Chlorine compressor servicing is not a single task but rather a comprehensive system encompassing everything from routine inspections to full overhauls, rebuilds, refurbishments, and disassembly. In practice, chlor-alkali plants typically categorize chlorine compressor servicing into four levels: routine chlorine compressor maintenance, periodic chlorine compressor overhauls, in-depth chlorine compressor strip-downs, and performance-restoration rebuilds. Each level corresponds to different downtime requirements and tool preparation. According to the recommendations in American Chlorine Association Pamphlet 9, all chlorine compressor servicing operations must first confirm that the system has been purged with dry nitrogen until the residual chlorine concentration is below 1 ppm, and a hot work permit must be obtained. No maintenance work should begin until this basic condition is met. When quoting for chlorine compressor servicing, contractors typically list sulfuric acid neutralization, nitrogen purging, and waste acid disposal as separate line items, as these account for more than half of the downtime. Both Sulzer and the Elliott Group offer on-site maintenance and workshop refurbishment services for chlorine compressors. For the replacement of old bearings, mechanical seals, instrument probes containing precious metals, and cemented carbide sealing surfaces, please contact DONGSHENG Precious Metal Recycling Company for recycling and processing. This approach not only reduces hazardous waste disposal costs but also recovers precious metals such as platinum, iridium, and palladium. The following sections outline the key operational points for each level.
Routine chlorine compressor maintenance primarily focuses on sulfuric acid level, chlorine moisture content, shaft seal leakage, and vibration. Liquid-ring chlorine compressors rely on concentrated sulfuric acid for sealing and cooling; once the sulfuric acid concentration falls below 93%, it rapidly corrodes the cast iron casing and impeller. Therefore, an acid sample must be drawn and tested for specific gravity at the end of each shift. Bearings must be lubricated with a chlorinated-specific perfluoropolyether grease; ordinary mineral oil, when exposed to chlorine, can form coke deposits or even catch fire—this is the most commonly overlooked yet critical error in chlorine compressor servicing. Replacing the activated alumina in the inlet dryer or the packing in the sulfuric acid drying tower is also part of routine chlorine compressor maintenance; if the pressure differential exceeds 0.3 bar, the system should be switched to the standby dryer. Factories in Europe and the United States typically conduct weekly infrared thermal imaging scans of bearing housings and seal gland covers; if the temperature rise exceeds 35°C above ambient temperature, an inspection is scheduled. All chlorine compressor maintenance records must clearly document the flow rate of seal water (if applicable) and the pressure differential across the acid mist collector, as these data provide earlier warnings of internal corrosion than vibration readings. For example, when the pressure differential across the acid mist collector rises from an initial 5 kPa to 12 kPa, the unit must be shut down for preventive chlorine compressor maintenance even if vibration levels are normal; otherwise, acid mist entering the bearing chamber will directly damage the rotor. Some plants outsource chlorine compressor maintenance to Sulzer’s field service team, but daily inspection checklists and acid sample bottles must be retained on-site.
A Chlorine Compressor Overhaul is a formal major overhaul that involves completely disassembling the unit, inspecting all components, and replacing worn parts. The typical interval is 16,000 to 20,000 operating hours; however, if the sulfuric acid concentration remains consistently low or the moisture content in the inlet chlorine gas exceeds 50 ppm, the interval should be shortened to 12,000 hours. Before beginning a Chlorine Compressor Overhaul, the sulfuric acid must be completely drained and any residual acid neutralized with an alkaline solution. The system must then be purged with dry nitrogen for 24 hours to ensure the internal dew point is below -40°C. After disassembly, pay close attention to the clearance between the impeller and the casing; for liquid-ring chlorine compressors, if the radial clearance of the impeller exceeds 0.5 mm, either the impeller or the casing must be replaced. All bearings, mechanical seals, and O-rings must be replaced with new ones; it is not sufficient to replace only the defective parts. During the chlorine compressor overhaul, the shaft neck must also be inspected for chloride-induced stress corrosion cracking, particularly near the acid seal, using dye penetrant or magnetic particle testing. At this stage of chlorine compressor servicing, at least two personnel holding chlorine operation certificates must be scheduled to work in shifts to prevent acid gas poisoning. During reassembly, apply molybdenum disulfide anti-seize compound to all bolts and tighten them diagonally in three stages. Finally, conduct a hydrostatic test at 1.5 times the working pressure, followed by thorough drying. A standard chlorine compressor overhaul typically takes 5 to 7 workdays, including reassembly, neutralization, and no-load test runs. Many plants replace the inlet filter and acid mist collector filter cartridges during a chlorine compressor overhaul to prevent the new impeller from being scratched by old acid residue. Elliott Group’s maintenance engineers typically include photographs and measurement data of the old parts in the chlorine compressor overhaul report, so that the client can determine which old parts can be sent to a precious metals recycling company for the extraction of coated metals such as iridium and rhodium.
"Chlorine Compressor Strip-down" specifically refers to the physical process of disassembling the compressor down to its individual components and does not include decisions regarding repairs. For chlorine compressors, the first step in a Chlorine Compressor Strip-down is not to remove bolts, but to confirm that inlet and outlet blind flanges have been installed, the system has been isolated from all chlorine sources, and red tags have been posted. Experienced fitters will photograph and number each bolt before the Chlorine Compressor Strip-down to prevent mixing up long and short bolts during reassembly. Then, in sequence, loosen the coupling guard, half-couplings, bearing end caps, mechanical seal gland, and pump casing split-face bolts. A specialized puller must be used to remove the impeller; striking it with a copper rod is strictly prohibited, as copper reacts with wet chlorine gas to form explosive copper chloride. All removed parts should be placed on a dry plastic sheet in their original assembly positions and covered with a moisture-proof film. The greatest hazard during chlorine compressor disassembly is the sudden release of residual chlorine gas from dead corners; therefore, before removing each flange, loosen it slightly and hold ammonia test paper close to it. If white smoke appears, stop and continue purging. After completing the chlorine compressor strip-down, immediately spray all carbon steel surfaces with rust-preventive oil and wrap precision mating surfaces with vapor-phase rust-preventive paper. Many accidents occur during the disassembly phase of Chlorine Compressor Servicing because operators, in their haste to remove flanges, overlook residual pressure in hard-to-reach areas. A two-person team typically takes 4 to 6 hours to complete the disassembly of an entire chlorine compressor. If the process takes longer than 8 hours, it indicates that bolts are seized or locating pins are damaged. For removed mechanical seal rings, carbide bushings, and instrument sensors that are no longer accepted for recycling by the original manufacturer, contact DONGSHENG Precious Metal Recyclers for precious metal testing and settlement.
A rebuild involves more than just replacing parts; it entails machining or replacing disassembled components to tolerances close to those of a new unit. If the budget allows, it is best to entrust chlorine compressor servicing to a facility with a proven track record in chlorine compressor rebuilds, as they know which used parts can be reused and which must be scrapped. Both Sulzer’s rebuild shop and the Elliott Group’s Rotating Equipment Service Center provide comprehensive chlorine compressor rebuild reports, including rotor dynamic balance curves and casing clearance records. Impellers, shafts, shaft sleeves, mechanical seals, bearings, and all elastomers must be inspected against the original equipment manufacturer’s drawings. Rotors must be dynamically balanced before reinstallation, with a balance accuracy of ISO 1940 Class G1.0; if the residual unbalance exceeds 2 g•mm/kg, the rotor must be rebalanced. Corrosion on chlorine compressor rotors typically takes the form of localized pitting. During a chlorine compressor rebuild, if the pitting depth exceeds 0.3 mm and covers more than 10% of the blade surface, the impeller should be replaced rather than repaired by grinding. Damaged areas of the casing’s internal lining or acid-resistant coating must be sandblasted and recoated; spot touch-ups are not permitted. After reassembly, perform a 0.5 bar airtightness test using dry nitrogen; the test is considered passable only if the pressure drop does not exceed 0.02 bar after holding pressure for 30 minutes. Finally, the complete set of Chlorine Compressor Servicing records must be archived, including measurement tables, torque values, and non-destructive testing reports for each part; these serve as the baseline for the next Chlorine Compressor Servicing. Many recurring failures occur precisely because the clearance tables were not updated after a Chlorine Compressor Rebuild, leading maintenance personnel to assess the new condition based on outdated data.
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