The heater is to be of the tube or plate heat ex- changer type.
The required heating temperature for different oil viscosities will appear from the ‘Fuel oil heating chart’. The chart is based on information from oil suppliers regarding typical marine fuels with vis- cosity index 7080.
Since the viscosity after the heater is the control- led parameter, the heating temperature may vary, depending on the viscosity and viscosity index of the fuel.
Recommended viscosity meter setting is 05 cSt. Fig. 7.05.01: Fuel oil heating chart
Fuel oil viscosity specified ... up to 700 cSt at 50°C Fuel oil flow ... see capacity of fuel oil circulating pump Heat dissipation ...see ‘List of capacities’ Pressure drop on fuel oil side ...maximum bar Working pressure ...0 bar Fuel oil inlet temperature ...approx. 00 °C Fuel oil outlet temperature ... 50 °C Steam supply, saturated ...7 bar abs To maintain a correct and constant viscosity of the fuel oil at the inlet to the main engine, the steam supply shall be automatically controlled, usually based on a pneumatic or an electrically controlled system. 4EMPERATURE AFTERæHEATER # .ORMALæHEATINGæLIMIT !PPROXIMATEæPUMPINGæLIMIT C34# SEC2Wæ& C34# !PPROXIMATEæVISCOSITY AFTERæHEATER C3T SEC 2W 178 06 280.1
MAN Diesel
MAN B&W MC/MC-C engines,
MC/ME Engine selection guides 198 47 35-0.1
Fuel oil filter
The filter can be of the manually cleaned duplex type or an automatic filter with a manually cleaned bypass filter.
If a double filter (duplex) is installed, it should have sufficient capacity to allow the specified full amount of oil to flow through each side of the filter at a given working temperature with a max. 0. bar pressure drop across the filter (clean filter). If a filter with backflushing arrangement is installed, the following should be noted. The required oil flow specified in the ‘List of capaci- ties’, i.e. the delivery rate of the fuel oil supply pump and the fuel oil circulating pump, should be increased by the amount of oil used for the backflushing, so that the fuel oil pressure at the inlet to the main engine can be maintained during cleaning.
In those cases where an automatically cleaned filter is installed, it should be noted that in order to activate the cleaning process, certain makers of filters require a greater oil pressure at the inlet to the filter than the pump pressure specified. Therefore, the pump capacity should be adequate for this purpose, too.
The fuel oil filter should be based on heavy fuel oil of: 10 cSt at 80 °C = 700 cSt at 50 °C = 7000 sec Redwood I/100 °F.
Fuel oil flow ...see ‘List of capacities’ Working pressure ...10 bar Test pressure ... according to class rule Absolute fineness ... 50 µm Working temperature ... maximum 150 °C Oil viscosity at working temperature ...15 cSt Pressure drop at clean filter ...maximum 0. bar Filter to be cleaned at a pressure
drop of ...maximum 0.5 bar Note:
Absolute fineness corresponds to a nominal fine- ness of approximately 30 µm at a retaining rate of 90%.
The filter housing shall be fitted with a steam jack- et for heat tracing.
( ( ( ( ( 4OPæOFæFUELæOILæ SERVICEæTANK 6ENTæPIPE NOMINALæ$ #ONE )NLETæPIPE NOMINALæ$ 0IPE NOMINALæ$ /UTLETæPIPE NOMINALæ$
Fuel oil venting box
The design of the Fuel oil venting box is shown in Fig. 7.05.02. The size is chosen according to the maximum flow of the Fuel oil circulation pump, which is listed in section 6.0.
178 38 393.3
Flushing of the fuel oil system
Before starting the engine for the first time, the system on board has to be flushed in accordance with MAN Diesel’s recommendations ‘Flushing of Fuel Oil System’ which is available on request.
Flow m3/h Q (max.)* Dimensions in mm D1 D2 D H1 H2 H H4 H5 1. 150 2 15 100 600 171. 1,000 550 2.1 150 40 15 100 600 171. 1,000 550 5.0 200 65 15 100 600 171. 1,000 550 8.4 400 80 15 150 1,200 .5 1,800 1,100 11.5 400 90 15 150 1,200 .5 1,800 1,100 19.5 400 125 15 150 1,200 .5 1,800 1,100 29.4 500 150 15 150 1,500 402.4 2,150 1,50 4.0 500 200 15 150 1,500 402.4 2,150 1,50 * The maximum flow of the fuel oil circulation pump
MAN B&W
7.06
Page of 2
MAN Diesel
MAN B&W MC/MC-C, ME/ME-C/ME-GI/ME-B engines 198 38 828.3
The emulsification of water into the fuel oil reduc- es the NOx emission with about % per % water added to the fuel up to about 20% without modifi- cation of the engine fuel injection equipment. A Water In Fuel emulsion (WIF) mixed for this pur- pose and based on Heavy Fuel Oil (HFO) is stable for a long time, whereas a WIF based on Marine Diesel Oil is only stable for a short period of time unless an emulsifying agent is applied.
As both the MAN B&W twostroke main engine and the MAN Diesel GenSets are designed to run on emulsified HFO, it can be used for a common system.
It is supposed below, that both the main engine and GenSets are running on the same fuel, either HFO or a homogenised HFO-based WIF.
Special arrangements are available on request for a more sophisticated system in which the GenSets can run with or without a homogenised HFO- based WIF, if the main engine is running on that. Please note that the fuel pump injection capacity shall be confirmed for the main engine as well as the GenSets for the selected percentage of water in the WIF.
Temperature and pressure
When water is added by emulsification, the fuel viscosity increases. In order to keep the injection viscosity at 0-5 cSt and still be able to operate on up to 700 cSt fuel oil, the heating temperature has to be increased to about 70 °C depending on the water content.
The higher temperature calls for a higher pressure to prevent cavitation and steam formation in the system. The inlet pressure is thus set to 3 bar. In order to avoid temperature chock when mixing water into the fuel in the homogeniser, the water inlet temperature is to be set to 7090 °C.
Safety system
In case the pressure in the fuel oil line drops, the water homogenised into the Water In Fuel emul- sion will evaporate, damaging the emulsion and creating supply problems. This situation is avoid- ed by installing a third, air driven supply pump, which keeps the pressure as long as air is left in the tank ‘S’, see Fig. 7.06.0.
Before the tank ‘S’ is empty, an alarm is given and the drain valve is opened, which will drain off the WIF and replace it with HFO or diesel oil from the service tank.
The drain system is kept at atmospheric pressure, so the water will evaporate when the hot emulsion enters the safety tank. The safety tank shall be designed accordingly.
Impact on the auxiliary systems
Please note that if the engine operates on Water In Fuel emulsion (WIF), in order to reduce the NOx emission, the exhaust gas temperature will de- crease due to the reduced air / exhaust gas ratio and the increased specific heat of the exhaust gas. Depending on the water content, this will have an impact on the calculation and design of the fol- lowing items:
• Freshwater generators
• Energy for production of freshwater • Jacket water system
• Waste heat recovery system • Exhaust gas boiler
• Storage tank for freshwater
For further information about emulsification of wa- ter into the fuel and use of Water In Fuel emulsion (WIF), please refer to our publication titled:
Exhaust Gas Emission Control Today and Tomorrow
The publication is available at: www.mandiesel.com under ‘Quicklinks’ → ‘Technical Papers