What are the requirements for the installation location of thermometers on horizontal pressure vessels?

The installation location of thermometers on horizontal pressure vessels must accurately reflect the process temperature and avoid measurement interference. For gas phase temperature measurement points, the measurement point should be located within the top 1/4 diameter of the vessel, avoiding turbulent areas such as the inlet and outlet. Liquid phase thermometers are typically installed at 1/3 of the height from the bottom, where they represent the temperature of the bulk material and are unaffected by sediment. For stratified media (such as oil-water mixtures), multiple measurement points at different heights or multi-point averaging thermometers should be used. The design of the thermometer sheath is crucial; the material must be the same as the vessel, and the insertion length should be 1/3 to 1/2 of the pipe diameter to ensure sufficient thermal contact area. The sheath end should be machined into a conical or hemispherical shape to reduce fluid resistance, and the wall thickness must withstand greater shear forces under higher operating pressures.

The installation angle affects the measurement response speed. Radial vertical installation is suitable for most situations, while a 45° inclined installation optimizes the temperature measurement accuracy for gas-liquid two-phase flow. For stirred vessels, thermometers should be installed away from the direct action zone of the impeller, typically behind the baffle or at a distance of 1.5 times the impeller diameter from the stirring shaft. Special attention must be paid to the continuity of insulation for cryogenic vessels; the connection between the thermometer sheath and the connecting pipe must be filled with insulating material to prevent cold bridging. Temperature sensors in explosion-proof areas must comply with ATEX/IECEx certification, and intrinsically safe instruments must be equipped with safety barriers. Signal transmission lines should be shielded against electromagnetic interference, and thermocouples should use matched compensating leads. Regular calibration is essential to ensure accuracy; industrial thermometers should undergo on-site comparison or laboratory calibration at least once a year, and redundant temperature measurement systems should be configured at critical process points.