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Maintenance and repair of tower-type equipment. 1. Maintenance tasks 1.1 Mid-term maintenance 1.1.1 Inspect, clean, or replace some trays and support structures. Adjust the dimensions and levelness of various parts of the tray, and replace the sealing packing. 1.1.2 Inspect, repair, or replace the bubble caps and floating valves, and adjust the dimensions of various components. 1.1.3 Measure the verticality and deflection of the tower, as well as the wall thickness. 1.1.4 Inspect, repair, and calibrate various types of instruments, as well as inspect and calibrate safety valves. 1.1.5 Clean, inspect, and repair the top separator, condenser, and spray device. 1.1.6 Repair of tower body, fences, ladders, and platforms. 1.1.7 Check the corrosion of the tower wall. Inspect and repair the anti-corrosion layer and insulation layer. 1.1.8 Conduct a sealability test. 1.1.9 Inspect and repair auxiliary pipelines and valves. 1.2 Major Overhaul 1.2.1 includes the contents of the medium overhaul. 1.2.2 Remove all trays for inspection, repair, or replacement. 1.2.3 Repair and replacement of the tower bottom and tower supports, as well as partial replacement of tower sections. 1.2.4 Repair or replacement of the top separator, condenser, and spray device. 1.2.5 Repair the tower, inspect it, measure the wall thickness, and adjust its verticality. 1.2.6 Check for settlement and cracks in the tower foundation, repair the tower foundation, and repair or replace ladders, railings, and operating platforms. 1.2.7 Perform a gas-tightness test or, as specified, a hydrostatic test. 1.2.8 Rust removal, corrosion protection, and insulation inside and outside the tower. 2. Maintenance methods and quality standards 2.1 Maintenance methods 2.1.1 Demolition methods There are two ways to demolish tower equipment: complete demolition of the tower or demolition in sections. After lifting it down, it is disassembled; when taking apart the components inside the tower, the parts of the tray system should also be numbered for easy installation. 2.1.2 Maintenance methods a. The disassembled tower sections, tower components, and internal parts should be inspected one by one; those that do not meet the requirements should be repaired or replaced. b. For components such as tower sections and trays whose structural damage is severe and making manual removal difficult, sandblasting or chemical cleaning can be used for cleaning ； For cases with severe corrosion, methods such as electrostatic spraying and thermal spraying can be used to apply various corrosion-resistant coating layers in order to extend the service life. c. Before installing various internal components, surface contaminants such as oil, rust, sediment, and burrs must be removed. d. Pre-assembly should be carried out before installing the tray; the tray components should be assembled in one layer outside the tower according to the drawings, and it should be adjusted and checked to ensure that the tray meets the requirements. e. The plate assembly can be carried out in a horizontal or vertical manner. In principle, integral tray installation is carried out vertically. Before assembling the tray, it is necessary to check whether the roundness of the tower body is acceptable, as well as whether the specifications of the spacing elements, tie rods, bolts, packing pressure plates, packing rings, etc., meet the requirements. 2.1.3 Assembly methods for tower equipment a. The installation of tower equipment can be carried out through sectional assembly or overall lifting. Segmental assembly is further divided into the normal assembly method (that is, assembling section by section from bottom to top while ensuring levelness) and the reverse assembly method (that is, assembling section by section from top to bottom) ； Find a competent person in the end). b. The levelness of the tower sections can be checked using a level and water. When using the water filling method for testing, the water level should be raised gradually as the components are assembled section by section. c. The verticality of the tower can be measured using the plumb line method and the theodolite method. 2.2 Quality standards for trays 2.2.1 The fabrication of trays shall meet the requirements of the design drawings. It should also meet the technical specifications for trays specified in JB1205. 2.2.2 The inner and outer edges of the manufactured components shall not have burrs that could affect use, assembly, installation, or maintenance. 2.2.3 The local flatness of the tray plate is 2 mm over a length of 300 mm, while the flatness of the tray plate across its entire surface shall comply with the requirements specified in Table 3. Table 3 mm: https://mmbiz.qpic.cn/sz_mmbiz_jpg/hM2YtK3pbkMj55DYrQERicnCiaqn1yEIC4ibX3KnLzK9SZ7cwdRT0SJ5FxaANvtv24UYKasp9w6WDAAOMwOjBjMTQ/640?wx_fmt=jpeg2.2.4 The length deviation of the tray plates shall not exceed -4 mm, and the width deviation shall not exceed -2 mm. 2.2.5 The allowable deviations for the pore diameter and pore spacing of the sieve plates in sieve plate towers are shown in Table 4. The percentage allowed for a slight deviation in aperture size and its permissible tolerance are shown in Table 5. Table 4 mm https://mmbiz.qpic.cn/sz_mmbiz_jpg/hM2YtK3pbkMj55DYrQERicnCiaqn1yEIC4wtDYEfUPiawdUwVZ0eHoF24IGgWU0hqtMEceI4NeFGnOdKlUP1Zmptw/640?wx_fmt=jpeg Table 5 mm https://mmbiz.qpic.cn/sz_mmbiz_jpg/hM2YtK3pbkMj55DYrQERicnCiaqn1yEIC4NX0fiaeaJ9e5fKXRtQqmKbwNUOEoQhs4a9zMRWeibGGKjqltxllCqXjQ/640?wx_fmt=jpeg 2.2.6 For tongue-shaped towers, the allowable deviation between the centers of adjacent fixed tongue plates is as specified in Table 4. The allowable deviation for arbitrarily fixing the center distance of the tongue plates shall not exceed ±6 mm, while the allowable deviations for the dimensions of the fixed tongue plates and tongue holes are specified in Table 5. 2.2.7 The hole diameter of the tray plates in a floating valve tower should be Φ39 (+0.5–0.1 mm), and the allowable deviation between adjacent holes shall not exceed ±2.5 mm. The allowable deviation for any hole spacing shall not exceed ±6mm. 2.2.8 The allowable deviation for the diameter of the holes in adjacent rising gas pipes on the tray plates of a bubble column shall not exceed ±2.5 mm, and the allowable deviation for any hole spacing shall not exceed ±6 mm. 2.3 Quality standards for bubble blister maintenance 2.3.1 The manufacturing of circular bubbles shall comply with the JB1212 standard; its structure is shown in Figure 1. The main dimensions are shown in Table 6. 2.3.2 The bubble bottom gap depends on the cleanliness of the material, as generally shown in Table 7. 2.3.3 When installing the circular bubble caps, it is necessary to adjust their height so that the distance from the root of each bubble cap tooth on the same tray layer to the upper surface of the tray meets the requirements specified in the drawings; the allowable deviation shall not exceed ±1.5 mm. 2.3.4 After the bubble cover is installed, its coaxiality with the lift pipe shall not exceed 3 mm. 2.3.5 For strip-shaped bubble caps and S-shaped bubble cap roots, the allowable deviation from the tray plane is ±1 mm. The quality requirements are specified in the attachment to HGJ211, \"Code for Construction and Acceptance of Chemical Tower Equipment\". Table 6: https://mmbiz.qpic.cn/sz_mmbiz_jpg/hM2YtK3pbkMj55DYrQERicnCiaqn1yEIC4mwgOkcDJLGM2DJvia0flapJKpaHl53lDIH41brXk5oZaYzygXySW5icA/640?wx_fmt=jpeg Continue to Table 6: https://mmbiz.qpic.cn/sz_mmbiz_jpg/hM2YtK3pbkMj55DYrQERicnCiaqn1yEIC4djbAFqIsdGxtfpZPGfD18AUvn0B3CYXDic6BODGfDtIQEZE08XrEfhg/640?wx_fmt=jpeg Table 7: https://mmbiz.qpic.cn/sz_mmbiz_jpg/hM2YtK3pbkMj55DYrQERicnCiaqn1yEIC40CJp3qGibHnWkP5eVotgOUs1Wn2icS8IN4cXeUPIn9KQDicxFibLsKz4sQ/640?wx_fmt=jpeg 2.3.6 For other types of blisters, follow these procedures. 2.4 Quality standards for the maintenance of floating valves 2.4.1 The quality of floating valves shall comply with the specifications of JB1118—F1 type. 2.4.2 During installation, the weight of the float valve should be checked, and the height, flatness, as well as any surface defects or burrs of the float valve should be measured. 2.4.3 For float valve packing, it is necessary to check the connection of the float valve legs within the tray holes. The bending length and angle of the float valve legs shall meet the design requirements. When the floating valve is in place, it should be able to move up and down, with a consistent opening degree, and there should be no sticking. 2.4.4 The installation of float valves of other models can be carried out with reference to these regulations. 2.5 Quality standards for the maintenance of internal components in plate towers 2.5.1 The levelness of the support rings inside the tower and the surface of the trays shall comply with the requirements specified in Table 9. 2.5.2 The deviation in the spacing between adjacent support rings is ±3 mm, and the deviation in the spacing of any 20 support rings shall not exceed ±10 mm. 2.5.3 After the liquid receiving tray, the liquid dropping plate, and the tower body are assembled, the deviation of K, which is the vertical distance between the bottom end of the liquid dropping plate and the upper surface of the liquid receiving tray, as well as the tolerance for D, which is the horizontal distance between the liquid dropping plate and the vertical edges of the liquid receiving tray, shall comply with the specifications in Figure 3. 2.5.4 Deviations at other positions of the pedal component shall comply with the provisions in Figure 4. Table 9 https://mmbiz.qpic.cn/sz_mmbiz_jpg/hM2YtK3pbkMj55DYrQERicnCiaqn1yEIC4RibodLmQ3lRfm5ibFKS33bbNpCUZWOErQj93oY0wxJdn1R8PnFOib80JA/640?wx_fmt=jpeg2.5.5 The levelness of the top of the overflow weir and the deviation in its height shall comply with the requirements specified in Table 10. 2.6 Quality standards for the maintenance of internal components in packed towers 2.6.1 The packing support structure shall be installed smoothly and firmly; its levelness (referring to the structured packing) shall not exceed 0.2% of the tower diameter, and must be greater than 4 mm. 2.6.2 The allowable installation tolerances for the spray device and the liquid redistribution device shall comply with the provisions in Table 11. Table 10: https://mmbiz.qpic.cn/sz_mmbiz_jpg/hM2YtK3pbkMj55DYrQERicnCiaqn1yEIC4vb3zLXFXk9bN8pyH8fXL7ACAItJ7OCTtN6RqZ2uID8nHj64l3f7ROQ/640?wx_fmt=jpeg Table 11: https://mmbiz.qpic.cn/sz_mmbiz_jpg/hM2YtK3pbkMj55DYrQERicnCiaqn1yEIC4QBDDIreWQgicqssJeI22XYWJRKiabTMibmYpFq0mXh0ZRJKTLG92TDT6Q/640?wx_fmt=jpeg 2.6.3 The lower edge of the opening in the overflow tank branch pipe (the bottom of the teeth) should be on a horizontal plane, with an allowable deviation of 2 mm. 2.6.4 When filling the packing, it should be clean, free of sediment, oil, and other contaminants; any broken or deformed pieces must be removed. 2.6.5 The particles filled in the regularly arranged sections should be neatly and properly arranged in circles against the wall, with the allowable deviation in their positioning being one-quarter of their outer diameter. 2.6.6 The randomly piled granular filler should also be evenly filled from the tower wall toward the center of the tower. When filling, wet methods are generally used for tall towers (the tower is filled with water). The filler is poured in from the top of the tower); low towers use dry stacking. 2.7 Quality standards for tower body maintenance 2.7.1 The allowable deviation for the roundness of the tower body is shown in Table 12. 2.7.2 The verticality and straightness of the tower shall not exceed one thousandth of the tower height, with a maximum value of 30 mm; for corrugated mesh towers, this limit is 20 mm. 2.7.3 After repair, the anti-corrosion coating of the tower shall have no bubbling, delamination, or cracks; any damage detected must be repaired. 2.7.4 The insulation material and insulation thickness shall meet the requirements. Table 12: https://mmbiz.qpic.cn/sz_mmbiz_jpg/hM2YtK3pbkMj55DYrQERicnCiaqn1yEIC4t2gBQoODGVJOI2eO1dibbanZTvUNp5oPJeK8IqeMXp52nZpcOLWBrWg/640?wx_fmt=jpeg2.7.5 The fastening bolts should be arranged symmetrically and evenly. After tightening, the exposed length of the bolt should be two pitches. In the following cases, bolts and nuts should be coated with molybdenum disulfide, graphite oil, or graphite powder. Stainless steel and alloy steel bolts and nuts ； Bolts and nuts on flanges and pipe flanges designed for temperatures above 100°C or below 0°C ； Outdoor installations, with atmospheric corrosion and medium corrosion affecting the bolts and nuts on flanges and pipe connections. 2.7.6 When maintaining tower-type equipment that falls under the category of pressure vessels, repairs to the tower body such as making openings, welding repairs, and replacing tube sections must be carried out in accordance with the relevant regulations for pressure vessels, by formulating specific construction plans and welding procedures. And approved by the plant’s technical supervisor. 3. Commissioning and Acceptance 3.1 Preparations before Commissioning 3.1.1 Check that all components and accessories are properly installed, and that all bolts are tightened. 3.1.2 Check and verify whether the quality of the maintenance work is satisfactory, and whether the maintenance records are complete and accurate. 3.1.3 Remove blind plates and close manholes, and connect all inlet and outlet pipes and valves. 3.1.4 Remove the equipment and clean up the site. 3.2 Commissioning 3.2.1 The plate tower shall undergo a single-tower bubbling test. Spray tests were conducted on the packing tower as a spray device and redistributor; after the bubbler ensured uniform spraying, it was integrated into the production system for trial operation. 3.2.2 When a bubble tray needs to undergo a water filling test and a bubbling test after installation, the following requirements shall be met: During the water filling test, the tear holes must be blocked; it is considered successful if the settlement does not exceed 5 mm within 10 minutes after water filling. Once the test is successful, the tear holes should be reopened ； Before conducting the bubbling test, water should be continuously poured into the liquid receiving tray, and air should be introduced at the bottom of the tray; the wind pressure should be below 100 mm of water column, and the airflow volume should not be too high. It is required that bubbles form evenly in all the gaps between the teeth, and there should be no vibration of the bubble caps. 3.2.3 When testing the floating valve tower, observe through the sight glass to check whether the floating valves are stuck. 3.2.4 When conducting a spray test on the liquid distribution device of a packed tower. The spray in the tower cross-section should be uniform. The spray holes must not be blocked. 3.2.5 Tower equipment, inlet and outlet pipelines. After installation, all types of instruments should undergo a gas-tightness test. The test pressure is the design pressure. Keep it for at least 30 minutes. Check all connection points and welds for any leaks. 3.2.6 After cleaning and purging the tower in accordance with the process requirements, start the tower for operation. 3.3 Acceptance 3.3.1 After 24 hours of operation, if all control parameters meet the requirements and there are no abnormal phenomena. With all types of instruments being sensitive and accurate, and no leaks or losses, the handover and acceptance procedures can be carried out. 3.3.2 During acceptance, the following technical documents shall be compiled and archived: original maintenance records (including spare parts used, materials, costs, labor hours, quality specifications, assembly dimensions, etc.) ； Test run records ； Data on the inspection and maintenance of pressure vessels.