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The Sulzer RT-Flex engine is essentially a standard Sulzer RTA low-speed two-stroke marine diesel engine except that, instead of the usual camshaft and its gear drive, fuel injection pumps, exhaust valve actuator pumps, reversing servomotors, and all their related mechanical control gear, the engine is equipped with a common-rail system for fuel injection and exhaust valve actuation, and full electronic (computer) control of engine functions. Two control oil pumps are provided near the engine local control stand and one of these must always be operational in order to ensure that the common rail fuel and exhaust valve operation systems can function.

The engine is monitored and controlled by a WECS (Wartsila Engine Control System) - 9520 unit. This is a modular electronic system with separate microprocessor control units for each cylinder; overall control and supervision is by means of separate, duplicated microprocessor control units. The cylinder microprocessor control units are mounted on the front of the engine at the common rail which is located below the top engine platform.

The engine is a single acting, two-stroke, reversible, diesel engine of crosshead design with exhaust gas turbocharging and uniflow scavenging. Tie rods bind the bedplate, columns and cylinder jacket together. Crankcase and cylinder jackets are separated from each other by a partition, which incorporates the sealing gland (stuffing) boxes for the piston rods. The cylinders and cylinder heads are fresh water cooled.

Illustration 2.1.1a Main Engine

HYUNDAI-SULZER 11RT-flex96C-B

Maersk Seletar Machinery Operating Manual

The exhaust gases flow from the cylinders through the hydraulically operated exhaust valves into an exhaust gas manifold. The exhaust gas turbochargers work on the constant pressure charging principle.

The charge air delivered by each turbocharger flows through an air cooler and water separator into the common air receiver. Air enters the cylinders through the scavenge ports, via valve groups, when the pistons are nearly at their bottom dead centre (BDC) positions. At low loads two electrically driven auxiliary blowers supply additional air to the scavenging air space.

The pistons are cooled by bearing lubricating oil, supplied to the crossheads by means of articulated lever pipes. The thrust bearing and turning gear are situated at the engine driving end. The fuel and servo oil pumps for the common rail fuel system and exhaust valve actuation are driven by gear wheels from the crankshaft.

The engine is started by compressed air, which is controlled by the electronic starting air system. In case of failure of the engine remote control system (bridge and ECR control system), the engine can be controlled from a local (emergency) control stand located at the forward end of the engine at middle

Main bearing oil system

The engine main bearings and thrust block are supplied with lubricating oil by

Crosshead bearing oil system

Two crosshead LO pumps, one working and one on standby, take suction from the main LO supply to the engine and boost the pressure of the crosshead supply. The bottom end bearings are also supplied with LO from the associated crosshead, oil flowing down a bore in the connecting rod. The lubrication of crossheads and connecting rod bottom end bearings is made through articulated lever pipes.

turbocharger Lubrication

The turbochargers are supplied with lubricating oil from the turbocharger LO system. There are two turbocharger LO pumps, one operating and one on automatic standby. These pumps supply oil to the turbocharger bearings from the turbocharger LO service tank via a cooler. The pumps have suction filters and there is also a tank filter unit with its own circulation pump. This pump should be operating whenever the turbocharger pumps are running.

Cylinder Lubrication system

The engine is fitted with a Pulse Jet cylinder lubrication system which operates by the spraying of cylinder lubricating oil on to the liner surface from a single row of quills arranged around the liner, each quill having a number of nozzle holes. There are eight quills with each quill having five oil jets giving a total of 40 lubricating points on the liner surface.

The oil jets are individually directed to separate points on the liner surface.

There is no atomisation and no loss of lubricating oil to the scavenge air. The quills are simple non-return valves. Cylinder lubricating oil is delivered to the quills by a lubricator pump. There is one CLU4 pump unit for each engine cylinder and this incorporates the cylinder oil reservoir, the pump unit and the solenoid valves for operating the pump unit. The pump unit is operated by means of oil from the servo system with servo oil being directed to and from the servo unit of the cylinder oil pump by the solenoid valves. These solenoid valves are controlled by the WECS-9520.

The WECS-9520 determines the optimum amount of cylinder lubricant required at each piston stroke and also determines when the lubricator will operate in order to direct the cylinder lubricant at the liner surface so that the

The cylinder lubricator pump box is replenished by gravity with oil from the cylinder oil measuring tank. The supply pipe is trace heated in order to ensure flow of the cylinder oil in all temperature conditions. The cylinder oil

Cooling Water system (see section 2.5.1, high temperature fresh Water Cooling systems)

The cooling water must be treated with an approved cooling water inhibitor to prevent corrosive attack, sludge formation and scale deposits in the system. pump and the other as the standby pump. HT cooling water is used as the heating source for the fresh water generator and this is the only direct cooling to which the HT system is subjected. A jacket cooling water preheater is fitted and this is used to maintain the engine temperature when the engine is stopped or running at low load; it may also be used for supplementary heating should that be necessary for operation of the fresh water generator.

fuel oil system (see section 2.6.1, Main engine fuel oil service system) The fuel oil is supplied to a common rail by the fuel supply pumps which are driven from the crankshaft by a gear system. The fuel pumps are arranged in a V form with four pumps in each bank. The pumps deliver pressurised fuel oil to a collector which then supplies the common fuel rail; this fuel rail is maintained at a pressure of 1,000 bar. All parts of the high pressure fuel system are sheathed in order to prevent high pressure fuel from entering the engine room spaces. The fuel supply pumps are driven by a camshaft via three lobed cams. The three-lobed cams and the speed of the camshaft means that each pump makes several strokes during a crankshaft revolution. There are eight fuel supply pumps and the output of the pumps is such that seven pumps have the capacity to meet full load needs of the engine; with only six pumps operational the engine load must be reduced below maximum. The common fuel rail is divided into two sections, one serving the forward five cylinders and the other serving the aft six cylinders. The common rail volume is such that the fuel pressure is constant throughout the operation of the engine.

There are three fuel injectors fitted in each cylinder cover and high pressure fuel oil is supplied to these from the common rail. Each cylinder has its own injection control unit which controls the fuel supply to the injectors from the common fuel rail. Each injection control unit has three rail valves and three injection control valves, one of each for each injector. The rail valve is an electrically operated spool valve which can be moved to each end of its casing by electrical signals from the WECS-9520. The spool valve acts as an open or closed valve and when in the open position it directs control oil to the injection control valve. The injection control valve opens and allows high pressure fuel from the common rail to pass to the fuel injector thus beginning fuel injection at that injector. When the WECS-9520 signals the spool valve to close, the injection control valve is closed and hence fuel injection stops. Control oil is supplied by the servo and control oil manifold at a pressure of 200 bar. The rail

Maersk Seletar Machinery Operating Manual

valves are bi-stable solenoid valves with a fast actuation time; the valve is not energised for more than 4ms at any time.

The WECS 9520 controls the fuel injection system via the cylinder control module (CCM), which not only regulates the start and end of injection but also monitors the quantity of fuel injected. The fuel quantity sensor measures the actual amount of fuel injected and this information is relayed to the control system. The control system calculates any change in fuel timing required from the engine operating conditions and the actual fuel quantity injected. The functioning of the fuel injection system is monitored at each cycle and changes are made for the next cycle if necessary.

Operation of the rail valves is under the control of the WECS-9520, which can adjust the timing and quantity of fuel injection to suit operating conditions.

Normally all three cylinder fuel injectors, which are of the hydraulically actuated type, operate together but as they are independently controlled it is with the high fuel pressure maintained by the common rail. With injector(s) cut out the operating injector(s) are changed over every 20 minutes in order to prevent overheating of the cut out injector(s) and ensure that all injectors have equal running.

The fuel quantity delivered to the engine by the fuel conditioning module is considerably greater than is actually required by the engine, the excess fuel flows back to the mixing unit of the main fuel conditioning module. The mixing unit is located at the FO circulation pump suction and it also takes a FO are provided with trace heating and are insulated. For reasons of safety, all high-pressure pipes are encased by a metallic hose. Any leakage is contained and led to an alarmed fuel oil leakage tank. The engine may be operated on MDO if necessary.

starting air system (see section 2.10.1 starting air system)

The starting air system of the RT-Flex engine is similar to that of a standard

The cylinder starting valve is operated by pilot air and the pilot air valve is controlled electrically by the cylinder control module. The starting pilot air valve is opened and closed directly by the cylinder control module (CCM) once every revolution at defined crank angles during the starting period. When the engine has started the starting system is shut down.

Cylinder exhaust Valve

Each cylinder has a single exhaust valve centrally located in the cylinder cover.

The exhaust valve is hydraulically opened; it is closed by air pressure acting on the air piston, which is located below the hydraulic actuating cylinder.

When hydraulic pressure is applied to the actuating piston in order to open the exhaust valve, the air trapped below the air piston is compressed. When the hydraulic opening pressure is removed the air pressure acts on the piston to close the exhaust valve; this is known as the ‘air spring’. The space above the air piston is then vented and make-up air is supplied to the space below the air piston, from the control air system, via a non-return valve, in order to replace any leakage from the air spring cylinder.

The exhaust valve is fitted with a series of vanes on the stem, known as a spinner. When the exhaust valve is opened exhaust gas escaping from the cylinder acts on the spinner and causes the valve to rotate. Rotation of the valve evens out the temperature of the valve and as the valve is still rotating when it reseats, this creates a light grinding effect which removes deposits from the valve seat and valve face.

The cylinder control module (CCM) controls the exhaust valve opening and closing. Hydraulic pressure for opening the valve comes from the servo oil common rail. The servo oil common rail is pressurised to a pressure of 200 bar piston with the exhaust valve piston (the hydraulic pushrod) is filled with engine bearing oil and a connection with the bearing circulation system ensures that the space is always fully charged. This arrangement provides a complete separation of servo hydraulic system and valve actuation/bearing lubricating oil systems and enables the exhaust valves to be serviced without disturbing the servo oil system.

Charge air system

Charge air for combustion in the cylinders is provided by three exhaust gas driven turbochargers. The turbochargers draw air from the engine room through a filter and deliver it to the scavenge air receiver via a cooler and a water separator. The charge air is cooled by water circulating in the low

temperature fresh water cooling system. Immediately after passing over the cooling elements in the scavenge air cooler the air flows through a water separator where water droplets are removed. It is essential that water droplets are removed from the charge air; any water droplets entering the cylinder with the scavenge air can remove the lubricating oil film from the cylinder liner, resulting in excessive liner wear. Water entering the cylinder can also combine with the sulphurous products of combustion and cause cold corrosion in the cylinder system and uptakes.

The scavenge air coolers (SACs) must be monitored closely whilst the engine is operating as the scavenge air temperature has a significant influence on cylinder performance. The charge air temperature must be maintained at 40 to 45°C during normal climatic conditions. In tropical waters the temperature may be allowed to increase by 5°C but it must never be allowed to rise above 50°C.

High charge air temperature reduces the air density which can result in poor cylinder combustion. A high air inlet temperature produces a high exhaust temperature and there is a maximum allowed exhaust temperature. If the air inlet temperature is too high then the engine output may have to be reduced in order to maintain the exhaust temperature within set limits. Too low an air temperature can cause thermal shock in the cylinder.

A high air temperature and an increased temperature difference between cooling water inlet and outlet can indicate fouling of the SAC on the water side.

A high air temperature accompanied by an increased air pressure drop across the cooler, together with a reduced temperature difference between the cooling water inlet and outlet, is indicative of fouling on the SAC air side.

The SACs must be cleaned according to the engine builder’s instructions and the frequency of cleaning will depend upon operating circumstances.

The turbocharger turbine and impeller must also be cleaned at intervals recommended by the engine builder or as operating circumstances dictate.

Facilities are provided for in-service cleaning of the turbine and impeller and loads three electrically driven auxiliary blowers are provided. These should be selected for automatic operation and they will start prior to starting the engine or when the operating speed falls below a predetermined value.

The auxiliary blowers will stop automatically when the engine speed rises above a predetermined value and sufficient scavenge air is supplied by the turbochargers.

Maersk Seletar Machinery Operating Manual

scavenge air space fire fighting system

The engine is provided with a water mist fire fighting system for the scavenge air space.