How to choose a thermometer for installing one upward with a sleeve on the lower plate of a liquid ammonia spherical tank
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Under a 1,000-cubic-meter liquid ammonia spherical tank, a thermometer is to be installed with its sensing element facing upward. A thermometer sleeve, extending 300 mm inward from the top of the tank, has been welded in place; the top end of this sleeve is sealed. The thermometer flange has a DN40 specification, with its sealing surface oriented downward, necessitating that the thermometer be installed upward. There is a gap between the inner wall of the thermometer sleeve and the thermometer itself, and air is normally present in this space. How should one select an appropriate level gauge?
When selecting a thermometer for installation with the lower plate of a 1000-cubic-liter liquid ammonia sphere tank facing upward, the following factors need to be considered: 1. **Temperature range**: First, determine the storage and operating temperature range of liquid ammonia, and choose a thermometer that can cover this range. 2. **Installation method**: Since the thermometer needs to be installed upward via a DN40 flange, and the length of its extension into the sleeve is 300 mm, it is necessary to select a thermometer with the appropriate length and diameter to ensure that its measuring end can get as close as possible to the liquid ammonia, thereby improving measurement accuracy. 3. **Materials and Chemical Resistance**: The material of the thermometer chosen must be able to withstand the corrosion caused by liquid ammonia; stainless steel is generally a good choice. 4. **Sealing and protection**: Given that there is air present and the sealing surface of the thermometer flange faces downward, it is necessary to select a thermometer with good sealing properties to prevent any leakage of ammonia gas. Furthermore, it may be necessary to reinforce the connection between the sleeve and the thermometer additionally to ensure its sealing and safety. 5. **Reading method**: Depending on the convenience of taking readings on site, one can choose a thermometer with a local display or an electronic thermometer that transmits output signals remotely. Taking all the above factors into account, a resistive or thermocouple-type thermometer made of stainless steel, with good sealing properties and an appropriate length to reach deep into the sleeve, can be chosen. Ensure that its specifications match those of a DN40 flange, and that it has the capability for remote data transmission, so as to enable better temperature monitoring and control. .
The outside of the tube is filled with liquid ammonia, and the thermometer is installed inside a 300 mm long tube; there is air between the inside of the tube and the thermometer. Can this ensure the accuracy of the thermometer’s readings?
Apply some thermally conductive silicone grease a few centimeters ahead of the thermometer tip, and fill the gap between the thermometer and the sleeve with it to conduct heat. When installed vertically upward, it’s not easy to fill it with heat transfer oil.