Handbook Of Shaft Alignment Episode 1 Part 5 pps

It is important for the personnel who maintain rotating machinery to have a basic under- standing of how machinery should be supported and what problems to look for in their foundations, baseplates, and frames to insure long-term alignment stability in their machinery. In addition to the machinery to ground or structure interface, attention must also be directed to any physical attachments to the machinery such as piping, conduit, or ductwork. It is desirable to insure that these attachments produce the minimum amount of force on the machinery to also insure good stability. This chapter will hopefully provide the reader with the basic foundation design principles and some techniques to check equipment in the field to determine if problems exist with the foundation and frame, or the interface between the machinery and the foundation, or piping and conduit attached to the machine itself. 3.1 VARYING COMPOSITION OF EARTH’S SURFACE LAYER The best place to start this discussion is at the bottom of things. All of us realize that there is a major difference in stability as we walk along a sandy beach and then step onto a large rock outcropping. Different soil conditions produce different amounts of firmness. Since rotating machinery could potentially be placed anywhere on the planet, the soil conditions at that location need to be examined to determine the stability of the ground. For new installations or where foundations have shifted radically, it may be a good idea to have boring tests conducted on soils where rotating machinery foundations will be installed. Table 3.1 shows safe bearing load ranges of typical soils. The recommended maximum soil load from a combination of both static and dynamic forces from the foundation and attached machinery should not exceed 75% of the allowable soil bearing capacity as shown in Table 3.1. 3.2 HOW DO WE HOLD THIS EQUIPMENT IN PLACE? I suppose someone has attempted to sit a motor and a pump on the ground, connected by the shafts together with a coupling, and started the drive system up without bolting anything down. My guess is that they quickly discovered that the machines started moving around a little bit after start up, then began moving around a lot, and finally disengaged from each other hopefully without sustaining any damage to either of the machines. Maybe they tried it again and quite likely had the same results. I am sure they finally came to the conclusion that this TABLE 3.1 Soil Composition Bearing Capacities of Soils: Safe Bearing Capacity Type of Soil t/ft 2 MPa Hard rock (e.g., granite, trap, etc.) 25–100 2.4–9.56 Shale and other medium rock (blasting for removal) 10–15 0.96–1.43 Hardpan, cemented sand and gravel, soft rock (difficult to chisel or pick) 5–10 0.48–0.96 Compact sand and gravel, hard clay (chiseling required for removal) 4–5 0.38–0.58 Loose medium and coarse sand medium clay (removal by shovel) 2–4 0.20–0.38 Fine loose sand 1–2 0.10–0.20 Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C003 Final Proof page 90 29.9.2006 5:53pm 90 Shaft Alignment Handbook, Third Edition was not going to work for long periods of time and decided to ‘‘hold the machines’’ in their starting position somehow. How are we going to do this exactly? What should we attach them to? How about some wood? No, better yet, something like metal or rock, something that is strong. Our rotating equipment needs to be attached to something that will hopefully hold it in a stable position for long periods of time. I have seen just about every possible configuration you can imagine. Even the scenario mentioned above. The most successful installations require that the machinery be attached to a stable platform that enables us to detach one or more of the machines from its platform in the event that we want to work on it at another location. Classically we attach and detach our equipment with threaded joints (i.e., bolts and nuts). You could, I suppose, glue or weld the machines to their platform, and it would just be a little more difficult to detach them later on. The devices that we have successfully attached our machinery to are baseplates, soleplates, or frames. There are advantages and disadvantages to each choice. The baseplates, sole- plates, or frames are then attached to a larger structure, like a building, ship, aircraft and automotive chassis, or Earth. There are many inventive ways of attaching rotating machinery to transportation mechanisms (e.g., boats, motorcycles, airplanes), and design engineers are still coming up with better solutions for these types of machinery-to-structure interface systems. Our discussion here will concentrate on industrial machinery. The vast majority of rotating machinery is either held in position by a rigid foundation (monolithic), attached to a concrete floor, installed on an inertia block, or held in position on a frame. There are advantages and disadvantages to each design. There are also good ways and poor ways to design and install each of these methods to keep our machinery aligned and prevent them from bouncing all over the place when they are running. In summary, machines are attached to intermediary supports (i.e., baseplates, soleplates, and frames) that are then attached to structures (i.e., buildings, floors, foundations). Figure 3.1 shows a typical rigid FIGURE 3.1 Rigid foundation for induced draft fan. Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C003 Final Proof page 91 29.9.2006 5:53pm Foundations, Baseplates, Installation, and Piping Strain 91 foundation design, Figure 3.2 shows a typica inertial block (aka floating) design, and Figure 3.3 shows a typical frame design. 3.2.1 BASEPLATES Baseplates are typically either cast or fabricated as shown in Figure 3.4 and Figure 3.5. A fabricated baseplate is made using structural steel such as I-beams, channel iron, angle, structural tubing, or plate, cutting it into sections, and then welding the sections together. It is not uncommon to replace structural steel with solid plate to increase the stiffness of the base similar to Figure 3.6. 3.2.1.1 Advantages 1. Most commonly used design for industrial rotating machinery 2. Provides excellent attachment to concrete foundations and inertia blocks assuming the anchor bolts were installed properly and that the grout provides good bonding 3. Can be flipped upside down and grout poured into the cavity before final installation FIGURE 3.2 Spring isolated inertia block with motor and pump. FIGURE 3.3 Frame supporting a belt drive fan. Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C003 Final Proof page 92 29.9.2006 5:53pm 92 Shaft Alignment Handbook, Third Edition FIGURE 3.4 Cast baseplate. FIGURE 3.5 Fabricated baseplate. FIGURE 3.6 Weak structural steel was replaced with solid plate on this baseplate. Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C003 Final Proof page 93 29.9.2006 5:53pm Foundations, Baseplates, Installation, and Piping Strain 93 4. Machinery can be placed onto the baseplate prior to installation and roughly aligned in the lateral and axial directions to insure that the foot bolt locations are drilled and tapped accurately to hopefully prevent a bolt bound condition or incorrect shaft end to shaft end spacing 5. Equipment mounting surfaces can be machined flat, parallel, and coplanar prior to installation 6. Some designs include permanent or removable jackscrews for positioning the machinery in the lateral and axial directions 3.2.1.2 Disadvantages 1. Usually more expensive than using soleplates or frames 2. Equipment mounting surfaces are frequently found not to be flat, parallel, and coplanar prior to installation 3. Difficult to pour grout so it bonds to at least 80% of the underside of the baseplate 4. Possibility of thermally distorting baseplate using epoxy grouts if pour is thicker than 4 in. 5. Frequently installed with no grout 3.2.2 SOLEPLATES Soleplates are effective machinery-mounting surfaces that are not physically connected together. Figure 3.7 shows a soleplate being prepared for grouting on a medium-sized fan housing. They are typically fabricated from carbon steel and there are usually two or more soleplates required per concrete foundation or inertia block. Correct installation is more FIGURE 3.7 Soleplate being prepared for grouting. Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C003 Final Proof page 94 29.9.2006 5:53pm 94 Shaft Alignment Handbook, Third Edition tedious than baseplates due to the care required to insure that the individual soleplates are in level and in the same plane. On larger machinery where the soleplates can be six or more feet apart, using machinist levels is not going to work effectively and either optical or laser alignment tooling is recommended to get the plates level and in the same plane. Ideally the soleplates should be level to 1 mils=ft (1 mils ¼ 0.001 in.), and there should not be a deviation of more than 5 mils at any point on all soleplates from being coplanar. Figure 3.8 shows an optical jig transit used to level and plane the soleplates shown in Figure 3.7. 3.2.2.1 Advantages 1. Works best for large machinery where a contiguous baseplate would be too heavy or cumbersome 2. Somewhat easier to properly grout to concrete foundation or inertia block 3.2.2.2 Disadvantages 1. More difficult to insure that surfaces of soleplates are flat, coplanar, and parallel 3.2.3 FRAMES Frames are typically constructed from structural steel such as channel iron, I-beams, angle iron, or structural tubing and are often custom made for each application. The frames are then attached to a larger structure such as a building frame, floor, or concrete foundation. They are classically not as rigid as equipment mounted to baseplates or soleplates and frequently will exhibit higher level of vibration amplitude. However, it is common to provide vibration isolation from the structure or floor with springs or damping isolators (e.g., rubber FIGURE 3.8 Optical jig transit being used to level a soleplate. Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C003 Final Proof page 95 29.9.2006 5:53pm Foundations, Baseplates, Installation, and Piping Strain 95 mounting isolators). Due to the fact that most frames are welded construction, the surfaces that the machinery attaches to are often not coplanar or parallel to each other. Figure 3.9 through Figure 3.11 show a variety of rotating machinery mounted on frames. 3.2.3.1 Advantages 1. Most practical design for machinery that cannot be attached to Earth or building structures 2. Used in situations where excessive floor loads are exceeded with concrete construction 3. Easier to fabricate and install than rigid foundations or inertia blocks 3.2.3.2 Disadvantages 1. Due to the low frame-to-machinery weight ratio, vibration levels are typically higher than equipment located on rigid foundations or inertia blocks 2. Subject to more rapid deterioration from environment 3. Difficult to insure flatness of machinery-mounting surfaces during construction 4. Excitation of structural natural frequency more prevalent with this design FIGURE 3.9 Motors and pumps sitting on structural steel frames. The unistrut used for the motors is not recommended. FIGURE 3.10 Main lube oil pump coupled to outboard end of motor sitting on a fabricated frame bolted to the motor’s end bell. Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C003 Final Proof page 96 29.9.2006 5:53pm 96 Shaft Alignment Handbook, Third Edition 3.2.4 MONOLITHIC RIGID FOUNDATIONS Rigid foundations are typically found at the ground level. The basic design of a rigid foundation is shown in Figure 3.12. Their sole purpose is to provide an extremely stable platform for the rotating machinery with no intention of supporting any other object but the machinery that is placed on it except perhaps piping, ductwork, or conduit that attaches to the machines in the drive system. Effectively, the rigid foundation consists of a poured reinforced concrete block with anchor bolts that have been imbedded in the concrete. FIGURE 3.11 Series of water bearings held in place on a dredge frame. Reinforcement rods Concrete foundation Grout Baseplate or soleplate Pipe (allows for slight anchor bolt adjustment) Nut (see alternative ways for leveling) Frost line 75% of total pedestal height Anchor bolt imbedded in concrete Concrete Isolation matting (if desired) Protective sleeve FIGURE 3.12 (See color insert following page 322.) Section view of a typical rigid foundation. Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C003 Final Proof page 97 29.9.2006 5:53pm Foundations, Baseplates, Installation, and Piping Strain 97 Reinforcement rods should be spaced no more than 12 in. apart, using a minimum rod size of 1=2 in. (12.7 mm). The concrete should be rated at a compressive strength of 4000 psi for 28 d. Once the concrete has set to at least 50% cure (typically 7 d for most concrete) the baseplate or soleplates are set into a level and coplanar condition slightly above the top of the concrete (usually 1–2 in.). The baseplate is then grouted to the concrete foundation as illustrated in Figure 3.12. Here are some basic design ‘‘rules of thumb’’ for concrete foundations: 1. Whenever possible, mount every machine in the drive system on the same foundation. 2. The mass of the foundation should be three to five times the mass of centrifugal machinery it supports and five to eight times the mass of reciprocating machinery it supports. 3. The width of the foundation should be 1.5 times the distance from ground level to the centerline of rotation. 4. Use baseplates or soleplates to attach the machinery to the concrete foundation. 3.2.4.1 Advantages 1. Provides a stable platform to attach rotating machinery using the surrounding soil to absorb motion or vibration 2. Ability to design foundation mass to effectively absorb any vibration from attached machinery and isolate residual motion by segregating the foundation block with vibra- tion absorptive material preventing transmission of vibration to surrounding area 3.2.4.2 Disadvantages 1. If located outdoors, eventually degradation of foundation imminent especially if located in geographical area where climatic conditions change radically throughout the year 2. For machinery with attached, unsupported piping or ductwork, extreme forces from improper fits can occur causing damage to machinery 3. Potential settling of foundation causing instability and potential transmission of forces from attached piping 3.2.4.3 Tips for Designing Good Foundations 1. Insure that the natural frequency of the foundation–structure–soil system does not match any running machinery frequencies or harmonics (such as 0.43Â,1Â,2Â,3Â, 4Â, etc.) with the highest priority being placed on staying þ20% away from the operating speed of the machinery sitting on the foundation being considered. Also watch for potential problems where running speeds of any machinery nearby the proposed foundation might match the natural frequency of the system being installed. 2. In case the calculated natural frequency of the structure does not match the actual structure when built, design in some provisions for ‘‘tuning’’ the structure after erection has been completed such as extension of the mat, boots around vertical support columns, attachments to adjacent foundations, etc. 3. Minimize the height of the centerline of rotation from the baseplate. 4. Rotating equipment that will experience large amounts of thermal or dynamic move- ment from off-line to running conditions should be spaced far enough apart to insure that the maximum allowable misalignment tolerance is not exceeded when the shafts Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C003 Final Proof page 98 29.9.2006 5:53pm 98 Shaft Alignment Handbook, Third Edition are located in the off-line position. Refer to Chapter 16 for more details on off-line to running machinery movement. 5. Design the foundation and structure to provide proper clearances for piping and maintenance work to be done on the machinery, and provisions for alignment of the machine elements. 6. Install removable jackscrew devices on the baseplate for moving (i.e., aligning) equip- ment in all three directions: vertically, laterally, and axially. If jackscrews will not be used, provide sufficient clearance between baseplate and rotating equipment for inser- tion of hydraulic jacks for lifting equipment during shim installation or removal. 7. Provide vibration joints or air gaps between the machinery foundation and the sur- rounding building structure to prevent transmission of vibration. 8. If possible, provide centrally located, fixed anchor points at both the inboard and outboard ends on each baseplate in a drive train to allow for lateral thermal plate expansion. Insure there is sufficient clearance on the casing foot bolt holes to allow for this expansion to occur without binding against the foot bolts themselves. 3.2.4.4 Tips for Installing Foundations and Rotating Machinery 1. Select a contractor having experience in installing rotating machinery baseplates and foundations or provide any necessary information to the contractor on compaction of base soils, amount and design of steel reinforcement, preparing concrete joints during construction, grouting methods, etc. 2. If the concrete for the entire foundation is not poured all at once, be sure to chip away the top 1=4 in. to 1=2 in. of concrete, remove debris, keep wet for several hours (or days if possible), allow surface to dry and immediately apply cement paste before continuing with an application of mortar (1–6 in.) and then the remainder of the concrete. If not done, the existing concrete may extract the water from the freshly poured concrete too quickly and proper hydration (curing) of the new concrete will not occur. 3. Use concrete vibrators to eliminate air pockets from forming during the pouring process but do not over vibrate, causing the larger concrete particles to settle toward the bottom of the pour. 4. Check for baseplate distortion prior to installing the baseplate. Optical alignment or laser tooling equipment can be used to measure this. Mounting pads should be machined flat and not exceed 2 mils difference across each individual pad (i.e., machin- ery foot contact point). If there is more than one pad that each individual machine will come into contact with, insure that those pads are coplanar within 5 mils. Insure that the contact points for each machine are parallel to the contact points for every other machine on that baseplate within 10 mils=ft. If the baseplate is slightly distorted it may be possible to stress relieve by oven baking or vibratory shakers. If the distortion is excessive, the contact surfaces may have to be machined flat, coplanar, and parallel. 5. Sandblast the underside of the baseplate. If sandblasting is unreasonable, grind at least 90% of the surface to bare metal. If cement-based grout is going to be used, coat with inorganic zinc silicate primer as per coating manufacturers specifications to prevent corrosion and provide good bonding to cement-based grout. The primer should not exceed 5 mils in coating thickness. If epoxy-based grout is going to be used, do not coat with primer and grout within 48 h of sandblasting to insure that excessive oxidation does not occur to the sandblasted surface. 6. Insure that the baseplate has leveling jackscrews at each of the anchor bolt locations. Try not to use wedges to level the baseplate. If jackscrews were not provided, weld 3=4 in. or 1 in. fine threaded nuts to the outside perimeter of the baseplate near the anchor bolts Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C003 Final Proof page 99 29.9.2006 5:53pm Foundations, Baseplates, Installation, and Piping Strain 99 [...]... Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C003 Final Proof page 11 5 Foundations, Baseplates, Installation, and Piping Strain FIGURE 3.36 Beveling the edges FIGURE 3.37 Cleaning the threads of the jackscrews FIGURE 3.38 Setting the baseplate 29.9.2006 5: 53pm 11 5 Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C003 Final Proof page 11 6 11 6 29.9.2006 5: 53pm Shaft Alignment Handbook, ... 0.800 in 17 .787 in Pad C Pad B 17 .799 in 0.802 in 0.809 in 0.806 in 0.802 in 0.8 01 in 0. 810 in 17 .788 in 17 .800 in 17 .840 in Pad F 0.800 in 0.799 in Pad G 0.806 in 0.802 in Top view 17 . 812 in 0.807 in Side view 17 .840 in 17 .796 in Pad H Steam turbine 0. 811 in 17 .807 in 0. 811 in 17 .793 in North 17 .803 in Pad D 17 .833 in 17 .832 in Pump 0.803 in Pad E 17 .800 in 17 .797 in 17 .808 in View looking north Up... foundation 29.9.2006 5: 53pm 11 3 Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C003 Final Proof page 11 4 11 4 29.9.2006 5: 53pm Shaft Alignment Handbook, Third Edition FIGURE 3.34 Cleaning the top surfaces of each mounting point edges as shown in Figure 3. 35 The flat file was then used to bevel each edge of the mounting pads as shown in Figure 3.36 A tap was ran through each of the jackscrew... 40 ft3 ¼ 1. 47 yd3 The epoxy grout is sold as a unit, which consists of one can of resin, one bottle of hardener, and four bags of filler or aggregate Each unit yields Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C003 Final Proof page 11 9 29.9.2006 5: 53pm 11 9 Foundations, Baseplates, Installation, and Piping Strain No 15 BFW baseplate before grouting Pad A 0.802 in 0.800 in 17 .787 in... Protective sleeve Anchor bolt FIGURE 3. 25 Section view of solid baseplate with leveling device at anchor bolts Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C003 Final Proof page 11 1 29.9.2006 5: 53pm Foundations, Baseplates, Installation, and Piping Strain 11 1 FIGURE 3.26 Scarifying the top surface of a concrete foundation 3.2 .12 CASE HISTORY OF INSTALLING A BASEPLATE USING EPOXY-BASED... with two independent observers FIGURE 3.43 Jig transit observing scale targets FIGURE 3.44 Observers view from jig transit 29.9.2006 5: 53pm 11 7 Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C003 Final Proof page 11 8 11 8 29.9.2006 5: 53pm Shaft Alignment Handbook, Third Edition bolt (i.e., lowering a point) then tightening down an adjacent jackscrew (i.e., to raise a point) At foot pads... Figure 3.34 shows the top surfaces of each foot being cleaned with ScotchBrite to remove any rust A fine flat file was then used to remove any burrs on the top surface and used to bevel the outside FIGURE 3.27 Close-up of one of the anchor bolts Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C003 Final Proof page 11 2 11 2 29.9.2006 5: 53pm Shaft Alignment Handbook, Third Edition FIGURE 3.28... Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C003 Final Proof page 10 5 29.9.2006 5: 53pm 10 5 Foundations, Baseplates, Installation, and Piping Strain TABLE 3.3 Component Ratios of Low- and High-Strength Concrete Low Strength (%) High Strength (%) 15 7 78 20 14 66 Water Cement Aggregates Proper curing of the concrete requires that the water remain in the mixture for an acceptable period of time... FIGURE 3 . 15 Solid metal baseplate bonded to a concrete floor or pad Concrete bonding glue Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C003 Final Proof page 10 2 10 2 29.9.2006 5: 53pm Shaft Alignment Handbook, Third Edition 2 Possibility of anchor bolts pulling out, loosening, or breaking if proper precautions are not taken during the installation of the anchor bolts 3 Possibility of baseplate... process as illustrated in Figure 3.20 One of the problems Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C003 Final Proof page 10 6 10 6 29.9.2006 5: 53pm Shaft Alignment Handbook, Third Edition FIGURE 3 .18 Cement-based grout (Courtesy of Unisorb, Jackson, Michigan.) with a two-step procedure is that a poor bond could occur between the mating surface of the first grout pour and the second grout . present Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C003 Final Proof page 10 4 29.9.2006 5: 53pm 10 4 Shaft Alignment Handbook, Third Edition Proper curing of the concrete requires. pump baseplate. Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C003 Final Proof page 10 8 29.9.2006 5: 53pm 10 8 Shaft Alignment Handbook, Third Edition 5. Pour the grout: Insure that. / Shaft Alignment Handbook, Third Edition DK4322_C003 Final Proof page 98 29.9.2006 5: 53pm 98 Shaft Alignment Handbook, Third Edition are located in the off-line position. Refer to Chapter 16