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CDL/CDLF Vertical Multistage Pump

Complete Troubleshooting & Diagnostic Guide

1. Pump Not Discharging Water

1.1 Possible Causes

Cause	Probability	Check Method
No priming water	High	Visual inspection
Air in suction line	High	Listen for air sounds
Incorrect rotation	Medium	Check motor direction
Suction lift too high	Medium	Measure vertical distance
Clogged impeller	Low	Disassemble and inspect

1.2 Solutions

2. Insufficient Flow or Head

2.1 Diagnostic Steps

1. Check discharge pressure gauge – Compare with performance curve
2. Measure motor current – Low current indicates low load
3. Inspect suction strainer – Clean if clogged
4. Check valve positions – Ensure fully open
5. Verify pump speed – Should match nameplate RPM

2.2 Common Causes & Remedies

Symptom	Cause	Remedy
Low pressure	Worn impellers	Replace impeller assembly
Low flow	Clogged diffuser	Clean or replace diffuser
Both low	Wrong rotation	Reverse any two power leads
Fluctuating	Air in system	Bleed air from piping

3. Excessive Vibration or Noise

3.1 Vibration Analysis

Vibration Level	Status	Action
0-2.8 mm/s	Excellent	No action needed
2.8-4.5 mm/s	Good	Monitor trend
4.5-7.1 mm/s	Acceptable	Plan maintenance
7.1-11.2 mm/s	Poor	Schedule repair
>11.2 mm/s	Unacceptable	Stop immediately

3.2 Noise Diagnosis

4. Motor Overheating

4.1 Temperature Limits

Insulation Class	Max Temperature	Rise Limit
Class B	130°C	80K
Class F	155°C	105K
Class H	180°C	125K

4.2 Troubleshooting Steps

1. Check ventilation – Clean motor cooling fins
2. Measure voltage – Should be ±10% of rated
3. Check current balance – Phase imbalance <5%
4. Verify load – Compare with pump curve
5. Check ambient temperature – Must be ≤40°C

5. Mechanical Seal Leakage

5.1 Leakage Classification

Leakage Rate	Status	Action
No visible leakage	Excellent	Continue operation
<3 drops/min	Acceptable	Monitor
3-10 drops/min	Warning	Plan replacement
>10 drops/min	Critical	Stop and replace
Continuous stream	Failure	Immediate shutdown

5.2 Common Seal Failures

6. Bearing Failure

6.1 Bearing Life Expectancy

L10 Life = (C/P)³ × 1,000,000 revolutions

• Normal life: 25,000-50,000 hours
• Premature failure indicators: Noise, heat, vibration

6.2 Failure Analysis

Failure Pattern	Cause	Prevention
Spalling	Fatigue overload	Reduce load, proper sizing
Brinelling	Static overload	Proper handling during install
Peeling	Insufficient lubrication	Regular grease replacement
Rust	Water contamination	Improve sealing

7. Cavitation Damage

7.1 NPSH Calculation

NPSHa = Ha ± Hz – Hf – Hvp

• Ha = Atmospheric pressure head
• Hz = Static suction head (positive or negative)
• Hf = Friction loss in suction line
• Hvp = Vapor pressure of liquid

7.2 Cavitation Symptoms

• ✓ Noise like gravel in pump
• ✓ Vibration increase
• ✓ Head and flow reduction
• ✓ Pitting on impeller vanes

8. Performance Testing

8.1 Test Parameters

Parameter	Measurement Tool	Frequency
Flow rate	Flow meter	Quarterly
Head	Pressure gauges	Quarterly
Power	Power analyzer	Quarterly
Efficiency	Calculated	Quarterly
Vibration	Vibration analyzer	Monthly

9. Emergency Procedures

10. Documentation & Records

Maintain troubleshooting log with:

• Date and time of issue
• Symptoms observed
• Diagnostic steps taken
• Root cause identified
• Corrective action performed
• Technician name

11. Technical Support

Shanghai Chaodun Machinery Manufacturing Group Co., Ltd.

Website: https://cd-pump.com