Maintenance and Repair Procedures for SZ-Type Vacuum Pumps

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Table of Contents 1 General Provisions.1 1.1 Scope of Application...1 1.2 Brief Description of Structure... 2 1.3 Equipment Performance:... 2 2 Integrity Standards... 2 2.1 Parts and Components... 2 2.2 Operational Performance... 2 2.3 Technical Documentation... 2 2.4 Equipment and Environment... 2 3 Equipment Maintenance... 3 3.1 Daily Maintenance... 3 3.2 Regular Inspection Items... 3 3.3 Common Fault Resolution Methods... 3 3.4 Emergency Shutdown... 3 4 Maintenance Periods and Tasks... 3 4.1 Maintenance Periods... 3 4.2 Maintenance Tasks... 3 5 Maintenance Methods and Quality Standards... 4 5.1 Casing and Pump Cover... 4 5.3 Sealing Devices... 5 5.4 Rolling Bearings... 5 5.5 Elastic Couplings... 5 6 Commissioning and Acceptance... 5 6.1 Preparations Before Commissioning... 5 6.2 Commissioning... 5 6.3 Acceptance... 6 7 Safety Precautions for Maintenance... 6 7.1 Safety Precautions for Maintenance... 6 7.3 Safety Precautions for Commissioning... 6 1 General Provisions 1.1 Scope of Application These regulations apply to the maintenance and repair of SZ-type water ring vacuum pumps in chemical plants (hydrogen pumps in chlor-alkali plants can follow these guidelines as well). 1.2 Brief Description of Structure The SZ-type pump consists of a circular pump body, an eccentric pump cover, bearing brackets, impellers, shafts, couplings, and other main parts and components. The impeller is equipped with several radial blades; by causing the impeller to rotate eccentrically within the pump casing, a liquid ring is formed inside the pump, which changes the volume of gas within the blades thereby enabling continuous transportation of the gas medium. 1.3 Equipment performance: The performance of SZ-type water ring vacuum pumps and compressors is shown in Table 1. Table 1: Serial Number, Model, Exhaust Rate in m3/min, Maximum Vacuum Level in %, Water Consumption in L/min, Rotational Speed in L/min, Motor Power in kW
1. SZ-1: 1.5, 84, 10, 1450, 4
2. SZ-2: 3.4, 87, 30, 1450, 10
3. SZ-3: 11.5, 92, 70, 975, 30
4. SZ-4: 27, 93, 100, 730, 70

2. Standards for Good Condition:
2.1 Parts and Components
2.1.1 The main body is intact; all protective covers for parts and components are present and in good condition, and the quality meets the required standards. 2.1.2 Control valves and vacuum gauges shall be sensitive and accurate, and calibrated regularly. 2.1.3 The inlet and outlet valves and associated pipelines are installed properly, in a horizontal and vertical position, without any blockages or leaks; the color-coded markings are clear and meet the requirements. 2.1.4 The foundation and pump base are stable and reliable; the anchor bolts and all other bolt connections are tight and neat, meeting the technical requirements. 2.1.5 The anti-corrosion and anti-freezing facilities are complete and effective, meeting the requirements. 2.2 Operating Performance 2.2.1 The equipment’s output should meet the values specified on the nameplate, or be sufficient to meet the requirements of normal production. 2.2.2 The equipment is properly lubricated, the lubrication system is unobstructed, the oil used meets the required standards, and the bearing temperature does not exceed 75°C. 2.2.3 The equipment operates smoothly, without any abnormal phenomena such as vibration, looseness, or noise. 2.2.4 Operating parameters such as temperature, pressure, speed, flow rate, and current in various sections meet the requirements. 2.2.5 The water flow rate into the pump should be appropriate, unobstructed, and stable, with an idle vacuum level of not less than 0.087 MPa. 2.3 Technical Documentation 2.3.1 Equipment records, maintenance, and inspection records are complete and accurate. 2.3.2 There are records of equipment operation. 2.3.3 There are drawings for the vulnerable parts of the equipment. 2.3.4 The equipment operation procedures and maintenance rules are complete. 2.4 Equipment and Environment 2.4.1 The pump body should be clean, with no oil residues or dust on its surface. 2.4.2 There is no water accumulation, waste liquid, or other debris on and around the surface of the foundation and base. 2.4.3 There are no leaks at valves, pipelines, joints, flanges, etc. 2.4.4 Shaft seal leakage rate: The packing seal shall not exceed 15 drops per minute, and the mechanical seal shall not exceed 5 drops per minute. 3 Equipment Maintenance 3.1 Routine Maintenance 3.1.1 Check for leaks in the packing seal; tighten the packing regularly. If the packing is worn and can no longer provide the necessary sealing, it should be replaced. 3.1.2 Rolling bearings should be kept well lubricated. 3.1.3 Check the vibration of the pump body and listen for any abnormal noises during operation. 3.1.4 Check the water supply to ensure an adequate amount of water is available. 3.1.5 When in use during winter, drain all the water from within the pump and the steam-water separator after parking, to prevent the equipment from cracking due to freezing and to avoid disruptions in operation. 3.1.6 Keep the pump body and accessories clean. 3.2 Contents of regular inspections The contents of regular inspections are shown in Table 2. Table 2 Inspection Items, Cycle, Content, Judgment Criteria, and Recommended Instruments. Inspection of the operating condition of rolling bearings: Once a month. Measurement of the vibration of rolling bearings: SZ-1, SZ-2; ⅴ≤0.72 mm/s indicates good condition. 206 seismograph, ZFY-1 vibration analyzer. 3.3 Common fault handling methods: The common fault handling methods are listed in Table 3. 3.4 Emergency Shutdown In the following situations, an emergency shutdown should be carried out: a. Abnormal noises suddenly occurring inside the pump ； b. Sudden interruption of the circulating water, t. Sudden severe vibration of the pump body, d. Other emergency shutdowns specified in the operating procedures. 4 Maintenance Cycle and Maintenance Tasks Table 3 Phenomenon Cause Solution Phenomenon Cause Solution Low vacuum level and insufficient exhaust volume 1. Pipeline leaks 2. Wear of packing seals 3. Wear of the moving and stationary rings of mechanical seals or misalignment of springs 4. Excessive gap between the impeller and the end cover 5. Excessively high temperature of the water ring 6. Insufficient water supply 1. Eliminate leakage points 2. Replace packing materials 3. Perform maintenance 4. Adjust the gap 5. Increase water supply and lower the water supply temperature 6. Increase the water supply rate Excessive vibration and overheating of components 1. Excessive circulation water volume 2. Bent shaft 3. Improper fit between the shaft and the impeller, resulting in rotor skew 4. Unbalanced rotor 5. Damaged bearings 6. Tight packing 7. Poor bearing lubrication 8. Loose foundation bolts 1. Adjust the water volume 2. Straighten or replace the shaft 3. Adjust or perform maintenance 4. Balance the rotor 5. Replace bearings 6. Adjust the gland 7. Check the lubrication condition 8. Tighten bolts 4.1 Maintenance Cycle The maintenance cycle is shown in Table 4. 4.2 Maintenance Tasks 4.2.1 Minor Repairs 4.2.1.1 Inspect and tighten all connection bolts. 4.2.1.2 Replace the packing and adjust the mechanical seal. 4.2.1.3 Inspect the coupling and replace the elastic rubber ring to correct its coaxiality. Table 4: Maintenance categories – Minor repair, Medium repair, Major repair. Maintenance cycle, in months: 3–6, 12–18, 24–36. Note: 1. Pumps of category Sz-3 and below are not subject to major repair; the tasks related to major repair are included in the medium repair. 2. When the unit’s condition monitoring capabilities enable predictive maintenance to be carried out, with the approval of the unit’s higher-level supervising authority, it is not subject to the restrictions outlined in the table above. 4.2.1.4 Inspect the bearings and replace the lubricating oil (grease). 4.2.1.5 Clean and inspect the circulating water system. 4.2.2 Mid-term repair 4.2.2.1 includes the contents of minor repairs. 4.2.2.2 Check the vibration of the rotor and verify its static balance. 4.2.2.3 Check or correct the straightness of the shaft. 4.2.2.4 Replace the rolling bearings and lubricating oil. 4.2.2.5 Inspect the mechanical seal, and repair or replace the rotating and stationary seal rings. 4.2.2.6 Check and adjust the clearance between both ends of the impeller and the front cover serta the rear cover. 4.2.2.7 Verify the instrument. 4.2.3 Major Overhaul 4.2.3.1 includes the contents of the medium overhaul. 4.2.3.2 Perform a disassembly inspection to assess the wear and corrosion of various components, as well as the degree of damage to the ceramic linings, and inspect or replace any defective parts. 4.2.3.3 Replace the impeller, shaft sleeve, and pump cover. 4.2.3.4 Adjust the level of the pump body. 4.2.3.5 Inspect and repair the motor. 4.2.3.6 Corrosion protection of the hull. 5 Maintenance Methods and Quality Standards 5.1 Cylinder Block and Pump Cover 5.1.1 The cylinder block and pump cover must be free from defects such as cracks or large areas of pitting; the ceramic lining must not be damaged. 5.1.2 If the cast iron pump cover and housing end faces are severely corroded or eroded, and the sealing requirements cannot be met, they should be scrapped. If the lining of the ceramic pump cover is damaged, it can be repaired by replacing the lining. 5.2 Spindle, impeller, and shaft sleeve 5.2.1 The spindle shall be free from defects such as corrosion and cracks. 5.2.2 The fit between the spindle and the rolling bearings is H7/js6 or H7/k6. 5.2.3 The fit between the spindle and the impeller is H7/m6. 5.2.4 The clearances between the two ends of the impeller and the front and rear covers shall comply with the specifications in Table 5: Table 5 Model Total clearance between the two ends of the impeller and the pump’s front and rear covers Model Total clearance between the two ends of the impeller and the pump’s front and rear covers Installation clearance Maintenance clearance Replacement clearance Installation clearance Maintenance clearance Replacement clearance Sz-1 Sz-2 0.30 0.30 0.40 0.40 1 1 Sz-3 Sz-4 0.40 0.40 0.50 0.50 1 1 5.2.5 The straightness of the main shaft shall be Φ0.08–0.10 mm/m. 5.2.6 The blades of the impeller shall be free of burrs and cracks. 5.2.7 The rotor should be replaced if the corrosion is severe or the blade thickness is reduced by half. 5.2.8 The coaxiality between the outer circumference of the impeller and the shaft hole is Φ0.06mm. 5.2.9 The impeller shall be subjected to balancing tests when necessary, and the requirements shall comply with those specified in Table 6: Table 6 Pump Model Impeller Rotation Speed r/min Impeller Width/Impeller Diameter Type of Balancing Allowable Deviation Measured on Impeller Diameter Allowable Deviation for Static Balancing, g Allowable Residual Amplitude for Dynamic Balancing, mm SZ-2 SZ-3 SZ-4 1450 975 730 220/200=1.10 320/332=0.93 520/450=1.15 Dynamic Balancing Zone Static-Dynamic Balancing Zone Static-Dynamic Balancing Zone 5 8 10 0.06~0.08 0.07~0.10 0.07~0.10 5.2.10 After the impeller is assembled with the shaft, the circular runout of its end face shall be 0.10 mm. 5.2.11 The bushing and the shaft must not be made of the same material to avoid seizure. 5.2.12 The perpendicularity of the bushing end face to the axis is Φ0.01mm. 5.2.13 The surface roughness of the contact surface between the bushing and the shaft shall not exceed 1.6, with a fit of H7/h6. 5.3 Sealing Devices 5.3.1 Packing Sealing 5.3.1.1 The end face of the packing gland should be parallel to the end face of the packing box, and the tightness of the fastening bolts should be consistent to avoid uneven pressure. 5.3.1.2 The depth to which the gland is pressed into the packing box is generally equal to the height of one layer of packing, but it must not be less than 5.00 mm. 5.3.1.3 The cuts in the filler material should be parallel, neat, and not loose; the cuts should form a 30º angle, and when installing the filler, the joints should be offset by 120º. 5.3.2 Mechanical Seals 5.3.2.1 The surfaces of the rotating and stationary rings must be of good quality; defects such as imperfections, cracks, or radial scratches are not allowed. 5.3.2.2 All seals must be in good condition, and the rubber sealing rings should be replaced each time they are removed. 5.3.2.3 The spring has good performance with no obvious deformation. 5.4 Rolling Bearings 5.4.1 The rollers of rolling bearings as well as the surfaces of their raceways should be free of pits and spots; the contact surfaces must be smooth, and there should be no abnormal noises during rotation. 5.4.2 The fit between the outer ring of the rolling bearing and the bearing housing shall be H7/h6. 5.4.3 When installing the bearings, the rear bearing should be fixed, while the front bearing (on the side of the motor) should have an axial clearance of 0.20–0.30 mm. 5.4.4 When heating bearings, immerse them in an oil bath at 100–120°C for 10–15 minutes, or use an electric heater for heating; direct flame heating is strictly prohibited. 5.5 Elastic couplings 5.5.1 Elastic couplings and shafts are fitted using the H7/js6 or H7/k6 fit. 5.5.2 The radial runout of the two-half coupling shall not exceed 0.07–0.09 mm. ’ 5.5.3 The axis alignment deviation of the elastic sleeve pin coupling and the end face clearance of the coupling shall comply with the requirements specified in Table 7: 6 Commissioning and Acceptance 6.1 Preparatory work before commissioning 6.1.1 Check whether all bolts are tight, and whether the components, instruments, and auxiliary equipment are complete. 6.1.2 Check whether the bearings are properly lubricated and whether the circulating water system is unobstructed. 6.1.3 The turning of the disk should be free from jamming or uneven forces. Table 7 Maximum outer diameter of coupling, end face clearance, alignment deviation. Maximum outer diameter of coupling, end face clearance, alignment deviation, radial displacement, axial tilt, radial displacement, axial tilt: 71–106, 130–190, 3, 4; <0.04, <0.05, <0.2/1000, <0.2/1000. 224–315, 315–400, 5, 5; <0.05, <0.08, <0.2/1000, <0.2/1000. 6.2 Testing: After two hours of operation, the following requirements should be met: a. Smooth operation without any abnormal noises ； b. The shaft seal leakage is within acceptable limits, and there should be no leaks or drips in the associated piping ； c. The bearing temperature shall not exceed 75℃ ； d. The bearing amplitude shall meet the requirements ； e. The vacuum level reaches the value indicated on the nameplate ； f. The current is stable and does not exceed the rated value. 6.3 Acceptance: If the quality of the maintenance work meets the requirements of these regulations, if the maintenance records are complete and accurate, and if the trial operation proceeds smoothly, then the acceptance procedures can be carried out as specified, and the equipment can be put into production use. 7 Safety Precautions for Maintenance and Repair 7.1 Safety Precautions for Maintenance 7.1.1 It is strictly prohibited to loosen or tighten bolts and other fittings on parts under pressure while they are in operation. 7.1.2 During operation, the rotating parts of the pump must not be wiped or repaired. 7.1.3 During pump operation, the operator should regularly check its operating condition; if any abnormalities are detected, the pump must be stopped immediately, and maintenance can only be carried out once the pressure has dropped to zero. 7.2 Safety Precautions for Maintenance 7.2.1 Before maintenance, close the inlet and outlet valves and install blind flanges to isolate the system. Power must be cut off, a “Do Not Operate” sign must be placed, and the equipment handed over before maintenance can proceed. 7.2.2 When maintaining equipment, the safety operating procedures specific to this type of work must be strictly followed. 7.2.3 The disassembly and assembly of maintenance equipment shall be carried out in sequence, and special tools should be used as much as possible. 7.2.4 When assembling and disassembling equipment components, avoid forceful knocking to prevent damage to the mating surfaces. 7.3 Safety precautions during commissioning 7.3.1 The start-up and shutdown operations shall be carried out by designated personnel, who must hold a \"Safety Operation Certificate\" for this position. 7.3.2 Start the pump strictly in accordance with the startup procedure ； Before starting up, the test operator should stand in a safe position. 7.3.3 If any abnormality is detected during testing, the machine should be stopped immediately; after the issue is resolved, testing can be resumed. This post was last edited by QHDKD on 2007-11-27 11:52.]