Boiler Automation Systems

Boiler Water Sample Cooler: Accurate Sampling for Water Analysis

A sample of hot boiler water taken into an open container gives misleading results because of flash evaporation. A sample cooler cools it in a closed circuit for accurate analysis.

ORFA Technical TeamUpdated: Oct 30, 20263 min read

Boiler water sample cooler with cooling coil

Boiler water quality directly affects efficiency, operating safety and equipment life, so values such as conductivity (TDS), pH and hardness must be analysed regularly. However, when hot boiler water under pressure is drawn into an open container, part of it immediately flashes to steam. A boiler water sample cooler prevents this loss by cooling the sample inside a closed coil, so that the analysis result can be trusted.

This article explains how a sample cooler works, the correct sampling procedure and typical technical data.

What Is a Boiler Water Sample Cooler?

A sample cooler is a small heat exchanger that cools high-temperature boiler water to a temperature suitable for analysis. It consists of a stainless steel shell with a coil running through it. Boiler water flows inside the coil while cooling water flows through the shell around it; the two fluids never mix.

Why Is Flash Evaporation a Problem?

Under pressure, boiler water is far above its atmospheric boiling point. When a sample is taken straight into an open container, some of the water escapes as steam, but the dissolved salts stay behind, so their concentration in the remaining sample rises. Conductivity and TDS therefore read higher than they really are, which can lead to unnecessary blowdown. Drawing boiling water in the open is also a serious scalding hazard.

Working Principle

Start the cooling water: Cold water is fed to the shell and kept flowing around the coil.
Take the sample: Boiler water is admitted slowly into the coil through the sample inlet valve.
Cooling: The sample gives up heat through the coil wall to the cooling water; as the circuit is closed, nothing evaporates.
Collect the sample: The cooled sample is drawn from the coil outlet into a clean container and analysed.

Tip: Always open the cooling water before opening the sample valve. When finished, close the sample valve first and then the cooling water. Let the line run for a while before analysis to flush out stagnant water.

Benefits

Accurate results: With no flash loss, the measured values truly represent the boiler water.
Safety: Reduces the scalding risk of drawing hot water in the open.
Ease of use: Permanently mounted next to the boiler, making sampling quick and repeatable.
Durability: Stainless steel shell and coil resist corrosion.
Better blowdown control: Reliable TDS readings help set the right blowdown rate and avoid wasting water and energy.

Technical Data

Typical values for the sample cooler supplied by ORFA are listed below. Please confirm suitability for your application against the product data sheet.

Property	Value
Shell material	AISI 304 stainless steel
Coil material	AISI 316L stainless steel
Shell nominal pressure	PN 16
Coil nominal pressure	PN 40
Sample inlet valve	1/4″ BSP stainless steel (max. 100 bar, 350 °C)
Cooling water inlet valve	1/2″ BSP
Cooling water side	Max. 10 bar, 100 °C
Shell size	3″ (DN80)

Applications

Steam boilers and steam generators
High-temperature hot water boilers
Power plants and process facilities
Boiler water treatment and blowdown control

Frequently Asked Questions

Why not take the sample straight from the boiler into an open container?

Hot water under pressure partly evaporates in an open container while the dissolved salts remain in the sample. Conductivity and TDS then read too high, and there is a risk of scalding.

Does the sample mix with the cooling water?

No. The sample flows inside the coil and the cooling water through the shell. Heat is transferred through the coil wall and the fluids never mix.

In which order should the valves be opened?

Open the cooling water first, then the sample valve. When closing, shut the sample valve first and then the cooling water, so no uncooled hot water remains in the coil.

Conclusion

A boiler water sample cooler is a simple but critical piece of equipment that makes boiler water analysis accurate and safe. Accurate measurement means correct blowdown and a longer boiler life. For boiler level and control equipment, see our Level Control Devices page.

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