The correct dosing of chemicals into a closed-circuit system requires an understanding of the system's volume. Overdosing leads to unnecessary expenditure on chemicals and potential damage to the system. Underdosing: will render the treatment ineffective, leading to problems such as microbial growth, scaling, or corrosion.
It may be possible to estimate the system volume from Manufacturer’s Data or Engineering Drawings: but unfortunately, in many older buildings this information is no longer available.
In the absence of any system volume date the following methods may be used to estimate system volume:
- Most chillers or boilers of heating systems will give a kW output rating. This information will generally be on a plaque on the equipment plant itself. If this is a new system, kW ratings may be specified by the installer, and it may be possible to obtain the kW ratings from this specification.
For commercial pressurised systems multiply the kW rating by the figure given below to obtain an estimate of system volume:
- Systems comprising of perimeter heating, convectors etc = 6 litres / kW
- Ventilation systems (Air handling units, fan coils etc), chilled water systems = 8 litres / kW
- Steel panel radiators = 11 litres / kW
- Cast iron radiators = 14 litres / kW
- Distant heating systems in large sprawling buildings = 20 litres / kW
- Underfloor heating = 23 litres / kW
- Stepwise Addition: Add the chemical in small, controlled amounts and monitor the system's response. Use pH meters, conductivity meters, or other relevant test methods to gauge the effect and gradually reach the desired concentration.
- Tracer Method: Introduce a tracer substance (harmless and easily measurable) into the system and calculate the volume based on its concentration after mixing. This is where our Systemtrace CC comes in……………. Systemtrace CC contains PTSA (1,3,6,8-pyrenetetrasulfonic acid tetrasodium salt) is a fluorescent tracer dye commonly used in various industrial applications, including closed circuit water systems like Low Pressure Hot Water (LPHW) and chiller systems.
- Stability: It is chemically stable and does not react with other chemicals commonly used in water treatment, ensuring reliable performance.
- Solubility: PTSA is highly soluble in water, which facilitates even distribution throughout the system.
- The simplicity of sampling and measuring PTSA fluorescence makes it a convenient tool for operators to use regularly.
How to Use Systemtrace CC
A photometer with the ability to measure the PTSA levels will be required for example The MD640 is a portable fluorometer designed for field-based measurement of PTSA and other fluorescent tracers in water treatment systems. PTSA standards to calibrate the fluorometer according to the manufacturer's instructions. Will also be required
Dilution Information:
1 litre of Systemtrace CC will yield a concentration of 75 µg/L of tracer when diluted in 10,000 litres of system fluid.
Dosing Instructions:
Carefully measure the required volume of Systemtrace CC based on the system volume and desired tracer concentration.
Add to System: Introduce the measured Systemtrace CC into the system at an appropriate dosing point, typically through a dosing pot in closed systems.
Recirculate: Ensure the system is fully recirculating. Allow the tracer to disperse evenly throughout the system by maintaining circulation for a minimum of 2 hours.
Collect Samples: After the dispersion period, take samples from representative points within the system.
Measurement: The tracer chemical, PTSA, is a fluorescent dye that emits light at wavelengths between 400-500 nm when exposed to UV light. Use an appropriate photometer to measure the fluorescence.
Match Calibration Temperature: For the most accurate measurements, ensure that sample temperatures are as close as possible to the temperature of the calibration standard. Although fluorescence can be temperature-sensitive (with a 1.26% decrease for every 10°C increase), this effect is relatively minor.
Calculation of System Volume
If you dose 1 litre of Systemtrace CC into 10,000 litres, the resulting tracer concentration should be 75 µg/L (ppb). If you get a different reading, you can calculate your system volume using the following formula:
System volume (l) = 750,000
Tracer concentration (ppb)
Example Calculation:
Suppose you dose 1 litre of Systemtrace CC.
After dispersion, measure the tracer concentration. For example, if the concentration is found to be 50 µg/L (ppb).
Using the formula: System volume (l) = 750,000
Tracer concentration (ppb) 50
So, if the measured tracer concentration is 50 µg/L, the system volume would be 15,000 litres.
By applying this formula, you can accurately determine the system volume based on the concentration of the tracer detected.
Accurate chemical dosing in Low Pressure Hot Water (LPHW) and chiller systems is crucial for maintaining system efficiency, longevity, and safety and the use of Systemtrace CC allows for accurate system volumes to be calculated so that accurate chemical dosing of inhibitors, biocides, azoles and glycol can be done every time. It is also the case that by focusing on the benefits of accurate chemical dosing, you can provide more compelling and precise quotes, leading to better client satisfaction and successful project outcomes.
PTSA is an invaluable tool in the maintenance and monitoring of closed-circuit systems such as LPHW and chiller systems. Its properties of high fluorescence, stability, and solubility, combined with its ease of measurement, make it ideal for accurate system volume calculation, chemical dosing, and leak detection, ultimately leading to more efficient, cost-effective, and reliable system operation.
Contact us on ownlabel@bvwater.co.uk for more information on our Systemtrace CC
