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Guide for diagnosing and correcting water hammer in a backflow valve

Technical analysis: Troubleshooting check valve water hammer: slam analysis, closing speed diagnosis, damper selection,

Guide for diagnosing and correcting water hammer in a backflow valve

1. Problem description and scope

This guide is intended for the diagnosis and correction of water hammer in check valves in water supply systems, chemical production and energy installations. Water hammer occurs due to rapid closure of the valve, resulting in pressure waves in the pipeline. During water hammer, noises, vibrations, incorrect pressure readings, even damage to pipelines or equipment may occur. According to DSTU 3043-2006 and ISO 5149:2017, water hammer is considered a critical issue that may lead to leaks, safety violations and loss of productivity. This guide covers systems with pressure up to 10 bar, temperature up to 80°C and working environments including water, chemical solutions and gases.

2. Safety and protective measures

Important! Before starting the diagnosis, perform the lockout/tagout (LOTO) procedure in accordance with DSTU 3043-2006. Use personal protective equipment (insulating gloves, safety goggles, pressure measuring devices). Check for stored energy in the system before diagnosis.

3. Required diagnostic tools

Tool Name Model/Specification Measurement range Objective
Multimeter Fluke 434 II 0–1000 V, 0–200 A Measurement of electrical parameters of valves
Vibration Analyzer BBE VIBRO-15 0–20000 Hz Vibration Activity Measurement
Thermocamera FLIR T1020 -20°C to 650°C Detection of thermal anomalies
Acoustic sensor SoundPLAN 2020 20 Hz to 20 kHz Noise Measurement
Pressure gauge Testo 220 0–100 bar Pressure Measurement

4. Before Diagnosis: Check List

Step Action
1 Determine the type of valve, pressure, temperature, and medium.
2 Record the values of pressure, temperature, and noise before starting the diagnostics.
3 Check the latest changes in the system (installation of valves, modification of piping, disconnection of components).
4 Record the alarm history (alarms, explosions, shutdowns).
5 Check for vibration, noise, and leaks.

5. Systematic Diagnostic Scheme

  1. Symptom: Unusual noises, vibrations, leaks, pressure deviations.
    1. Confirmation: Use a thermal camera and acoustic sensor to detect noise and thermal anomalies.
      1. If: High noise level (more than 85 dB) or high temperature (more than 70°C) is detected – possible cause: water explosion.
      2. If: Vibration detected (more than 10 mm/s) – possible cause: rapid closure of the valve.
  2. Confirmation: Measure the valve closing speed.
    1. If: Closing speed more than 2000 mm/s – possible cause: incorrect valve selection.
    2. If: Closing speed within 1000–2000 mm/s – possible cause: water explosion.
  3. Confirmation: Measure the pressure in the system during water explosion.
    1. If: Pressure above 10 bar – possible cause: water explosion.
    2. If: Pressure within the range of 5–10 bar – possible cause: water explosion.

6. Cause Matrix for Water Ingress

Symptom Possible Causes (by Probability) Diagnostic Testing Expected result, if the cause is confirmed
Noise, vibration
  1. Water Explosion (70%)
  2. Quick shut-off valve (20%)
  3. Damaged valve (10%)
  1. Measure noise (dB) and vibration (mm/s).
  2. Determine the pressure level.
  1. Noise > 85 dB or vibration > 10 mm/s.
  2. Pressure > 10 bar.
Turns
  1. Water Explosion (50%)
  2. Pipe damage (30%)
  3. Incorrect valve selection (20%)
  1. Measure pressure and vibration.
  2. Determine the location of the leak.
  1. Pressure > 10 bar.
  2. Leak at the valve connection.
Pressure deviation
  1. Water Explosion (60%)
  2. Incorrect valve selection (30%)
  3. Damaged valve (10%)
  1. Measure the pressure during explosion.
  2. Determine the valve closure speed.
  1. Pressure > 10 bar.
  2. Closing speed > 2000 mm/s.

7. Investigation of Causes of Defects

7.1 Water Explosion

Water hammer occurs due to rapid closure of a valve, causing a pressure wave in the pipeline. This can happen due to incorrect valve selection, absence of a damper or change in system parameters. Water hammer can lead to damage of pipes, valves and other equipment. To confirm water hammer, measure the noise (more than 85 dB), vibration (more than 10 mm/s) and pressure (more than 10 bar).

7.2 Quick Valve Closure

Fast closure of the valve occurs due to high closing speed, which may be caused by incorrect valve selection or absence of a damper. This leads to water hammer and vibration. To confirm the fast closure of the valve, measure the closing speed (more than 2000 mm/s) and pressure (more than 10 bar).

7.3 Damaged Valve

Valve damage may occur due to wear, corrosion, or lack of proper maintenance. This leads to water explosions, vibrations, and leaks. To confirm valve damage, perform pressure, noise, and vibration measurements, as well as check for visual signs of damage.

8. Step-by-step correction procedures

8.1 Water Explosion

  1. Install the damper on the valve or in the system to reduce closing speed.
  2. Check the valve closing speed and set it within the range of 1000–2000 mm/s.
  3. Measure the pressure after installing the damper and note the changes.
  4. Check noise and vibration to confirm the correction.

8.2 Quick Valve Closure

  1. Install the damper on the valve or in the system.
  2. Check the valve closing speed and set it within the range of 1000–2000 mm/s.
  3. Measure the pressure after installing the damper.
  4. Check noise and vibration to confirm the correction.

8.3 Damaged Valve

  1. Perform a visual inspection of the valve for the presence of damage.
  2. Replace the valve if damage is detected.
  3. Install the new valve and measure the closing speed and pressure.
  4. Check noise and vibration to confirm the correction.

9. Preventive Measures

Cause of failure Preventive strategy Control Method Recommended interval
Water Explosion Installation of the damper Closure speed and pressure measurement Every 6 months
Quick shut-off valve Installation of the damper Closure speed and pressure measurement Every 6 months
Damaged valve Regular maintenance and inspection Visual inspection and pressure measurement Every 12 months

10. Parts and Components

Component description Specification When to replace Category UNITEC-D
Valve damper Setting to closing speed 1000–2000 mm/s After detection of water explosion Category 102
Check Valve Minimum closing speed 1000 mm/s After detection of damage Category 101
Pressure gauge Range 0–100 bar After detection of water explosion Category 201
Acoustic sensor 20–20000 Hz After detection of water explosion Category 301

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11. References

  • DSTU 3043-2006 – Technical specifications for the safety of maintenance and operation of equipment.
  • ISO 5149:2017 – Pressure and Closure Speed Measurement Standard.
  • OEM Technical Manuals – Additional instructions from valve manufacturers.
  • UNITEC-D Maintenance Guides – Additional Resources for Servicing Systems.

Зверніться до UNITEC-D для отримання запчастин та компонентів: https://www.unitecd.com/e-catalog/

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