Introduction to Sample Cooler
Sample Coolers are small shell and tube heat exchangers that are used to cool the sample from a process stream to the required temperature conditions for safe and immediate analysis. It is one of the most critical components of a sampling system suitable for most applications in liquid, gas or steam process. The sample to be cooled flows through the tube side of the cooler, and the cooling fluid, usually water, flows through the shell side. The cooled sample then is taken to a laboratory for analysis or piped to in-line process instrumentation for continuous monitoring of properties such as conductivity, pH or other chemical constituents.
Sample coolers are not only used to cool samples but also to temper the sample to the appropriate temperature for
the analysis being performed. This is important as some analysis procedures can be affected by interference’s directly or indirectly due to the fluid temperature. Allow the sample to run for a while before collection. This will ensure that a true sample is collected for analysis.
Basic Design of Sample Cooler
Sample coolers are available in numerous sizes and configurations depending on the application that they will
be used in. Mainly sample cooler is constructed of a single, one-piece heat transfer tube, wound as a coil and housed in a cylindrical container known as shell. The process fluid stream is admitted to the coil from top. The cooling fluid is passed through the shell of the sample cooler in an opposite direction to the process fluid in order to ensure optimum efficiency. The cooling fluid absorbs the heat of process fluid, resulting in a drop in the process fluid temperature that is later collected as sample.
The shell is mounted through flanged connections and it can be removed without disturbing sample lines. The sample cooler should be installed as close as possible to the system take of point at a height to facilitate convenient operation. The sample cooler should be mounted in the vertical position.
Must have Features of Sample Cooler
- Safe and accurate sampling.
- High efficiency – Outlet temperature to be very close to what is desired.
- Designed to handle high pressure & high temperature samples.
- No welded joints in coil – A complete single piece coil assures trouble free operations with no risks of failure of joints inside the shell.
- Corrosion resistant materials.
- Counter-current flow to achieve very close temperature approach of the sample to the cooling fluid.
- Cooling fluid requirement must be minimum.
- Size must be small and compact. This makes the mounting of sample cooler easy and minimize the cooling fluid utilization.
- Facilitation of routine on-site maintenance easily. Coils can be cleaned or replaced, if required, easily.
- Some designs have in-built safety relief valve to prevent accidents in the field in case of an (unlikely) event of coil failure.
- Self-draining design to eliminate sample retention. (inlet top, outlet bottom).
- Shell must be easily removed without disconnecting the sample lines, for inspection or maintenance purposes.
- Low pressure drop system.
Applications of Sample Cooler
- Power generation
- Oil & Gas
- Other industries like Sugar, Paper, Cement, Textile, Steel etc.
Operation of Sample Cooler
- Open the cooling fluid inlet valve fully and ensure cooling fluid is flowing to drain.
- Open the sample-regulating valve slowly until process fluid stream starts to flow. Then allow sample to run to waste for a suitable period to purge the stagnant process fluid in the sample line.
- Regulate the sample flow until a stable desired temperature is achieved. Then collect sufficient volume of sample in a suitable container.
- When sample has been acquired then first close the sample-regulating valve and then the cooling fluid inlet valve.
Precautions while Operating Sample Cooler
- To avoid the risk of scalding, it is essential that a full flow of cooling water is present before opening the sample inlet valve.
- Always close the sample inlet valve before turning off the cooling water.
- Sample pipework becomes very hot under normal working conditions and will cause burns if touched.
- After closing the sample inlet valve the sample outlet connection may drip for a few minutes while the coil drains.
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