Leakage detection
Detection of ammonia leakage into brine
Written by: Michael Elstrøm
How to use a pH sensor
This guide describes how a pH sensor can be used to detect ammonia leakage into brine systems in refrigeration and chiller applications.
Influence of brine composition
The type of brine affects how quickly and how clearly the pH value changes when ammonia is present:
- Water, glycol and ethanol mixtures: rapid pH increase
- NaCl and potassium-based brines: slower response due to buffering effect
- Potassium formate/acetate brines: higher base pH with similar reaction trend
As shown in the diagram on page 3, even small amounts of ammonia cause a measurable increase in pH across different brine types.
Principle of detection
When ammonia leaks into a brine solution, the pH value increases. This change can be monitored continuously using a pH sensor.
The method is suitable for most brines used in refrigeration systems, including mixtures of water with glycol, ethanol or methanol
Sensor installation
The pH sensor should be installed directly in the brine circuit where continuous flow is ensured.
For temperatures below –15°C, the sensor should be installed in a bypass line where the brine can be heated to remain within the operating range of the sensor.
Note: The sensor requires water-based fluids and cannot be used in hydrocarbon liquids.
Signal and output
The pH sensor provides a 4–20 mA analog output corresponding to the measured pH value. This signal can be used for monitoring, logging and alarm handling in a PLC or control system.
Calibration
The sensor is delivered with a basic calibration. Calibration is typically not required for freshwater or mixtures of water with glycol, ethanol or methanol. For brines with higher base pH values (e.g. NaCl or potassium-based brines), calibration is recommended to ensure accurate readings.
Alarm setup
A two-level alarm system is recommended.
Example for systems with base pH ~7:
- Warning: pH > 8 or pH < 6
- Alarm: pH ≥ 9
This setup allows early detection of sensor drift and clear identification of ammonia leakage. For other brine types, alarm limits should be adjusted according to the normal operating pH range.
Functionality check
To verify sensor functionality in water-based systems:
- Prepare a solution with approximately 0.1% ammonia in water
- Immerse the sensor in the solution
- Confirm that the pH reading increases as expected
Regular verification is recommended, especially in critical systems.
Summary
A pH sensor provides a simple and continuous method for detecting ammonia leakage into brine systems. Correct installation, calibration and alarm configuration are essential to ensure reliable detection.
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