CAPITULO II PLANTEAMIENTO OPERACIONAL
3. ESTRATEGIASDE RECOLECCION DE DATOS
Onboard water content is tested by using a calcium carbide. The tested is carried out by mixing 5ml of oil with 15ml of a petroleum reagent (paraffin, toluene). The two liquors are thoroughly mixed and then a measured amount of reagent (calcium carbide) is placed on floating on the oil/reagent surface. The test unit is sealed and thoroughly mixed to bring all liquids together. If water is present the carbide will produce acetylene gas, and the resultant pressure rise will indicate the level of water contamination.
185. What is the material of a boiler valve?
Valve body: Cast Steel
Spindle, valve seat, valve disc and other parts: Monel Metal, Bronze or stainless steel 186. What will be the effect of water in fuel oil?
The effects of water content on fuel oil are a. Loss of calorific value of the fuel oil
b. Corrosion in the lines, fuel pump (plunger/barrel), injectors
Class4exam.com Register Yourself In Our Forums c. Water in oil can lead to vapor lock in the line leading to fluctuating engine RPM,
seizure of fuel pumps
d. In case of seawater contamination, it would lead to high temperature corrosion in the exhaust system
e. Results in increased cylinder liner wear
f. Cause increased fouling of the exhaust gas ways and turbocharger blades 187. What are actions you would take if a purifier starts overflowing?
Some or all of the following should be checked for in case the purifier overflowing:
a. Sealing water low
b. Excessive fuel back pressure
c. Low pressure, chocked water line (check the water filter) d. Gravity disc oversized for the density of the fuel oil in question e. Oil temperature high
f. Excessive sludge deposition inside the purifier bowl g. Excessive feed rate
h. Sealing ring damaged (between the Bowl and Hood) i. Check RPM and direction of rotation of bowl j. Leaking three-way valve
188. How do you calculate the specific fuel oil consumption?
a. Take the fuel oil flow meter readings for a specific time interval usually for an hour b. Calculate the volume (difference between the above readings)
c. Using the fuel oil sample test results provided by the shore facility, calculate the density of the fuel oil at the temperature near the flow meter
d. Calculate the mass of the fuel consumed by multiplying the results in b and c e. Calculate the shaft power of the engine during this interval of time, take an average
value
f. Specific fuel consumption is calculated by mass of fuel consumed/Avg.shaft power
developed by the engine in the time interval.
Express the result in the Units of specific fuel oil consumption: g/Kw-h 189. How do you calculate the shaft power of main engine?
[Procedure for MANBW Engines]
During an interval of time, 1Hour measure engine a. Fuel index of each unit
b. Engine RPM
c. Scavenge Air temperature
d. Ambient air temperature (Engine Room Temp.) e. Fuel oil preheating temperature
f. Obtain the specific gravity of the fuel oil at 15˚C, its sulfur content & Lower calorific value
g. Obtain the cylinder constant (engine data)
Calculate the average fuel pump index, Pθ = sum of all individual fuel index/total number of cylinders.
Corrected fuel index, Pθ‟ = average fuel index x K Where K = Correction factor for fuel pump index
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= K X K X specific gravity of fuel @ 15˚C
An example of calculation is shown with the following data to calculate K, Hence Pθ‟
Lower calorific value of fuel: 9700Kcal/Kg, Specific Gravity @ 15˚C: 0.947, Preheated Temperature: 104˚C, Engine room temperature: 30˚C, Scavenge air temperature:
32˚C K1 = 0.953, K2 = 0.926
K = K1 x K2 x Sp.Gr. @ 15˚C = 0.836. Hence Pθ‟ = Pθ x K 1 2
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Mean Effective Pressure Pe = Horizontal coordinate in the above graph
Brake Horse Power (BHP) = C x Pe x Ne
Where C = Cylinder coefficient = 8.811 for 6S60MC MANBW engine Pe = Mean Effective Pressure
Ne = Engine RPM
OUT PUT OF THE ENGINE (Shaft Power in Kw) = BHP x 0.7355
190. What is P-Alkalinity and T-Alkalinity?
P-Alkalinity: phenolphthalein is less alkaline than hydroxides or carbonates, and when it is added to a sample containing hydroxides and or carbonates it will first neutralize the hydroxides forming salts, it will turn pink in color. The acid used after this coloration will first neutralize the hydroxides forming salts, it will then react with the carbonate molecules present forming bicarbonate molecules. Bicarbonate molecules are less alkaline than phenolphthalein, hence, the pink coloration disappears once all the hydroxides and
carbonates have been dealt with by the acid. One bicarbonate molecule is formed from two carbonate molecules, hence in the test the quantity of acid used is a measure of the alkalinity due to the hydroxides (caustic) present and half the carbonates.
T-Alkalinity: Methyl-orange indicator is less alkaline than phenolphthalein and bicarbonates.
It can be used initially in place of phenolphthalein or in continuation after the alkalinity to phenolphthalein test. If no yellow coloration results when the methyl-orange is added to the alkalinity to phenolphthalein sample no bicarbonates are present. Hence no carbonates are present. Therefore, the alkalinity as determined in the alkalinity to phenolphthalein test has been due to hydroxides alone.
191. What is the difference between an over speed governor and a constant speed governor?
If within a governor, an over speed detection/actuation mechanism is provided to trip the engine in case of over speeding and or rapid increase of speed then the governor is called an over speed governor. These were the obsolete governors and commonly had fly or bob weights restrained by spring. When the engine exceeds a predetermined speed, the weight moves out to strike some form of fuel cutoff.
Governors designed to maintain the engine speed at the set point are called constant speed governors. These are also referred to as isochronous governors like the ones usually installed on COPT and main engine.
192. What are the properties of steering gear lube oil?
a. Satisfactory flow properties b. High viscosity index c. Low compressibility d. Good lubricating properties e. Low vapor pressure
f. Compatibility with system materials g. Chemical stability
h. Protection against corrosion
i. Rapid air-release and water separation j. Good thermal conductivity
k. Fire resistance (desirable)
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193. What is the material of connecting rod bolt? What is the importance of elongation? What is the nature of stresses in this component and why should these bolts be replaced after some time in service?
The connecting rod bolt in service is subjected to:
a. A dynamic tension loading due to centrifugal force of the mass of connecting rod rotating with the crank pin
b. A dynamic tension loading owing to inertial forces of the reciprocating mass of the piston which is fluctuating with angular displacement of the crank and having the peak value at an instant of 360˚ after the firing TDC in a cycle of operation c. A dynamic shear stress at the parting of the two halves of the bearing housing Dowel pins with fitted bolts or serrations at the face or both are used to reduce shear loading on bolts and possibility of fretting.
Bolts should be constructed of materials having high resilience and should not be stiffer w.r.t bearing housing.
Pretension of the bolts should be regarded as the single most important factor which contributes towards the fatigue life of the material of the bolt. Pretension must be kept high enough, so that the increase in stress owing to dynamic loading remains within the range of stress already given by pretension.
Some routine checks on this part are (rejection criteria of the bolt)
a. Check for corrosion by acidic lube oil, discard if any present on shanks
b. Check the length of the bolt against a new or bolt tolerances. If longer, yielding of the material should have taken place. Renew the bolt in this circumstance
c. Check for mechanical damage, especially on shanks d. Check for fractures by NDT
e. Check the landing faces for uneven tightening
f. Discard the bolt when either designated life, over speed failure or piston seizure has occurred
194. What are the bunker specifications? What changes would you make in the event of a bad bunker?
THE INTERNATIONAL STANDARD
In 1982 the working group responsible for the development of the international standard issued a draft proposal which became ISO 8217 Petroleum products – Fuels (Class F) – Specification of marine fuels. Another draft proposal was issued at the same time which became ISO 8216 Petroleum products – Fuels (Class F) – Classification Part 1 – Marine Fuels. In 1987 the first edition of the international standard was published followed by the publication of BS MA 100 in 1989, which was identical to the International Standard. The second edition of ISO 8217 was issued in 1996 and this is denoted as ISO 8217 : 1996.
Table 1 from ISO 8217
Limi Category ISO - F
Characteristic t DMX DMA DM DMC
B
Appearance Visual -
-Density at 15°C, kg/m Max 890. 900 920.
Viscosity at 40°C, mm /s*
0 .0 0
Min 1.40 1.50 -
-Max 5.50 6.00 11. 14.0
0 3
2
Flash point, °C Min 43 60 60 60
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Winter quality Max - -6 0 0
Summer quality Max - 0 6 6
Cloud Point, °C Max -16 - -
-Sulfur, % (m/m) Max 1.0 1.5 2.0 2.0
Cetane Number Min 45 40 35
-Carbon residue, (micro method,
10% (v/v) Max 0.30 0.30 -
-Distillation bottoms), % (m/m)
Carbon residue, (micro method, Max - - 0.3 2.50
10% (m/m) 0
Aluminium & silicon, mg/kg Max - - - 25
* mm² / s = cst Distillate Fuels
There are four grades of marine distillate fuels – DMX, DMA, DMB AND DMC. The
„DM‟ denotes „Distillate Marine‟ and the third letter distinguishes the different grades.
Grade DMX is a pure distillate used for emergency equipment external to the machinery space. Grade DMA is the equivalent of a gas oil and is also a pure distillate. Grade DMB is equivalent of a clean diesel, although it may contain some residue giving it a black color.
This means that an appearance test cannot be used on DMB as it is for grades DMX and DMA. Grade DMC relates to a blended diesel oil which contains a residual component, normally up to 10 %
Viscosity
Grades DMX and DMA have a specified minimum viscosity to ensure the fuel has sufficient lubricity.
Flash Point
The flash points for marine fuels is determined by the closed cup method corresponding to the opening of a previously closed vessel. The minimum flash point is 60°C for all fuels within the machinery space of a merchant ship classed for unrestricted service, as laid down by SOLAS national and classification regulations. Grade DMX, used for emergency equipment external to the machinery space, must have a flash point greater than 43°C. It should be noted in some countries gas oil and diesel oil are produced for local land based market to a national specification. A minimum flash point is usually included in such a specification, however, this value may be below that required by international legislation for normal marine use.
Pour and Cloud Point
The pour point parameter specifies a winter and summer quality temperature. Normally vessels burning DMA, DMB, and DMC do not have tank heating. Purchasers should ensure the pour point is suitable for the equipment on board, particularly if a vessel is operating in both Northern and Southern hemispheres.
The cloud point is the temperature at which wax begins to crystallize from a clear distillate fuel. These wax crystals will cause rapid filter blockage. This parameter is only applicable to
Class4exam.com Register Yourself In Our Forums grade DMX and is a technical limitation so that emergency equipment can start and
operate at an ambient temperature of –15°C.
Ignition Quality
The Cetane number is the measure of the ease of ignition of a distillate fuel determined by a special engine test with a variable compression ratio. The higher the number the easier it is for fuel to ignite in the engine.
The Cetane index is an empirical measure of ignition quality for distillate grades of fuel.
This index is calculated in a number of ways, such as from the mid-boiling point and density. Bear in mind, these empirical equations do not take account of any cetane index improver which may have been added in the manufacture of the fuel.
Sediment
The sediment test for the DMB is sediment by extraction which defines the insoluble residues remaining after extraction of the fuel by toluene. For the blended diesel grade DMC, the sediment test specified is the Total Existent Sediment. This is the combination of inorganic and hydrocarbon sediments existing in fuel when delivered. This test is aimed at limiting the maximum amount of sludge present that could be separated by the filters or centrifuges.
Catalyst Fines
In distillate fuels the elements vanadium and aluminium, plus silicon for grade DMC,
relate to he residual component of the blend.
RESIDUAL FUELS
From table 2, ISO 8217 : 1996, there are fifteen grades of residual fuel which are distinguished by three letters and two numbers. The first two letters are common to all residual grades, „RM‟ denotes „Residual Marine‟, and the third letter refers to the characteristic of the fuel. The two numbers are the viscosity of the fuel at 100°C. Grade RMA relates to a residual fuel which normally does not require tank heating because of the defined low pour point. Other residual grades require tank heating as they may have a considerably higher pour point as defined in the specification.
ISO FUEL STANDARD 8217, 1ST REVISION 1996, FOR MARINE RESIDUAL FUELS
RMA RMB RMC RMD RME RMF RMG RMH RMK RMH RMKRM LRMH RMK RML CHARACTERISTIC UNITSLIMIT 10 10 10 15 25 25 35 35 35 45 45 45 55 55 55
DENSITY @ 15°C kg/m Max 975 981 981 985 991 991 991 991 1010 991 1010 - 991 1010 -VISCOSITY @ 100°C mm2/SMax 10 10 10 15 25 25 35 35 35 45 45 45 55 55 55 APPROX VISC. @ 50°C *mm2/s 50 50 50 100 225 225 390 390 390 585 585 585 810 810 810 FLASH POINT °C Min 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 POUR POINT, WINTER °C MAX 0 24 24 30 30 30 30 30 30 30 30 30 30 30 30 POUR POINT, SUMMER °C Max 6 24 24 30 30 30 30 30 30 30 30 30 30 30 30
MCR %m/m Max 10 10 14 14 15 20 18 22 22 22 22 -- 22 22
--ASH %m/m Max 0.1 0.1 0.1 0.1 0.10 .1 50.15 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2
WATER % V/V Max 0.5 0.5 0.5 0.8 1 1 1 1 1 1 1 1 1 1 1
SULFUR %m/m Max 3.5 3.5 3.5 4 5 5 5 5 5 5 5 5 5 5 5
VANADIUM mg/kg Max 150 150 300 350 200 500 300 600 600 600 600 600 600 600 600 ALUMINIUM & SILICON mg/kg Max 80 80 80 80 80 80 80 80 80 80 80 80 80 80 80 TOTAL SEDIMENT POT %m/m Max 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1
Density
Grades RMA 10 to RMA 15 have a restricted density so as to give acceptable ignition quality characteristics when empirically determined from either the Calculated Carbon Aromaticity
Class4exam.com Register Yourself In Our Forums Index (CCAI) or Calculated Ignition Index (CII). The density limit of 991 kg/m³ at 15°C is the technical limit for the efficient removal of water by a centrifuge set up as a purifier operating with a water seal. Three grades (RMK 35, 45, 55) have a density limit of 1010 kg/m³ which are suitable for vessels with fuel treatment plant capable of receiving such densities. The two grades with no density limit (RML 45, 55) are intended for machinery installations where the fuel treatment plant does not include centrifuges, namely a steam ship.
Viscosity
The below table shows the approximate equivalent viscosities at 50°C to those shown in table 2. The data in the below table.
cSt
Kinematic viscosity @ 10 15 25 35 45 55
100°C
Kinematic viscosity @ 50 100 225 390 585 810
50°C
Carbon residue
The carbon residue of a fuel depends on the refining processes used in the manufacture.
Two grades have no defined carbon residue or density limit (RML 45 and RML 55), a maximum of 22 per cent m / m applies to Rmh, RMK, 35, 45, and 55, while a limit of 18 per cent m / m applies to RMG 25. The lower limits for viscosity grades 10, 15 and 25 reflect the use of diluents to cut back heavy residual fuel to produce light intermediate fuel.
Ash
In general there is a relationship between the specified ash level in a residual fuel and that for vanadium. This is because vanadium is the major ash forming component in residual fuel.
Water
The specification limit for water in residual fuel is based on traditional limits.
Excessive water represents a loss of energy to the fuel purchaser, potential engine operational problems and possible waste disposable problems.
Sulfur
Sulfur limits in residual fuel provides guidance to lubricant suppliers as to the level of alkalinity required to neutralize corrosive compounds originating from the combustion of sulfur.
Vanadium
The level of vanadium in residual fuel depends on the source of crude oil and the refining process used in manufacture. On a global basis this varies considerably, from 50-100mg / kg to over 500mg / kg, and the specification differentiates between low and high vanadium fuels, such as RME 25 and RMF 25.
Catalyst Fines
The purpose of a control for aluminium and silicon is to limit the amount of catalyst fines delivered with the fuel. Globally, the composition of catalyst fines varies considerably and can be controlled using limits for aluminium and silicon, considered better than the historical method of just controlling the level of aluminium.
Sediment
Total Sediment Potential (TSP) provides a measure of the stability of a fuel.
Following are the points to be looked at when using new bunker
a. Start consuming the fuel only after the fuel analysis report from a shore lab with recommendations is available
b. Bunkers should be stored in the bunker tanks above the minimum transferable temperature mentioned by the shore lab
Class4exam.com Register Yourself In Our Forums c. A watch should be kept on the line filters/strainers soon after changing over. Clean
the filters and ensure no excessive debris
d. Ensure that fuel oil transfer pump is in good operating condition
e. Monitor the purifier / clarifier operation and make adjustments if problems arise like considering another gravity disc if the purifier starts overflowing
f. Make adjustments like decreasing purifier throughput, preheating temperatures or operating the purifiers in parallel / series inline with the analysis report
g. Frequently drain the settling and service tanks to asses the amount of water in the fuel and take further steps in line with the findings like increasing / decreasing desludging intervals
h. Monitor the line filters/strainers before pumps viz. purifier feed p/p, booster pump and circulating pump
i. Adjust the back flushing interval of the automatic fuel oil filter based on the findings j. Adjust the viscotherm to attain the recommended viscosity prior engine inlet
(altered preheating temperature) k. Adjust VIT/FQS if required
l. Cylinder lubrication, sometimes the scavenge air and JCFW out let temperatures may be required to be altered if the sulfur content warrants the changes
m. Low load operation of the engine should be limited incase the fuel report shows high CCAI value
n. Exhaust gas economizer soot blowing & cleaning interval may have to be reduced if the Conradsen number, CCAI, ash, water content is high. Boiler water circulating temperature should be monitored so as to ensure that economizer operates above pinch point
o. Fuel injectors/exhaust valve overhaul intervals may also be altered basing on high ash, sodium/vanadium, Conradsen number, asphaltenes and CCAI values
p. Soon after the engine is put to consume new bunkers take the performance of the engine with draw cards to ensure good health of the engine. Further changes in fuel injection settings may have to be effected if the indicator card diagrams show deviation
195. How do you select a gravity disc of a purifier?
Makers nomogram is an aid to select a tentative gravity disc in purification, when the density of the oil at a temperature of 15˚C is known.
The hole diameter of the first gravity disc to be tried appears directly from the nomogram.
However, in practical operation the best result is obtained by using the gravity disc with the largest hole diameter that will not cause a break of the liquid seal in the bowl or an emulsification in the water outlet.
The presence of seawater may demand the use of a gravity disc with larger hole than indicated in the nomogram. (the nomogram is based on the properties of fresh water) The nomogram consists of two graphs arranged in series, one consists of density of fuel at 15˚C Vs Separating temperature and the other graph is divided into different zones of disc hole diameters against through put of the purifier.
196. Explain running direction interlock
Running direction interlock is provided to withhold the fuel supply during maneuvering if the running direction of the engine is not coincident with the setting of the engine
Running direction interlock is provided to withhold the fuel supply during maneuvering if the running direction of the engine is not coincident with the setting of the engine