Application note · Industrial Water
A sampling and measurement framework for cooling and boiler systems: control limits, the parameter set, sampling points, and the handling mistakes that make a correct instrument report a wrong value.
The short answer
Cooling and boiler systems are controlled by a small number of measurements taken often, at points that are easy to get wrong. The chemistry is not complicated. The difficulty is that the sample changes between the system and the bench: it cools, it degasses, it deposits, and it picks up contamination from the sample line.
The treatment programme defines the limits: cycles of concentration, alkalinity, hardness, chloride, pH and dissolved oxygen in the feed. Write those limits down before choosing instruments, because the limit and its tolerance decide whether a titration, a meter or a separation method is appropriate — and how much precision the method actually needs.
| Parameter | What it controls | Typical method | Sample handling |
|---|---|---|---|
| pH | Corrosion and scale tendency | Benchtop meter, temperature compensated | Measure at once; do not aerate |
| Conductivity | Cycles of concentration | Benchtop meter | Cool to a fixed temperature before reading |
| Total hardness | Scale formation | Complexometric titration | Cool quickly; titrate before precipitation |
| Alkalinity | pH stability and treatment dose | Acid titration to a fixed endpoint | Titrate promptly; limit air exposure |
| Chloride | Corrosion risk | Titration, or ion chromatography at low levels | Filter if turbid; record the dilution |
| Dissolved oxygen | Feed-water corrosion | Meter with a flow cell where possible | No air contact; measure in a closed cell |
Three rules carry most of the value. Sample from a point that represents the system rather than a dead leg. Cool the sample in a closed coil rather than an open beaker, because an open beaker loses dissolved gases and gains oxygen. Flush the line long enough that the sample is the system’s water rather than the line’s water.
None of these requires an instrument, and all three change the number that the instrument reports.
Titration is fast and adequate for mg/L levels in most cooling water. Ion chromatography becomes the better choice when the level is low, when several ions are reported together, or when the sample is coloured enough to obscure the endpoint. The decision is about the level and the report, not about precision in the abstract.
A system under stable control can be checked on a fixed schedule. A system that has just been cleaned, restarted or put on a new treatment needs daily checks until the trend settles. Write the schedule as a rule rather than a table: what triggers an increase in frequency, and who decides.
Three appear most often: hardness measured on a sample that cooled slowly and precipitated, conductivity read at whatever temperature the sample happened to be, and dissolved oxygen measured by pouring sample into an open beaker. Each produces a number that looks reasonable and is wrong, which is the most expensive kind of error a water programme can make.
The configuration described above, with the full specification of each model.
KM Series
The split-type design effectively reduces signal/electromagnetic interference, improving measurement accuracy.
4 models
5-inch LCD screen with 150° viewing angle for clear reading out of 5 meters.
IC Series
This is the latest integrated ion chromatograph with dual anion and cation channels
Because hardness salts precipitate as the sample cools and stands, and the precipitate is no longer titrated. Cool quickly in a closed coil and titrate promptly; a sample held in an open beaker reports the water, not the system.
For mg/L levels in most cooling water, yes — it is fast and needs no infrastructure. Ion chromatography becomes the better choice when the level is low, when several ions are reported together, or when the sample is coloured enough to obscure the endpoint.
If dissolved oxygen is a control parameter, yes — and with a flow cell rather than a beaker. It is the measurement most easily ruined by handling, and a meter used occasionally without a membrane check is worse than no reading.
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