What is sleeve in pipelines

The immersion sleeve (also immersion tube) is simply described as a metallic shell that can be inserted into media lines to measure temperatures. The sleeve has thin outer walls. It is hollow inside and can accommodate the sensor of a temperature meter. Immersion sleeves protect sensors from liquids and allow the temperature measurement devices to be exchanged easily.

Properties and tasks of the immersion sleeve

An immersion sleeve is a hollow piece of pipe that is inserted into lines carrying media to measure temperatures. It has a thread on one side with which craftsmen can screw the component tightly and tightly in the pipe. The material of the metallic immersion tubes is basically based on the medium whose temperature is to be measured and the tube material in which it flows. You can choose from immersion sleeves made of brass, copper, steel or stainless steel. If the sensor or measuring probe is inserted, the immersion tubes can be closed or flushed with the respective liquid.

Tasks and advantages of the dip tubes

The thin-walled tubes accommodate temperature sensors, which in turn record the temperature values ​​of heating water, cooling water, drinking water or the solar fluid. This is necessary, for example, for a heat meter or heating control. Without the inserted sensor, however, the immersion tubes themselves are tight. They enable the uncomplicated exchange of the sensors without having to drain the corresponding media from the pipes. This is necessary, for example, for maintenance, calibration or repair work.

The professional assembly of dip tubes

So that the sensors can correctly record the temperature of the various liquids, immersion sleeves and sensors must reach at least to the pipe axis (half the diameter of the pipes). In addition, an undisturbed heat transfer from the medium to the sensor must be ensured. While this is not a problem with sleeves with direct flow through them, installers should fill tight components with a suitable oil or thermal paste. In a different way, air cushions form in the immersion tube, which interrupt the heat conduction from the shell to the sensor and can lead to measurement errors.

Be careful when installing in insulated pipes

Insulated pipelines generally have a very large outside diameter with the insulation. If the immersion sleeve is in a T-piece, the additional length must be taken into account. Otherwise it can happen that the sensor barely reaches the media flow. It is then only plugged into the T-piece and records incorrect temperature values.

Heat pockets for quick and accurate readings

If the respective area of ​​application requires very precise measured values ​​very quickly, skilled craftsmen insert the immersion sleeve into the pipe carrying the medium at an angle of around 45 degrees. The component points against the direction of flow and the respective liquid flows against it over the entire length. So-called heat pockets are formed and the temperatures can be recorded correctly.

Technical alternatives for the immersion sleeve

If the use of dip tubes is not desired or not permitted, there are now a number of alternatives. An example of this are sleeveless measuring devices. These consist of a screw connection in which a sealing element is integrated. If craftsmen push the sensor through the screw connection into the pipe, it penetrates the seal and is located directly in the media flow. If you pull out the sensor, the sealing element closes the opening and the liquid does not escape. This is beneficial because the installation depth of the sensor elements can be individually adapted to the place of use in this way.

However, temperature values ​​can also be measured completely without contact with the media flow. This is possible, for example, with a system sensor or a strap-on thermostat. The measuring devices record the outside temperature of the pipe walls, which corresponds to the medium temperature in inert systems. It is important to know that the temperature sensors must be insulated here. Otherwise heat sources in the vicinity could falsify the measurement result. The contact sensors are mainly used for smaller pipe diameters in which immersion sleeves are not suitable.

Conclusion by Alexander Rosenkranz

The immersion sleeve is a hollow piece of pipe that can be screwed into lines carrying media. It takes temperature sensors and enables relatively accurate temperature measurement. For this to work, however, it depends on a professional installation. If the immersion tubes are not suitable for small tube diameters, for example, contact sensors can also be used.

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