Cutting cylinder oil costs without a break in service - Wärtsilä

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p [ MARINE / IN DETAIL ] [ MARINE / IN DETAIL ] vessel. Wärtsilä’s two-stroke center and the Wärtsilä services network are thus working in close co-operation to minimize the required installation time so that RPLS can be retrofitted in a ship while on passage and during a normal port stay. For example, Wärtsilä in Korea is manufacturing all pipework and other mechanical parts. Before dispatching the material to the vessel, it is prefitted on a dummy in the Wärtsilä workshop in Noksan, South Korea, to verify that the work is correct. RPLS is an independent system with few connections or interfaces to other systems, and utilizes the engine’s existing cylinder liners. Thus preparation and installation are easy and fast. All equipment, including prefabricated piping, is supplied with installation and commissioning work being undertaken by Wärtsilä service engineers. To a substantial extent this material can be installed during the voyage, thereby considerably reducing the port time required for fi nishing the installation and for the commissioning. Installation of controls, pumps, wiring, and interface connections to remote and alarm monitoring systems, is executed during the voyage. Ample attention is paid to commissioning, fi ne adjustment and the running-in of the RPLS in port and during a confi rmation voyage. The whole retrofit and commissioning on the first vessel, the 7500 TEU container ship “COSCO SHENZHEN” with a 12cylinder Wärtsilä RTA96C main engine, could be completed in five steps without interrupting the vessel’s schedule: 1. Pre-inspection in Hong Kong on 22 June 2006. 2. First installation trip from Hong Kong to Yantian during 26–27 August. Installation work continued in Yantian and during the Pacifi c crossing to Long Beach (USA), arriving there on 9 September. 3. The second and fi nal installation period in Long Beach during 9– 11 September, included pistonrunning related modifi cations. 4. The commissioning was carried-out while on passage from Long Beach to Oakland, where on 13 September the final inspection was also carried out. 5. Finally, on her ‘maiden’ passage to China, measurements and documentation of the RPLS performance were carried out. 52 indetail Cylinder oil tank Alarm monitoring system Filter WECS Main bearing oil Servo oil supply unit Junction box Pressure sensors Servo oil overfl ow Fig 2. – Schematic of the RPLS. Working principle The basic principle of the Pulse Lubricating System is to deliver metered quantities of cylinder lubricating oil under pressure at precise timing exactly into the piston ring package, from where it is evenly distributed around the circumference of the cylinder liner. The RPLS is based on a lubricating module for each cylinder with a dosage pump and monitoring electronics, which delivers pressurized cylinder lubricating oil to newly developed lubricators (formerly known as quills) that fit existing cylinder liners of the Wärtsilä RTA and RT-flex engine types. Each lubricating module is equipped with two separate supply lines – for cylinder lubricating oil and servo oil. A separate servo oil supply unit is needed to drive the lubricating module for RTA engines, whereas on RT-fl ex common rail engines, the servo oil is taken from the servo oil common rail through a pressure reducing valve. Once the Wärtsilä Engine Control System (WECS) switches the 4/2-way solenoid valve in the lubricating module Lubricator ALM-20 Dosage pump Cylinder CAN bus Power supply Cylinder oil Servo oil Servo oil return to the open position, servo oil fl ows to the drive side of the central piston of the dosage pump in the lubricating module. As the central piston is actuated, it feeds cylinder lubricating oil from the lubricating oil supply to the metering ducts, and then discharges it from the lubricators at high pressure. The cylinder oil is accurately supplied at defined positions of the working piston whose position is constantly detected by the control system from the reference signal given by the crank angle sensor. At the end of the lubrication work cycle, the directional valve in the lubricating module directs the servo oil to the return-fl ow side of the central piston of the dosage pump, which then returns to its initial position. The metering chamber is fi lled again with cylinder lubricating oil to be ready for the next lubricating cycle. A separate servo oil supply unit is provided for RTA engines. It includes two gear pumps, one supplying the lubricating module with servo oil taken from the main engine oil system, with the second pump as a standby. The oil supply unit also includes a pressure limiting and safety valve, pressure gauge, pressure sensor, and
Photo: Nordcapital Pressure sensor Shut-off valve for lubricating oil Cylinder oil inlet To system oil drain tank Relief valve for servo oil Shut-off valve for servo oil Fig. 3 – The RPLS lubricating module with lubricator connections and associated electronics for eight lubricators. WÄRTSILÄ TECHNICAL JOURNAL 02.2007 Cylinder oil outlet to lubricators Venting plug for cylinder oil Venting plug for servo oil 4/2-way solenoid valve Diaphragm accumulator Fig. 4 – One of the nine container ships managed by E.R. Schiffahrt, which have been completely retrofitted with the Pulse Lubricating System. The ships are powered by Wärtsilä RTA96C low-speed diesel engines. shut-off valve. For RT-flex engines, servo oil is drawn from the engine servo oil system through a pressure reducing valve by which the oil pressure is reduced from 200 bar to 50 bar. The reduced pressure is monitored by pressure transmitters directly connected to the alarm system; the pipes are SOLAS compliant. The reduced pressure can be adjusted and its level is shown on an analogue pressure gauge. The lubricating module for each cylinder consists of a dosage pump, a 4/2-way solenoid valve, monitoring electronics, pressure sensor, and diaphragm accumulator on a base plate. The timed lubricating module feeds a predefi ned metered quantity of cylinder oil at high speed to the lubricators at the precise timing ascertained by the engine control system. Part of the control oil fl ow from the servo oil line is routed to the 4/2-way solenoid valve. At the same time, the loaddependent cylinder lubricating oil needs of the respective cylinders are ascertained by the engine control system, which sends a corresponding signal to the monitoring electronics of the lubricating module. The ALM-20 (Advanced Lubricating Module) checks that the dosage pump is working correctly. The ALM-20 communicates with the master control unit through a redundant bus system, sends the signal to the 4/2-way solenoid valve, and processes the data from the pressure transmitter. The redesigned lubricator delivers the cylinder oil radially as compact oil pulse feeds exactly into the piston ring package, from where it is equally distributed around the circumference of the cylinder liner. The lubricators (up to eight) are arranged around the liner in one row to ensure an excellent distribution of the cylinder oil on the cylinder liner. The vertical distribution is governed by the lubricating oil injection timing as a function of the crank angle. A generously dimensioned 40micron cylinder lubricating oil fi lter is arranged before the lubricating modules. It effectively removes any particles of dirt, thereby ensuring reliable operation of the lubricating modules. A 12 litre buffer tank is provided with a scaled sight glass that enables cylinder oil consumption measurements of up to five litres. The buffer tank also allows the filter to be changed while the engine is running. When the filter is dirty, the integrated sensor gives a signal on the excessive differential pressure. p indetail 53
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Cutting cylinder oil costs without a break in service - Wärtsilä

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