1810717_v4 System Description

Fuel Conditioning Module

System DescriptionPrintedBook No.

Aug 20081810717-02 V 4

Alfa Laval reserves the right to make changes at any time without prior notice.

Any comments regarding possible errors and omissions or suggestions for improvement of this publication would be gratefully appreciated.

Copies of this publication can be ordered from your local Alfa Laval company.

Published by: Alfa Laval Tumba AB Marine & Diesel Equipment SE - 147 80 Tumba Sweden

Copyright Alfa Laval Tumba AB Aug 2008.

Contents

1810717-02

1 System Description ..............................................................................................21.1 Purpose of the system...................................................................................... 21.2 Application ........................................................................................................... 21.3 Typical System ................................................................................................... 31.4 Typical Layout..................................................................................................... 41.4.1 Day tank ................................................................................................................... 61.4.2 Low pressure supply pumps .................................................................................... 61.4.3 Oil filters.................................................................................................................... 6

1.4.4 Flow transmitter ........................................................................................................ 61.4.5 Mixing tube with deaeration function ....................................................................... 61.4.6 Circulating pumps .................................................................................................... 71.4.7 Heaters ..................................................................................................................... 7

1.4.8 Viscosity sensor........................................................................................................ 71.4.9 Control cabinet ......................................................................................................... 8

1 SYSTEM DESCRIPTION FUEL CONDITIONING MODULE SYSTEM DESCRIPTION

on1 System Descripti

1.1 Purpose of the system All low speed engines and most modern medium speed engines operate today on heavy fuel oil. To ensure proper treatment and a good combustion, a fuel conditioning system is needed. The principal purpose of the system is to ensure proper conditioning of the heavy fuel oil fed from the daily service tank to the diesel engines. The system ensures that correct flow, pressure, and viscosity are maintained.

1.2 ApplicationFuel conditioning systems are primarily suitable for ships or power stations using HFO diesel engines. There are generally two separate conditioning systems for shipboard applications where HFO engines are in use, since heavy fuel is commonly used both for the auxiliary engines (Unifuel system) as well as for the main engines. For safety reasons, these fuel conditioning systems are usually independent of each other.

All ships designed to operate on HFO above 180 cSt/50 C should have pressurized systems (a fuel system specified by all engine builders). Modern high viscosity fuels require high injection temperatures. To prevent excessive and harmful vaporization of the light fractions and possible remaining water in the fuel, sufficient pressure has to be maintained. This is done using pressurizing supply pumps.

The primary control parameter is viscosity.

The Alfa Laval Conditioning Module is a two stage pressurized system.

Pressure in the low-pressure section is maintained at 4 bar, and in the high-pressure section, 6 16 bar depending on engine manufacturer requirements.2 1810717-02

FUEL CONDITIONING MODULE SYSTEM DESCRIPTION 1 SYSTEM DESCRIPTION1.3 Typical System

Low pressure stage

The low pressure stage includes two supply pumps (one in operation, one on standby), an Alfa Laval automatic filter with a manual bypass filter as back up, and a flow transmitter to provide infor-mation on fuel consumption. The last part of the low-pressure section is the mixing tank where fresh fuel is mixed with hot fuel returning from the engine. As engine speed changes so will fuel consumption so a special pressure control valve allows fuel to recycle within the low-pressure section so that the flow of fresh fuel entering via the three way valve exactly matches the fuel consumption of the engine. Should the supply pump in operation fail, then the system will automatically change over to the standby pump.

From the mixing tank the fuel enters the high-pressure section. The flow rate in this section is always set at a multiple of the actual fuel consumption rate in order to prevent fuel starvation at the injectors. The flow rate multiples and the pressure in the system are set by the engine manufacturer.

High pressure stage

The high-pressure stage includes the circulation pumps, fuel heaters and the viscosity sensor. The viscosity sensor measures the viscosity of the fuel and sends a signal to the controller where it is compared with the value for viscosity set by the engine manufacturer.

Deviations from the set point are then corrected by adjusting the flow of heating medium to the heater. Pressure in the system is maintained by a pressure control valve after the injectors (normally part of the engine installation) and the excess fuel returns to the mixing tank.1810717-02 3

1 SYSTEM DESCRIPTION FUEL CONDITIONING MODULE SYSTEM DESCRIPTION1.4 Typical Layout

PDS

PT

HFO

DO

FT

Change-over valve

Supply pumps Automatic/Manual filters.Note! The filters can also be positioned after viscosity sensor.

Flow transmitter Pressure transmitter

Pressure control valve

Pump strainers

Filter drain valve4 1810717-02

FUEL CONDITIONING MODULE SYSTEM DESCRIPTION 1 SYSTEM DESCRIPTION

VT

Temperature sensor

Viscosity sensor

Pressure control valve (customer supplied)

ransmitterPT TT

LS

EPC-50B

Mixing tube with deaeration function

Circulation pumps

Heaters Pressure tLevel switch Deaeration valve1810717-02 5

1 SYSTEM DESCRIPTION FUEL CONDITIONING MODULE SYSTEM DESCRIPTION1.4.1 Day tank

The clean heavy fuel oil is pumped into the daily service tank. The temperature in the tank is between 70-90 C. The daily service tank is usually situated high up in the engine room. From the daily service tank the oil flows by gravity into the mixing pipe.

1.4.2 Low pressure supply pumps

Oil from the day tank enters the system via the three way valve and into the suction of the low pressure supply pumps. Operation of this section under pressure eliminates the problems of gasification and cavitation that are associated with high fuel temperatures (120 150 oC). This will ensure an even fuel flow and prevent damage to the pumps.

1.4.3 Oil filters

An Alfa Laval automatic back flush main filter backed up by a manual by-pass filter remove any particles present in the fuel that could cause engine damage. Continuous automatic back flushing and robust disc type filter elements guarantee high efficiency and minimum maintenance requirement. As an alternative, the filtration stage can be moved over to the high-pressure stage but because of the higher flow rates this normally will require a larger filter for a given engine.

1.4.4 Flow transmitter

A flow transmitter is installed on the pressure side of the supply pumps to monitor fuel consumption. As an alternative a mass flow transducer can be installed.

1.4.5 Mixing tube with deaeration function

The purpose of the mixing tube is to mix the cold fuel from the daily service tank with the excess hot fuel which comes from the diesel engines. 6 1810717-02

FUEL CONDITIONING MODULE SYSTEM DESCRIPTION 1 SYSTEM DESCRIPTIONThe mixing tube is made of steel, insulated and often heat traced with a diameter of 300-400 mm and a height of 1.0-1.5 meter.

Gases that accumulate in the mixing pipe are manually or automatically vented back to the day tank and a permanent air cushion within the mixing tube dampens out pressure fluctuations within the system

1.4.6 Circulating pumps

Circulating pumps feed the engine with HFO at the required flow rate and pressure. Pump capacities are always multiples of the recommended maximum fuel consumption rates to ensure ample filling of the injection pumps. The pressure required in the circulating system is specified by the engine builders. This pressure is controlled by a pressure regulating valve mounted on the engine, or directly after the engine in the return line to the mixing tube.

1.4.7 Heaters

Prior to injection into the diesel engine, the temperature is increased to reach the correct injection viscosity (normally circa 10 15 cSt).

The module has two electric or Shell & Tube heat exchangers, one in operation, and one in standby. These heat exchangers are especially designed for operation at high pressures and high oil temperatures.

1.4.8 Viscosity sensor

The viscosity sensor measures the injection viscosity of the fuel oil against a value set by the engine manufacturer, and signals the controller. The controller then adjusts the heating medium supply to the heaters thus maintaining the correct viscosity.1810717-02 7

1 SYSTEM DESCRIPTION FUEL CONDITIONING MODULE SYSTEM DESCRIPTION1.4.9 Control cabinet

The control cabinet has two separate compartments, a lower one that contains motor starters and an upper compartment that contains the EPC50B controller.

Controller

The EPC 50 B controller controls the following functions:

Change-over DO/HFO

Pump standby function

Dearation of mixing tank

Viscosity control by steam, thermal oil, or electric heating

Automatic filter drain interval

If the controller stops working, all functions can be operated manually.

Remote Control and Monitoring

The fuel conditioning module is prepared for 4 levels of remote control. The levels are:

1 Basic Level1

2 Extended Level 2

3 Advanced Level 3

4 Fully automated Level 4

For more information, see the Operating Instructions booklet.8 1810717-02

H1-Heading1TOC - 1 System Description 2H2-Heading2TOC - 1.1 Purpose of the system 2H2-Heading2TOC - 1.2 Application 2H2-Heading2TOC - 1.3 Typical System 3H2-Heading2TOC - 1.4 Typical Layout 4

H1-Heading1 - 1 System DescriptionH2-Heading2 - 1.1 Purpose of the systemH2-Heading2 - 1.2 ApplicationH2-Heading2 - 1.3 Typical SystemH2-Heading2 - 1.4 Typical LayoutH3NP-Heading3NewPage - 1.4.1 Day tankH3-Heading3 - 1.4.2 Low pressure supply pumpsH3-Heading3 - 1.4.3 Oil filtersH3-Heading3 - 1.4.4 Flow transmitterH3-Heading3 - 1.4.5 Mixing tube with deaeration functionH3-Heading3 - 1.4.6 Circulating pumpsH3-Heading3 - 1.4.7 HeatersH3-Heading3 - 1.4.8 Viscosity sensorH3-Heading3 - 1.4.9 Control cabinet

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