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Analysis of Axial Split Case Pump Starting Failures and Excessive Load Causes with Preventive Maintenance Guide
Excessive starting load of an axial split case pump is one of the primary causes leading to motor tripping and rotor damage. According to statistics, more than 60% of starting failures are caused by improper operation procedures.
This article analyzes the causes from three dimensions: operation procedures, mechanical blockage, and electrical abnormalities. Based on the Fault Tree Analysis (FTA) method, it provides a detailed troubleshooting checklist, standardized handling procedures, and full life-cycle preventive maintenance strategies, helping enterprises achieve zero-failure equipment start-up.
I. In-Depth Analysis of Failure Causes: Three-Dimensional Perspective
Starting failures of axial split case pumps do not occur without warning. Most failures can be accurately identified and located through three dimensions: operation, mechanical system, and electrical system.
1. Improper Operation Procedures (Human Factors)
This is the most frequent type of failure occurring on site. It is usually caused by failure to follow the basic principle of centrifugal pump operation: starting the pump with the discharge valve closed.
| Failure Cause | In-Depth Failure Mechanism Analysis | Typical Symptoms |
| Discharge valve not closed | If the discharge valve is not fully closed during start-up, the system static pressure (back pressure) acts directly on the impeller, causing the starting torque to increase significantly. | The motor produces a dull humming sound, current rises instantly, and the protection device trips. |
| Air entering the pump (air binding) | Incomplete priming or failure to open the vent valve causes air accumulation inside the pump. The impeller cannot generate sufficient centrifugal force and cannot establish the required suction condition. | Motor speed is normal but there is no flow or pressure output. Abnormal noise may occur, and the load fluctuates. |
| Suction strainer blockage | Foreign materials blocking the suction strainer increase suction resistance, causing excessive vacuum inside the pump and increasing the risk of cavitation. | Severe vibration, sharp abnormal noise, and difficulty during start-up. |
| Abnormal operating medium | In winter, freezing of the medium may cause rotor friction. A medium viscosity much higher than the design condition (such as heavy oil) increases fluid shear resistance. | Manual shaft rotation becomes extremely difficult or impossible, and the motor cannot start. |
Correction of misunderstanding:
Note: Excessive medium viscosity mainly affects operating performance (reduced flow rate and lower efficiency). Its influence on instantaneous starting load is relatively limited. However, under high-viscosity operating conditions, the required motor torque must be carefully calculated.
2. Mechanical Blockage and Jamming (Equipment Body)
Mechanical resistance is the direct physical cause of excessive starting load, usually indicated by difficulty in manually rotating the shaft.
| Component | Failure Cause | Consequence |
| Flow passage foreign objects | Sand, stones, welding slag, rust deposits, or tools left during maintenance may become trapped between the impeller and casing or between the wear rings. | Hard friction occurs, significantly increasing starting resistance and potentially causing shaft failure in severe cases. |
| Bearing system | Lubricating grease deterioration, emulsification failure, bearing ball or raceway pitting and spalling, or loosened bearing lock nuts causing axial movement. | Bearing seizure, rotor sinking, wear ring contact, or even motor rotor-stator rubbing. |
| Rotor components | Pump shaft bending deformation, rotor dynamic balance failure caused by long-term operation, or contact between rotating and stationary parts due to uneven thermal expansion. | Uneven rotation resistance, severe vibration, and periodic friction noise. |
| Sealing device | Packing gland tightened excessively, excessive compression of mechanical seal springs, or lack of flushing fluid in the seal chamber causing dry friction. | Continuous friction on the shaft sleeve surface, generating excessive heat and making shaft rotation difficult. |
| Coupling | Severe wear of coupling rubber elements or elastic pads; excessive radial or axial misalignment between the two coupling halves. | Additional bending moment and vibration during start-up, increasing motor load. |
3. Electrical System Abnormalities (False Load)
Electrical problems are often mistakenly diagnosed as “pump seizure”. In reality, the problem may be insufficient power output or incorrect control logic.
| Failure Category | Specific Symptoms | Inspection Points |
| Power supply | Supply voltage too low (<85% of rated voltage); three-phase voltage imbalance >5%; excessive voltage drop caused by long cable distance. | Low voltage causes starting torque to decrease significantly, making it appear as excessive load while the actual problem is insufficient driving power. |
| Motor itself | Inter-turn short circuit in windings, insulation aging, broken rotor bars in squirrel-cage motors, or slight stator-rotor rubbing. | Motor overheating, failure to reach rated speed, and electromagnetic noise. |
| Starting control system | Star-delta starting: poor contact of switching contacts or incorrect timer settings (switching too early or too late). Soft starter/VFD: thyristor failure, parameter drift, or acceleration time set too short. | Starting mode switching failure causes excessive current impact; soft starter or VFD failure results in insufficient output torque. |
| Protection system | Thermal overload relay setting too low; incorrect current transformer wiring; protection device malfunction. | False trip signals interrupt normal equipment start-up. |
II. Standardized Troubleshooting Procedure: Fault Tree Analysis (FTA) Method
Troubleshooting should follow the principles of “from external to internal, from mechanical to electrical, and from simple to complex”, avoiding unnecessary disassembly and inspection.
Step 1: Quick On-Site Diagnosis (Within 1 Minute)
Listen to the sound:
Immediately after energizing, check whether the motor produces a “humming” sound indicating locked rotor condition, or whether there is no sound at all, which may indicate an open circuit or protection action.
Check the current:
Observe whether the ammeter shows current indication. Determine whether the current rises sharply at the instant of start-up or whether there is no current response.
Check the valves:
Confirm that the discharge valve is fully closed before starting.
Step 2: Mechanical System Inspection (Power Off and Lockout/Tagout Required)
Key Operation: Manual Shaft Rotation Check
| Shaft Rotation Condition | Failure Diagnosis | Corrective Measures |
| Shaft cannot rotate | Mechanical seizure or blockage. | 1. Check whether the packing gland is tightened excessively and loosen it appropriately. 2. Disassemble the pump casing and remove foreign objects between the impeller and wear rings. 3. Check whether the bearings are seized; replace lubricating grease or bearings if necessary. |
| Shaft rotation is heavy | Excessive friction resistance. | 1. Adjust the compression of the sealing device. 2. Check coupling alignment. 3. Check the concentricity between the motor shaft and pump shaft. |
| Rotation resistance varies periodically | Bent rotor shaft or contact between rotating and stationary components. | 1. Measure pump shaft straightness and straighten or replace the shaft if necessary. 2. Check rotor dynamic balance. |
| Shaft rotates smoothly | Mechanical system is normal; fault is likely related to electrical system or operating conditions. | Proceed to the third step: electrical inspection. |
Step 3: Electrical System Inspection (Performed by Qualified Electrical Personnel)
Measure Voltage
Use a multimeter to measure the three-phase voltage and ensure that voltage balance meets requirements:
380V ± 5% of rated voltage
Check the Control Circuit
Check whether contactor contacts are burned or damaged.
Check the thermal overload relay setting (normally 1.1–1.25 times the motor rated current).
Check whether the star-delta starter switching logic operates correctly.
Separate Testing (Critical Step)
Operation:
Disconnect the coupling between the pump and motor.
Test:
Start the motor independently.
Judgment:
If the motor starts normally when separated from the pump → the fault is on the pump side (mechanical blockage or excessive resistance).
If the motor still has difficulty starting independently → the fault exists in the motor or electrical control circuit.
III. Preventive Maintenance Strategy (Full Life-Cycle Management)
Establishing a standardized preventive maintenance system can reduce starting failure rates by more than 80%.
Daily Inspection and Operating Standards
| Item | Standard Operation / Inspection Content | Frequency |
| Start-up and shutdown operation | Strictly follow the principle of “start with discharge valve closed and operate after opening the valve gradually”. After stopping the pump, close the inlet and outlet valves and drain residual liquid inside the pump. | Every start-up and shutdown |
| Manual shaft rotation inspection | Standby pumps must be manually rotated 180° to prevent shaft bending. For operating pumps, check vibration and temperature. | Weekly / Daily |
| Seal inspection | For packing seals, leakage of 10–30 drops per minute is recommended. Mechanical seals should have no leakage or only minimal leakage. | Daily |
| Sound monitoring | Check whether the pump and motor operate smoothly without abnormal friction noise or cavitation noise. | Daily |
Periodic Maintenance Schedule
| Maintenance Level | Maintenance Contents | Frequency / Trigger Condition |
| Monthly maintenance | 1. Clean foreign materials from the suction strainer. 2. Check and tighten electrical terminal connections. 3. Measure motor insulation resistance (>0.5 MΩ). | Monthly |
| Quarterly maintenance | 1. Check coupling alignment and adjust deviation. 2. Inspect bearing lubrication condition and replenish or replace grease (grease quantity should be controlled at 1/3–2/3 of the bearing housing volume). 3. Calibrate pressure gauges and vacuum gauges for accuracy. | Every three months |
| Annual overhaul | 1. Complete pump disassembly inspection: remove internal scaling and foreign materials. 2. Clearance adjustment: check wear ring clearance (standard 0.3–0.5 mm, maximum not exceeding 2 mm). Replace wear rings if required. 3. Rotor inspection: check pump shaft bending and perform rotor dynamic balancing test. 4. Electrical inspection: check motor winding insulation between turns and inspect contactor contact wear. | Annually or every 8,000 operating hours |
IV. Conclusion
Excessive starting load of an axial split case pump is not an unsolvable problem. Its fundamental cause is an imbalance between torque demand and torque supply:
Required starting torque > Available driving torque
Maintenance personnel should focus on the following key points:
Operational Red Lines:
Never start the pump with the discharge valve open. Ensure complete pump priming and air venting before start-up.
Diagnostic Key Point:
Manual shaft rotation inspection is the most effective method for distinguishing mechanical failures from electrical failures.
Troubleshooting Logic:
Check operating conditions first, then inspect mechanical components, and finally verify the electrical system.
Maintenance Focus:
Perform regular shaft rotation checks, lubrication, and suction strainer cleaning.
Through refined operation management and scientific preventive maintenance, the long-term reliable operation of axial split case pumps can be effectively ensured, providing continuous production support and minimizing unexpected downtime.
FAQ – for Split Case Pump
Learn about the key spare parts commonly used in split case pumps.
| Split Case Pump Spare Parts & Qty (2 Years) | ||||||||
| For Packing Seal Pump | ||||||||
| Spare Parts/Qty | Pump Qty (Including Spare Pump) | |||||||
| 1 | 2 | 3 | 4 | 5 | 6 | 8 | ≥10 | |
| Shaft Sleeve | 1 | 1 | 1 | 2 | 2 | 3 | 4 | 5 |
| Bearing Collar | 1 | 1 | 1 | 2 | 2 | 3 | 4 | 5 |
| Impeller Collar | 0 | 0 | 0 | 1 | 1 | 1 | 2 | 3 |
| Packing Seal | 1 | 2 | 3 | 4 | 5 | 6 | 8 | 10 |
| O Ring | 1 | 2 | 3 | 4 | 5 | 6 | 8 | 10 |
| Shaft | 0 | 0 | 0 | 1 | 1 | 1 | 2 | 3 |
| Impeller | 0 | 0 | 0 | 1 | 1 | 1 | 2 | 3 |
| Wear Ring | 1 | 1 | 1 | 2 | 2 | 3 | 4 | 5 |
| Packing Ring | 0 | 0 | 0 | 1 | 1 | 1 | 2 | 3 |
| Packing Gland | 0 | 0 | 0 | 1 | 1 | 1 | 2 | 3 |
| Bearing | 1 | 1 | 1 | 2 | 2 | 3 | 4 | 5 |
| For Mechanical Seal Pump | ||||||||
| Spare Parts/Qty | Pump Qty (Including Spare Pump) | |||||||
| 1 | 2 | 3 | 4 | 5 | 6 | 8 | ≥10 | |
| Shaft Sleeve | 1 | 1 | 1 | 2 | 2 | 3 | 4 | 5 |
| Bearing Collar | 1 | 1 | 1 | 2 | 2 | 3 | 4 | 5 |
| Impeller Collar | 0 | 0 | 0 | 1 | 1 | 1 | 2 | 3 |
| Mechanical Seal | 1 | 1 | 1 | 2 | 2 | 3 | 4 | 5 |
| O Ring | 1 | 2 | 3 | 4 | 5 | 6 | 8 | 10 |
| Shaft | 0 | 0 | 0 | 1 | 1 | 1 | 2 | 3 |
| Impeller | 0 | 0 | 0 | 1 | 1 | 1 | 2 | 3 |
| Wear Ring | 1 | 1 | 1 | 2 | 2 | 3 | 4 | 5 |
| Mechanical Gland | 0 | 0 | 0 | 1 | 1 | 1 | 2 | 3 |
| Bearing | 1 | 1 | 1 | 2 | 2 | 3 | 4 | 5 |
Discover how to select the right split case pump materials based on fluid properties and operating conditions.
| Pump Parts | For Clear Water | For Sewage | For Seawater |
| Casing | Cast Iron | Ductile Iron | S.S / Super Dulex |
| Impeller | Cast Iron | Cast Steel | S.S / Super Dulex / Tin Bronze |
| Shaft | Steel | Steel | S.S / Super Dulex |
| Shaft Sleeve | Steel | Steel | S.S / Super Dulex |
| Wear Ring | Cast Iron | Cast Steel | S.S / Super Dulex / Tin Bronze |
| Remark | Final material depends on the liquid condition or the client’s request. | ||
Follow the essential installation steps to ensure safe and reliable operation of the split case pump.
| Standardized Installation Procedure for Split Case Pump | |||
| Work Stage | No. | Main Steps | Key Operations & Notes |
| I. Pre-Installation Preparation | 1 | Site & Foundation Inspection | • Clean the installation site and ensure sufficient space for operation and lifting. • Check the concrete foundation strength, dimensions, elevation, and anchor bolt positions according to drawings. The foundation surface should be flat and free of oil. |
| 2 | Equipment Unpacking & Inspection | • Verify that the pump, motor, and accessories match the contract specifications. • Inspect the equipment for any transportation damage and ensure all parts are complete. • Check that all accompanying documents (drawings, manuals, certificates) are complete. | |
| 3 | Tools & Material Preparation | • Prepare lifting equipment (hoist, sling), shims, level, dial indicator, wrenches, feeler gauge, lubricants, sealant, etc. • Prepare cleaning agents and cloths for cleaning mating surfaces. | |
| II. Pump Body Installation | 4 | Lifting & Positioning | • Lift the pump using the lifting holes or lugs; never lift by the pump shaft or inlet/outlet pipes. • Place the pump on the foundation, insert anchor bolts into base holes, do not tighten yet. |
| 5 | Initial Leveling & Alignment | • Place a level on the pump’s inlet/outlet flange or machined surface, adjust shims to roughly level the pump (tolerance ≤0.1 mm/m). • Use the pump shaft centerline as a reference to preliminarily align the pump. | |
| 6 | Primary Grouting | • Pour high-strength non-shrink grout into the anchor bolt holes; the grout layer should be dense and slightly below the foundation surface. • Curing: wait until the grout is fully cured (usually 3–7 days) before fine adjustment and tightening. | |
| 7 | Final Leveling & Alignment | • After grout curing, tighten anchor bolts. • Recheck pump level with a precision level. • Motor installation & alignment: lift the motor in place, use a dial indicator or laser alignment device, align the motor to ensure pump and motor shafts are coaxial (radial & axial deviation ≤0.05 mm). Tighten motor anchor bolts after alignment. | |
| III. Piping & Accessories Installation | 8 | Piping Connection | • Principle: never force pipe connections using the pump flanges to avoid stress on the pump body. • Piping should be independently supported, ensure natural alignment without stress. • It is recommended to install expansion joints near the pump inlet/outlet to absorb thermal expansion/contraction and installation errors. |
| 9 | Seals & Cooling System | • For mechanical seals, connect flushing/cooling piping, ensure smooth flow, flushing pressure 0.05–0.15 MPa higher than seal chamber. • For packing seals, install packing and adjust gland tightness (do not overtighten initially). | |
| 10 | Lubrication & Instruments | • Add specified grade and quantity of lubricant to bearing housing to oil mark midline. • Install pressure gauge, thermometer, etc.; pressure gauge should be between pump outlet and first valve. | |
| IV. Post-Installation Checks & Test Run | 11 | Final Checks | • Manual rotation: rotate coupling, ensure rotor turns smoothly, no friction or binding. • Check all bolts are tightened and guards are in place. • Jog motor: confirm rotation direction matches pump casing arrow. |
| 12 | Priming & Test Run | • Open inlet valve, fill pump with conveyed medium, completely expel air. • Close outlet valve, start motor. • Slowly open outlet valve to desired condition, check pressure, flow, vibration, noise, bearing temperature (≤80 ℃), and seal leakage. Test run ≥2 hours. | |
Explore proper disassembly and maintenance procedures to maximize the split case pump service life.
| Standardized Disassembly & Maintenance Procedure for Split Case Pump | |||
| Work Stage | No. | Main Steps | Key Operations & Notes |
| I. Pre-Disassembly Preparation | 1 | Shutdown & Isolation | • Safety first: slowly close the outlet valve, cut off power, and apply lockout/tagout (LOTO). • Close the inlet valve, open the pump vent and drain valves, completely drain the medium. For toxic or hazardous media, perform purging and verify safe conditions. |
| 2 | Disconnect External Connections | • Remove coupling guard and connecting bolts. • Disconnect all pipes, instrumentation lines, and cooling/seal water lines if the pump will be lifted as a whole. Seal open ends to prevent foreign object entry. | |
| 3 | Tools & Preparation | • Prepare pullers, hydraulic wrenches, copper bars, lifting equipment, and various wrenches. • Prepare parts boxes and labels to organize and mark removed bolts and small parts for easier reassembly. | |
| II. Pump Body Disassembly | 4 | Remove Accessories | • Remove pressure gauges, thermometers, and other instruments. • Open bearing housing oil drain and collect used lubricant. |
| 5 | Remove Coupling & Bearing End Covers | • Use a puller to smoothly remove the half-coupling from the pump shaft; avoid hammering. • Remove bearing end covers and gland bolts in sequence, then remove the covers. | |
| 6 | Lift Out Rotor Assembly | • Remove bearing housing bolts on both sides of the pump and horizontally lift the entire rotor assembly (shaft, impeller, bearings, sleeves) smoothly. Avoid collisions. | |
| 7 | Disassemble Split Case Pump Body | • Loosen and remove pump casing bolts in a diagonal sequence. • Lift the pump casing carefully and place on a padded or wooden platform. Protect the split case mating surface—avoid dents or scratches. | |
| 8 | Remove Internal Components | • Before disassembly, measure and record key clearances (e.g., impeller to wear ring, bearing clearance). • Use special wrenches to remove impeller locknut, then remove impeller. Remove shaft sleeve, mechanical seal or packing housing sequentially. | |
| III. Inspection, Maintenance & Reassembly | 9 | Parts Cleaning, Inspection & Measurement | • Clean all parts thoroughly, inspect for wear, corrosion, cracks. Focus on: – Impeller: cavitation, wear, dynamic balance. – Wear ring/seal ring: measure wear gap; replace if exceeding limits (typically >1.5× original gap). – Pump shaft: check straightness (total runout ≤0.05 mm). – Bearings: check clearance, rolling surface for pitting or spalling. – Mechanical seals: check stationary/rotating faces and spring elasticity. • Decide whether to repair or replace parts. |
| 10 | Reassembly (Reverse Order of Disassembly) | • Core principle: clean, align, and tighten evenly. • Replace all seals (O-rings, gaskets). Apply a thin layer of sealant (e.g., anaerobic) on split case mating surfaces. • Lift pump casing, tighten bolts diagonally in stages to manufacturer torque. • Reinstall rotor assembly, adjust impeller axial clearance to manufacturer spec. • Install bearings and adjust bearing clearance. • Reinstall coupling and perform precise pump-to-motor alignment (same as installation standard). | |
| 11 | Final Verification | • Manually rotate to ensure smooth, unrestricted motion. • Connect piping, add new lubricant to specified level. • Conduct final verification according to installation procedure “Priming & Test Run” to ensure normal operation parameters. | |
Find practical solutions to the most common split case pump operating issues.
| Split Case Pump Common Faults and Solutions | ||
| Problem | Causes | Solutions |
| 1. Pump not priming / Cannot discharge liquid | 1. Suction pipe, suction valve, foot valve not primed; air ingress. 2. Pump casing or suction pipe contains trapped air. 3. Motor rotation reversed. 4. Suction inlet leakage or failure. 5. Suction lift exceeds allowable maximum. | 1. Prime suction line and foot valve; eliminate air leaks. 2. Vent casing & suction line. 3. Correct motor wiring/rotation. 4. Repair suction inlet. 5. Reduce suction lift or add booster. |
| 2. Flow insufficient / Small discharge | 1. Inlet valve closed or partially closed; suction screen blocked. 2. Impeller blockage, foreign objects. 3. Wear at suction port (seal ring), impeller or casing wear. 4. Suction line contains air. 5. Pump speed too low. | 1. Fully open inlet valve; clean filter/screen. 2. Remove blockage/clean impeller. 3. Repair/replace worn components. 4. Purge air from suction. 5. Restore correct operating speed. |
| 3. Low head / Insufficient pressure | 1. Impeller clearance too large or impeller damage. 2. Low rotation speed. 3. Cavitation. 4. Suction pipe diameter too small. 5. Discharge head exceeds pump capacity. | 1. Adjust or replace impeller. 2. Increase speed within rating. 3. Improve suction conditions or reduce NPSH. 4. Increase suction pipe size. 5. Reduce discharge head. |
| 4. Excessive vibration / Abnormal noise | 1. Shaft misalignment. 2. Bearing damage. 3. Loose motor mounting. 4. Coupling or impeller imbalance. 5. Motor vibration. 6. Base/frame loose. 7. Improper pipe support causing resonance. | 1. Re‑align pump & motor. 2. Replace bearings. 3. Secure motor base. 4. Correct balance; inspect coupling. 5. Reduce motor vibration. 6. Tighten base. 7. Add pipe supports. |
| 5. Bearing overheating | 1. Improper lubrication (insufficient, wrong type, contaminated). 2. Bearing damage. 3. Poor alignment. 4. Bearing housing misfit. 5. Insufficient cooling. 6. Excessive rotational speed. | 1. Re‑lubricate with correct grease/oil. 2. Replace bearings. 3. Realign pump & motor. 4. Adjust housing fit. 5. Improve ventilation/cooling. 6. Operate within speed rating. |
| 6. Mechanical seal leakage | • Seal faces worn, uneven, O‑ring aging, spring failure. • Packing not lubricated or tightened. | • Replace mechanical seal and O‑rings; inspect shaft finish. • Adjust packing gland; ensure correct packing and tension. |
| 7. Motor overload / Tripped protection | 1. Insufficient power supply. 2. Phase loss / Power imbalance / Poor wiring. 3. Excessive load (impeller blockage), pump stalled. 4. Excessive starting current. 5. Motor overheating. 6. Short‑circuit or earth fault. | 1. Restore proper supply voltage. 2. Check wiring and phases; correct imbalance. 3. Remove blockage; clear shaft rotation. 4. Use soft start or reduced voltage starter. 5. Improve cooling. 6. Find & repair electrical fault. |
| 8. Cannot start or slow start | 1. Power supply abnormal (voltage drop). 2. Starter contactor open. 3. Motor winding open circuit. 4. Control circuit faulty. | 1. Check power and restart. 2. Check and replace contactor. 3. Repair/replacement of winding. 4. Correct control wiring. |
| 9. Pump vibration increases at no load | 1. Rotor imbalance, bent shaft. 2. Loose rotating parts. 3. Coupling looseness. 4. Pump suction/delivery line back‑pressure issue. | 1. Balance rotor or repair shaft. 2. Tighten rotating assembly. 3. Tighten coupling. 4. Eliminate back‑pressure and correct piping. |
| 10. Efficiency drop / Performance deterioration | 1. Wear of impeller & casing. 2. Internal passage clogging, scale/slag. 3. Air entrainment in suction. 4. Operating point far from BEP. | 1. Replace worn parts. 2. Clean flow passages; flush. 3. Eliminate suction air leaks. 4. Adjust operating conditions toward BEP. |
Learn the maintenance practices that help improve split case pump reliability and reduce downtime.
| Daily Maintenance and Care for Split Case Pumps | ||
| Maintenance Category | Maintenance Item | Details & Standards |
| I. Pre‑Operation Inspection | 1. Visual & Connection Check | • Check the pump casing, motor, coupling, etc., for cracks, deformation or damage. • Check all connection fasteners (especially pump‑to‑base and base bolts) for tightness to prevent leakage or vibration. • Check piping and joint areas for looseness. |
| 2. Lubrication Inspection | • Oil lubrication: Check if the oil level in the oil chamber is at the center mark; whether the oil is clean. Replace promptly if oil is turbid or contains impurities. • Grease lubrication: Check if the grease is sufficient and clean. Note: Water‑based bearings use grease X; motors use grease Y — the two must not be mixed. | |
| 3. Turn Shaft & Rotation Confirmation | • Manually rotate the coupling to check if the pump shaft rotates freely with no friction noise. • Start motor briefly to confirm the rotation direction is consistent with the direction indicated by the pump arrow. | |
| 4. Seal & Suction Check | • Check the mechanical seal and packing seal condition. • Open pump suction valve and drain water until the casing is full, then vent air (no dry running). | |
| II. Monitoring During Operation | 1. Parameter Monitoring | • Pressure & Flow: Monitor inlet and outlet pressures and flow to ensure operation within the rated range for optimum efficiency. • Bearing Temperature: Bearing temperatures should remain between 40–60 °C, and the motor temperature should not exceed 80 °C. If overheated, check lubrication and cooling systems. |
| 2. Vibration & Noise | • Listen to running noise: should be smooth hum. If there are abnormal noises, impacts, etc., stop and inspect immediately. • Observe vibration condition; abnormal vibration may indicate imbalance, bent shaft, uneven wear, or cavitation. | |
| 3. Seal & Leakage Monitoring | • Mechanical seal: Normal leakage rate should not exceed 5 drops per minute. • Packing seal: Through adjustment tighten, leakage rate should be controlled at about 10‑15 drops/min (approx. 30 ml/min) depending on packing size. Adjust to desired leakage. | |
| 4. Instruments & Motor | • Check all instruments (pressure gauge, temperature gauge, etc.) for normal readings. • Check motor current and electrical system; no abnormal heating. | |
| III. Periodic (Planned) Maintenance | 1. Lubrication Management | • Oil lubrication: Change first after 100 operating hours, then every 500 hours. • Grease lubrication: Generally replenish or change every 3 months; follow manufacturer service schedule. |
| 2. Seal System Maintenance | • Packing seal: Replace packing rings as needed; ensure stuffing box is properly tightened and align packing ring gaps at 90°–120°. • Mechanical seal: Check flushing liquid pressure; it should be 0.05–0.1 MPa. Replace seal if excessive wear or leakage. | |
| 3. Bearing & Coupling Check | • Monthly manually check coupling and shaft for smooth rotation, no abnormal noise. • Periodically check bearing housing for dirt, wear and proper lubrication. | |
| 4. Impeller & Flow Passage Cleaning | • Every 3 months or based on water quality, check impeller for buildup, corrosion, wear; clean off sediment, debris.• Check impeller clearance; if gap is too large (e.g., >0.1 mm), replace as required. | |
| 5. Alignment & Tightening | • Periodically check alignment between pump and motor; allowable deviation ≤0.05 mm. • Retighten base bolts and major fasteners as needed. | |
| IV. Shutdown & Long‑Term Stop | 1. Normal Shutdown | • Procedure: close outlet valve first → power off → close inlet valve and pressure gauge valves. |
| 2. Winter Anti‑Freeze | • When ambient temperature is ≤ 0 °C, after shutdown drain water from pump body, and ensure piping is drained to prevent freezing. | |
| 3. Long‑Term Storage | • Drain all internal water and clean thoroughly. • Apply rust preventive oil (shaft, impeller, contact areas), reinstall and protect for storage. | |
| V. Cleaning & Record Keeping | 1. Equipment Cleaning | • Weekly wipe pump body, motor, and base surfaces; especially clean motor cooling fins. • Regularly clean around instrument panels to prevent dust accumulation. |
| 2. Operation Records | • Establish and maintain operation & maintenance logs including operating hours, pressures, temperature, vibration, lubrication replacement time, fault handling, etc., to facilitate equipment condition tracking and planned maintenance. | |
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