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FUEL SYSTEM TANKER (HEAVY FUEL OIL SYSTEM)

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FUEL SYSTEM TANKER (HEAVY FUEL OIL SYSTEM)

FUEL SYSTEM TANKER (HEAVY FUEL OIL SYSTEM)

The fuel system is a system used to supply fuel needed by the main motor. This fuel system is designed for two types of fuel, namely: MDO (marine diesel oil) and HFO (heavy fuel oil). 

a. How the Fuel System Works

This fuel system generally consists of fuel oil transfer, filtery and purifering; fuel oil circulating, fuel oil supply, and heater. Fuel on ships is stored in storage tanks. The heating coil must be installed on the bunker tank so that the fuel temperature on the bunker tank can be maintained at a temperature of 40 – 500C. From the fuel bunker it is pumped to the settling tank, where before entering the fuel pump the strainer will go through to filter out the impurities. 
The settling of the tank is also heated and the temperature is maintained in the range of 50 – 700C. Then from the settling tanks pumped into centrifuges to clean it from dirt and water. Then after the centrifuges go into the service tank From the service tank, the fuel is flowed towards the supply pump which has a pressure of 4 bars. 
This supply pump is also called the low-pressure part of the fuel circulating system. To avoid the formation of gas / air in the fuel, a venting box is installed .. The Venting box is connected to a service tank through an automatic deaerating valve which is tasked to free gas / air that is present and will hold liquid / liquid.
From the low-pressure part of the fuel system (supply pump), the fuel is then channeled to the circulating pump which will pump the fuel through the heater (to be heated to 1500C) and the full flow filter (filtering) to then enter the main motor. To ensure sufficient supply of fuel, the capacity of the circulating pump is made greater than the amount of fuel consumed by the main motor. And the excess fuel will be recirculated from the motor through a venting box which will then go to the circulating pump again.
To ensure constant pressure on the injection pump on all main motor workloads, Spring Loaded Overflow is installed in the engine fuel system. The fuel pressure that enters the engine must be 7-8 bars, equivalent to the pressure on the circulating pump which is equal to 10 bars. 
When the engine stops, the circulating pump will continue to work to circulate the Heavy Fuel that has been heated and keep going through the fuel oil system engine with the aim of keeping the fuel hot and the fuel valve still rated. 

b. Fuel Oil Description 

In constant engine operation, the engine must use heavy fuel. If this recommendation is not done, then Latent risk will occur or hidden damage to the quality  (even if it is of small value) diesel oil and heavy fuel is the formation of an imperfect mixture during fuel replacement. For this reason, manufacturers strongly recommend not using 
diesel oil for engine operation at all workloads. 
In special circumstances, the use of diesel oil is allowed and needed and can be done at any time when the engine is not operated. This replacement becomes necessary for a moment. In this use, the ship is required not to work or stop for a long time with cold engine conditions.
These conditions are: 
– When the ship is docking
– Stop for more than 5 days 
– Perform repairs on the main fuel system 
– Environmental conditions that occur. 
The fuel specifications (HFO) used by the S 26 MC engine based on MAN BW recommendations (S26MC Project Guide, 6.02.06) are as follows: 

c. Engine Acessories
If there is, a built-in overflow pump must be installed on the supply pumps and set to a pressure of 5 bar and there is also an external by-pass valve set at a pressure of 4 bar. Piping between tanks and supply pumps must have a path of at least 50% greater than the pipe between pupply pump and circulating pump. On the engine there is a quick-closing valve on the “X” inlet. Installation of this valve is highly recommended by MAN-B & W to stop engine work (Stop the engine immediately), especially during quay and sea trial. The main purpose of the “AF” drain is to collect pure fuel from the umbrella sealing system, which is from fuel leakage from high pressure pipes. The liquid in this drain is flowed to the tank and can be pumped back to the HFO service tank or to the settling tank.

d. Definition of Equipment
In the fuel system of the MAN B & W engine there are a number of equipment that support the system, including: 
1) System Transfer, Filtering and purification
This system is responsible for transferring fuel from storage tanks to settling tanks, and cleaning fuel from impurities originating from storage tank. Heavy fuel oil must be cleaned first by passing it through a centrifuge before entering the daily tank. In the centrifuge the impurities found on HFO which consist of particles and water will be separated from HFO. 

i. Storage Tank / bunker / storage tank 
Is the main tank of all the fuel needed by the main motor during sailing. 

ii. Settling tank
This tank is designed to be able to precipitate dirt and water that is carried by the fuel. Tank settling capacity is designed to be able to supply minimum fuel for 24 hours (I days) of engine operation when the settling tank is fully filled. Tank design is made so that the removal of dirt / sediment and water can be carried out efficiently. 

iii. Filter 
Filter is a device that functions to filter out impurities mixed in the fuel. 

iv. Heater tank (Heating tank) 
Is a fuel heater, so that it can maintain the desired viscosity of the fuel in accordance with the specifications. 

v. FO Fuel Transfer Pump The 
pump used is the gear pump which functions to drain fuel from the storage tank to the settling tank to be deposited.

vi. FO Feed Pump 
Serves to move the fuel from the Setling tank to the service tank. The pump used is a gear type pump. 

vii. Centrifuges 
Centrifuges function to separate fuel with clean water and fuel flowed into the service tank while dirt and water are channeled to the sludge tank. Centrifuges are principally equipped with 2 sets of the same type where 1 set is used for service and the second is stand-by. 

2) Fuel Oil Circulating and Fuel Oil Supply
System This system is responsible for supplying fuel to the engine. This system is better known as the “Fuel Oil Supply Unit”. 

i. Tank Service
Is a tank that serves to supply fuel to the engine during operation and has a capacity of 8-12 hours. This tank is equipped with a tank shaking. This heating aims to maintain HFO viscosity. 

ii. Three Way Cock. 
This valve is used when there is a change in fuel supply to the main engine from HFO to MDO or vice versa. 

iii. Supply Pump The 
pump used is a screw or gear type pump. This pump sucks fuel from the service tank. The pump used is a screw wheel or gear wheel. The requirements for the pump are: 
Fuel oil viscosity, specified up to ……… 700 cSt at 500C 
Fuel oil viscosity maximum …………………… 1000 cST 
Fuel oil flow ……………………………………… 0.6 m3 / h 
Pump head …………………………………………… .4 bar
Delivery pressure …………………………………… .4 bar 
Working temperature ……………………………… .1000C 
Because this pump is used to drain liquid with a high temperature then before being operated first first done heating before the pump is run. 

iv. Circulating Pump 
This pump functions to continue transporting fuel from the supply pump and also from the venting box. The pump used is a screw wheel or gear wheel. The requirements for the pump are: 
Fuel oil viscosity, specified up to ……… 700 cSt at 500C 
Fuel oil viscosity is normal …………… .. …………… ..20 cSt 
Fuel oil viscosity maximum ………………… 1000 cST 
Fuel oil flow ………………………………………… 2 m3 / h 
Pump head …………………………………………… .6 bar 
Delivery pressure …… …………………………… .10 bar
Working tempereture ……………………………… 1500C 
Because this pump is used for the flow of liquid with high temperature, before it is operated it is first warmed up before the pump is run. 

v. Fuel oil heater 
Serves to heat the fuel before it enters the engine according to the recommended temperature. The heater type used is a tube type or plate heat exchanger type. Heater must be able to work at: 
Recommended viscosity meter setting ……… .10-15 cSt 
Fuel oil viscose, specified up to ……… 700 cSt at 500C 
Fuel oil flow ……………………………………… … 2m3 / h 
Heat dissipation ……………………………………… kWh 
Pressure drop on oil side ……………… maximum 1 bar 
Working pressure … … …………………… ………… 1500C
Fuel oil inlet temperature ………………. approx. 1000C 
Fuel oil outlet temperature ………………… … 1500C 
Steam supply, saturated …………………… 7 bar abs. 

vi. Fuel flow filter The 
filter used can be a duplex type with manual cleaning or automatic filter with manual cleaning by-pass filter. The specifications are as follows: 
Fuel oil filer must be based on HFO with: 130 cSt at 800C = 700 
cSt at 500C = 7000 sec Red-wood l / 100 0F. 
Working pressure ………………………………… 10 bar 
Absolute fineness ………………………… .. ……… 50μ m 
Working temperature ………………… maximum 1500C 
Oil Viscosity at working temperature …………… .15 cSt 
Pressure drop at clean filter ………… maximum 0.3 bar 

vii. Fuel oil venting box.
Duty to free the gas / air that is available and to hold liquid / liquid 

viii. Auto de-aerating tank 
Is the equipment used to separate the remaining fuel from the main engine output, liquid fuel enters the venting box while the steam-shaped fuel is supplied to the service tank

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