform the necessary lubrication between two surfaces.

Analysis of the used engine lube oil is a good way to review the operation of the engine. This analysis should be performed regularly. Analyze the lube oil after every 250 hours of operation of the engine. The most important parameters are described below.

Viscosity

If the viscosity is too low, thin oil films will result. This thin oil film will lead to poor lubrication or no lubrication. If the viscosity of the oil is too high, cooling problems will result and losses from friction in the engine will increase. A high viscosity of the lube oil may be a sign of oxidation. Oxidized lube oil may contribute to deposit formation (piston crown deposit). The viscosity of the lube oil should not change more than ± 20 to 25% from the value of the fresh lube oil at 40 °C.

Oxidation

Oxidation of the lube oil may cause an increase in viscosity. The amount of organic acids will increase. This accumulation will lead to an increase in viscosity. Poor thermal stability will also cause cracking and polymerisation of the molecules of oil in hot areas. These processes lead to deposits and lacquer. This high viscosity may result in corrosion of the bearing and deposits on the piston and liner.

Contamination

Soot accumulates in the hot zones and the sludge accumulates in colder zones.

Base Number (BN)

A low BN may lead to corrosion of the engine when the ability to neutralize the products of combustion decreases. As corrosion increases, the ability of the lube oil to keep the engine clean decreases. The minimum BN value of new lube oil must be 20 times the sulfur content of the fuel oil. The maximum allowable BN is 40. The minimum allowable BN value of the used lube oil is 50 % of the nominal value of the new lube oil.

Flash Point

The flash point is the temperature which will ignite the vapors of a lubricant. Limit the flash point in order to minimize the risk of an explosion in the crankcase. The minimum flash point should never be more than 30 °C below the value of the fresh lube oil.

Water Content

Water in lube oil reduces lubricating capability of the oil. Water may also cause foaming problems with the lube oil and the formation of sludge. The water content should not exceed 0.2%. If the water content reaches 0.3%, either the lube oil must be centrifuged or the lube oil must be changed.

Insolubles

The following items are collected in the lube oil: combustion products, dirt and engine wear. Not all of the insolubles are removed in the separator or in the oil filters. Therefore, the amount of insolubles may increase substantially in the lube oil. Companies measure this value of insolubles with different methods. The coagulated n-pentane method ASTM D893 is the standard. Similar values are obtained with the same method if n-heptane is used. An n-pentane insoluble value above 1.5% calls for attention. An n-pentane insoluble value above 2% is not accepted.

Used Lube Oil

Used lube oil must not be blended with the heavy fuel oils. Without approval from the factory, special blending equipment is required. Additional replacement of the fuel filter and the corrosion and wear of the fuel system is possible. When used oil is added to the fuel, discoloration of various fuel system components may result.

Disposal of used lube oil should be done in accordance with all laws and regulations.

Wear Metals

Analysis of the lube oil may be used to determine the wear of components. Refer to the table 5 for a list of the elements that may be found in lube oil. Table 5 also lists the most likely origin of the corresponding elements.

Table 5

Origins Of Elements Found In Lube Oil Analysis
Element (Symbol)	Possible Origin
Aluminum (Al)	Contaminants from fuel oil, possibly cylinder liner bearings.
Antimony (Sb), Arsenic (As), Kalium (K), Tin (Sn)	Bearings
Calcium (Ca)	Lubricating oil additives, contaminants from fuel oil.
Chromium (Cr)	Piston rings, possibly cylinder liners.
Copper (Cu)	Connecting rod bearings, rocker arm bearings, big end bearings, and main bearings. High copper in the lube oil may also indicate exhaust gas leakage near the air intake. Sulfur from the exhaust gas may dissolve copper from the surface.
Iron (Fe)	Cylinder liners and pistons, contaminants from fuel oil, other engine parts.
Lead (Pb)	Bearings, possibly contaminants from fuel oil.
Magnesium (Mg)	Sea water, possibly contaminants from fuel oil.
Molybdenum (Mo)	Other engine parts, possibly cylinder liners.
Nickel (Ni)	Bearings, contaminants from fuel oil, other engine parts, possibly cylinder liner.
Phosphorous (P)	Lubricating oil additives, possibly cylinder liners.
Silicon (Si)	Contaminants from fuel oil, cylinder liners, lubricating oil additives, possibly cooling water.
Sodium (Na)	Contaminants from fuel oil, cooling water, sea water.
Vanadium (V)	Contaminants from fuel oil.
Zinc (Zn)	Lubricant additive elements, possibly contaminants from fuel oil.

Lube Oil Centrifuge

Operation

The advancement of technology includes the improved thermal stability of modern lube oils. These oils improve the operation of a centrifuge by increasing the separation temperature to a maximum of 95 °C. The former recommendation of 85 °C was based on the properties of previous lube oils. Operational efficiency may be increased up to 25% when you apply the increased temperature.

The optimum interval for the separator bowl of the centrifuge must be determined in order to ensure proper efficiency. The initial setting should be 30 minutes. Inspect the centrifuge after one week of operation in order to check the cleanliness of the bowl. The control may then be adjusted in order to achieve the optimum time for cleaning the bowl. The bowl may be cleaned manually or certain models may be cleaned by a remote flushing machine.

The lube oil centrifuge should continue operating for a period of at least 4 hours after the engine is shut down. The shutdown ensures the proper cleanliness of the oil prior to the restart of the unit.

Continuously centrifuge the lube oil when the engine operates on lube oil. The lube oils for heavy fuel engines have low carbon dispersants. These lube oils must be constantly cleaned regardless of the fuel that is used.

Sizing

The flow rate is determined by the engine power output. The oil must be continuously processed at a minimum flow rate of 0.3 L/bkW h (0.026 gal/bhp h). Due to requirements for frequent cleaning, a centrifuge with a solid bowl is not recommended. A single centrifuge per engine is the preferred configuration. Multiple configurations of centrifuges will be considered under special circumstances. These configurations have several inherent risks, which include the following risks:

• Potential mixing of different engine lube oils

• Multiple engines that are not centrifuged during long periods of maintenance or repair periods.

• Maximum operating time without centrifuging the lube oil is 8 hours.

Benefits Of Clean Engine Lubricant

The following list contains the benefits of using a clean engine lubricant:

• Reduces the cost of maintenance over the life of an engine.

• Reduces the cost of replacement parts.

• Keeps the parts of the engine clean.

• Reduces the time required to overhaul the engine.

• Lessens the chance of abrasive wear.

• Keeps the zones of the piston ring clean and prevents the sticking of the ring.

• Prevent piston crown deposits and deposits on the valve seats.

• Give consistent performance under the limits of loading of the engine and temperatures of the engine.

• Prevents corrosion.

• Withstands pressures in the bearings and running gear.

• Have good water shedding properties.

• Have good characteristics of centrifuging.

Heavy Fuel Oil Handling - General Guidelines

This section provides information about the following items:

• the fuel system design

• the separators and the sizing of these separators

• the operating water quality specification for the separators

• the storage tanks and the settling tanks

• the fuel oil conditioning module

Illustration 4	g00551603
Typical Heavy Fuel Schematic (1) Vent (2) Diesel Fuel Oil Bunker Tank (3) Heavy Fuel Bunker Tank (4) Settling Tank (5) Fuel Conditioning Module (6) Day Tank For Diesel Fuel (7) Day Tank For Heavy Fuel Oil (8) Water Separator (9) Engine (10) Supply Pumps (11) Fuel Cooler (12) Circulating Pumps (13) Final Heaters (14) Viscometer (15) Auto-Flushing Filters (16) Duplex Filters (A) Heater (B) To Sludge Tank (C) Pre-Heater (D) 3-Way (E) 4 Bar Flow Engine Consumption (F) Items Located On Booster Module (G) 6-8 Bar Flow: 4 x Engine Consumption (H) For Multiple Engine Plants: Add a distillate pump and a three-way valve in order to allow the individual engines to be started and stopped on light fuel oil.

Fuel System Design

Frequently clean the filters in the system that is used to unload the fuel oil. Attention must be paid to the maintenance of the fire extinguishing system. The system should have sufficient drainage. New bunkered oil should always be filled into an empty tank. This isolation of the new bunkered fuel will ensure the quality of the fuel prior to treatment.

Storage Tanks

Heavy fuel oils are very viscous and these oils will not flow at low temperatures. Therefore, this oil must be heated to 10 °C above the pour point in order to ensure that the oil may be pumped.

The temperature of the storage tanks must be closely controlled. The storage tanks must be heated to this temperature. Otherwise, fuel could solidify in the pipes when no fuel is consumed. The viscosity of the heavy fuel in the entire tank must be below 1000 cSt. This viscosity enables the fuel oil to flow to the suction bell. The fuel lines must be adequately heated in order to transfer the fuel.

The temperature at the surface of the heating coil must not exceed 170 °C (338 °F) or carbon will settle on the coils. Overheating of the fuel oil may cause oxidation and sludge deposits. General estimates for the temperatures in the storage tank are shown in Table 6.

Note: Always determine the pour point of the actual fuel through fuel analysis, and use the value to calculate the correct temperature in the storage tank. The minimum temperature must be 10 °C greater than the pour point.

Table 6

Recommended Storage Tank Temperatures
Fuel Viscosity at 50 °C (122 °F)	Storage Tank Temperatures
180 cSt	37 °C (99 °F)
380 cSt	40 °C (104 °F)
500 cSt	43 °C (109 °F)
600 cSt	46 °C (115°F)
700 cSt	48 °C (118 °F)

Fuels from different suppliers or different shipments should not be mixed. This is a precautionary measure in order to avoid problems with the mixture of fuel. These problems include incompatibility and thermal instability. In order to avoid these problems, a tank should be pumped as low as possible before you start to refill with new fuel from a different origin. The tank should be completely refilled before use. This procedure will minimize the mixing between the old fuel and new fuel. Thus, problems with fuel will be minimized.

All information on the delivery of the fuel should be kept in a detailed log. All information on the changeover of the tank should also be kept in a detailed log. Pay attention to the location of fuel by tank and maintain the corresponding reports.

Never attempt to blend the fuels in order to lower the viscosity. This procedure involves specialized equipment for blending and testing. On-site blending may lead to the development of layers within a tank. If blending is attempted with an unstable fuel, separation from the heavy fuel may occur. Fuel with the desired viscosity should be provided by the fuel supplier.

The fuel may be blended by the supplier with a distillate fuel in order to lower the viscosity. The distillates which are added to the heavy fuels contain paraffin. These distillates may also cause the asphaltenes in the heavy fuel to separate and this results in the formation of heavy sludge.

Preheat the heavy fuel before the fuel enters the settling tank. The heat stabilizes the temperature in the settling tank.

Settling Tanks

The separation of water and particles in the heavy fuel oil by settling is a slow process. The fuel oil must not be disturbed in the settling tank for a long period of time in order to allow sufficient settling to occur. The tank must also maintain a very stable temperature. The level of fuel in these tanks shall be kept as high as possible.

Note: It is very important to drain the sludge and water from the settling tanks on a daily basis.

Caterpillar recommends the use of two settling tanks if the viscosity of the fuel is equal to 180 cSt at 50 °C (122 °F). Caterpillar also recommends the use of two settling tanks if the viscosity of the fuel is greater than 180 cSt at 50 °C (122 °F). Each tank should have sufficient capacity in order to operate the plant for 24 hours at full load.

Note: A single larger 48 hour tank is not recommended. Insufficient time for settling would result.

Table 7

Temperatures Of Settling Tank Fuel
Fuel Viscosity cSt at 50 °C (122 °F)	Normal °C (°F)	Minimum °C (°F)
80	60 °C (140 °F)	45 °C (113 °F)
81 - 180	70 °C (158 °F)	55 °C (131 °F)
181 - 700	80 °C (176 °F)	60 °C (140 °F)

A minimum temperature of 60 °C (140 °F) must be maintained in the settling tank for all fuels over 180 cSt at 50 °C (122 °F). This temperature ensures the proper settling of the fuel. Refer to table 7. The temperature should be automatically regulated in order to minimize consumption of steam and variations of temperature in the tanks. The probe for the temperature should be located at a low level in order to ensure that the probe is never uncovered. This exposure may cause the fuel to overheat. Overheating leads to cracking or the separating of asphaltene from the fuel.

The guidelines pertain both to the storage of fuel in tanks and to the fuel in the settling tanks. According to the guidelines, fuels should not be combined. The settling tanks should properly separate the fuel and the settling tanks should properly drain.

Note: Drain from the bottom of the settling tanks three times daily in order to remove any water that may have accumulated. The design of the system should provide a tank for the drainage of oily water. If any water is found in the tank, immediately check the separators and check the steam coils.

The fuel in the tank should settle for the maximum amount of time. When you change the settling tanks, simultaneously divert the day tank's suction line and the return line for the overflow. Change over the day tank when you change over the two settling tanks. Immediately after you change over the tanks, fill the settling tank. Use the transfer pumps to fill the settling tank in two to four hours. This rate of fill will allow the fuel to settle for a minimum of 20 hours during the 24 hour operation of the other tank.

Note: Another common name for a day tank is a service tank.

Fuel Oil Separator

Note: Another common term for a separator is a centrifuge.

The separator must be operated and maintained in accordance with the manufacturer's published guidelines. These guidelines should be the minimum requirements for operation and maintenance. (A separator that is improperly operated may act as a expensive transfer pump.)

Do not add chemical by-products or used lubricating oil to the supply of fuel. The efficiency of the separator may be reduced and chemical corrosion of separators and the aggregates is possible. Certain lubricating oils may be burned if special equipment is used. Consult with the factory for approval.

The addition of chemical waste (caustic soda) raises the pH into the alkaline section (>8) and the by-products have the following negative effects:

• Chemical waste causes corrosion of the aluminum hoods on the separator and the waste also causes corrosion of the other components.

• Water forms a stable emulsion together with the fuel and the water cannot be separated with sufficient efficiency.

• A sufficient reduction of sodium and potassium contents is not possible. A chemical that is used to destroy an emulsion is not effective at removing salt from the module.

The addition of chemical waste lowers the pH enough to form an acid (<5) and the by-products have the following negative effects:

• Chemical waste causes corrosion of the aluminum hoods on the separator and the waste also causes corrosion of the other components.

• Chemical corrosion of steel and stainless steel components is possible.

The addition of waste oil to the separator has the following negative effects:

• Increased share of solids

• Increased water content

• Additives and stabilizers in the waste oil may reduce the ability of the separator to remove water and solids.

Separation is the best method of removing water and contaminants from heavy fuels. Proper operation of the system for the heavy fuel ensures that the separator may work under ideal conditions. Even when you use separators, removal of the water may constitute a problem. The densities of heavy fuel and water are nearly equal. This means that the difference in density that is needed for efficient separation is small. A modern separator may process a fuel oil with a maximum density of 1010 kg/m³ at 15 °C.

Note: There are more dense fuels that exist. Caterpillar recommends a maximum temperature of 98 °C (208 °F) for the most efficient separation.

Water which has formed an emulsion with heavy fuel may prove difficult to remove, even if the fuel is substantially lighter than water. The efficiency of the separators may be determined by testing the heavy fuel for the amount of water. Perform this test before separation and perform this test after separation. A simple test apparatus is available from several different companies. One example is the Zematra BV from ABS Oil Testing Services.

Note: The maximum amount of water in the heavy fuel that may enter the engine is 0.2%.

Problems with performance of the separator may be observed if a large amount of sludge is produced. All dirty oil and water from the separator is discharged to a tank for sludge. The level of the sludge in the tank should be monitored on a daily basis. If the separator produces an excessive amount of sludge, perform the following procedure:

• Determine the cause immediately.

• Take corrective action.

• Record the results in the log.

The fuel must be sampled before the separator and the fuel must be sampled after the separator in order to verify the proper operation of the separator. The discharge side of the unit is for the clean fuel. Large amounts of solid particles on the discharge side of the unit indicate the incorrect operation or adjustment of the separator. Immediate attention must be placed on finding and correcting the problem.

One of the most critical factors for all separators is the correct supply of heat. Small variations in the temperature of the fuel oil to the unit may cause a large change in the relative density. Proper separation is dependent on the difference in densities of the lighter and heavy phases. Regulate the temperature so that the inlet temperature to the separator varies by no more than ± 2 °C. It is important to keep the temperature of the settling tank stable. The maximum temperature shall be 98 °C from the outlet of the heater into the separator. This temperature depends on the viscosity of the actual heavy fuel oil. It is important to keep the fuel temperature constant. Also, the separator must operate at the right temperature. The heater must raise the temperature of the fuel that comes from the settling tanks to the recommended temperature (98 °C maximum). This constant control of the temperature is especially critical on separators with gravity discs.

On the separators that use gravity discs, the correct size of the disc is essential for proper separation. When a new fuel is supplied, the correct disc must be installed. This installation is done by continually changing the gravity disc to the next larger diameter until oil breaks over the seal. The next smaller size should then be reinstalled. This gravity disc then becomes the correct size for that particular density of fuel. Refer to the manufacturers instructions for details.

Note: The size of the disc becomes especially critical when any changes in the fuel occur. Liquids with different densities require gravity discs with different inner diameters in order to separate.

Regular maintenance of the separator is another important factor in the efficient operation of the unit. The intervals of cleaning should be adjusted according to on-site conditions. The use of a device that cleans the separator without disassembly of the separator is highly recommended. An example of such a unit is manufactured by Alfa Laval. The space between discs in the stack of discs is very small. When the buildup in the stack of discs becomes too large, the passage of the fuel is restricted. This buildup causes the fluid velocity to increase and the buildup reduces the efficiency of separation. Inefficient operation can lead to one of the following problems: contamination of the day tank, plugging of the filters and wear of the fuel injection equipment. Low velocity through the bowl of the separator provides the most effective separation.

The total flow of the separators should be optimized. This procedure will provide an excess rate of flow of only ten percent over the current total consumption of the engine. This will provide the best possible cleaning of the fuel. This rate of flow will maintain the level of the day tank at the maximum level. The excess fuel will overflow to the settling tank. If a separator is inoperable for any extended period of time, the rate of flow will be maintained by the remaining units. Do not exceed the manufacturer's recommendations. The rate of flow will be maintained at the level of ten percent excess.

All alarms should be promptly answered. Damage to the engine due to inadequate treatment of the fuel is a cumulative problem. The operator should strive for superb operation of the separator. The operator must silence the alarm and the operator must correct the cause of the alarm. Problems with fuel quality may not be tolerated under any circumstances.

Fuel Oil Separator Sizing

The separator is sized in accordance with the recommendations of the supplier. Separators have traditionally operated in series as a purifier-clarifier. The present recommendation is the use of a separator with controlled partial discharge of sludge, and the separator is operated on a continuous basis.

The minimum capacity of the system is determined with the following formula:

• Qmin = N x [ 1.18 x (P x b x 24) / (R x t)]

• Qmin = Minimum Separator System Capacity (Liter per hour)

• N = Number of Engines

• P = Max. Continuous Rating Of The Engine (bkW)

• b = Brake Specific Fuel Oil Consumption (g/bkW h)

• R = Density Of The Fuel Oil (kg/m³) (Use 950 kg/m³ For Heavy Fuel Oil)

• t = Daily Separation Time In Automatic Service (hr) (23 = In Purifier-Clarifier Mode; 24 = Using Controlled Partial Discharge Separators)

Note: The margin of 18 percent (1.18) allows for the following conditions: conditions that are not in compliance with the standards of the ISO, wear and fuel contamination. The margin for a separator may be reduced if the contaminants in the fuel oil are low. An allowance must also be made for conditions that are not in compliance with the standards of the ISO. The reduced margin requires approval from the factory.

CAPACITY OF THE SEPARATOR (EXAMPLE)

Calculate the minimum capacity of the system for three 3616 engines. These engines operate at 900 rpm with a published brake specific fuel consumption of 203 g/bkW h. The maximum continuous rating is 4180 bkW. The density of the fuel oil is 950 kg/m³. A separator that uses a controlled partial discharge will be selected.

• N = 3 Engines

• P = 4180 bkW

• b = 203 g/bkW h

• R = 950 kg/m³

• t = 24 hr

• Qmin = 3 x [1.18 x (4180 bkW x 203 g/bkW h x 24 hr) / (950 kg/m³ x 24 hr)

• Qmin = 3,162 Liter per hour

Note: The consumption of additional auxiliary engines or boilers that will use heavy fuel oil from the day tank must be added to the capacity of the separators.

In order to determine the number of separators, divide the minimum capacity of the separators by the maximum flow of the separators. This determination must be made at the given viscosity of fuel oil. Refer to the manufacturer's specifications in order to determine the maximum flow through the separator for a given viscosity. All separators are derated. The derated capacity is based on the viscosity of the fuel oil. (Refer to table 8 for typical derated capacities.)

Table 8

Typical Separator Derates
Fuel Oil Viscosity cSt at 50 °C (122 °F)	Separation Temperature °C (°F)	Maximum Flow Rate (% Of Rated Capacity)
180	95 °C (203 °F) - 98 °C (208 °F)	31
380	95 °C (203 °F) - 98 °C (208 °F)	26
460	95 °C (203 °F) - 98 °C (208 °F)	22
700	95 °C (203 °F) - 98 °C (208 °F)	18

Note: Follow the manufacturer's recommendations in determining the maximum flow rate of the separator. The flow rate of a separator must not exceed the manufacturer's recommendation.

Caterpillar requires the use of one redundant separator in all applications except for single engines. In this case, distillate fuel oil must be available as a backup. Distillate fuel would be used if the separator is down for a prolonged period of time.

SELECTION OF THE SEPARATOR (EXAMPLE)

Select a separator that is capable of cleaning 3162 Liter per hour of fuel oil. This fuel oil has a viscosity of 380 cSt at 50 °C (122 °F). Refer to the ""Capacity of the Separator (Example)" " section of this manual.

The following information is provided by the manufacturer of the separator.

Table 9

Manufacturer Information For 133-0843 Centrifuge Module Group
Viscosity cSt at 50 °C (122 °F)	Capacity (Liter per hour)	Separation Temperature °C (°F)
Rated	16000	-
180	6400	98 °C (208 °F)
380	4200	98 °C (208 °F)
460	3500	98 °C (208 °F)
600	2600	98 °C (208 °F)

Note: Capacities are shown as examples only. Follow the manufacturer's recommendations in order to determine the actual capacity.

Number of separators = [Qmin (Liter per hour)] / [maximum capacity of the separator (Liter per hour)]

Number of separators = (3,162 Liter per hour) / (4,200 Liter per hour)

Number of separators = 0.75 separators rounded up to 1, plus one redundant separator

This example requires two of the 133-0843 Centrifuge Module Groups .

Caterpillar recommends operating the redundant separator during normal operation. Adjust the flow rate of the separators to no more than 110 percent of the consumption of the engine. This change in the flow rate will increase the efficiency of the separator. If one separator is not in operation for a prolonged period of time, the flow of the remaining separator(s) should be increased. The total flow rate of the separators should be no more than 110 percent of the consumption of the engine(s).

The separator should be installed in accordance with the manufacturer's recommendations. Auxiliary equipment for the separator should be provided or approved by the manufacturer.

Quality Specification For Separator Operating Water

Operating water is used in the separator for several different functions: to operate the discharge mechanism and to lubricate and cool mechanical seals, etc. Poor quality of the operating water may cause the following problems: erosion, corrosion and operating problems with the separator. Therefore, the operating water must be treated in order to meet certain demands.

The following fundamental requirements are of great importance.

• Turbidity-free water, solids content <0.001% by volume. Deposits must not be allowed to form in certain areas in the separator.

• Maximum particle size is 50 µm.

• Total hardness must be less than 180 mg CaCO³ per liter, which corresponds to 10° dH or 12.5° E. Hard water may form deposits in the operating mechanism. The precipitation rate is accelerated with increased operating temperature and low discharge frequency. These effects become more severe as the hardness of the water increases.

• The maximum chloride content is 100 ppm NaCl, which is equivalent to a maximum of 60 mg Cl per liter. Chloride ions contribute to corrosion on the surfaces of the separator that are in contact with the operating water, which includes the spindle. Corrosion is a process that is accelerated by the following factors: increased separation temperature, low pH and high concentration of chloride ions. A chloride concentration that is above 60 mg per liter is not recommended.

• The pH must be greater than six. This required level exists because distilled water contains carbon acid and the water has a pH of 5.6. A lower pH indicates an increased acidity. This increased acidity increases the risk for corrosion. The process of corrosion is accelerated by increased temperatures. The process of corrosion is accelerated by a high content of chloride ions.

If these demands can not be met, the water should be pre-treated.

Day Tank

Note: Another common term for a day tank is a service tank.

The operating temperature of the day tank is specific to the installation, and the temperature depends on the design of the fuel system. Automatic regulating valves supply steam to the heaters in the tanks in order to maintain this temperature. This temperature is determined by the sizing of the heaters on the fuel booster module group from the initial design of the engine. Fluctuations in temperature of the day tank may lead to unstable viscosity at the engine and possible separation of the fuel into layers. Overheating the tank may cause separation of the fuel or the buildup of sludge. Overheating could thus result in the rapid plugging of the filter and overheating could result in problems with the injection. These conditions are unacceptable.

The day tank should be maintained at the point of overflow through the continuous operation of the centrifuge. This overflow should then be routed back to the settling tank which is currently in service. Do not route the overflow back to the settling tank which is isolated and settling. Changeover valves are required on the line for the overflow in order to ensure that the flow is correctly directed.

Frequently sample the fuel that is supplied to the day tank. The fuel at this point has been processed by the separators and the fuel is ready to send to the engine. Take a sample from the line that supplies fuel to the tank. This sample is preferable to the sample that is taken directly from the tank.

Fuel Conditioning Module

Fuel conditioning modules (fuel booster module group) should be operated on viscosity control during all normal operations. This automatic sensing and control will account for slight variations in the supply of fuel. These variations in the fuel even occur within a single shipment of fuel. The viscosity control should be properly adjusted in order to account for losses of heat in the engine piping as fuel is delivered. The viscosity of the fuel at the engine must be between 10 cSt and 20 cSt. The temperature of the fuel at the engine must not exceed 135 °C (275 °F).

When the supply of fuel is changed, the viscometer should be monitored throughout the change in order to ensure that the viscosity control is responding correctly. A diagram (Illustration 2) may be used to convert the viscosity to a value at a standard temperature.

The proper operation of the manual or automatic deaeration valve at the deaeration chamber must be carefully checked. If this valve is not correctly operating, air may become mixed with the fuel and the mixture may cause the engine to operate roughly. In extreme cases, the engine may stall. A valve which is stuck open will cause fuel losses. Refer to ""Fuel Conditioning Module Maintenance" ".

At The Engine

Correct fuel temperature is important at the engine. The fuel must be sufficiently preheated before the injectors, or extremely high pressures in the injection system will result. This insufficient preheating will also increase the mechanical load on many components. This same problem will also cause poor atomization of the fuel in the cylinder, and this leads to deteriorated combustion. This problem also increases the thermal load and the mechanical load. The combustion chamber will be fouled and the system for the exhaust gas will also be fouled. Preheating temperatures that are too high may also cause thermal breakdown of the fuel, especially if the fuel contains large amounts of cracked constituents. This thermal breakdown may lead to plugging of the system that is used to treat the fuel, and deposits may also form in the system.

The fuel system components must be carefully operated and maintained continuously. The delivery of clean fuel at the proper viscosity is essential to reliable engine performance. Frequently sample and test the fuel for cleanliness at the engine. These samples should be carefully documented in case future questions arise regarding quality of the fuel or operation of the engine. Immediately resolve any problems, if a discrepancy is detected.

The engine operator must remember that there are no alarms for fuel quality. Only the proper operation and maintenance of the entire system may lead to successful operation of heavy fuel engines. The proper operation also includes the sampling and testing of fuel oil.

Operation And Maintenance

The proper handling and management of fuel oils helps to ensure the successful operation of the heavy fuel engine. This section provides information for the following parameters:

• the fuel analysis laboratories of DNV Petroleum Services Inc. and of Fuel Oil Bunkering Analysis Service (FOBAS)

• exhaust temperature management

• the fuel temperature at the engine and to the unit injector

• the sampling of the heavy fuel oil as bunkered

• the sampling of the heavy fuel oil before the separator

• the sampling of the heavy fuel oil after the separator

• the sampling of the heavy fuel oil at the engine

The sampling interval and the sampling procedure are described in this section. The maintenance of the fuel conditioning module is also included in this section.

DNV And FOBAS Analysis

A fuel analysis is required for all projects. The analysis ensures that the specification represents the actual fuel. In most cases, a fuel analysis by DNV or FOBAS is recommended. These analyses provide more complete information than typical specifications from the supplier. Refer to Table 12 for the standard parameters of an analysis.

Exhaust Temperature

Exhaust port temperatures should be emphasized as a tool for extending the life of an exhaust valve. Exhaust port temperature must be operationally managed to a level below 430 °C (806 °F) with an absolute maximum of 450 °C (842 °F). This temperature will allow the valve to have an acceptable life on heavy fuel oil. Vanadium levels over 300 ppm will require a request for a special rating. A ratio of vanadium to sodium under five will also require a request for a special rating. A high performance aftercooler (HPAC) has been released for the 3616 HFO engines in order to improve exhaust temperatures. Special attention to the cooling system size is required when using the HPAC.

Fuel Viscosity And Temperature At The Unit Injector

The acceptable range of the viscosity at the engine inlet is 10 to 20 cSt. This range of viscosity improves the margin of application of the unit injector. The temperature limit of the fuel at the engine inlet is 135 °C (275 °F).

Fuel Temperature At The Engine

Correct fuel temperature is important at the engine. The fuel must be sufficiently preheated before the injectors, or extremely high pressures in the injection system will result. This insufficient preheating will also increase the mechanical load on many components. This same problem will also cause poor atomization of the fuel in the cylinder, and this leads to deteriorated combustion. This problem also increases the thermal load and the mechanical load. The combustion chamber will be fouled and the system for the exhaust gas will also be fouled. Preheating temperatures that are too high may also cause thermal breakdown of the fuel, especially if the fuel contains large amounts of cracked constituents. This thermal breakdown may lead to plugging of the system that is used to treat the fuel, and deposits may also form in the system.

HFO Fuel Sampling

Regularly sample the fuel in the system in order to ensure the proper operation and the successful operation of the system. This oil sampling is required because of differences in fuel, even within a single shipment. Therefore, do not take samples of the fuel solely when the fuel is delivered.

Note: The following topics should act only as guidelines. The following parameters will dictate variations in the frequency or locations of sampling: on-site conditions, fuel quality, engine performance and performance of the overall system for the fuel.

As Bunkered

Obtain a report of the fuel from the fuel supplier at the earliest possible time. When the fuel becomes available to the operator, take a sample and immediately forward the sample to an independent laboratory. Do not use the fuel until an analysis of the fuel is completed. When these results are obtained, the two reports should be compared. The reports may become the first indication of a fuel with large variances of some parameters internally. The reports may also indicate an error at the laboratory. Immediate retesting is required for inconsistent parameters.

When you bunker the oil, take multiple samples of the fuel in order to verify the consistency of the fuel. The exact number of samples are dependent on the amount of fuel that is bunkered.

If fuel is delivered by trucks, take samples of approximately five percent of the deliveries. Take one sample from one truck out of every 20 trucks. Assume that the fuel in each truck is a large source and a constant source. If the source is considerably smaller, then the sampling should be accordingly adjusted. An independent laboratory should regularly test the samples of fuel for composition throughout the deliveries. Store the remaining samples.

Thoroughly label all the stored samples so that these samples may be easily identified in the future. These stored samples become important if questions arise in the future regarding the following parameters: fuel quality, stability and compatibility. These samples may then be taken from storage so that specific tests may be performed on the samples. These tests depend on the nature of the inquiry.

Before And After Fuel Oil Separator

Take a sample of fuel from the inlet of the separator and take a sample from the outlet of the separator. Take this sample on an alternate weekly basis for engines in continuous operation. Forward these samples to the laboratory for testing in a timely manner. Acquire a sample from pipes before the separator and acquire a sample from the pipes after the separator during normal operation. Keep in mind that this accounts for the total processing of the fuel through all of the separators. If trouble is suspected, sample the fuel before each separator and sample the fuel after each separator independently. These independent samples are preferred to the combined sample.

Sampling At The Engine

Weekly samples should be taken after the final fuel filter. Obtain these samples from a sample valve over a long period of time. This particular method of sampling is the best indication of the total management of the fuel and quality. Since this is the fuel that is actually delivered to the engine, the fuel must be carefully monitored. Any discrepancies must be remedied immediately.

Weekly samples should be taken from different engines in plants with multiple engines.

Note: High quality fuel to the engine is the basis for all reliable engine operations. Proper documentation of the quality of the fuel may greatly increase the reliability of the engine and the life of the component. Pay attention to problems in order to greatly increase the reliability of the engine and the life of the component.

Sampling Interval (Example)

• Type of delivery: 10 × 3616 Power House, fuel delivered by trucks

Weekly sample the fuel in two of the trucks. Send every fourth sample for analysis.

Table 10

Monthly Sampling Schedule
Day	As Bunkered	Before & After Separator	At Engine
1	Test	Test	Test
4	Retain	-	-
8	Retain	-	Test
11	Retain	-	-
15	Test	Test	Test
18	Retain	-	-
22	Retain	-	Test
25	Retain	-	-
29	Test	Test	Test

This example shows the normal oil sampling that is performed during regular operations. Fuel supply changes or concerns over quality would involve additional testing. Under normal conditions, 11 samples are tested per month. Any special observations regarding operations should be noted. Also note the fuel that was in operation at the time.

If very large shipments of fuel are used from a single supply, the number of samples may be slightly reduced once the fuel has proven successful. However, the samples should still be taken from the engine and the samples should be tested regularly.

This may appear costly, but the efficient operation of the engine is dependent upon the collection of these samples. The inefficient operation of the fuel system may greatly reduce the availability of the engine and the output of the engine. This inefficient operation will also increase the maintenance costs.

Recommended HFO Sampling Procedure

There are four primary locations for sampling, but testing is not limited to only these four locations.

• The fuel may be sampled as the fuel is bunkered.

• The fuel may be sampled before the separator, which is located after the settling tank.

• The fuel may be sampled after the separator, which is located before the day tank.

• The fuel may be sampled at the engine, which is located after the final fuel filter.

There are two basic types of samples that can be taken. These two sample procedures are differentiated by the technique that is used to acquire the fluid. The two techniques are called the grab sample and the drip sample.

In order to obtain a grab sample, open a valve and fill a container with the fluid. This technique provides a sample of the fuel at one very short period of time.

In order to obtain a drip sample, take a sample very slowly over a long period of time. Therefore, this technique may be considered to be an average sample of the fluid. This technique provides the most representative result for any tested liquid. Apply this technique to these fluids:fuel, lubricant and water. Illustration 5 shows two possible arrangements for a drip sample.

Illustration 5	g00552472
Drip sample techniques. (1) Tube diameter 4.5 ± 1.5 mm (0.18 ± 0.06 inch) (A) 45 degrees (B) Central (diameter/3) zone in which the probe end is located.

Note: Never take a sample from the filter or take a sample from the connections to the strainer. These connections will inherently show high levels of contamination.

1. Establish a flow of fluid through the pipe. Allow time for the flow to stabilize. This method eliminates oil samplings that show high levels of solids or other false information. These problems are due to the following reasons: the accumulation of sludge in the tank, fuel in the pipes from a previous shipment and other possibilities. Once the flow has been established, the sample valve should be thoroughly purged.

   Note: All samples should be taken in approved oil sample bottles. These oil sample bottles provide good sealing and these bottles provide the proper labeling. The oil sample bottles should be rinsed before you take the actual samples.

2. Set the sample valve to a very low drip rate in order to allow the bottle to fill over a period of approximately 30 minutes. Immediately after the bottle has been filled, the cap should be placed on the bottle. Then attach the seal and the information to the bottle. Refer to Illustration 11 for the form on the sample. Label all of the samples in a similar manner. Include any notes on the performance of the engines with the fuel sample. Also include any notes on the performance of the separators with the fuel sample. Be sure to include these notes, especially if an analysis is performed.

Forward all the samples to the laboratory within 2 or 3 days. The settling of the fluids may give faulty readings even though mixing is performed before the testing.

Table 11

BOTTLE LABEL TO LAB
Name Of Vessel/Site			Owners
Bunkering Port/Site And Date			Sampling Date
Bunker Supplier			Seal No. Supplier
Bunkering Barge Installation			Seal No. Ship
SAMPLING POSITION
Bunker Manifold		Other (Specify)
SAMPLING METHOD
Automatic	Drip	Composite	Other (Specify)
ADVISED BUNKER INFORMATION
Grade	Viscosity		Density
Quantity	Other
SAMPLE REPRESENTS FUEL FOR USE IN:
Main Engines	Auxiliary Engines	Boilers	Other (Specify)
Signature-Supplier's Rep.		Signature-Ship/Site Rep.

Note: Table 11 is a sample of the form that labels the bottle.

Fuel Conditioning Module Maintenance

The following list is the recommended maintenance schedule for the fuel conditioning modules. Refer to the maintenance schedule of the manufacturer for information on the other equipment.

Daily

• Verify and record the difference in the inlet pressure and the outlet pressure of the automatic backflush filter.

• Slightly open all the lines to the transducer and verify the presence of a flow of heavy fuel oil.

• Verify temperature of steam jacket.

• Check for leaks.

• Vent any air that is entrained in the fuel.

• Always follow the maintenance schedule and follow the recommendations of the manufacturer.

Weekly

• Verify the operation of the duplex selector valve.

1000 Hours Of Operation

• Inspect the inside of the bypass filter and clean the bypass filter.

• Inspect the filter elements.

1500 Hours Of Operation

• Install the new filter elements if the filter elements are not already replaced.

3000 Hours Of Operation

• Install the new filter.

Fuel Specification

The recommended fuel specification is similar to IF380. Fuels with higher viscosity up to "International Standard Organization" ISO8217 RMK 55 and "The International Council On Combustion Engines" CIMAC K55.

Note: The addresses of these international organizations are as follows:

International Organization For Standardization (ISO)
1, rue de Varembé
Case postale 56
CH-1211 Genève 20
Switzerland
Telephone: +41 22 749 01 11Facsimile, +41 22 733 34 30E-mail: central@iso.chWeb site: http://www.iso.ch

CIMAC Central Secretariat
Lyoner Strasse 18
60528 Frankfurt
Germany
Telephone: +49 69 6603 1567Facsimile: +49 69 6603 1566

Table 12

Typical Fuel Analysis Parameters
Density (Kg/m3)	Total Sediment Potential	Iron (mg/kg)	-	Aluminum (mg/kg)	Microcarbon Residue
Viscosity (cSt at 50 °C)	Ash (%)	Nickel (mg/kg)	CCAI	Silicon (mg/kg)	Lead (mg/kg)
Viscosity (cSt at 80 °C)	Vanadium (mg/kg)	Calcium (mg/kg)	Aluminum + Silicon (mg/kg)	Sulfur (%)	Zinc (mg/kg)
Water (%)	Sodium (mg/kg)	Magnesium (mg/kg)	Viscosity (cSt at 100 °C)	-	-

Table 13

Recommended "CIMAC G35" and "ISO RMG35" Specifications for Heavy Fuel Oil Caterpillar 3600 Series Engines That Are Configured To Use Heavy Fuel Oil
Characteristic	ASTM Test	ISO Specification	Bunkered Fuel "CIMAC G35" "ISO RMG35"	Fuel that is Delivered to the Unit Injectors
Kinematic Viscosity	"D445"	"3104"	35 cSt at 100 °C (212 °F) maximum	10 to 20 cSt at 135 °C (275 °F) maximum (1)
Density	"D287"	"3675"	(991 kg per m3) maximum at 15 °C (59 °F) (2)
		"12185"
Flash point	"D93"	"2719"	60 °C (140 °F) minimum
Pour point	"D97"	"3016"	30 °C (86 °F)
Carbon residue	-	"10370"	18% maximum (weight)
Ash	"D482"	"6245"	0.15% maximum (weight)	0.10% maximum (weight)
Total sediment after settling	-	"10307-2"	0.10% maximum (weight)
Water	"D1744"	"3733"	1% maximum (volume)	0.1% maximum (volume)
Sulfur	"D3605"	"8754"	5% maximum (weight)
Vanadium (3)	"D3605"	"14597"	300 ppm maximum
Aluminum and silicon	"D3605"	"10478"	80 mg per kg (2)	5 mg per kg
Sodium (3)	"D3605"	-	-	50 ppm maximum
Ratio for vanadium over sodium (Va/Na) (3)	-	-	-	5 minimum
Calcium	"D3605"	-	-	40 mg per kg maximum
Zinc	"D3605"	-	-	10 mg per kg maximum
Asphaltnes	"D1319"	-	-	10% maximum (weight)
Calculated carbon aromaticity index limit (CCAI) (4)	-	-	850 maximum
Water and sediment	"D1796"	-	-	0.1% maximum (weight)

( 1 )	The temperature of the fuel at the fuel inlet to the engine must not exceed 135 °C (275 °F).
( 2 )	This limit is ONLY for engines that have a suitable system for treatment of the fuel.
( 3 )	Compounds of vanadium and sodium are corrosive at high temperatures. See the "Vanadium and Sodium" topic. Consult the factory about fuel that has more than 200 ppm of vanadium. Also consult the factory about fuel that has more than 30 ppm of sodium. Consult the factory in order to ensure that the system for treatment of the fuel and the engine are properly equipped for the fuel.
( 4 )	For applications with loads that are less than 50 percent of the rated output (kW) and for applications with load cycling, the CCAI limit is 840.

Illustration 6	g00552532

Table 14

Maximum Limits for Fuel Specifications Heavy Fuel Oil for Caterpillar 3600 Series Engines That Are Configured To Use Heavy Fuel Oil
Characteristic	ASTM Test	ISO Specification	Bunkered CIMAC K 55	Bunkered RMK 55
Kinematic viscosity	"D445"	"3104"	55 cSt at 100 °C (212 °F) maximum
Density	"D287"	"3675"	1010 kg per m3 (63 lb per ft3) maximum (2)
		"12185"
Flash point	"D93"	"2719"	60 °C (140 °F) minimum
Pour point	"D97"	"3016"	30 °C (86 °F)
Carbon residue	-	"10370"	22% maximum (weight)
Ash	"D482"	"6245"	0.15% maximum (weight)	0.20% maximum (weight)
Total sediment after settling	-	"10307-2"	0.10% maximum (weight)
Water	"D1744"	"3733"	1% maximum (volume)
Sulfur	"D3605"	"8754"	5% maximum (weight)
Vanadium (3)	"D3605"	"14597"	600 ppm maximum
Aluminum and silicon	"D3605"	"10478"	80 mg maximum per kg (2)

( 2 )	This limit is ONLY for engines that have a suitable system for treatment of the fuel.
( 3 )	Compounds of vanadium and sodium are corrosive at high temperatures. See the "Vanadium and Sodium" topic. Consult the factory about fuel that has more than 200 ppm of vanadium. Also consult the factory about fuel that has more than 30 ppm of sodium. Consult the factory in order to ensure that the system for treatment of the fuel and the engine are properly equipped for the fuel.

HFO Refineries

In a simple refinery, fuel oil consists of long residue that is diluted with gas oil. Industrial gas oil will consist of a blend of the following items: kerosene, light gas oil, medium gas oil and heavy gas oil.

The fuel oil in a semi-complex refinery will generally consist of residue that is diluted with thermally cracked gas oil. Some residue and a diluted mixture will generally be incorporated in the fuel oil. The diluted mixture comes from the atmospheric distiller. Industrial gas oil will mainly be thermally cracked gas oil plus some pure material.

Table 15

REFINING PROCESSES
Component	Process Derived From	Feedstock To Process	Principal Aim Of Process
Residues
Long Residue	Atmospheric Distillation	Crude Oil	To extract distillate material
Short Residue	Vacuum Distillation	Long Residue	To extract additional distillate material from crude oil
Thermally Cracked Long Residue	Thermal Gas Oil Unit Or Visbreaker	Long Residue	To maximize gas oil production and/or reduce feedstock's viscosity
Thermally Cracked Short Residue	As above	Short Residue	As above
Propane Asphalt	Solvent Deasphalting Unit	Short Residue	To prepare lube oil bright stock
Butane Asphalt	As above	As above	To prepare feedstock for conversion units
Thermally Cracked Propane/Butane Asphalt	Thermal Cracker	Propane/Butane Asphalt	To extract distillates and reduce feedstock's viscosity
Flashed Cracked Residues	Vacuum Flasher	Thermally Cracked Residue	To maximize production of distillates
Hydrodesulfurised Residues	Hydrotreater	High Sulfur Residues	To reduce residue sulfur content to commercial level
Diluents
Heavy Naphtha Kerosene Light Gas Oil Medium Gas Oil Heavy Gas Oil	Atmospheric Distillation	Crude Oil	See above
Thermally Cracked Kerosene And Gas Oil	Thermal Gas Oil Unit Or Visbreaker	Long Or Short Residue	See above
LCCCO HCCCO Cycle Oil Slurry	Catalytic Cracker	Vacuum Distillate	To produce gasoline blending components
Hydrodesulferised: Gas Oil, Thermally Cracked Gas Oil, and Cycle Oil	Hydrotreater	St. run gas oil cracked gas oil cycle oil	To reduce sulfur content of feedstock

Engine Attachments To Improve Performance

The 3600 Attachment Selection Guide has been modified to include the following list of configuration requirements for 3600 HFO Engines.

The following items are required for all new orders.

Torsional Detection System (723 Plus Digital Governor Control)

All 3600 HFO Engines sold into electrical power generation (EPG) applications will require the use of torsional detection to detect misfire. This requirement is accomplished by installing an additional magnetic pickup on the output side of the torsional coupling. This signal is fed back into the 723 Plus Digital Governor Control or the governor's equivalent. This signal is compared with the signal from the magnetic pickup on the input side of the torsional coupling. The circuitry in the governor compares the two signals and the governor determines if there is a misfire in the engine. The engine then shuts down prior to serious damage. The additional magnetic pickup and wiring have been released as Caterpillar part numbers and may be ordered when either "Low Viscosity Heavy Fuel" or "High Viscosity Heavy Fuel" feature code is selected in the configurator.

Torsional detection is now a requirement. Therefore, all heavy fuel oil 3600 Engines in EPG applications will require the use of the 723 Plus Digital Governor Control and these engines will require the use of the EGB hydra-electric actuator or the actuator's equivalent. The 723 Plus Digital Governor Control is available when the "Gov.Gp. - 723 Plus" is selected as a feature code in the configurator.

Heinzmann Governor

The Heinzmann Governor is not able to provide the torsional detection feature as required. Therefore, this governor is no longer compatible with engines that operate on heavy fuel oil.

Injector Tip Cooling Module

Recommended cooling fluid is 30 wt engine oil. Other fluids may be considered if a special request is made. A single tip cooling module is preferred for each engine. If installations with multiple engines have the tip cooling modules, there is a risk of contaminating the cooling fluid of all the engines. This contamination will occur if an injector develops a leak into the tip cooling circuit. A Custom Quote Request must be submitted for this attachment.

Separate Circuit Cooling System

All HFO Engines require a separate circuit cooling system with regulators that are set at a water temperature of 32 °C (90 °F) for the AC/OC circuit. Combined circuit cooling only provides water at a temperature of 50 °C (122 °F) to the aftercooler/oil cooler (AC/OC) circuit. The separate system may provide water at a temperature of 32 °C (90 °F) to the aftercooler (AC). This lower water temperature lowers the exhaust gas temperatures. Low exhaust gas temperatures prevent the vanadium in the fuel from damaging the exhaust valve. This separate circuit system is available by selecting the "Separate Circuit" feature code in the configurator.

High Volume, Normal Duty Air Cleaners

All HFO Engine installations are required to use the high volume, normal duty air cleaner because of the additional air flow requirements. These air cleaners may be selected by choosing one of the following feature codes in the configurator:

• "ACL-Standard Duty-High Vol-Hor"

• "ACL-Standard Duty-High Vol-Ver"

• "Air Cleaner-Heavy Duty"

For applications in dusty environments, oil bath air cleaners are required. These cleaners are recommended in order to reduce the operating costs and the maintenance costs in all other applications.

Three Element Oil Cooler

In order to provide adequate oil cooling to the Vee configured HFO Engines, a three element oil cooler is standard, except on front mounted turbocharger arrangements. Due to the contaminants present in the HFO Engine and the dispersion of these contaminants to the lubrication oil, a thicker lube oil film between the bearings and journals is required. Use a lube oil of higher viscosity to provide this oil film. The three element oil cooler keeps the lube oil temperature low which keeps the lube oil viscosity high. This oil cooler configuration is available by selecting code 125.2 in the Quoter.

Exhaust Stack Height

The height of the exhaust stack may have a significant effect on the life and the reliability of the components of the air inlet. Exhaust contaminants, such as sulfur dioxide, must be dispersed into the atmosphere well away from the engine air inlet. Contaminants in the exhaust may clog the following components and these contaminants may cause premature failures: air filters, turbochargers and aftercoolers. All EPG HFO 3600 Engine applications are required to have an exhaust stack height of at least 2.5 times the height of the building that houses the generator set. This industry standard may be found in more detail in the "Marks Engineering Handbook". A study of the dispersion may also be used to determine the correct height of the exhaust stack.

Engine Protection

The following items are required for all HFO engine orders: shutdowns, alarms and derates. The "Gen Set" and "HFO Option" feature codes will automatically be selected in the configurator on heavy fuel applications. Submit a Custom Quote Request (CQR) for the required additions to the upgrade for the protection system on HFO engines. Refer to the following lists:

Shutdowns

• AC/OC coolant temperature high

• Air inlet manifold temperature high

• Crankcase pressure high

• Engine overspeed

• Generator bearing temperature high

• Generator stator temperature high alarms

• Lube oil filter differential pressure high

• Lube oil to jacket water differential temperature high

• Lube oil metal particle detection

• Lube oil pressure low

• Lube oil temperature high

• Jacket water detection (loss)

• Jacket water outlet temperature high

• Raw water pressure low

• Torsional detection

Alarms

• AC/OC coolant temperature low

• AC/OC inlet water pressure low

• AC/OC inlet water temperature high

• Air starting pressure low

• Boost (air inlet manifold) temperature high

• Boost (air inlet manifold) pressure high

• Crankcase pressure high

• Exhaust port temperature deviation high

• Exhaust manifold back pressure high

• Exhaust turbocharger inlet temperature high

• Fuel filter differential pressure high

• Fuel pressure low

• Fuel temperature high (DO)

• Fuel temperature low (HFO)

• Generator bearing temperature high

• Generator stator temperature high

• Jacket water expansion tank level low

• Jacket water inlet pressure low

• Jacket water temperature high

• Lube oil centrifuge fault

• Lube oil filter differential pressure high

• Lube oil pressure low

• Lube oil sump level high

• Lube oil sump level low

• Lube oil temperature high

• Metal Particle Detection

• Raw water pressure low

• Speed pickup failure

• Torsional detection

• Turbocharger speed (left) high

• Turbocharger speed (right) high

• Unit injector tip coolant pressure low

• Unit injector tip coolant temperature high

Derate Strategy

• AC/OC water temperature high

• Boost (air inlet manifold) pressure high

• Boost (air inlet manifold) temperature high

• Exhaust port temperature deviation high

• Generator stator temperature high

• Jacket water temperature high

• Lube oil centrifuge fault

• Lube oil temperature high

• Raw water pressure low

• Torsional detection

• Turbocharger speed high

Additional requests can be quoted for the following items: shutdowns, alarms and derates.

Combined Heat And Power (CHP)

An HFO Engine may benefit from the installation of Exhaust Gas Boilers (EGB). The steam provided by the EGB may be used for the equipment in the plant and for operations in the tanks. The additional steam may also be provided to other equipment. Feedwater Heat Exchangers may also be used for the engine jacket water system to improve overall efficiency.

The steam system should have condensers in order to condense the excess steam when the demand for steam is lower than normal, but the production of power is still high. The condenser is recommended over the conventional diverter valve. Diverter valves are prone to failure due to the excessive heat and pressure pulses.

Never combine two engine exhaust systems into a single exhaust gas boiler. Operation of only one unit may result in feeding the exhaust back into an engine that is not operating. The exhaust will form sulfuric acid, and the sulfuric acid will attack the internal components of the engine.

Each EGB should have a soot blowing steam system for auto cleaning during continuous engine operation.