Quality requirements for the installation of cooling tower fans

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Quality requirements for the installation of cooling tower fans: 1. To ensure the quality of installation and improve work efficiency, it is necessary to carry out proper preparatory work before installation: (1) Familiarize oneself with the design drawings, technical documentation, and other related materials of the equipment to be installed. This includes being familiar with the installation requirements and structural characteristics of the fan, its operation and function within the system, as well as the acceptance status of the fan’s foundation. The specifications, type, and rotation direction of the impeller should be checked against the design drawings, along with the power requirements of the motor used, as well as the center distance between the holes of the anchor bolts. The diameter and orientation of the flanges on the inlet and outlet ducts, as well as their center distance, must also be verified. It is necessary to check whether the elevation of the axis meets the design requirements (for the foundation surface: height error < 5 mm, slope < 2 mm). (2) The accessories, piping, and components of the fan should be counted according to the packing list, taking note of their specifications and quantities. (3) After the counting is completed, these items should be kept under the responsibility of a designated person. In principle, fans are all packaged in wooden boxes, while small parts are stored in smaller wooden boxes that have been nailed shut. 2. Gearbox: To facilitate installation, commissioning, and maintenance, it is advisable for the gearbox and motor to be equipped with bases. (1) Clean the surface of the foundation concrete and check whether the foundation meets the requirements. (2) Place the gearbox base and motor base on the foundation; insert shims between the surface of the foundation and these bases. By adjusting the thickness of the shims, the installed equipment can be brought to the designed height and specifications (the horizontal error in both the longitudinal and transverse directions for the gearbox base and motor base should be ≤ 0.10/1000 mm). This improves the stability of the equipment and facilitates subsequent grouting. It is also important to place the shims on both sides of the anchor bolts; if they are placed only on one side of the bolts, shims with a diameter one size larger than that of the anchor bolts should be used. The size and area of the shims, as well as the number of shims used and their placement method, should be determined based on the weight of the equipment and the size of its base. Shims must be used in pairs; their surfaces must be flat, and those within the same set should be arranged neatly, with no more than two shims per set, to ensure sufficient stiffness and stability. After adjustment, the shims in the same set should be welded together to prevent them from loosening during use. (3) The user-provided base must be of standard quality; its two surfaces should be flat, to prevent issues such as precision drift or increased vibration after the fan is installed, which can result from deformation or instability of the base. 3. After the gearbox base has been leveled, the gearbox can be installed first, followed by the hub. All mating surfaces should be lubricated with grease. Install two blades diagonally (the blades and hub must be installed according to the same numbering). Align its central position within the air duct, with an allowable error of ≦5mm. 4. Connect the drive shaft. Try to keep the gap between the two flange surfaces of the coupling at: less than 0.12 mm on the left and right, and less than 0.12 mm above and below. Perform secondary grouting of the reserved holes, and carry out the final alignment after 2 to 3 weeks. Coupling alignment: ① Preliminary alignment. Without rotating the two halves of the coupling, use a square or steel ruler to check the outer circular surfaces of the upper and lower sowie left and right halves of the coupling, until the planes at both ends are perpendicular to each other or the gaps are uniform throughout. ②Precise alignment. Rotate the coupling by hand, and use precision measuring tools such as feeler gauges, dial calipers, or micrometers to measure the coaxiality and parallelism of the coupling. Example: Dial indicator measurement. Attach the magnetic base of the dial indicator to the shaft shoulder of one half-coupling, place the indicator rod across the two half-couplings while ensuring that the gauge face is directed toward the surface of the other half-coupling. Rotate the couplings by one full turn, observe the reading on the dial indicator, and fine-tune the position of the gearbox or motor. Repeat this process until the indicator shows a reading of less than 0.12 mm. In this component, the wear-prone parts are the elastic pin and diaphragm. Operators should check regularly and replace them promptly if wear is detected. After the entire machine is installed, turning the coupling by hand should feel even in terms of effort. 5. Impeller installation (1) Remove the gland on the upper part of the gearbox output shaft (impeller shaft). Wipe clean the conical portion of the output shaft, apply machine oil to it. Also wipe clean the conical hole in the hub and apply machine oil there as well. Finally, fit the hub onto the impeller shaft. Install the cover, tighten the screws, and compress the hub. (2) Install the blades on the hub in sequence by number. The fixing seats on the blade and hub must be installed in the correct positions; they must not be exchanged arbitrarily to avoid vibration. The method for adjusting the blade mounting angle is as follows: The tools used for measuring angles are a ruler and a protractor. First, set the protractor to the specified angle, then place the ruler at the position where the blade mounting angle is to be measured. Place the protractor on top of the ruler, and rotate the blade until the level bubble on the protractor is centered. After all the blade angles have been adjusted and the bolts tightened, check the blade angles again. The tolerance for the blade installation angle is 0.5 degrees.