‘Soft-foot’ (‘spongy’ support) at the machine feet. The bore machined into a coupling must be central to within 0.02 mm (0.001”). Bore couplings on-center making sure the bore is parallel with the hub and square with the face so there is no run-out (wobble) as it turns. Make sure looseness in bearings that cause shafts to rattle and rotate off centre is taken-up. Machine components damaged, poorly made and worn. On 2.2 – 11 kW drives use 16 mm diameter bolts, from 15 – 75 kW use 20 mm bolts, for 100 kW and above use 25 mm bolts. Hold down bolts must stop the equipment flexing. Hold down bolts must be bonded to the concrete and not just held in place by friction. Base plates must be thick and stiff to prevent distortion when the equipment applies torque. This is usually only possible if the plinth is formed in the floor. Insubstantial foundations, bases and hold down bolts.Ĭoncrete foundation mass must be 5-times the mass of the equipment it supports. Table 2 lists the most common causes of misalignment and explains what to do in each case. To prevent misalignment becoming a serious cause of equipment failure it is necessary to understand why it occurs so it can be corrected. The common practice of measuring between and across the coupling faces can produce a coupling within alignment tolerance but with backends on both machines still skewed. This approach of aligning the whole machine guarantees parallel shafts and accurate coupling alignment. Figure 1 Types of Misalignment Figure 2 Achieving radial and Angular Alignment of Shafts Figure 2 shows an overhead view (plan view) of how Table 1 is applied. Table 1 shows alignment tolerances recommended by specialists after compiling equipment reliability data over many years and industries. Table 1 Alignment Tolerances for Rotating Equipment. In order to prevent rapid failure of equipment the shafts must be purposefully aligned to within very close tolerances. The motion that causes the most damage is the axial movement of the shaft. The axial, radial and bending forces developed by the ‘push- pull’ action, and the resulting non-circular shaft motion, is transferred through to bearings, shaft seals and, in pumps, to the mechanical seal. The coupling reacts to the distortion by pulling or pushing each shaft. If the positions in the orbits are not directly opposite each other the coupling is distorted. When misaligned shafts are coupled together each shaft rotates about a different centre. Misaligned shafts are the single greatest reason for failure of rotating equipment and connected components. The proper shaft alignment process from start to finish.The common causes of misalignment and their remedies.The correct accuracy for satisfactory alignment.Why shaft misalignment causes equipment failures.Keywords: axial alignment, laser alignment, dial indicator, soft foot, shaft coupling. Shaft alignment is a precision maintenance requirement that requires exacting care and detail and if not performed will cause much production down time. Rotating misaligned shafts produce vibration and complex fluctuating radial and axial loads that lead to breakdowns. Shaft misalignment is one of the most common reasons for bearing and mechanical seal failures. 5-day Reliability Black Belt ® Live Course.5-day Reliability Green Belt ® Live Course.Root Cause Analysis and the 8D Corrective Action Process course.Reliability Analysis Methods online course.14 Ways to Acquire Reliability Engineering Knowledge.Reliability Engineering Management DRAFT.Innovative Thinking in Reliability and Durability.Equipment Risk and Reliability in Downhole Applications.Musings on Reliability and Maintenance Topics.Product Development and Process Improvement.Rooted in Reliability: The Plant Performance Podcast.
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