Handbook Of Shaft Alignment Episode 3 Part 6 ppsx

21.1.11.1 Additional Information on Gearboxes and Fluid Drives Moderate to excessive off-line soft foot conditions have been experienced on virtually every gearbox regardless of frame construction design. Gearboxes are frequently bolted to the frame in more than four points and soft foot correction can be more difficult to correct the Side view Scale: North South Side view Scale: West East 30 in. 10 mils 30 in. 10 mils Upper bearing Thrust bearing Lower bearing Position A Position B Position C Position D Turbine guide bearing Upper wear ring Lower wear ring Position of rotor Centerline of rotation of rotor Thrust bearing out of level by 6.5 mils with the south side low Thrust bearing out of level by 5.5 mils with the west side low FIGURE 21.75 Alignment models of the rotor in the north to south and west to east positions. Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C021 Final Proof page 720 6.10.2006 12:19am 720 Shaft Alignment Handbook, Third Edition machines bolted in three of four points. Uncorrected soft foot can distort the housing causing meshing problems as shown in Figure 21.80 through Figure 21.82. Since there is typically a rise in casing temperature from OL2R conditions, not only will the shafts move upward, but they will also spread apart. Several OL2R studies have shown that gearboxes and fluid drives can twist or warp when operating. If dowel pins are used, casing distortion can occur if all four corners are pinned to the frame. FIGURE 21.76 Gearbox. FIGURE 21.77 Steam turbine, gearbox, and fan drive system. Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C021 Final Proof page 721 6.10.2006 12:19am Alignment Considerations for Specific Types of Machinery 721 One method to compensate for the lateral expansion of a gearbox is to pin the high-speed shaft and allow the low-speed shaft to move into alignment during normal operation as shown in Figure 21.84. The one dowel pin at the high-speed shaft acts as the control point for the gearbox. The dowel pin at the opposite end of the high-speed shaft allows expansion in the axial direction but prevents the gear case from translating laterally. The bolts nearest to the dowel pins should be 90%–100% of final torque value. The torque on the foot bolts should be less as the distance from pins increases. This lower torque setting will hopefully allow the case to slide between the underside of the bolt head and the gear case foot, yet still provide a hold-down force to the baseplate or soleplates. 21.1.12 COOLING TOWER FAN DRIVES Although cooling tower fan drives are not usually thought of as glamorous rotating machin- ery systems, they are very critical to the operation of the plant and can experience alignment problems as acute as any other type of rotating equipment. In fan drive systems where a right- angled gearbox drives a six- or eight-bladed fan assembly where the drive motor is located outside the plenum and the motor is connected to the input shaft of the gear by a long spool piece or ‘‘jackshaft,’’ OL2R movement is usually not measured and in many cases ignored. The saving factor in these designs is that the flexing points in the coupling are separated by a FIGURE 21.78 Motor, gearbox, compressor drive arrangement. FIGURE 21.79 Motor, fluid drive, pump drive arrangement. Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C021 Final Proof page 722 6.10.2006 12:19am 722 Shaft Alignment Handbook, Third Edition considerable distance, thereby allowing for considerable amounts of centerline-to-centerline offsets at the flexing points. For example, if there is a 100-in. separation between the flexing points, you could have up to 100 mils of centerline-to-centerline deviation and still be at 1 mil=in. misalignment (100 mils=100 in. ¼ 1 mil=in.). The shaft to coupling spool method shown in Chapter 13 or the face–face technique shown in Chapter 14 is recommended for aligning these types of drives. Since most cooling towers are located outside, an interesting phenomenon can occur when aligning these drive systems during daylight hours with the sun shining. If the drive is kept stationary, the long coupling spool can get unevenly heated from the sun and thermally bow the spool piece. As you begin rotating the shafts to capture a set of readings, the hot or sunny side of the spool piece now begins to rotate into the shade and the sun starts to heat a different side of the spool piece. As the hot side cools and the shaded side warms up, the spool piece begins to change its shape causing erroneous readings. FIGURE 21.80 Irregular gear tooth wear pattern due to a soft foot condition distorting the gear housing. FIGURE 21.81 Corner of gearbox in Figure 21.80 showing that the foot bolt is not supported on the outer edge (in addition to the soft foot problem shown in Figure 21.83). Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C021 Final Proof page 723 6.10.2006 12:19am Alignment Considerations for Specific Types of Machinery 723 21.1.13 ALIGNING SHIP RUDDERS This section may seem like a radical departure from typical rotating machinery alignment measurement methods but alignment problems occur in virtually every industry and the marine industry is not an exception. In the life of a seagoing vessel, over time, the main steering device known as a rudder will require repairs to its stationary and rotating compon- ents. Erosion or corrosion of these devices and the occasional mishap of the rudder hitting an object or the sea floor will require maintenance and replacement of defective components. Figure 21.85 shows a view of the major components of a ship rudder. The key components are the rudder horn (part of the ship hull), the rudder, the rudder stock (which is the shaft that rotates the rudder), the pintle pin, and the bearings. The pintle pin is the hinge pin for the rudder. It carries about 95% of the horizontal force of the rudder when the rudder is turned. The pintle pin is secured in a pintle pin bore in the rudder and held in place with a nut. The pin is forced on with significant force to form an interference fit. The rudder has a cast iron pintle pin boss as part of its structure and the rest of the ‘‘skin’’ of the rudder is welded on using plate steel on internal frames. The rudder is hollow and is usually filled to about 1 psi with air. It actually floats. The rudder is held vertically by East Gearbox soft foot lift Gearbox Motor Extruder 1 234 5678 0 50 10 40 20 30 + _ 10 40 20 30 0 50 10 40 20 30 + _ 10 40 20 30 0 50 10 40 20 30 + _ 10 40 20 30 0 50 10 40 20 30 + _ 10 40 20 30 1–4 up 2–12 up 3–17 up 4–20 up 5–19 up 6–20 up 7–21 up 8–21 up 1–0 2–5 up 3–12 up 4–17 up 5–18 up 6–20 up 7–23 up 8–22 up 1–0 2–0 3–0 4–1 east 5–1 east 6–1 east 7–0 8–3 east Final–14 east 1–4 not measured 5–0.5 up 6–3 up 7–8 up 8–9 up 1–4 not measured 5–5 up 6–8 up 7–14 up 8–16 up 1–1 south 2–1.5 south 3–3 south 4–3 south 5–3 south 6–3 south 7–3 south 8–3 south Final–5 south The bolts were loosened in sequence (1–8). The indicators measured the amount of movement that was observed as each bolt was loosened. 0 50 10 40 20 30 + _ 10 40 20 30 0 50 10 40 20 30 + _ 10 40 20 30 FIGURE 21.82 Soft foot lift check on above gearbox. Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C021 Final Proof page 724 6.10.2006 12:19am 724 Shaft Alignment Handbook, Third Edition the pintle pin riding in a bearing surface on the rudder horn, by the rudder stock which is secured by multiple bearing strakes internal to the hull, and by the mechanical arrangement inside the hull which moves the rudder stock. The rudder stock bore and the pintle pin bore are located in the rudder. They are about 20 in. ID at the tip and about 18 in. at the bottom with a taper of 1 in 12 in. The bores are usually of cast iron welded to rudders that can weigh over 35 t. The pintle pins are usually a metal-to- metal tapered fit (some with keys, others without) and 85% fit is usually required. The rudder stock bore has at least one keyway, which mates up with a key on the rudder stock. Sometimes (especially older German vessels) the keys are in the bore and the keyway is on the rudder stock. The keys are very large and are always bolted securely in place. The rudder is usually removed from the ship (usually weighs about 35 t) for this sort of work. The typical disassembly sequence is shown in Figure 21.86 and Figure 21.87. The rudder is held in place with chain falls and the rudder stock is then removed along with the mechanical connections inside the ship. The rudder stock is then lifted out through holes in the ship decks. The rudder is then lowered and tilted until the pintle pin is free of its bearing surface in the rudder horn. The access panels in the rudder are cut out after the ship is in dry dock. The rudder is then removed and set up vertically in a work bay. The pintle pin nut access panel is removed and the pintle pin nut is removed. The pintle pin is then removed. East Gearbox soft foot gaps and shims Gearbox Feeler gauge measurements (in mils) 0 5 8 8 5 3 25 22 22 20 10 7 7 3 20 12 10 14 12 15 0 22 15 37 15 31 15 27 13 24 0 15 6 25 20 2 3 3 4 3 4 4 2 10 10 5 10 3 10 2 10 2 15 15 5 2 10 2 3 5 2 Motor Extruder FIGURE 21.83 Soft foot map of above gearbox. Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C021 Final Proof page 725 6.10.2006 12:19am Alignment Considerations for Specific Types of Machinery 725 Now that the rudder has been removed from the ship, another issue needs to be addressed. Before getting into the tapered pintle pin alignment, one should investigate whether the center- line of rotation of the rudder stock is concentric to the bore of the pintle pin bearing in the rudder horn. If it is possible for the ship to run aground or hit something under water, it is possible for the rudder horn to get bent causing a misalignment between the rudder stock bearing and the pintle pin bearing. Assuming the rudder has been removed and the rudder stock is in place, Figure 21.88 shows how the double radial method could be used to measure if the bore of the pintle pin bearing is not collinear with the centerline of rotation of the rudder stock. If you jumped to this part of the book because your boat is out of the water with a damaged rudder and are confused about the above diagram, you should probably review the basics of the double radial method as explained in Chapter 12. The amount of angular rotation of the rudder stock shaft may be limited to no more than about 208 to 308 from side to side (total of about 608). If you are limited in the amount of possible angular rotation, you could mathematically determine the full angular sweep based on the information given in Section 6.11. If you are not much of a math whiz and find that the section is boring or too intense, here is a trick I use in the event that you cannot rotate a shaft through 3608. High-speed shaft Pin Torque to 90% Torque to 100% Torque to 75% Torque to 50% Expansion occurs outward from this control point Slotted hole Pin View looking down on gearbox Low-speed shaft Offset the low- speed shaft to allow for lateral expansion Increase the shaft-to-shaft distance to allow for expansion in the axial direction Slotted hole allows case to expand in these directions only FIGURE 21.84 Pinning a gearbox at the high-speed shaft compensating and allowing the gear case to expand without warpage. Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C021 Final Proof page 726 6.10.2006 12:19am 726 Shaft Alignment Handbook, Third Edition 1. Mark off the inside or outside of the cylinder (i.e., shaft or bearing bore) into 908 arcs. Since the rudder stock is vertically oriented, I usually try to use compass directions (N, S, E, W) or ship coordinates (fore, aft, port, starboard) to designate the position at each quadrant. 2. Rotate the shaft (rudder stock) all the way in one direction until it stops. Clamp the bracket to the shaft, set the indicator at one of the quadrant marks, and zero the indicator. 3. Rotate the shaft as far as it can go in the other direction (in this case 608) taking care to observe what the indicator is reading as you do the rotation. When the shaft stops its rotation, record the dial indicator measurement and also scribe a mark with a pencil or soapstone exactly where the tip of the indicator stopped on the surface of the shaft or bearing bore. In this case, that is the bearing in the rudder horn. 4. Rotate the shaft back to its starting position, loosen the bracket on the shaft, rotate the entire bracket or dial indicator arrangement so that the tip of the indicator is positioned where it stopped at the pencil or soapstone mark, tighten the bracket, dial in the measurement you observed at this point, and start rotation again. Keep in mind that you only have 308 to go before so that you get to your first quadrant mark. 5. Repeat step 2 through step 4 until you get all the way around the shaft (see Section 6.10, i.e., you do not have to rotate all the way around). Once the measurements have been taken at the top and bottom of the bearing bore, you could plot or model these measurements as described in Chapter 12. Remember, you are Rudder stock Ship hull Rudder horn Rudder stock nut Access panel Rudder (hollow) Pintle pin Bearing Pintle pin is fixed to rudder and moves with it Pintle pin nut access panel Metal-to-metal interference fit Bearing FIGURE 21.85 A typical rudder arrangement on a large ship. Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C021 Final Proof page 727 6.10.2006 12:19am Alignment Considerations for Specific Types of Machinery 727 taking bore measurements, not OD measurements; so be careful how you plot the points. If the centerline of rotation of the rudder stock shaft is concentric with the bore of the bearing in the rudder horn, you will sweep zeros all the way around the bore at the top and bottom of the bearing in the rudder horn. Notice that in Figure 21.88, they are not zeros all the way around. This is telling you that the rudder horn bearing is not aligned with the rudder stock shaft. You have got a major problem. Somehow, someway, you are going to have to position the rudder horn bearing to the centerline of rotation of the rudder stock shaft. If you do not figure out Rudder is supported with chain falls Rudder stock nut is removed Rudder or pintle pin assembly is lowered and moved away from the hull 1 2 3 FIGURE 21.86 Removing the rudder from the ship. Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C021 Final Proof page 728 6.10.2006 12:19am 728 Shaft Alignment Handbook, Third Edition how to do this at this point, the rest of this procedure is not going to help you. If we get the tapered bores of the rudder to be collinear, the alignment of the rudder stock bearing and the pintle pin bearing are not in line with each other, and none of this is going to work right. As far as I am concerned, the pintle pin is nothing more than an extension of the rudder stock shaft. For those of you who luckily swept zeros or painstakingly positioned the rudder horn bearing so it does sweep zeros, we can now go back to getting the rudder and pintle pin right. Traditionally, a tight wire is strung via jigs from the top to the bottom and the centerline is found b y trial and error Pintle pin is remachined if necessary Pintle pin and nut are removed from rudder 4 5 FIGURE 21.87 Final steps of removal. Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C021 Final Proof page 729 6.10.2006 12:19am Alignment Considerations for Specific Types of Machinery 729 [...]... and pulsed with high current Piotrowski / Shaft Alignment Handbook, Third Edition DK 432 2_C022 Final Proof page 748 748 26. 9.20 06 8:51pm Shaft Alignment Handbook, Third Edition 27 23 23 2f 2a 24 a 25 26 21 33 22 32 34 33 34 6 6 43 57 46 29 40 35 30 31 55 36 37 7 32 ' 39 37 36 59 41 42 46 44 xx 51 43 56 47' 44' 54 56' 55 49 52 47 45 50 FIGURE 22.14 Ferris’ shaft aligner patent, 1908 1970—The Charge Couple... for shaft alignment device utilizing proximity probes for measurement (see Figure 22.18) Piotrowski / Shaft Alignment Handbook, Third Edition DK 432 2_C022 Final Proof page 749 26. 9.20 06 8:51pm 749 The History of Machinery Alignment 33 29 30 15 25 27 26 21 31 Z 32 28 34 18 19 20 41 31 ' 42 33 29 30 23 24 27 28' 33 ' 34 ' 29' 30 ' 23' 24' 15 14 21' 19' 18' 13 26 25 11 17 12 25' 16 37 37 ' 22 40 35 17' 16' 26' ... 12 15 13 11 16 5 14 6 10 9 19 22 1 18 20 42 3 44 46 45 43 41 44 33 0 48 47 54 55 56 53 32 24 33 0 34 200 33 52 58 59 60 49 51 26 32 2 29 28 27 23 25 FIGURE 22.12 Kinkead’s shaft leveler patent, 1901 Piotrowski / Shaft Alignment Handbook, Third Edition DK 432 2_C022 Final Proof page 747 747 The History of Machinery Alignment L R N A R 26. 9.20 06 8:51pm O M P C J E B D I G H F FIGURE 22. 13 Miller’s shaft. ..Piotrowski / Shaft Alignment Handbook, Third Edition DK 432 2_C021 Final Proof page 730 6. 10.20 06 12:19am 730 Shaft Alignment Handbook, Third Edition Upper indicator 0 Fore + 26 Port Starboard +37 Aft + 63 Lower indicator 0 Fore 20 30 +38 30 Port Starboard 10 40 50 _ 0 + 10 40 20 –5 20 30 30 10 40 50 _ 0 + 10 40 20 Aft +33 FIGURE 21.88 Using the double radial method to determine if the centerline of rotation of. .. 35 17' 16' 26' 36 ' 36 38 ' 38 39 Z 35 ' 40' 39 ' FIGURE 22.15 Christian’s shaft alignment device, 19 46 19 83 Malcolm Murray files U.S patent for alignment brackets illustrating use of reverse indicator method (see Figure 22.19) 1984—John Zatazelo files U.S patent for electronic shaft alignment calculator 19 86 John Zatazelo files U.S patent for a variety of methods used to determine shaft alignment 1987—Heinrich... D., Duncan, W., Cline, R., Alignment of Vertical Shaft Hydrounits, Facilities Instructions, Standards, and Techniques, Vol 2–1, United States Department of the Interior, Bureau of Reclamation, 1 967 –2000 Piotrowski / Shaft Alignment Handbook, Third Edition DK 432 2_C022 Final Proof page 735 22 26. 9.20 06 8:51pm The History of Machinery Alignment The historical path of shaft alignment encompasses many... Edition DK 432 2_C022 Final Proof page 741 26. 9.20 06 8:51pm 741 The History of Machinery Alignment Chain Wood “walking beam” Water tank Piston Cold water jet Cylinder Drain Pump rod Mine shaft Valving Boiler Fire box FIGURE 22.5 Newcomen’s mine pump FIGURE 22 .6 Eighteenth century theodolite Piotrowski / Shaft Alignment Handbook, Third Edition DK 432 2_C022 Final Proof page 742 742 26. 9.20 06 8:51pm Shaft Alignment. .. (also known as Hooke Piotrowski / Shaft Alignment Handbook, Third Edition DK 432 2_C022 Final Proof page 738 738 26. 9.20 06 8:51pm Shaft Alignment Handbook, Third Edition FIGURE 22 .3 Da Vinci’s smokejack or Cardan joint) Georgius Agricola (Georg Bauer) writes De Re Metallica, a 10-volume series of books in chemical and mining engineering covering ores, theory of formation of mineral veins, surveying, tools,... smelting, and manufacture of salt, soda, alum, vitriol, sulfur, bitumen, and glass These works were later translated to the English language by American President Herbert Hoover ´ 15 76 Francois Viete introduces use of decimal fractions ¸ Piotrowski / Shaft Alignment Handbook, Third Edition DK 432 2_C022 Final Proof page 739 The History of Machinery Alignment 26. 9.20 06 8:51pm 739 160 0—Dutch optician Johann... Proof page 7 36 7 36 26. 9.20 06 8:51pm Shaft Alignment Handbook, Third Edition FIGURE 22.1 Ctesibius pump 38 4—Aristotle was born Credited with much of the initial discoveries in physics, biology, and psychology contained in his book Historia Animalum Aristotle or his student Straton publishes Mechanika discussing the lever and gearing 32 3—Euclid writes his first book on geometry called Elements 30 0 . pump. Piotrowski / Shaft Alignment Handbook, Third Edition DK 432 2_C022 Final Proof page 7 36 26. 9.20 06 8:51pm 7 36 Shaft Alignment Handbook, Third Edition 1280—Roger Bacon discusses the basic operation of the. 1 967 –2000. Piotrowski / Shaft Alignment Handbook, Third Edition DK 432 2_C021 Final Proof page 734 6. 10.20 06 12:19am 734 Shaft Alignment Handbook, Third Edition 22 The History of Machinery Alignment The. poured. Piotrowski / Shaft Alignment Handbook, Third Edition DK 432 2_C021 Final Proof page 733 6. 10.20 06 12:19am Alignment Considerations for Specific Types of Machinery 733 BIBLIOGRAPHY Campbell, A.J., Alignment