REPAIR & MAINTENANCEf you operate a vessel, its machin- lated causing misalignment. If left un- When machinery is correctly aligned, a thrust bearingsery, without a doubt, will require treated or not replaced, improper support 1-3% increase in energy ef? ciency can • Gear tooth wearalignment many times during the of the engine will cause it to shift and be achieved. • Mechanical rubbingIcourse if its life. When misalign- could compromise the running gear. Since misalignment is a major source • Structural resonancement is present components will be “Depending on the arrangement and of vibration, the most accurate, ef? cient, • Machinery soft-foot conditionsworn, ef? ciency will be lost, and, if left installation, mounts should be changed and economic way to diagnose misalign- Another way to diagnose misalign-uncorrected, mechanical failures are im- every 5-10 years since this is when the ment is to conduct a vibration analysis. ment is by conducting periodic align-minent. This translates into a strain on properties of rubber are most likely to Vibration analysis can identify what me- ment checks. In accordance with good mechanical systems, your budget, and degrade and begin causing problems. chanical issues a vessel is having and marine practice, alignment should be your peace of mind. It’s considered good practice to change eliminates the guesswork that way too checked six months to a year after a new When speaking of alignment in marine main propulsion thrust bearing mounts often comes into play with repair ser- installation; when experiencing a shaft applications, it is usually shaft alignment more frequently, as the absorption of vices. More speci? cally, it can determine seal or bearing failure or when a bearing that is being referenced. Shaft alignment force reduces their life span,” said Rich exactly where misalignment is present. is replaced. Once the data from a vibra-is de? ned as the positioning of two or Merhige, President, Advanced Mechani- “When a client ? rst calls requesting tion analysis or laser check is analyzed more machines which so that at the point cal Enterprises, a mechanical engineer- service work, most speci? cally an en- a proper course of action can be imple-of power transfer from one shaft to an- ing services ? rm headquartered in South gine alignment, the ? rst thing my staff mented, which includes an alignment other, the axes of rotation of both shafts Florida. “Mounts should also be kept asks, is if they’ve had a vibration analy- procedure based on the mechanical ar-should be collinear when the machine is free of any oil, as its contact with rubber sis, to verify and pinpoint the cause of rangement of the components involved running under normal conditions (DB will also cause premature wear.” the misalignment,” said Merhige. “It’s in the misalignment, as well as the spe-Pruftechnik, An Engineer’s Guide to Running aground is another frequent very easy to proceed on the presump- ci? c issue at hand. Shaft Alignment, Vibration Analysis & cause of misalignment. Even getting tion that the cause and location of the Generally speaking, misalignments are Dynamic Balancing, courtesy of LUDE- some line tangled in a propeller can shift misalignment is known. But, without a corrected with either laser and/or opti-CA, Inc.). the struts, causing them to move out of proper diagnosis with vibration analy- cal alignments. Optical alignments are The symptoms of misalignment are alignment. Other causes of misalignment sis, a simple service call could turn into performed using optical borescopes, and often noticeable, and include increased include the changing of the hull shape a major ordeal when issues are continu- must be done out of the water when the vibration, which can shorten machine (hull de? ection), which is why pre-and ously uncovered.” running gear has been removed. Laser life; extra load and added stress on com- post-hull de? ection measurements are Data is collected in accordance with alignment is the process of measuring ponents; and, an increase of heat output crucial for proper alignments. AME uses guidelines set forth by the Society of misalignment between mechanical com-from prime movers, which draws more the Levalign Ultra, a self-leveling rotat- Naval Architects and Marine Engineers, ponents, usually one or more shafts. It is current. This causes increased fuel con- ing laser system to conduct this proce- as well as different class societies. This a precise way to align machinery while sumption, in turn, increasing carbon dure which is vital to successful haul- data provides a thorough machine condi- minimizing the likelihood of human er-emissions. Misalignment in rotating ma- outs. Likewise, a ? nal laser alignment tion evaluation and can detect a multi- ror. It utilizes laser beam transmitters chinery increases energy costs, coupling check should be done oncethe vessel has tude of problems using known frequen- and receivers to attain alignment within damage, and repetitive shaft seal, as well been waterborne, and has had a chance cies speci? c to the vessel, including, but extremely high tolerances.as bearing failure. to settle 24 hours. Hull de? ection is of- not limited to: The ? rst laser alignment systems sur-There are many causes of misalign- ten overlooked during the build process • Misalignment of shaft couplings, faced in the early 1960’s. Laser beams ment, and one of the most common is resulting in misalignment. ? exible machine couplings were applied later to alignment applica-the aging of the engine mounts. Engine Misalignment, regardless of its origin, • Misalignment of underwater run- tions to maintain a line of sight. Prior to mounts have rubber elements which can cause rapid wear on bearings, dam- ning gear such as propeller struts the use of lasers, piano wire was often over time degrade and harden, causing age shafts requiring them to be repaired, • Propeller defects used for alignment. Wire posed prob-wear and an inability to properly isolate and in more extreme cases replaced. • Bent shafts lems, as one could imagine. The weight the forces transmitted by the engine and Extreme vibration can cause increased • Unbalance of rotating components of a wire can cause sagging, and even maintain alignment during operation. damage to engine mounts, and the reduc- • Main engine mis? re problems environmental factors can cause it to Likewise, if the improper mounts were tion gears, sometimes even causing fail- • Mechanical looseness move, causing great inaccuracies. Since used or incorrectly installed, engine ure. Shaft sealing systems can also be- • Deterioration of rolling-element light travels in a straight line, lasers were forces would again not be correctly iso- come damaged, and need to be replaced. bearings within transmissions and an easy choice as a replacement for pre-40 Maritime Reporter & Engineering News • AUGUST 2014MR #8 (34-41).indd 40 MR #8 (34-41).indd 40 8/4/2014 11:22:11 AM8/4/2014 11:22:11 AM