G60ME-C9 Vibration Performance. Successful vibration measurements completed on sea trial

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1 G60ME-C9 Vibration Performance Successful vibration measurements completed on sea trial

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3 Contents Background...5 Cooperation with hull designer...5 Vibration focus...5 Basic considerations when selecting engine and rating...5 Vibration measurements...6 Measurement results...7 Main engine frame...7 Ship structure: navigation deck and wings...7 Top bracing system...8 Other vibration measurements...8 Vibrations on 6G50ME-C9...8 Summary...9 Notes...9

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5 G60ME-C9 Vibration Performance Successful vibration measurements completed on sea trial MAN Diesel & Turbo has succesfully completed structural vibration measurements on the first Green Dolphin 64,000 dwt bulk carrier propelled by the new»green«g-type ultra-long stroke 5G60ME-C9 main engine. Background The S60ME-C8 type engine is already a well-proven propulsion plant for the 64,000 dwt bulk carrier class vessels and, from a vibrational point of view, this hull/engine combination has shown excellent vibration performance. But the market demand for G-type engines is increasing, and shipyards and designers are now offering the 5G60ME- C9 type engine for the 64,000 dwt bulk carrier class vessels, which previously had S-type engines installed. Compared with the S-type engine, the new G-type engine offers a higher power at lower engine speeds. As expected, this changes the main engine s external forces and moments transmitted to the ship hull (vibration forces). Cooperation with hull designer MAN Diesel & Turbo (MDT) has been working in close cooperation with both the hull designer (SDARI) and the engine builder on important installation Fig. 1: Disembarkation from sea trial on 19 January 2014 aspects influencing the engine and hull vibration characteristics and performance. MAN Diesel & Turbo has supplied the engine calculation model (5G60ME-C9) used by the hull designer when performing the global vibration analysis of this 64,000 dwt bulk carrier newbuilding ordered by an Asian owner (Note 1). Based on the hull designer s advanced calculation model of the ship hull, the steel structures have been optimised on both the engine and the hull. Vibration focus The G-type delivers higher, but fully controllable, guide force moments compared with the S-type engine. (Note 2). Special attention has therefore been directed towards the structural vibrations related to this excitation source. Both global hull response (vibration) and local main engine vibration performance was carefully measured and analysed, covering the full operational speed range of the vessel. Basic considerations when selecting engine and rating Avoiding problematic resonance conditions is a key factor in achieving a successful vibration performance. Fig, 2: Hull calculation model (SDARI) with MDT supplied engine model (5G60ME-C) Resonance The frequency of a harmonic excitation coincides with the natural frequency of the mass-elastic system. Depending on the damping of the system, a considerable magnitication of the response will take place at resonance. Magnifications of 5 to 50 times will not be unusual. G60ME-C9 Vibration Performance 5

6 When choosing the optimal engine type and rating, low hull sensitivity towards the excitation frequency range (firing frequency in the engine s operational speed range) is often the most influential factor for a successful vibration performance. In case of resonance in the operational speed range, vibrations can be amplified by a factor of 5-10 as compared to the non-resonant situation. The increase in guide force moment between the G and S type can be a factor of only 1.25 to 1.5, depending on ratings. Therefore, the actual level of the guide force moment has less importance to a successful installation as long as a non-resonant situation is achieved for the engine hull combination. Vibration measurements The actual vibration measurements were taken during sea trials in the East China Sea near Shanghai in January Propulsion of the bulk carrier: Main engine: 5G60ME-C9 MCR: 8,500 kw x 77 rpm. Main particulars of the bulk carrier: Shipyard: New Hantong S/Y Deadweight at scantling: 64,000 dwt Length between pp: m Breadth lmd: m Draught design: 11.3 m Propeller: 5 blades th order Main Engine Frame 5G60ME-C9 Vibration [mm/s], 0-peak MDT recommended vibration limit: 25 mm/s (Zone 1) Per cent [%] of MCR speed G-type rating L4: MCR 77 rpm S-type average rating L1: MCR 105 rpm Fig. 3: Engine frame transverse vibration level (100% G-type (L4) = 77 rpm, 100% S-type (L1) = 105 rpm) 6 G60ME-C9 Vibration Performance

7 Measurement results Main engine frame The transverse vibration level of the engine frame (cylinder frame top) was dominated by vibrations at frequencies 5 times the engine speed (5th order). The excitation sources are the propeller (5 blades) and the main engine guide force moment (also 5th order, firing frequency). Vibration [mm/s], 0-peak Navigation Deck 5 th order 5G60ME-C9 ISO upper limit: 9 mm/s The vibration measurements illustrated in Fig. 3 show low and fully acceptable vibration levels for the main engine structure. The vibration level was well within MAN Diesel & Turbo s permissible limits for the engine frame (Note 3) Per cent [%] of MCR speed navigation deck - transverse navigation deck - vertical navigation deck - longitudial Fig. 4: Navigation deck vibration level (100% G-type (L4) = 77 rpm) Compared with an average vibration level for an S-type engine (based on 8 reference vessels, Note 4), it is clear that the hull and engine vibration performance has been improved for the G- type engine, see Fig. 3. Furthermore, the local main engine structures and components, such as turbochargers, seatings, platforms, exhaust gas receivers, etc., showed low and fully acceptable vibration levels. Vibration [mm/s], 0-peak Navigation Wings 5 th order 5G60ME-C9 ISO upper limit: 9 mm/s Ship structure: navigation deck and wings The vibration level of the navigation deck (5th order) was normal and fully acceptable (within ISO 6954 limits), see Figs. 4 and 5. The measured response was dominated by 5th order vibrations. Compared with measurements taken on the main engine frame, a higher propeller induced vibration was recorded Per cent [%] of MCR speed navigation deck wing - transverse navigation deck wing - vertical navigation deck wing - longitudial Fig. 5: Navigation deck wings vibration level (100% G-type (L4) = 77 rpm) G60ME-C9 Vibration Performance 7

8 Top bracing system The top bracings of the main engine connect the engine frame top level with the hull side structure. The main purpose of this system is to shift the natural frequency (H-mode) out of the operational speed range to avoid a resonance condition (Ref. 1). Average tanker/bulker hulls installed with 50/60 bore engine sizes normally show increased sensitivity for guide This makes the G-type engine a very suitable choice for these hull types, as it is designed to operate in a lower force moment excitations (H-type) speed range. in the higher speed ranges, which is where S-types often operate. Main Engine Frame 35 5 th order 5G60ME-C9 The 5G60ME-C engine was installed with a double-sided top bracing system. This system comprises top bracings on both sides of the engine structure (starboard side and portside). During sea trial, measurements were also taken with only single-sided top bracings connected (on starboard side). These measurements showed similar positive results on both the main engine frame (Fig. 6) and the navigation deck. Vibration [mm/s], 0-peak 30 MDT recommended vibration limit: 25 mm/s (Zone 1) Engine speed [rpm] Other G-type vibration measurements Vibrations on 6G50ME-B9 Recent measurements taken by MAN Diesel & Turbo research engineers on the first 6G50ME-B9 engine during sea trial in February 2014 indicate very promising results for the G-type engine series. top bracings (starboard side only) top bracings (starboard + portside) Fig. 6: Top bracing measurement results for 5G60ME-C9 (SDARI HT64-120) 5G60ME-C9.2 / 6G50ME-B9.3 Main Engine Frame Sea trial measurements performed on: 6G50ME-B9.3 7,700 kw x 93.4 rpm. Oil/chemical tanker (49,780 dwt) Vessel size 183 x 32m Vibration [mm/s], 0-peak MDT recommended vibration limit: 25 mm/s (Zone 1) The vibration values measured are equally low as measured for the 5G60ME-C9 engine, see Fig Per cent [%] of MCR speed 5G60ME-C9.2 - sea trial Januray 2014, MCR: 8,500 kw x 77 rpm 6G50ME-B9.3 - sea trial February 2014, MCR: 7,700 kw x 93.4 rpm Fig. 7: Sea trial vibration measurement results for G50/60 engine types 8 G60ME-C9 Vibration Performance

9 Summary Vibration measurements on the new G- type engine show low and fully acceptable global vibration conditions on both the main engine frame and the vessel superstructure. When comparing this G-type installation (HT ) with most other S-type installations, it is clear that the vibration response is improved. With the right design of the influential hull structures, the hull designer has succeeded in developing a smoothly performing hull/engine combination. Local main engine structures and components such as turbochargers, platforms, exhaust gas receivers, etc., benefit from the low main engine frame vibration. Local main engine structures show low and fully acceptable vibration levels. Vibration forces are controlled with well-proven standard countermeasures (top bracings). Improved fuel oil consumption is achieved with 5G60ME-C9. SDARI ship design of Green Dolphin 64,000 dwt bulk carrier with 5G60ME-C9 is available. Notes Note 1 A full range of engine calculation models (finite element model) are available (free of charge) from the MAN Diesel & Turbo extranet website called Nexus. The engine calculation models are added to the shipyard s hull model, thereby obtaining an accurate calculation model of the combined system. Note 2 The so-called guide force moments are caused by the gas force on the piston and by the inertia forces. The H-type type guide force, which is dominant on the 5-cylinder engine, tends to rock the engine top in transverse direction. Note 3 MAN Diesel & Turbo vibration limits (single order, 0-peak): Zone 1 [0-25 mm/s]: recommended. Zone 2 [25-50 mm/s]: acceptable for main engine. Under adverse conditions, annoying/harmfull vibrations may occur in the connected structure/vessel. Zone 3 [> 50 mm/s]: not acceptable for main engine. Note 4 S-type average vibration level. MDT vibration measurements used in average (5-cylinder S60 bore types): 5S60MC-C (11,300 kw x 105 rpm): oil products tanker (69,554 t), size: 228 x 32 m 5S60MC-C (11,300 kw x 105 rpm): bulk carrier (75,750 t), size: 225 x 32 m 5S60MC-C (11,300 kw x 105 rpm): oil products tanker (46,011 t), size: 183 x 32 m 5L60MC-C (6,650 kw x 111 rpm): fruit juice tanker (15,108 t), size: 146 x 22 m 5S60MC-C (8,990 kw x 92 rpm): bulk carrier (74,477 t), size: 225 x 32 m 5S60MC-C (11,900 kw x 105 rpm): general cargo ship (49,924 t), size: 208 x 32 m References Ref. [1] - Vibration Characteristics of Two-stroke Low Speed Diesel Engines, MAN Diesel & Turbo paper, Id. no.: p S60MC-C (11,300 kw x 105 rpm): crude oil tanker (73,626 t), size: 228 x 32 m 5S60MC-C (11,300 kw x 105 rpm): oil products tanker (46,098 t), size: 183 x 32 m G60ME-C9 Vibration Performance 9

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12 All data provided in this document is non-binding. This data serves informational purposes only and is especially not guaranteed in any way. Depending on the subsequent specific individual projects, the relevant data may be subject to changes and will be assessed and determined individually for each project. This will depend on the particular characteristics of each individual project, especially specific site and operational conditions. Copyright MAN Diesel & Turbo ppr Feb 2014 Printed in Denmark MAN Diesel & Turbo Teglholmsgade Copenhagen SV, Denmark Phone Fax MAN Diesel & Turbo a member of the MAN Group