Gemi kıç takıntılarında kalite kontrol ve iş planı

Abstract

Gemi hareketleri ve manevraları genellikle gemi kıç takıntıları olan pervaneler ve dümenler aracılığıyla gerçekleştirilir. Bu çalışmada geminin hareketlerini sağlayan kıç yapı elemanlarının atölye şartlarından başlayarak, gemi bünyesine montajı tamamlanıncaya kadar geçen süreç ele alınmıştır. Bu süreyi uygun iş akış şemaları oluşturularak en aza indirme yoluna gidilmiş ve bir iş sırası oluşturulmuştur. Bunun yanında yapılan işin kalitesini en üst seviyede tutabilmek için sağlanması gereken şartlar ve kısıtlar araştırılmıştır. înşa edilen gemileri klaslandırmak tersanelerin en önemli sorunlarındandır. Zira geminin çalışacağı sularda sağlanması gereken yapısal kısıtlar, çalışacak bölgede geçerli olan yada dünyaca geçerli olan klaslama kuruluşlarınca belirlenmiştir. İncelemekte olduğumuz gemi kıç takıntıları olan pervane ile dümenler ve bu elemanları gemi bünyesine bağlayan kıç yapılar hakkında dünya ülkelerince geçerliliği kabul edilmiş AB S (American Bureau of Shipping) ve DNV (Det Norske Veritas) klas kuruluşlarının istek ve kısıtlan yanında Türk Loydu'nun da kabulleri incelenerek, 'etkin bir kıç yapı ve elemanları nasıl oluşturulur?' sorusuna cevap aranmıştır. Gemi inşaatında bütün işler, atölyede başlar ve imal edilen bütün elemanların gemiye montajı ile son bulur. İmalatı yapılacak elemanların sağlaması gereken mekanik ve kimyasal yeterliliğin tesbiti ve oluşturulacak ürün malzemesinin sağlayacağı şartlar ve hazırlanması gereken sertifikalar araştırılacaktır. Bahsedilen elemanların imalatından, montaj sonuna kadar geçirdiği aşamalar ve hangi aşamada klaslama şirketinin ve gemi sahibi temsilcisinin onayının alınması gerektiği her bir iş adımında belirtilmiştir.

The classification process consists of, i) The development of rules, guides, standards, and other criteria for the design and construction of marine vessels structures, for materials, equipment and machinery. ii) The review of design and survey during and after construction to verify compliance with such rules, guides, standards or other criteria. iii) The assignment and registration of class when such compliance has been verified. Plans from designers and shipbuilders should generally be submitted in triplicate, one copy to be returned to those making the submission, one copy for the use of the surveyor where the vessel is being built, and one copy to be retained in the technical office for record. Manufacturers' plans are to be submitted in quadruplicate of the shipbuilder. However additional copies may be required when the plan review is to be performed by a Lloyd's technical office other than headquarters office or when the required attendance of the surveyors is anticipated at more than one location. All plan submission originating from manufacturers are understood to be made with the cognizance of the shipbuilder. A fee may be charged for the review of plans for which there is no contract of classification. For steel castings, the manufacturer's name or identification mark and pattern number is to be cast on all castings except those of such small size as to make this type of marking impracticable. If the results of the physical tests for any casting or any lot of castings do not conform to the requirements specified, the manufacturer may re- heat-treat the castings. Retests of additional specimen or specimens are to be made and are to conform to the requirements specified. All castings are to be either fully annealed, normalized or normalized and tempered in a furnace of ample proportions to bring the whole casting to uniform temperature above the transformation range on the annealing or normalizing cycle. At least one tension test is to be made from each heat-treatment charge. However, if the manufacturer's quality-control procedure includes satisfactory automatic chart recording of temperature and time, then one tension test from each heat for casting subject to the same heat-treating procedure may be allowed at the discretion of the attending surveyor. All castings are to be inspected by the surveyor after final heat treatment and through cleaning to insure that the castings are free from defects. Where stern posts and shoepieces are of cast steel are to be effectively attached to the adjacent structure preferably by a flushbutt cored out to avoid large masses of thick material likely to contain defects and to maintain a relatively uniform section throughout. Suitable radii are to be provide in way of changes in section. The strength of the rudder horn is to be based on the most critical location at any point up to and in way of the connection into the hull. Webs, extending down ÖZET Gemi hareketleri ve manevraları genellikle gemi kıç takıntıları olan pervaneler ve dümenler aracılığıyla gerçekleştirilir. Bu çalışmada geminin hareketlerini sağlayan kıç yapı elemanlarının atölye şartlarından başlayarak, gemi bünyesine montajı tamamlanıncaya kadar geçen süreç ele alınmıştır. Bu süreyi uygun iş akış şemaları oluşturularak en aza indirme yoluna gidilmiş ve bir iş sırası oluşturulmuştur. Bunun yanında yapılan işin kalitesini en üst seviyede tutabilmek için sağlanması gereken şartlar ve kısıtlar araştırılmıştır. înşa edilen gemileri klaslandırmak tersanelerin en önemli sorunlarındandır. Zira geminin çalışacağı sularda sağlanması gereken yapısal kısıtlar, çalışacak bölgede geçerli olan yada dünyaca geçerli olan klaslama kuruluşlarınca belirlenmiştir. İncelemekte olduğumuz gemi kıç takıntıları olan pervane ile dümenler ve bu elemanları gemi bünyesine bağlayan kıç yapılar hakkında dünya ülkelerince geçerliliği kabul edilmiş AB S (American Bureau of Shipping) ve DNV (Det Norske Veritas) klas kuruluşlarının istek ve kısıtlan yanında Türk Loydu'nun da kabulleri incelenerek, 'etkin bir kıç yapı ve elemanları nasıl oluşturulur?' sorusuna cevap aranmıştır. Gemi inşaatında bütün işler, atölyede başlar ve imal edilen bütün elemanların gemiye montajı ile son bulur. İmalatı yapılacak elemanların sağlaması gereken mekanik ve kimyasal yeterliliğin tesbiti ve oluşturulacak ürün malzemesinin sağlayacağı şartlar ve hazırlanması gereken sertifikalar araştırılacaktır. Bahsedilen elemanların imalatından, montaj sonuna kadar geçirdiği aşamalar ve hangi aşamada klaslama şirketinin ve gemi sahibi temsilcisinin onayının alınması gerektiği her bir iş adımında belirtilmiştir. 7) Alignment and fitting of rudder unit elements. Spotting out of surface and negative allowances of cones into holes. Result of alignment, fitting and negative allowances present to receipt by classification society surveyor and shipowner representative. Vertical and horizontal diaphragms are to be fitted within the rudder, effectively attached to each other and to the side plating. Propeller can be divided into the three main categories fixed pitch, cotrollable pitch and directional pitch. Fixed pitch propellers are most likely the to be found on deep sea merchant vessels the name suggests that the pitch is constant over the radius of the blade but this not so. The pitch varies from the root to the tip of the blade, the effective fitch being mean value found by calculation or experiment. The material of the propellers is to be tested in the presence of and inspected by a surveyor in accordance with the requirements. The bronze castings are to be free from injurious defects. At least one tension test is to be made from each melt and the tension test conform to an approved specification for chemical analysis may be taken from test coupons or represantative castings the manufacturer's name and other appropriate identification markings are to be stamped on each propeller or propeller blade in such location as to be discernible after finishing and assembly. The traditional method of attaching the propeller to the tail shaft was by taper and key. A taper of 1 in 15 or, more commonly, 1 in 12 was used, the propeller being driven up hard using wedges and spanners on the propeller nut. It can be appreciated that the mating surfaces of the tail shaft and propeller were of utmost importance. Scraping of the propeller boss taper demanded good workmanship to give the ruquired fit. The fit was tested by blueing the tailshaft, pushing on the propeller,and than examining the marking on the propeller boss taper. A contact of 70-80% concidered necessary, particularly at the top and of the taper, to give the necessary interference fit after final push up. A poor fit resulted in the key itself being subjected to extremes of torque and therefore the key suffering damage. The thrust from the propeller assisted in the push up and sometimes led to difficulties when the propeller had to be removed. The introduction of higher powers, and hence the high torque on the shaft, can cause high stress concentrations on the taper, in particular at the keyway. These stress concentrations are present if the key is taking any appreciable load and lead to shaft failure. To this end removal of the key and keyway is desirable. Various methods are available. There are several methods of fitting keyless propellers; flange mounting, pilgrim fitting, oil injection fitting. Flange mounting method is generally standard practice for controllable pitch propellers but can also be found on a number of fixed pitch propellers. With flange mounted propellers a muff coupling is required inboard to facilitate withdrawal of the tail shaft out through the stern. The flange attachment requires fitted bolts to transmit the torque to the propeller without risk of movement. This enables the propeller boss to be hollow which can be achieved in the casting process. Pilgrim fitting method was introduced in 1968 and has proved successful on large ships transmitting large powers. A cast-iron sleeve is set into the bronze boss of the propeller and the whole assembly is pushed on to the drive shaft, to the require degree of interference fit, using a pilgrim nut, the axial travel being monitored by use of a clock gauge. Mil Oil injection fitting is a major method of keyless fitting which does not employ the cast-iron sleeve but relies on the coefficient of friction between the propeller boss and the steel shaft. A typical value of coefficient of friction is 0.12 but depends on classification society rules. Oil is injected into the annular spaces around the propeller boss thereby expanding the boss. At the same time, the hydraulic nut is used to push the propeller up the shaft taper. It should be noted that the load on the hydraulic nut before oil is injected is recorded and should be approximately 10% of the final load. The most important aspect of the fitting is to monitor the axial movement of the boss up the shaft taper using clock gauges which ensures the corect degree of interference fit. If the oil pressure is out of line with that expected it indicates that some part of the boss is not expanding properly, and either oil is escaping too freely or there is a blockage in the hydraulic system. The key of propeller is to have a true fit in the hub. Where the propellers are fitted without keys, detailed stress calculation and fitting instruction are to be submitted for review. For oil injection method of fit the coefficient of friction is to be taken no greater than 0.13 for bronze/steel propeller bosses on steel shafts. For dry method of fit using cast iron on steel shafts the coefficient of friction is to be taken no graeter than 0.18. The exposed steel of the shaft is to be protected from the action of the water by filling all spaces between cap, hub and shaft with a suitable material the propeller assembly is to be sealed at the forward and with a well-fitted soft-rubber packing ring. When the rubber ring is fitted in an external gland, the hub counter bore is to be filled with suitable material, and clearances between shaft liner and hub counter bore are to be kept to a minimum. When the rubber ring is fitted internally, ample clearance is to be provided between liner and hub and the ring is to be sufficiently oversize to squeeze into the clearance space when the propeller is driven up on shaft; and, where necessary, a filler piece is to be fitted in the propeller-hub keyway to provide a flat unbroken seating for the ring. The recess formed at small and of the taper by the overhanging propeller hub is to be packed with red-lead putty or rust- preventive compound before the propeller nut is put on. Rubber, reinforced resins, plastic metarials, resinous, densehardwoods the length of the bearing, next to and supperting the propeller, is to be not less than four times the required tail-shaft diameter. The length of white-metal-lined, oil lubricated propeller and bearing fitted with an approved oil-seal gland is to be on the order of two times the ruquired tail shaft diameter. The length of the bearing may be less provide the nominal bearing pressure is not more than 0.80 N/mm2 as determined by static bearing reaction calculation taking into account shaft and propeller weight which is deemed to be exerted solely on the aft bearing, divided by the projected area of the shaft. The minimum length, however, is not to be less than 1.5 times the actual diameter. The thickness of bronze liners to be fitted to tail shafts or tube shafts of vessels is not to be less in way of bearings than add of 5.1 mm and 0.04 times the tail shaft diameter(mm). The post machining thickness of stainless steel clad liners to be fitted to tail shafts or tube shafts for vessels in salt water service is not to be less than one-half that required for bronze liners or 6.5 mm whichever greater. Continuous liners are to be in one piece or, if made of two or more lengths, the joining of the separete pieces is to be done by an approved method of fushion through not less than two-thirds the XIV thickness of the liner or by an approved rubber seal. If the liner does not fit the shaft tightly between the bearing portions, the space between the shaft and liner is to be filled by pressure with an insoluble noncorrosive compound. When adjusting the propeller to the shaft: Before first propeller fitting, the bore in the propeller boss to be adjusted to the shaft cone; contact area, between mating surface prior to pull-up to be at least 70% of total cone area. Contact places should be equally distributed all over the perimeter and length of the cone; special attention to be paid to proper contact at both ends of propeller bore. Adjusting the rudder cone to the rudder pintels can install same way.