PART B AMENDMENT OF THE GUIDANCE TO THE RULES AND ITS EXPLANATORY NOTES 3 1.3 Load Condition and Evaluation of Calculation Results 1.3.1 Light Draught Condition (Cold Condition) -1 Shaft alignment calculations are to be performed assuming that the ship is in the light draught condition and the main propulsion machinery is in the cold condition. In cases where the shafts are coupled before launching, the shaft alignment calculation is to be performed for the coupled condition instead of for the light draught condition without taking the buoyancy force on the propeller into account. -2 When the aftmost stern tube bearing consists of oil-lubricated white metal, an evaluation is to be made of the nominal bearing pressure together with either the relative inclination between the propeller shaft and aftmost stern tube bearing or the maximum bearing pressure in the aftmost stern tube bearing, either of which is determined in order to prevent edge loading on the bearing. Each calculated value is to be within the allowable limit shown in Table 1.3.1-2. Table 1.3.1-2 Allowable Limits for Aftmost Stern Tube Bearing (Oil-lubricated White Metal) Allowable limit Notes Nominal bearing pressure 0.8 MPa Relative inclination between the propeller shaft and the aftmost stern tube bearing 3 × 10 -4 rad Applicable where number of support points is one or two. For two support points, relative inclination is to be calculated at each end of the bearing (see Figure 1.3.1-2(a)). Maximum bearing pressure 40 MPa Applicable where the maximum bearing pressure is calculated (see Figure 1.3.1-2(b)). Figure 1.3.1-2(a) Relative inclination. Figure 1.3.1-2(b) Maximum bearing pressure. -3 The bending moment (absolute value) calculated at any bearing is not to be more than the value determined for the aftmost stern tube bearing. -4 In principle, the bearing load calculated at each bearing is to be a positive value. However, for the aftmost bearing of a two-stroke cycle diesel engine, a bearing load of zero may be accepted (negative value is not acceptable) subject to the agreement of the engine manufacturer. The direction of the bearing load is shown in Figure 1.3.1-4. Figure 1.3.1-4 Direction of bearing load. Propeller shaf t A ftmost stern tube bearing Relative inclination Pressure distribution Maximum bearing pressure Bearing load (positive) Shaft Bearing load (negative) Shaft PART B AMENDMENT OF THE GUIDANCE TO THE RULES AND ITS EXPLANATORY NOTES 4 1.3.2 Light Draught Condition (Hot Condition) -1 Shaft alignment calculations are to be performed assuming that the ship is in the light draught condition and the main propulsion machinery is in the hot condition. In this case, the increases in offset specified by the manufacturer for the engine bearings and the bearings in the reduction gear are to be considered for the hot condition. -2 The full immersion condition of the propeller may also be taken into account in the calculation. -3 When the shafts are coupled before launching, the calculation is to be performed under the assumption that there is no change in the bearing offsets from the reference line between the conditions before and after launching. -4 The bearing load calculated at each bearing is to be a positive value. -5 For shafting with a reduction gear, the difference in the bearing loads between the fore and aft bearings of the wheel gear in the hot condition is to be within the allowable limit specified by the manufacturer. -6 The bending moment due to eccentric thrust of the propeller may be taken into account in the calculation. 1.3.3 Full Draught Condition (Hot Condition) -1 The shaft alignment for oil tankers, ships carrying dangerous chemicals in bulk, bulk carriers, and general dry cargo ships is to be designed so as to satisfy the following criteria in order that all engine bearings are fairly evenly loaded, even under the hull deflection that occurs when the ship is in the full draught condition. The extent of relative displacement due to the difference between hull deflection that occurs in the light draught condition and hull deflection that occurs in the full draught condition which results in the second or third aftmost engine bearing becoming unloaded, as measured at the aftmost bulkhead of the engine room (calculated as δ B2 and δ B3 , respectively), is to be greater than the allowable lower limit δ BM shown in Fig. 1.3.3-1 (a). Figure 1.3.3-1(a) Allowable lower limit, δ BM , for δ B2 and δ B3 . The relative displacements, δ B2 and δ B3 , above are to be calculated using the equations shown in sub-paragraphs (1) or (2) below, depending on the type of bearing support adopted (elastic or rigid support) that is used to calculate the reaction influence numbers in the alignment calculations. (1) In the case of elastic support, δ B2 and δ B3 can be obtained with i =2 and 3, respectively: L ( m m ) Distance from the support point of the aftmost engine bearing to the aftmost bulkhead of the engine room (see Figure 1.3.3-1(b)). 5 7 9 11 13 15 x 10 3 10 8 6 4 2 0 δ BM ( mm ) PART B AMENDMENT OF THE GUIDANCE TO THE RULES AND ITS EXPLANATORY NOTES 5 δ B i = - R i / S i where, i: Engine bearing number as counted from the aft of the engine R i : Reaction force at engine bearing No. i determined by the calculation in 1.3.2 ( kN ) S i : Influence number for engine bearing No. i when the hull deflection at the aftmost bulkhead of the engine room becomes - 1 mm ; obtained from the following equation ( kN/mm ): ∑∑ − = −+ − = −+ +−= 1 5.1 ,1 1 1 ,1 )5.05.1( b an nnib a n nnibi xCxCS LXx nn /= n: Support point number of the shafting (counted from the aft of the shafting) a : Number of the nearest support point forward of the aftmost bulkhead of the engine room (counted from the aft of the shafting) b: Support point number of the aftmost engine bearing (counted from the aft of the shafting) X n : Distance from the support point b to the support point n ( mm ) L: Distance from the support point b to the aftmost bulkhead of the engine room ( mm ) C m, n : Influence number at the support point m when the relative displacement at the support point n becomes - 1 mm ( kN/mm ) (see Figure 1.3.3-1(b)). Figure 1.3.3-1(b) Engine bearing numbers and support point numbers. (2) In the case of rigid support, δ B2 and δ B3 can be obtained by solving the following simultaneous equations (1) and (2), respectively: S 1 δ B2 + (C 1, 1 -K) δ 1 + C 1, 3 δ 3 + C 1, 4 δ 4 + C 1, 5 δ 5 = C 1, 2 R 2 /K S 2 δ B2 + C 2, 1 δ 1 + C 2, 3 δ 3 + C 2, 4 δ 4 + C 2, 5 δ 5 = (C 2, 2 -K) R 2 /K S 3 δ B2 + C 3, 1 δ 1 + (C 3, 3 -K) δ 3 + C 3, 4 δ 4 + C 3, 5 δ 5 = C 3, 2 R 2 /K S 4 δ B2 + C 4, 1 δ 1 + C 4, 3 δ 3 + (C 4, 4 -K) δ 4 + C 4, 5 δ 5 = C 4, 2 R 2 /K S 5 δ B2 + C 5, 1 δ 1 + C 5, 3 δ 3 + C 5, 4 δ 4 + (C 5, 5 -K) δ 5 = C 5, 2 R 2 /K S 1 δ B3 + (C 1, 1 -K) δ 1 + C 1, 2 δ 2 + C 1, 4 δ 4 + C 1, 5 δ 5 = C 1, 3 R 3 /K S 2 δ B3 + C 2, 1 δ 1 + (C 2, 2 - K) δ 2 + C 2, 4 δ 4 + C 2, 5 δ 5 = C 2, 3 R 3 /K S 3 δ B3 + C 3, 1 δ 1 + C 3, 2 δ 2 + C 3, 4 δ 4 + C 3, 5 δ 5 = (C 3, 3 - K) R 3 /K S 4 δ B3 + C 4, 1 δ 1 + C 4, 2 δ 2 + (C 4, 4 -K) δ 4 + C 4, 5 δ 5 = C 4, 3 R 3 /K S 5 δ B3 + C 5, 1 δ 1 + C 5, 2 δ 2 + C 5, 4 δ 4 + (C 5, 5 -K) δ 5 = C 5, 3 R 3 /K Aftmost bulkhead of E/R Intermediate shaf t Pro p eller shaf t Crankshaft i L X 1 X 4 Aftmost engine bearing m, n = 1 2 3 4 (=a) 5(=b) 6 7 8 9 (1) (2) PART B AMENDMENT OF THE GUIDANCE TO THE RULES AND ITS EXPLANATORY NOTES 6 where, K: Stiffness of bearing support, given as K = 5,000 ( kN/mm ) S i : Influence number for engine bearing i (See (1) above) C i, j : Influence number for engine bearing i when the relative displacement at engine bearing j becomes - 1 mm ( kN/mm ). (The numbers i and j are counted from the aft of the engine.) δ i ( i =1, 2, 3, 4, 5): Elastic relative displacement at each engine bearing resulting from the relative displacement δ B2 and δ B3 . ( δ i is unknown.) -2 Notwithstanding the provisions of sub-paragraph 1.3.3-1, the Society may examine and accept alternative criteria, provided that a document is submitted that makes it possible to evaluate the condition of the engine bearings when the ship is in the full draught condition. -3 Other documents, such as those showing the results of structural analysis to evaluate the extent of hull deflection, may be required by the Society in cases where the stern hull construction is considered to be unconventional. 1.4 Matters relating to Shaft Alignment Procedures 1.4.1 Sags and Gaps between Shaft Coupling Flanges Sags and gaps between shaft coupling flanges in the uncoupled condition are to be calculated under the condition that the bearing offsets from the reference line are those used in the calculation described in paragraph 1.3.1 above. Figure 1.4.1 Sag and gap between shaft coupling flanges. 1.4.2 Procedure for Measuring Bearing Loads In cases where the bearing load is measured using the jack-up technique, a document describing the measurement procedures followed, including jack-up positions, load correction factors, and expected jack-up loads, is to be prepared. The immersion of the propeller at the time of the measurement is also to be considered in the bearing loads measured. SAG GAP 1 GAP 2 GAP = GAP 1 + GAP 2 PART B AMENDMENT OF THE GUIDANCE TO THE RULES AND ITS EXPLANATORY NOTES 7 EXPLANATORY NOTES 1.1 General 1.1.1 Application -1 In the design of shafting alignment, it is important to give the shaft as much flexibility as possible against changes in bearing offsets caused by the effects of temperature and hull girder deflections as well as to reduce the loads that concentrate at the aft end of the aftmost bearing due to the weight of the propeller. Therefore, the following measures are generally taken to accommodate these offsets: installation of the main engine below a predetermined reference line, installation of the intermediate shaft bearing at a location far away from the main engine to some extent, and other steps deemed suitable for the design adopted. In the Society’s previous version of the Guidance to the Rules, shafting alignment calculations were required only for oil-lubricated propeller shafts, where the length of the stern tube bearing is shorter than that determined by the Rules or where the shaft is intended to be classed as a Kind 1C type shaft. However, because shafting alignment is originally to be examined without any relation to these conditions, it was determined in the new version of the Guidance to the Rules that the calculations are to be applied to all ships with oil-lubricated propeller shafts excluding small ships, as described below. Figure 1.1 shows the relationship between the diameter of propeller shafts and main engine output. As can be seen from this figure, most of the oil-lubricated systems include a propeller shaft of 400 mm or more. In the range of 300 - 400 mm, the region of the oil-lubricated systems overlaps that of seawater-lubricated systems. However, comparatively few cases of damage are found in engine bearings as well as stern tube bearings in the oil-lubricated systems in this range. For this reason, small ships having a propeller shaft less than 400 mm in diameter are exempt from the application of the calculation requirement, even if the shaft is of an oil-lubricated type (see 6.2.13, Part D of the Rules). Figure 1.1 Relationship between propeller shaft diameter and main engine output. Shafting alignment is affected by changes in temperature and hull deflection. In the calculation sheets submitted until now, the examination of temperature changes has generally depended on the shipbuilders’ design; that is, some shipbuilders had examined only cold condition while other shipbuilders examined both cold and hot conditions. However, no shipbuilders had examined the 0 200 400 600 800 1000 1200 100 1,000 10,000 100,000 Main engine output (kW) Diameter of propeller shaft (mm) Oil-lubricated shaft (Kind 1C) Seawater-lubricated shaft PART B AMENDMENT OF THE GUIDANCE TO THE RULES AND ITS EXPLANATORY NOTES 8 effects of hull deflections due to changes in ship draught for the reason that highly accurate estimates were difficult and few measurement examples existed. In the amended Guidance , the calculation conditions to be applied were determined according to the type of main engine installed considering the effects of changes in temperature and draught, as shown in Table 1.1.1-1 in the Guidance . As can be seen from the table, the Guidance requires alignment calculations for both cold and hot conditions under the ship’s light draught condition, regardless of the type of main engine employed. In addition, when a two-stroke cycle diesel engine is installed, calculations are also required aimed at preventing unloading of the engine bearings due to hull deflection under full load condition (hot condition). The calculation equations used in this case are applied to ships with large differences in draught, such as tankers, bulk carriers, and the like, but not to container ships, pure car carriers, or similar types of ships. Also, paragraph 1.3.3 in the revised Guidance does not apply to two-stroke cycle geared diesel engines, because provisions for two-stroke cycle engines were prepared assuming a direct coupled engine. -2 Where the length of the stern tube bearing is made shorter than that determined by the Rules or where the propeller shaft is classed as a Kind 1C type shaft, provisions quite similar to those set in the previous version of the Guidance are applied to shafting systems having an oil-lubricated propeller shaft of less than 400 mm in actual diameter. -3 The shafting alignment design mostly depends upon the knowledge and know-how of shipbuilders and engine manufactures, and thus may not necessarily be based on the same or common criteria. Therefore, even if the criteria proposed differ from those stated in the Guidance , the Society will approve a design where the criteria are found to be acceptable. 1.1.2 Calculation Sheet of Shaft Alignment The diameter and length of shafts, bearing length, concentrated loads, loading points, bearing support points, and bearing offsets from reference line are input data for shafting alignment calculations. It is also necessary to check the calculations themselves. Therefore, these data should be specified in the drawing. The reaction influence number (also known as “reaction influence coefficient”) is an important parameter that relates to the flexibility of the shaft. As shown in Figure 1.2.2-3 in the Guidance , the alignment calculations are to be carried out considering five or more bearings from the aft of the engine, and all reaction influence numbers are to be specified in the drawing. However, a simplified description that includes only five engine bearings is acceptable in cases where the actual calculation is made considering five or more engine bearings (for example, all engine bearings). At a minimum, the bending moment acting on the shaft and the displacement of the shaft are to be illustrated in the calculation results, and bearing loads (bearing reactions) are to be shown in an accompanying table. The relative slope between the propeller shaft and the aftmost stern tube bearing is to be shown with the position of the bearing support in the figure. In cases where the bearing load (or pressure) acting on the aftmost stern tube bearing is calculated as a distributed load (or pressure), the maximum bearing pressure is to be shown with a figure illustrating the distribution. The sag and gap between coupling flanges and the jack-up load in the bearing load measurement (where required by the Guidance ) are important information to be confirmed by the field surveyor. Therefore, a document describing the measurement procedure employed including the calculated values is also to be submitted to the Society. Moreover, the calculated values (target values) are to be indicated with the applicable tolerances. PART B AMENDMENT OF THE GUIDANCE TO THE RULES AND ITS EXPLANATORY NOTES 9 1.2 Model of Shafting 1.2.1 Loads -1 In the amended version of the Guidance , a static load, i.e., the load acting on the shafting system when the shaft is in the stand-still condition, is to be used in the shaft alignment calculations. These provisions are the same as those in the previous version of the Guidance . However, there are some cases where the bearing strength and certain other factors cannot be assessed accurately using only a static load. Such examples are described below. Bending moment due to hydrodynamic propeller forces The center of effort of the propeller mean thrust force differs from the actual center of the propeller due to the non-uniform distribution of the ship’s wake. Figure 2.1 shows a schematic of this effect. When a propeller blade rotates in the wake, it generates a larger thrust force in the upper side of the propeller center than in the lower side This leads to the generation of an eccentric thrust that act on the propeller resulting in the generation of bending moment, M P , in the illustrated direction. Figure 2.1 Bending moment due to hydrodynamic propeller forces. In general, the bending moment, M P , can be said to be a kind of “safety enhancing” moment, because it acts so that edge loading on the aft portion of the aftmost bearing may be reduced. M P also causes a comparatively small change in load on the intermediate shaft bearings and engine bearings. However, in a shafting system that includes reduction gears, small changes in the inclination of the gear shaft may possibly affect the strength of the gear teeth. Therefore, in order to examine the strength of the gear teeth in detail, it is necessary to confirm the changes in load that take place on the gear shaft bearings using alignment calculations for the hot condition considering the effect of M P . Bending moment that acts on thrust shaft In a large two-stroke cycle diesel engine fitted with a crankshaft that is integrated with the thrust shaft, the thrust pads are, in most cases, not arranged over the entire circumferential plane of the thrust collar. In this case, a bending moment, M T , will act on the thrust shaft while the ship is underway, as shown in Figure 2.2. Figure 2.2 Bending moment acting on the thrust shaft. This M T need not be input in the alignment calculation because the calculation required by the Guidance is for the static condition. M T may also act as a kind of “safety enhancing” moment in view of the effect that it has on preventing the unloading of the second aftmost engine bearing Large thrust force Small thrust force M P M T Thrust collar Thrust Thrust pads Arrangement of thrust pads A ftmos t engine bearing PART B AMENDMENT OF THE GUIDANCE TO THE RULES AND ITS EXPLANATORY NOTES 10 caused by hull deflection. However, unloading of the aftmost engine bearing might occur in a ship in the light design draught condition. In order to prevent such a situation, it is important to confirm the load of the aftmost bearing by the alignment calculation considering M T . -2 Consideration needs to be given to buoyancy when evaluating the load that acts on a propeller. Since the extent to which the propeller becomes immersed varies depending on the draught condition of the ship, the load is to be obtained by subtracting the effect of buoyancy due to immersion of the propeller from the weight of the propeller for that condition. In addition, it is also recommended that buoyancy due to the lubricant in the stern tube also be considered, even though such buoyancy will only have a small effect on the calculation results. If the camshaft of the engine is driven by the crankshaft using a chain, the tension of the chain has a comparatively large effect on the load of the aftmost and second aftmost engine bearings in cases where the tension acts on the thrust collar. Consequently, this tension also needs to be included in the calculation. 1.2.2 Bearings -1 When performing a static alignment calculation, a model with one or two support points is used in most cases for the aftmost stern tube bearing. The position of the support points is usually assumed to be L/4 or D/3 (in the case of one-point support) or both ends of the bearing (in the case of two-point support), which is considered to be normal practice in alignment design. However, it is difficult to determine uniformly fixed positions for the support points in the Guidance because the position will depend on the design of the alignment. Hence, a support point position that differs from the above fixed positions will also be acceptable, unless it is significantly distant from the normally standard position. -2 With respect to the support condition of the bearings, a rigid (simple) support approach is used in many alignment calculations, whereas there are few examples in which elastic (spring) support is used. An oil-film support is needed for dynamic calculations. However, the effect of the oil-film need not be considered in the Guidance , as the Guidance focuses on static calculations. -3 In order to construct an exact model for alignment calculation, it is desirable to include all engine bearings in the model. However, there have been numerous examples of calculation done until now that have used a reduced number of engine bearings for the reason that there was little difference in the load acting on the intermediate shaft bearing. Figure 2.3 shows the effect that the number of bearings included in the calculation has on the bearing loads. Figure 2.3 Effect of the number of engine bearings included in the calculation of bearing loads. No. 1 - No. 3 No. 1 - No. 4 No. 1 - No. 5 No. 1 - No. 6 No. 1 - No. 7 No. 1 - No. 8 No. 1 - No. 9 Engine bearings calcul a ted ( 7 -cylinder engine) No. 1 (aftmost engine bearing) No. 2 No. 3 Identification number of engine bearings Bearing loads PART B AMENDMENT OF THE GUIDANCE TO THE RULES AND ITS EXPLANATORY NOTES 11 According to this figure, the loads on the aftmost and the second aftmost engine bearings change significantly with an increase in the number of engine bearings included in the calculation. It can be seen that five or more bearings are necessary in order to obtain a reasonably accurate calculation of the bearing loads. It was thus determined from this fact that at least five engine bearings from the aft of the engine are to be included in the calculation model. 1.2.3 Equivalent Diameter of Crankshaft When conducting an alignment calculation, the actual complex shape of the crankshaft needs to be replaced with a simple beam (round bar). In the previous version of the Guidance , the use of an equivalent shaft to represent the crankshaft was not prescribed. Consequently, there have been cases when a simple beam with a diameter equivalent to the crank journal had been used when carrying out alignment calculations. However, the diameter of the equivalent crankshaft model in recent two-stroke diesel engines used for propulsion has tended to become considerably smaller as the piston stroke has become longer. In large, long stroke engines, the diameter has become approximately 60% of the journal diameter. Because the bending stiffness of the equivalent shaft can differ markedly from that of the crank journal, a brief description of the equivalent crankshaft model has been added in the revised version of the Guidance in order that the most suitable equivalent diameter may used in the alignment calculations. In principle, calculation of the equivalent diameter is to be conducted in accordance with the instructions of the engine manufacturer. An approximation equation developed by the Society [1] is also available that may be used in addition to the guidelines of the manufacturer. 1.2.4 Shafting with Reduction Gear The calculation model for a shafting system with a reduction gear, such as a main steam turbine system or a geared diesel engine, generally ranges from the propeller to the fore bearing of the wheel gear shaft. This approach has been newly described in the Guidance . PART B AMENDMENT OF THE GUIDANCE TO THE RULES AND ITS EXPLANATORY NOTES 12 1.3 Load Condition and Evaluation of Calculation Results 1.3.1 Light Draught Condition (Cold Condition) -1 Shaft alignment calculation for the cold condition is the basic calculation method used when determining the positioning and installation of the shafting system. The calculation procedure consists of first determining the positions of the bearings so that the proper values for the bearing loads may be attained when the shafts are coupled in the cold condition. Next, the amount of sag and gap between the coupling flanges is calculated in order that the bearings may be installed in the calculated positions. Coupling of the shafts is generally done in the light ballast condition (the draught condition in which the propeller blades are exposed above the surface of the sea) after launching; however, in some cases it is done while the ship is in the drydock condition before launching. The approach adopted depends on the shipbuilder. It is therefore specified that application of the Guidance would also include such situations. -2 The strength of the aftmost stern tube bearing can be examined even by the alignment calculation intended for the cold condition, because the effect of temperature and hull deflection on the bearing load is small. If an exact assessment is required, the strength is to be determined based on the dynamic loads in the hot condition. However, bearing damage can be avoided by evaluating edge loading under the cold condition. Therefore, the allowable limit of the relative slope between the propeller shaft and the aftmost stern tube bearing (or maximum bearing pressure) has been prescribed for the cold condition, based on past practical experience and data summarized by the Japan Institute of Marine Engineering [2]. In principle, the relative slope is to be calculated at the position of the support point shown in Figure 1.2.2-1 in the Guidance . However, it should be noted that the bending moment due to hydraulic propeller force, shown in Figure 2.1 of these Explanatory Notes , is not to be considered in the calculation, because the allowable limit of the relative slope is prescribed for the static condition. The allowable limit of the nominal bearing pressure is the same as in the previous version of the Guidance . -3 The provisions of 1.3.1-3 in the revised Guidance are the same as in the previous version of the Guidance . In a marine propulsion system, it is generally given that the bending moment of the shaft becomes greatest due to the weight of the propeller at the position of the aftmost stern tube bearing. This type of typical shafting system is the object considered in the Guidance . -4 In ships with large differences in draught, the load of the aftmost engine bearing tends to increase due to the influence of hull deflections, whereas that of the second aftmost engine bearing tends to decrease (refer to paragraph 1.3.3 below). To prevent engine bearing damage that may occur in such a situation, some shipbuilders install the shafting so that the aftmost engine bearing becomes unloaded in the light ballast condition (cold condition) if the engine is of a recent two-stroke cycle type. Unloading of the aftmost bearing in the cold condition is acceptable because the strength of the bearing is examined by the alignment calculation for the hot condition. However, careful attention should be paid to this calculation for the cold condition. It should be noted that in alignment calculations commonly used, the top clearance of the bearing is not considered. Therefore, if the calculation results for the aftmost bearing load are negative, it is necessary to carry out the calculations again excluding the bearing, in order to confirm the displacement of the shaft at the position of the bearing. If the calculated displacement falls within the range for the bearing top clearance, the result means that the bearing is unloaded (see Figure 3.1). Moreover, calculation results that include a negative bearing load even though the bearing is unloaded means that other bearings are taking up the load for the minus portion, and that the . 12 1.3 Load Condition and Evaluation of Calculation Results 1.3.1 Light Draught Condition (Cold Condition) -1 Shaft alignment calculation for the cold condition is the basic calculation method. Draught Condition (Hot Condition) -1 Shaft alignment calculations are to be performed assuming that the ship is in the light draught condition and the main propulsion machinery is in the hot condition EXPLANATORY NOTES 3 1.3 Load Condition and Evaluation of Calculation Results 1.3.1 Light Draught Condition (Cold Condition) -1 Shaft alignment calculations are to be performed assuming