Study on Overhaul Plan for Flash Steam Compressors*

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Maintenance plan for flash steam compressor (X2208) after 8,000 hours of operation I. Equipment overview The flash steam compressor X2208 was delivered in June 2011, installed in June 2013, underwent air testing in July 2014, and completed process gas testing on August 14, 2015; it has been in operation ever since, with a total operating time of 8,000 hours. The specific parameters of the equipment are as follows: volumetric flow rate of 12.9 m3/min (at intake condition); primary intake pressure of 1.18 Mpa (A); primary exhaust pressure of 2.85 Mpa (A); primary intake temperature of -35 ℃; secondary exhaust pressure of 5.6 Mpa (A); temperature after cooling of the secondary exhaust gas ≤85℃; compressor shaft power of 672 kW; rotational speed of 375 rpm; stroke length of 280 mm; number of compression stages: 2; cylinder diameter: primary stage: 330 mm, secondary stage: 245 mm.

II. Preparatory work before disassembly and inspection
1. The required spare parts must arrive at the factory, as listed below:
Intake valve assemblies: X22084100h – 2 units (already arrived)
Intake valve assemblies: X22084100ah – 2 units (already arrived)
Intake valve assemblies: X22084200h – 2 units (already arrived)
Exhaust valve assemblies: X22085100h – 2 units (already arrived)
Exhaust valve assemblies: X22085200h – 2 units (already arrived)
Oil resistance rings: X22073802 – 4 units (already arrived)
Oil scraping rings: JN043803 – 4 units (already arrived)
Oil scraping rings: JN043804 – 8 units (already arrived)
Sealing rings: JX073805 – 4 units (already arrived)
Springs: JX073806 – 16 units (already arrived)
Primary piston rings: X22082101h – 16 units (already arrived)
Primary support rings: X22082102h – 8 units (already arrived)
Secondary piston rings: X22082201h – 20 units (already arrived)
Secondary support rings: X22082202h – 12 units (already arrived)
Leak-sealing rings: X22083102h – 8 units (already arrived)
Main sealing rings: X22083105h – 20 units (already arrived)
Throttling rings: X22083107h – 4 units (already arrived)

2. All the necessary tools for maintenance are available. 3. The maintenance personnel have arrived. 4. Safety measures for maintenance. 4.1 The replacement of the process system must be carried out properly, with blind flanges used to ensure effective isolation; the main motor must be powered off, a supervisor must be present, and regular tests for combustible gases as well as toxic and harmful gases must be conducted at the construction site to ensure safety during maintenance work. 4.2 A perimeter fence should be set up at the site; unauthorized personnel are not allowed to enter the maintenance area ； Check to ensure that the fire-fighting equipment is in good condition and ready for use. 4.3 Operation of the vehicle must be carried out by persons holding the required licenses, and operations must be conducted in strict accordance with the regulations governing its use. 4.4 Define clear safety evacuation routes. III. Disassembly steps 1. Stop the oil circulation to allow the lubricating oil to flow back into the oil tank. 2. Disconnect the pipes and flanges connected to gas, water, oil, etc., and inspect and clean the oil station filter and oil cooler ； Perform backwash cleaning on the primary and secondary coolers. 3. Use the specialized tools correctly, and disassemble and inspect the compressor in the following order. 3.1 First, remove the intake and exhaust valves, check the valve lift as well as any signs of leakage or sticking, and replace wear-prone components such as the valve spring if necessary. 3.2 Remove the cylinder head, loosen the connection between the crosshead and the piston rod, and take out the piston assembly (the threaded part of the piston rod should be fitted with a protective sleeve to safeguard the sealing rings, etc.). Measure the thickness of the support rings and piston rings, as well as the side clearance and settlement amount; replace wear-prone parts such as the piston rings if necessary. 3.3 Remove the oil scraper and packing, and inspect the primary and secondary oil scraping rings as well as the packing sets (the primary oil scraping ring and packing were replaced in August; the focus is on inspecting the secondary oil scraping ring and packing set). Lift the top cover of the engine housing, loosen the connecting rod bolts, disassemble the connecting rod, and check its vulnerable components. 3.4 Open the process gas inlet filter and check for cleaning. IV. Inspection Items and Requirements Inspection Area Inspection Content Requirements Remarks Air valve Air valve assembly Clean and perform leak testing; no leaks and smooth operation. Disassembly and reassembly are required. Cylinder Mirror surface Scratches and wear ； Measure the ellipticity of the cylinder bore; there should be no visible scratches and the ellipticity must meet the requirements. It is necessary to disassemble and inspect the piston, piston rings, and support rings; any wear requires replacement. The crosshead and sliding parts also need to be disassembled and inspected for wear and levelness; significant wear requires repair. The pins also need to be checked for wear; significant wear requires repair. The bearing shells, as well as the radial clearance between the crank pin and the big end bearing of the connecting rod, need to be measured; if there is significant wear and the clearance exceeds 0.35 mm, replacement is required. The radial clearance between the crosshead pin and the small end bearing of the connecting rod also needs to be measured; if there is significant wear and the clearance exceeds 0.32 mm, replacement is necessary. The circulating oil system, including the filter in the light oil station, needs to be cleaned according to the manufacturer’s instructions. The water side of the oil cooler and all levels of coolers also require cleaning, as well as treatment of pipeline vibrations and inspection of the exhaust buffer tanks. Professional evaluators are needed to ensure safe operation. V. Reassembly: 1. Install the connecting rod and crosshead by connecting the small end of the connecting rod to the crosshead, and then connecting the big end of the connecting rod to the crank pin. The radial clearances between the connecting rod big end bearing and the crankshaft pin, and between the small end bushing and the crosshead pin, shall meet the values specified in Table 5-2. Large-head tiles are thin-walled tiles, and the gap should not be adjusted by scraping. 2. Installation of the piston, packing, and oil scraper: First, insert the assembled packing into the packing holes in the cylinder block, tighten the fixing bolts evenly to compress the packing box. When assembling the packing, pay attention to the positions of the cooling holes and the air leakage recovery holes. When installing the oil scraper on the middle body, care should be taken to ensure that the oil leakage hole faces downward ； First, clean the piston components thoroughly, then assemble them according to the assembly diagrams for each component. Once the pistons at all levels are assembled, insert them into the corresponding cylinders and connect them to the crosshead ； After the piston rod is connected to the crosshead, the gap between the crosshead and the slide should remain unchanged; the piston rod must be parallel to the axis of the middle block’s slide, with a levelness error not exceeding 0.05/1000. Its inclination direction should match that of the middle block’s slide, and the gap between the piston and the cylinder should be even and symmetrical on both sides. . 3. Installation of the air valve: First, clean the components thoroughly, then assemble them according to the instructions. The valve disc should move freely without any sticking, and a kerosene test should be conducted to check for leaks; only slight leakage is allowed, with no more than 15 drops in 5 minutes. Finally, install the air valve into the valve hole of the cylinder. Special attention should be paid during installation: make sure to distinguish between the intake and exhaust valves, place the gaskets correctly, and ensure they are in the right position. Once the air valve is in place without any issues, cover it with the valve cap and tighten the nuts on the cap evenly. 4. Installation of auxiliary components and restoration of the isolation blind plate. 5. Table 5-1: Positional accuracy of major components in mm. Component type, Assembly requirements, Positional tolerance, Notes: Cylinder – Coaxiality of the cylinder axis with the crosshead slide axis; Radial displacement; Overall tilt. For first and second series: 0.1, 0.04. Piston rod – Levelness of the piston rod after assembly with the crosshead (in the same tilt direction): 0.05/1000. Table 5-2: Assembly clearances for key areas in mm. Sequence number, Component name, Clearance value, Notes: 1. Piston top dead center clearance – Axial side, Cover side; For first and second series: 3±0.5, 3±0.5. 2. Radial clearance between the crosshead and the slide: 0.35–0.40. 3. Radial clearance between the main journal and the main bearing: 0.20–0.28. 4. Radial clearance between the crank pin and the connecting rod big end bushing: 0.16–0.24. 5. Radial clearance between the crosshead pin and the connecting rod small end bushing: 0.145–0.225. 6. On-site maintenance management: 1. Strictly enforce the maintenance management system for factory-controlled equipment, ensure strict control over the maintenance process, and improve the quality of maintenance work. 2. Strictly implement the approval and execution systems for maintenance plans; if issues arise during maintenance, the workshop, the machinery repair department, and the motorization department must work together to find solutions. 3. Strictly implement the blind flange isolation system for process systems, as well as the management systems for maintenance work orders and safety permits. 4. Strictly enforce the measures related to safety management to ensure the safety of maintenance operations. 5. Strictly enforce the on-site maintenance hygiene management system to ensure that the maintenance area remains clean and tidy. VII. Trial operation: After the reinstallation and reset are completed, a trial operation is carried out to check whether the vibration levels, exhaust temperature, and exhaust pressure meet the specified standards; if not, the machine is stopped for inspection. Purification Workshop, January 20, 2016