LOW LOAD OPERATION FOR MAN B&W TWO-STROKE MARINE DIESEL ENGINES

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1 SQEMS WORKING INSTRUCTION WIN-TEC-33 1 of 5 1. SCOPE To provide a guidance on low load/slow steaming operation of MAN Diesel Main Engines 2. RESPONSIBILITY Master To advise Operation and Technical office if requested to slow steam or operate the vessel on low load for periods exceeding 24 hours. Consulting with the Chief Engineer on the most appropriate minimum safe continuous running speed of the Main Engine. Consulting with the Chief Engineer for allowing correct time for ME and exhaust gas piping/boiler cleaning before and after slow steaming operation. Chief Engineer Advising the Master of the most appropriate minimum safe continuous running speed of the Main Engine. Ensuring that engineering Staff are informed of the operating conditions and any necessary precautions. Monitoring Main Engine running parameters. Inform Technical Office and discuss with Vessel Superintendent any outcome. Vessel Superintendent Maintain contacts with ME Maker reporting to them any outcome. Overview any vessel report instructing any possiible suggestion/guidance on the matter. 3. GENERAL 3.1 Definitions Low Load operation: with ME load reduced up to around 24% of MCR (Pi) ~ 4700 BHP (Pi), for engines MAN B&W type MC/MC-C, ME/ME-C fitted with slide valves, alpha lubricator ALCU with MCU MK I, cylinder oil pumps without the retrofit kit, spare ME electrical blowers (one each side) Very Low Load operation: with ME load reduced up to around 10% of MCR. These conditions may be achieved only by MAN B&W type MC/MC-C ; ME/ME-C fitted with slide valve, alpha lubricator system ALCU or ALCU 1 (with latest version of MCU MK II vers.2.5 and retrofit kit for each of the cylinder oil pumps), spare ME electrical blowers (one each side) Temporary low load operation: Operation of Main Engine within the low load range for less than 24 hours. Short Term low load operation: Continuous operation of Main Engine within the low load range for more than 24 hours, but less than seven days. Prolonged low load operation: Continuous operation of Main Engine within low load range for more than seven days but less than one month. Extended low load operation: continuous operation of Main engine within the low load range for more than one month. Prepared by: Reviewed by: Approved by: Tech. Dept. Tech. Dept. Manager General Manager Distribution: to all managed vessels

2 2 of General description of low load operation effect One of the biggest benefits of low load operation is the fuel saving. Therefore, depending on market conditions, a vessel may be asked to slow steam over extended periods of time. Modern engines are designated to be operated on low load without any modifications. However there some disadvantages and risk associated with low load operation, which must be taken into consideration to ensure safe operation: Increased fouling of soot in the exhaust gas passages; Unstable combustion at minimum limit low load; In some cases increased thermal load on the exhaust valve; Increased running periods on the auxiliary blowers; Increased running periods for auxiliary machinery; Possible increased hull and propeller fouling, especially in tropical waters. The Main Engine Operating Manual and manufacturer s Service Letters on board provides specific guidelines of low load operation. 4. ACTION Continuous operation at low engine load will require more attention from the operator. Frequent inspections are of paramount importance to follow the fouling condition of the engine. Certain load areas may have to be avoided so as not to thermally overload engine components and increase fouling due to lack of air for the combustion. The operator must monitor the engine condition closely and take the necessary precautions if excessive fouling is observed. The inspection report template intention is to make a standard reporting tool to be used in the communication between the vessel and the operator s office, thereby gathering information and experience from the specific vessel during its low-load operation. Frequent inspection of the scavenge air receiver and cylinder condition must be performed. Early detection and removal of soot build up, coke and unburned fuel and lubricating oil is important to avoid scavenge air fires and jeopardising of the cylinder running condition. Residual inside the scavenge air receiver should be removed frequently. The exhaust gas receiver, exhaust valves and turbocharger inlet grids must be inspected frequently and cleaned as much as possible. Deposit built-up of unused lube oil and additives may be harmful to the cylinder condition, especially in connection with subsequent loading up to higher engine loads The maintenance condition of the fuel injection equipment, fuel cleaning equipment and the quality of the fuel used generally are responsible of the fouling grade. Even more, during the low load voyages, a correct setting of such systems and the use of RMG 380 within the standard are of paramount importance. There is a record of an increasing number of break downs of the Auxiliary Blowers which are running continuously in low load operation. Basically, the A/B are not designed for continuous running. Therefore an increased number of running hours will require increased maintenance, but still a number of breakdowns have occurred so far. As a safety precaution the maker recommends to have one full set of A/B on board. Exhaust gas boiler recommendation must be followed with regard to the cleaning in order to avoid Exhaust Gas Boiler Fire. Under normal condition a fire is most unlikely. If, however, carbon bearing deposits are allowed to accumulate on the heating surfaces of the boiler, a potential fire hazard is created. Incandescent particles carried out over from the engine in the exhaust gases will readily ignite the deposits. The incident of fires is highest during manoeuvring, leaving a port because the exhaust gases are more generated. The soot in exhaust gas will be increased when the ship is going to arrive at port, or is sailing at low speed. Slow running will cause engine inefficiency with increased carbon in the exhaust gases and, with reduced gas velocity; the carbon is more readily deposited on the element heating surfaces. The problem could be aggravated if an incorrect type of fuel valve nozzle for slow running is fitted or even if the fuel valve nozzles are not properly overhauled as per the Maintenance plan interval table.

3 3 of 5 Engine Load-up depends on the observations noted by the crew (e.g. more fouling of scavenging & exhaust system). The crew should monitor the overhaul fouling degree of the engine In way of e.g. excess lubricating oil in scavenging air system, which in turn would require more frequent cleaning. Should be kept in mind that generally speaking, the engine load-up must be minimised when running on low load. Frequent load-up could jeopardize the cylinder condition. In order to be able to judge and to update the low load orders, especially in regard to the load-up frequency, it is of upmost importance to have documented reports by the ship s command. This means that at the beginning of the low load voyage a deep inspection/cleaning of the ME exhaust gas ways should be done in order to be ready to match the same data when the low load voyage will end. (see SL Two Stroke low load operation Inspection report template). Based on the results, some adjustments in the low load operating procedures could be reformulated such as the elimination of the load-up sequence or the implementation of additional checks/frequency. 4.1 Operation Recommendations before undertake a low load voyage It is obvious that before operating the engine in a prolonged or extended low load voyage the following items should be inspected /cleaned. On the arrival the same inspections( before cleaning ) should be carried out for evaluating the operation condition of the ME and his ancillaries, to apply some additional adjustments depending on the inspections results and in the same time to be ready for any voyage( Low load or normal one). Therefore the vessel should be advised enough time in advance before set out on an eventual low load voyage keeping in mind that the ME will be not operable for sometimes in both conditions ( before starting the low load voyage and after the low load voyage ended). The cleanings/checks should be documented by filling an Inspection Report Template with pictures (see also SL with enclosed the inspection report template) and should be extended to the following main components as follows: - Scavenging air manifold: cleaning and/or general checks mainly concentrated to the: Scavenging manifold in general, Flap valves, E/Blower impellers, Piston ring lands & Top lands, Piston Crowns. - Me underpiston spaces: cleaning of the buffer spaces and check of the drain lines from the buffer spaces. - Exhaust Gas Receiver: cleaning and/or general checks mainly concentrated to the : Exhaust gas receiver, Exhaust valves from Exh.gas receiver, T/C safety grid, checking of the T/C nozzle ring and may be the turbine blade condition through the safety grid ( The latter only if is feasible). - Exhaust gas boiler(water tube) : washing of the steel fins and general internal checks of the exhaust gas boiler components with included the soot blowers, soot blower tubes and supports. 4.2 Operation recommendations during low load voyage sailing Auxiliary blowers ( A/B) - A/B flange venting hole must be free to blow air externally. If the hole is plugged or clogged there is an high risk to have the E/motor bearings contaminated by sludge, impurities pushed by the scavenging air which will also remove the lubricant from the bearing. Vice versa, if there is an excessive air amount coming out from the drain hole, the shaft sealing should be replaced. (see clear explanation with schematic drawing in SL pg 2 0f 4 ). - A/B running continuously during operation are subject to more wear than anticipated by designers. Consequently, the bearings should be frequently lubricated, if not of the closed type, and should be inspected for wear. Therefore the maintenance has to be reduced drastically in case of repeated low load operations (between approx Hrrs / refer to the maker s manual for specific instructions). - Never operate the engine in the A/B start/stop area avoiding frequent start/stop of the blowers. If this is the case is better to set in the ECS the blowers in MANUAL ON. - In case the low load operation is much lower than the A/B start/stop area, it is better to keep the ECS for the A/B in AUTO ON. In this case is not necessary to have the ER in manned condition. Vice versa, if the A/B are in MANUAL ON it is highly recommended to have the ER in manned condition due to the ECS which will block the ME to start from the Bridge due to the Auxiliary blowers not in auto mode. -Check the Main engine AA/BB often for excessive bearing temperature and abnormal vibrations.

4 4 of 5 Scavenge air receiver - If the A/B will operate in the start/stop area, the pressure pulsation generated in the scavenge air receiver, will cause an hammering phenomena which will damage and/or break the valves (non return valves) after a short period. This load area is simple to recognize by a distinct hammering noise. It is therefore recommended to avoid such load area skipping the same as fast as possible. During the scavenge receiver inspection, the flap valves should be carefully checked. Broken valves should be promptly replaced in order to avoid further damages downstream the scavenge receiver. Missing or partially broken flap valves will have a negative impact on the engine performance when the A/B are in running condition. - It is prudent practice to inspect the scavenge air received spaces within 7 days of starting to slow steam voyage. Depending on the result of the inspection the frequency should be then reduced or extended. -Ensure that the scavenger air receiver drain lines are free by carrying out the drain procedure at regular intervals. Turbocharger and Exhaust gas temperature - Fouling of the turbocharger gas side must be avoided by regular cleaning with soft blast( i.e. nutshells) according to the maker instructions.( minimum once every 24 hrs but could be also increased). If the turbine side cleaning is carried out routinely with nut shells there is no need to carry out water washing cleaning. - Turbocharger compressor side water washing cleaning to be carried out every 24 hrs according to the Maker instructions. - It is noted in the Man B&W SL ( June 2011) that the routine cleaning of the Man Turbochargers can be carried out without increasing the engine load. It is obvious that in case of load up procedure it is better to concentrate the turbocharger cleaning during the 2 hrs of higher load. - The exhaust gas temperature must be kept below the alarm limits. It might be necessary to avoid engine load areas just above auxiliary blower cut-in/out. If the desired engine load is in this area, it is recommended to switch the blowers into MANUAL ON, so as to reduce the exhaust gas temperature. In this case it is necessary to maintain manned the engine room as already explained above. - Acid Corrosion should be avoided by keeping the exhaust gas temperature after the cylinders as high as possible (preferably above 250 C). However this may not always be possible. Exhaust gas boiler - Exhaust gas boiler recommendation must be followed with regard to the cleaning. The soot blowers operation is not the complete answer but will remove dry loose deposits until washing can be carried out. Under normal operation conditions, soot blowing should be carried out at regular intervals determined by experiences and inspection of the heating surface. If the unit is operated under adverse soot forming conditions such as low speed operation of main engine, the soot blowers should be operated more frequently. Soot blowing should also be carried out immediately before shut down of the unit, before dry running and after turbo blower washing. Performance data of EGE: Max. Exh. gas drop ( inlet/outlet) of the economizer is 150 mmaq, exhaust gas outlet temperature is 204 C. The Exh. Gas loss ( from the U-Tube manometer ) and gas temperature should be measured regularly and recorded if necessary. If the Exh.gas drop is increased above 1.3 times as compared with that of normal condition, it means that the soot deposits were accumulated on the heating surface. In this case the soot blowers should be operated more frequently and water washing should be done as soon as possible. Furthermore, if the gas outlet temperature is increased abnormally, it means that the heating surface was fouled and the heat transfer efficiency was deteriorated. Also in this case the soot blowers have to be operated more frequently and the sooner water washing performed, the better efficiency promoted. It is obvious that in case of load up procedure it is better to concentrate the soot blowers cleaning during the 2 hrs of higher load sailing. - Acid corrosion is preventable by keeping the exhaust temperature at the economizer outlet as high as possible (preferably above 180 C). However this may not always be possible. Other ME items - Keep the jacket cooling water temperature close to the upper limit. - Keep the scavenge air temperature at the top of normal range. - Ensure that the Fuel valves are in good working condition before undertaking a low load voyage. - ME Critical speed (40-49 Rpm ) should be always avoided. (Product carrier Aframax 6S60MC-C)

5 5 of 5 ME LOAD-UP/DOWN PROCEDURE - Engine Load-up to approximately 50% engine load every second day could be used as a reference starting point. The load-up to approx. 52% MCR (Pi) should be continued for 1-2 hours after which could be reduced again. Based on the documented observation/ reports, the load-up procedure (from 24% MCR (Pi) to 52% MCR (Pi)) could be also disregarded or increased. When the vessel is operated at the higher load 50% ( approx.2 hrs) the cleaning of the Turbocharger and the blowing of Exhaust gas boiler should coincide which such increased load ( e.g. First should be washed the T/C and after blown the Economizer). 4.3 Other Items - During the low load operation due to the reduced exhaust gas economizer steam production there will be an increasing of the Aux. boilers FO consumption to be discussed and offset against the fuel saving. - Fresh water generator: fresh water (distillate) production will be heavily effected during low load operation due to the unusable ME jacket cooling water. The option of using the steam heating (aux.boiler in operation) for fresh water (distillate) production should be carefully considered where applicable. Fresh water (Distillate) produced on board could be segregated for boiler operations, and potable water bunkered in port. The cost of procuring potable water should be discussed and offset against the fuel saving as well the additional fuel consumed for providing the steam heating for operating the FW generator plant. References: MAN Service Letter SL /SBE MAN Service Letter SL /MTS MAN Service Letter SL /MTS Inspection Report Template ( enclosed in SL /MTS) Above Service Letters are normally kept as enclosure to ME Instruction Manual

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