Maintenance Guides 1 min read

A guide to finding and correcting insufficient flow or no discharge in a centrifugal pump

Technical analysis: Troubleshooting centrifugal pump low flow or no discharge: cavitation, impeller wear, air lock, suct

Гід по відшуканню та виправленню недостатнього потоку або відсутності випуску у центрифугальному насосі - UNITEC-D Industrial MRO
Цей гід присвячений відшуканню та виправленню недостатнього потоку або відсутності випуску у центрифугальному насосі. Він використовує систематичний підхід для визначення основних причин вини, включаю

1. Description of the problem and scope

This guide is dedicated to finding and correcting insufficient flow or no discharge in a centrifugal pump. Trouble messages can occur in many types of equipment, including chemical, energy, agricultural, and industrial systems. The importance of this issue is defined as critical, as a lack of flow can lead to production shutdowns, reduced efficiency and wasted energy.

2. Safety precautions

Disconnecting the power supply and blocking the mechanical equipment
Before starting the diagnosis, perform the blocking and tagging of the mechanical equipment according to DSTU 3013-2013 standards and ISO 12100. Use appropriate isolation and blocking to avoid accidental starting.
Protection against electric shock
Use insulating gloves (according to DSTU 3013-2013) and radiation protection glasses. In the absence of ventilation or the presence of chemical liquids, use breathing masks.
Energy Storage Precautions
Before accessing the pump, ensure that all energy sources (electrical, hydraulic, pneumatic) are disconnected. In the absence of electricity, use battery sources or suitable tools to measure the remaining energy.

3. Necessary diagnostic tools

Name of the tool Model/Spec Measuring range The goal
Multimeter Fluke 87V 0–2000 Ω, 0–600 V, 0–20 A Measurement of electrical resistance, voltage and current
Thermography FLIR T1020 -20°C to 650°C Determination of temperature anomalies on the surface of the pump
Vibration analyzer LDI VIBROSCOPE 0-10,000Hz, 0-10mm/s RMS Detection of vibrations that may indicate fatigue or deviation
Pressure sensor Testo 510 0–100 bar Pressure measurement on the inlet and outlet hose
Pressure booster Testo 520 0–100 bar Pressure boost for accurate measurements

4. Initial assessment and checklist

Control point action
Pump temperature Measure the temperature on the surface of the pump and compare with the nominal. A value above 60°C may indicate overheating.
Inlet hose pressure Use a pressure gauge to measure the pressure on the inlet hose. A value less than 1.5 bar may indicate an absorption problem.
Pressure on the outlet hose Measure the pressure on the outlet hose. A value less than 1.2 bar may indicate a decrease in flow.
The sound of the pump Listen for abnormal noises that may indicate vibrations or lack of flow.
Filter status Check the filter for dirt. The lack of flow may be due to a clogged filter.
The presence of air in the system Check for air in the system. This may occur due to incorrect filling of the system.

5. Systematic diagnostic scheme

  1. Symptom: No or reduced flow
    1. Measure the pressure on the inlet hose. If the pressure is less than 1.5 bar, proceed to the next step.
    2. Check the filter. If it is clogged, remove the dirt or replace it.
    3. Measure the pressure on the outlet hose. If the pressure is less than 1.2 bar, proceed to the next step.
    4. Check for air in the system. If detected, perform suction.
  2. Symptom: Pump vibration
    1. Use a vibration analyzer to measure the vibration. If the value is greater than 10 mm/s RMS, proceed to the next step.
    2. Check the increased distance between the shaft and the housing. If the increase is greater than 0.1 mm, proceed to the next step.
    3. Check the shaft and bearings for wear. If the wear is greater than 0.2 mm, proceed to the next step.
  3. Symptom: Increased pump temperature
    1. Measure the temperature on the surface of the pump. If the value is greater than 60°C, proceed to the next step.
    2. Check for air in the system. If detected, perform suction.
    3. Check the condition of the filter. If it is clogged, remove the dirt or replace it.

6. Matrix of causes of guilt

Symptom Probable causes (in order of probability) Diagnostic test Expected result
No flow or reduced flow
  1. Special exhaust ventilation
  2. Clogged filter
  3. Insufficient inlet pressure
  4. Air in the system
  1. Measure the pressure on the inlet hose
  2. Check the filter
  3. Check for air
  1. The pressure is less than 1.5 bar
  2. Clogged filter
  3. Air in the system
Pump vibration
  1. Shaft wear
  2. Increasing the gap between the roller and the housing
  3. Incorrect installation
  1. Measure vibration
  2. Check the clearance between the roller and the housing
  3. Check the installation
  1. Vibration greater than 10 mm/s RMS
  2. The gap is more than 0.1 mm
  3. Incorrect installation
Increased pump temperature
  1. Incorrect ventilation
  2. Air in the system
  3. Clogged filter
  1. Measure the temperature
  2. Check for air
  3. Check the filter
  1. The temperature is over 60°C
  2. Air in the system
  3. Clogged filter

7. Analysis of the main causes of guilt

7.1. Exhausted ventilation

The main cause of exhausted ventilation is insufficient pressure at the inlet. This can occur due to insufficient liquid lift height, insufficient inlet pressure, or lack of ventilation. If this is not corrected, air can build up in the system, resulting in no or reduced flow.

7.2. Clogged filter

The filter can become clogged due to the accumulation of dirt or improper cleaning. No flow or decreased flow may be related to this. Failure to correct may result in pump damage or reduced efficiency.

7.3. Air in the system

Air can enter the system due to incorrect filling or gaps in the pipelines. This results in no or reduced flow. Failure to correct may result in pump damage or reduced efficiency.

7.4. Shaft wear

Shaft wear can occur due to high pressure or improper use. This leads to vibration and reduced pump efficiency. Failure to correct may result in pump damage or reduced efficiency.

7.5. Incorrect installation

Improper installation can occur due to misuse or improper assembly. This leads to vibration and reduced pump efficiency. Failure to correct may result in pump damage or reduced efficiency.

8. Step-by-step correction procedures

8.1. Correction of poor ventilation

  1. Check the pressure on the inlet hose. If the pressure is less than 1.5 bar, do the following.
  2. Set the inlet pressure to the nominal value (1.5–2.5 bar). Use an amplifier or control valve.
  3. Check the ventilation. If ventilation is not up to standard, repair or replace.
  4. Measure the pressure on the outlet hose. If the pressure is more than 1.2 bar, perform the following actions.
  5. Check the system for air. If detected, perform suction.

8.2. Fixing a clogged filter

  1. Measure the pressure on the inlet hose. If the pressure is less than 1.5 bar, do the following.
  2. Remove dirt from the filter or replace the filter. Use a pressure gauge to measure pressure.
  3. Check the pressure on the outlet hose. If the pressure is more than 1.2 bar, perform the following actions.
  4. Measure the temperature on the surface of the pump. If the temperature is above 60°C, do the following.
  5. Check for air in the system. If detected, perform suction.

8.3. Correction of air in the system

  1. Measure the pressure on the inlet hose. If the pressure is less than 1.5 bar, do the following.
  2. Check for air in the system. If detected, perform suction.
  3. Measure the pressure on the outlet hose. If the pressure is more than 1.2 bar, perform the following actions.
  4. Check the filter. If it is clogged, remove the dirt or replace it.
  5. Measure the temperature on the surface of the pump. If the temperature is above 60°C, do the following.

8.4. Repair of worn shafts

  1. Measure the vibration. If the value is greater than 10 mm/s RMS, do the following.
  2. Check the clearance between the roller and the housing. If the gap is more than 0.1 mm, follow the steps below.
  3. Replace the worn shaft with a new one. Use measuring tools to measure the clearance.
  4. Check the installation. If the installation is not correct, follow these steps.
  5. Measure the vibration. If the value is less than 10 mm/s RMS, do the following.

8.5. Correcting incorrect installation

  1. Check the installation. If the installation is not correct, follow these steps.
  2. Correct the installation with measuring tools. Use measuring tools to measure distance.
  3. Check the vibration. If the value is less than 10 mm/s RMS, do the following.
  4. Measure the pressure on the inlet hose. If the pressure is less than 1.5 bar, do the following.
  5. Measure the pressure on the outlet hose. If the pressure is more than 1.2 bar, perform the following actions.

9. Preventive measures

The main reason is guilt Prevention strategy Monitoring method Recommended interval
Exhausted ventilation Regular check of pressure and ventilation Pressure measurement on the inlet hose 1 time per month
Clogged filter Regular cleaning or replacement of the filter Pressure measurement on the inlet hose 1 time per month
Air in the system Regular check for air Pressure measurement on the inlet hose 1 time per month
Shaft wear Regular measurement of vibration and clearance Vibration analysis 1 time per month
Incorrect installation Regular installation check Measuring the distance between the roller and the body 1 time per month

10. Spare parts and components

Description of the spare part Specification When to replace UNITEC-D category
Filter Material: stainless steel, size: 50 mm After hammering or after 1000 hours of operation Filters
shaft Material: stainless steel, size: 50 mm After wear or after 5000 hours of operation Vali
Inlet hose Material: stainless steel, size: 50 mm After wear or after 1000 hours of operation Hoses
Outlet hose Material: stainless steel, size: 50 mm After wear or after 1000 hours of operation Hoses
Ventilation Material: stainless steel, size: 50 mm After wear or after 1000 hours of operation Ventilation

Refer to our e-catalog to select the correct parts: https://www.unitecd.com/e-catalog/

11. Links

  • DSTU 3013-2013: Basic requirements for technical safety
  • ISO 12100: Machine safety
  • ISO 2372: Vibration measurement
  • ISO 5199: Pressure measurement
  • ISO 5198: Temperature measurement
  • UNITEC-D Maintenance Guide: Specialized guides for centrifugal pumps

Note: These guidelines comply with DSTU, EN and ISO standards. For more detailed information, please refer to the relevant documents.

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