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Issues related to the calibration of couplings in mechanical pumps (manufacturers of chemical-resistant pumps): On-site, it was found that many pumps had problems due to the absence of a calibration center; therefore, the fault did not lie in the pump itself. As the frequency of complaints increased, inquiries were made among end-users who believed that the pumps had been properly aligned with the drive units and did not require further adjustment before operation; it was found that these users would simply plug in the power supply and start the equipment. Later, when costly problems arose with the pump and it was pointed out to them that this was caused by poor alignment, end-users would ask, “Why wasn’t it aligned properly before leaving the factory?” ” The center of the pump is indeed aligned before it leaves the factory; although not with perfect accuracy, the drive motor will shift for various reasons thereafter. Therefore, we strongly recommend adjusting the center position of the pump at least 7 to 9 times during its operation, with 4 of these adjustments even needing to be done before turning the pump on. Experts and engineers in rotating equipment who work in top-tier facilities and are responsible for highly reliable equipment with long mean time between failures (MTBF) strongly agree with this. This article does not focus on guiding users through the process of achieving accurate centering step by step, as there are many such methods available on the market; instead, it aims to inform and persuade people that, first and foremost, centering should be checked multiple times throughout the entire installation process ； Secondly, it emphasizes the importance of doing so. Why spend time on centering? If you look at all the reasons for centering, you will find that the main factors listed are: extending the lifespan of mechanical seals, bearings, and couplings ； Premature wear of the pump ； Unacceptable vibration ； Shaft failures, noise, low efficiency, and related additional power costs, etc. This article explains all these issues, including the costly unplanned downtime. All of these will translate into a bottom line equivalent to the total cost. If the drive unit and the pump are not properly aligned, it will be necessary to incur higher costs during the period of using a pump whose lifespan has been shortened. The market often refers to this issue as TCO, also known as total cost of ownership. There is also a large amount of supporting documentation available on the market indicating that pumps without calibration centers consume 7% to 10% more electricity, with some even using 15% more. If the water pump could speak, it would say, “Spend some money on me now… or you’ll have to spend even more on me later.” ”Or in short: “Time is money.” ” Heinz P. Bloch, a renowned engineer and author in the field of rotating equipment, studied the reliability of pumps and found that it is related to the centering tolerance (see Figure 1). Note that the more precise the center correction, the longer the device can operate without any problems. Furthermore, the faster the device rotates, the higher the precision required for calibration. Refer to Figure 2, which lists the general guidelines. 9 centering adjustments for the pump: When people are told that the center of the pump needs to be adjusted 9 times, interesting expressions appear on their faces. First, the 9 calibration centers will be introduced below. 1. First centering: Before the pump leaves the factory, the drive unit is usually placed on a base and a rough alignment is performed to ensure that precise centering can be achieved on-site later. There may be exceptions to this rule, depending mainly on the type and size of the drive mechanism. Coarse calibration may only include edge-to-edge adjustments, without involving calibration for vertical or angular offsets, as these are addressed on-site. No matter how precise the calibration is done in the factory and no matter how carefully the equipment is moved, its center position changes during transportation. Second centering: When the pump and base are received on site and initially placed on the foundation, centering should be carried out at that time. It is very important to perform alignment or inspection before grouting or connecting the pipeline to the pump. This step is often missed, resulting in high costs. 3rd centering: After the grout in the base has cured, the centering should be checked again. During the grouting process of the base, it often bends or moves, causing alignment issues. When cement slurry cures, it generates a large amount of heat as well as expansion forces that may change the parameter settings. 4th calibration step: After the base is properly grouted and the drive mechanism is aligned with the pump, the pipeline should be connected to the pump. Care should be taken to ensure proper operation; when the pipeline is connected to the pump, its central alignment should not be altered. Based on 50 years of field experience, this can easily change the alignment of the pump and subject it to unnecessary stress. If the pipe must be forced to be connected to the flange, stress will be generated, and it may alter the center alignment. The absence of forced piping connection does not mean that no stress is applied to the pump. During operation, thermal expansion and contraction generate stress. Stresses within the pump can cause the bearings to become out of round and eccentric. 5th alignment check: After the pump has been running for some time (possibly several hours), it should be carefully shut down and realigned again to check for any changes, with adjustments made as necessary. It should be taken into account whether the driving device is a turbine, or whether the pump is operating under load. 6th centering: It can be said that the 5th and 6th centerings are the same, but it should be noted that in special cases such as when pumping hot fluids, it is necessary to determine the pumping temperature of the fluid in consultation with the manufacturer, as this varies depending on the pump’s design/geometry and the type of drive system. For liquids at the same temperature, the requirements for a pump driven by an induction motor and installed at the centerline position differ from those of a turbine-driven pump installed at the bottom. 7th alignment check: It is recommended to recheck the alignment of the new pump approximately 3 to 5 months after its initial startup, in order to verify its performance over that period. 8th calibration center: Inspection after maintenance. This is crucial for the backflow pump (OH1). After removing and reinstalling the wet end or the backflow, the pump cannot be aligned in the same way. 9th Center Calibration: Perform center calibration regularly. Foundations, bases, and supports – just as the foundation of your house can settle, crack, and shift. As proactive preventive maintenance, rechecking the center after a few years is a good habit. If there are good reliability or vibration testing procedures, there may be other reliable indicators that tell you the correct centering time.