A slight doubt about how deep to insert the thermometer

Please note regarding the length of the L-nozzle………… 1Q009: How is the length of the short section of the thermometer determined (the distance from the outer wall of the equipment/pipe to the flange surface)? A: In my opinion, this issue should be determined by specialists in piping and equipment (materials used for pipes and automatic control systems can also be taken into consideration). Generally, a value of 150 mm is used for piping and equipment; however, the specific value depends on factors such as the insulation material, the installation method (inclined insertion), and the requirements of the equipment. Different specialties have varying requirements; following the descriptions below, is the same principle applicable to the installation of drain pipes, pressure gauges, etc.? According to Article 6.0.2 of GB50235 \"Code for Construction of Industrial Metal Piping Projects\" and Article 7.2.6 of GB50236 \"Code for Construction of Welding of Field Equipment and Industrial Piping\", when the nominal diameter is less than 150 mm, the distance between the centers of the two pairs of welds on the same straight pipe end should not be less than the outer diameter of the pipe, nor less than 100 mm. Compiled as follows, taking into account different flange standards and conditions: HG20615 SW H height: 150lb, 300lb, 600lb, 900lb, 1500lb, 2500lb; DN25: 54, 60, 62, 73, 73, 89; DN40: 60, 67, 70, 83, 83, 111. Height of tee/straight pipe fittings: 33, 33, 33, 33, 33, 33. Length of straight pipe: 100, 100, 100, 100, 100, 100. Total length of DN25 sections: 187, 193, 195, 206, 206, 222. Total length of DN40 sections: 214, 227, 232, 256, 256, 300. Values for Chengda DN25 section H: 210, 210, 210, 240, 240, 240. Values for Chengda DN40 section H: 210, 210, 210, 240, 270, 270. July 19, 2022, Hualu: 180, 180, 220, 220, 220, 250. HG20592 SW H height: PN10, PN16, PN40, PN63, PN100, PN160; DN25: 40, 40, 40, 58, 58, 58; DN40: 45, 45, 45, 62, 62, 64. Height of tee/straight pipe fittings: 33, 33, 33, 33, 33, 33. Length of straight pipe: 100, 100, 100, 100, 100, 100. Total length of DN25 sections: 173, 173, 173, 191, 191, 191. Total length of DN40 sections: 185, 185, 185, 220, 220, 222. Values for Chengda DN25 section H: 200, 200, 200, 200, 200, 200. Values for Chengda DN40 section H: 200, 200, 200, 200, 200, 200

1Q005: Size and method of expanding the pipe for installing temperature instruments. A: According to 5.3.11 in SHT3005, e) when installing inside the pipe, the insertion depth should be between 1/3 and 1/2 of the pipe’s diameter, with at least 50 mm of insertion into the pipe (this indirectly indicates an expansion to DN100). The diagram in HGT21581 shows an expansion to DN100; earlier versions specified DN80. According to 5.2.3 in SHT3104, when thermocouples, thermal resistors, and bimetallic thermometers are installed in pipes with a diameter smaller than DN80, the pipe section concerned must be expanded (for details on how to expand the pipe for installing temperature instruments, see Appendix F), or they can be installed at bends. The requirements for expansion are as follows: a) For pipes with a nominal pressure of less than or equal to PN110 (Class 600), the pipe should be expanded to DN100； b) Pipes with a nominal pressure greater than PN110 (Class 600) are expanded to DN150. According to 6.2.2.4 of GB/T 50892-2013 Code for Design of Instrument and Control Systems in Oil and Gas Fields and Pipeline Projects, for pipes with a nominal diameter of not more than DN80, temperature measuring instruments can be installed at the elbow or at an angle of 45° opposite to the flow direction, with an enlarged pipe diameter. For thermocouples, thermal resistors, and bimetallic thermometers, the pipe diameter should be increased to DN100. The diameter of the expanded section of a pressure thermometer should be determined based on the calculated immersion length, with the length of this expanded section ranging from 250 mm to 300 mm. Therefore, in projects, expanding to DN100 is given priority; for pilot projects and similar ones with smaller pipe diameters (such as DN15, 20, 25), DN80 or DN50 expansion along with counterflow inclined installation can be used. As for the method of diameter expansion—top flat, bottom flat, or concentric—it can be chosen based on the requirements of the process piping and the properties of the material.

1Q010 How is the insertion depth of the temperature sensor determined? A: The insertion depth of the temperature sensing element into the pipe or equipment, or the length of the protective tube, should be determined by calculation based on the specific operating conditions. All of its temperature-sensing components should be placed inside the pipeline/equipment to ensure that the temperature-sensitive parts are in full contact with the medium being measured. Note: The sensitive section length of a thermocouple is approximately 20 mm, that of a thermal resistor and bimetallic thermometer is about 40 mm, while the sensitive section length of a pressure-type thermometer is equal to the length of its temperature sensing element. When installing on a pipe, the insertion depth should be at 1/3 to 1/2 to 2/3 of the pipe’s diameter, and it must extend at least 50 mm into the pipe ； When installing inside a container, the insertion depth should be no less than 150 mm from the inner wall of the container, and generally should not exceed 400 mm; however, for containers equipped with agitators or other internal components, the insertion depth can be appropriately reduced. The specifications require the following: According to HG/T 20507-2014, Standards for the Selection and Design of Automation Instruments, 4.1.2 states that the immersion depth of the temperature sensing element must meet the following requirements: 1 The choice of immersion depth for the temperature sensing element should be based on the principle of inserting it into a region of the medium where temperature changes are sensitive and representative. 2 When the temperature sensing element is installed vertically on a fully filled fluid pipeline or at an angle of 45° to the pipe wall, the length of the element’s tip that is submerged within the inner wall of the pipeline should be no less than 50 mm, and no more than 125 mm. 3 When installing the temperature sensing element in the equipment, the length of the end of the temperature sensing element that is submerged within the inner wall of the equipment should be no less than 150 mm. When installing on flues, furnaces, and equipment with insulated material constructions, the appropriate type should be selected based on actual needs. SH/T 3005-2016 Specification for the Selection and Design of Automation Instruments in Petrochemical Industries e) The insertion depth of the thermometer sleeve should ensure that the end of the temperature sensing element is located in the region where temperature changes of the medium being measured are most significant. When installing inside a pipe, the insertion depth should be at 1/3 to 1/2 of the pipe’s diameter, and it must extend at least 50 mm into the pipe ； When installing inside a container, the insertion depth should be at least 150 mm from the inner wall of the container; however, for containers equipped with agitators, this depth can be reduced appropriately. GB/T 50892-2013 Code for Design of Instrumentation and Control Systems in Oil and Gas Fields and Pipeline Projects 6.2.2 The installation of temperature measuring instruments shall comply with the following provisions: 6 The insertion depth of temperature measuring instruments shall meet the following requirements: 1) The insertion depth in the pipeline should be as close as possible to the center of the pipeline. When the pipe diameter is greater than DN250, it shall be determined through calculation based on specific operating conditions, and it shall be ensured that the sensitive part of the temperature sensing element is fully immersed in the medium ； 2) The insertion depth into the device should ensure accurate measurement of the medium temperature, and it should not collide with the internal components of the device ； 3) When installing on flue ducts, furnace chambers, and equipment made of insulated materials, the insertion depth of the sensing element should be determined based on the specific operating conditions. SH/T 3104-2013 Code for Installation and Design of Instrumentation in Petrochemical Industries 5.2.8 The insertion depth of temperature sensing elements in storage tanks should not exceed 400 mm, and their installation location should be 600 mm above the heating coils inside the tank. The temperature measurement elements installed on the floating roof tank should not hinder the movement of the floating roof. (Note: The length of the end of the wear-resistant thermocouple that protrudes from the outer casing of the equipment should be between 100 mm and 150 mm.) ) AQ 3036-2010 Specifications for the Installation of On-site Safety Monitoring Equipment in Hazardous Chemicals Facilities with Major Hazard Sources – Tank Areas. 6.1.3 The installation height of temperature sensors in storage tanks is generally between 1 m and 1.3 m (except for spherical and horizontal tanks); the insertion depth should be between 0.5 m and 1 m. For pressure storage tanks, one temperature monitor can be installed, with the monitoring point located more than 1 m deep inside the tank. Six to ten points are generally selected for monitoring average temperature. We can also take a look at the calculation process based on the version of SHT3104-2000: Paragraph 3 of Section 3.0.2 specifies the formula for calculating the insertion depth L of temperature measuring instruments: L = L1 + δ + U, where L1 is the length of the instrument’s connection head in mm ； δ — Wall thickness of the tube (mm) ； U — Submersion length (mm). When measuring liquids: UL = LS + 40 mm. When measuring gases: UG = LS + 25 mm. Where: UL – immersion length of the liquid (mm) ； UG — Immersion length of the gas (mm) ； LS — length of the sensitive section of the thermometer (mm). Note: the sensitive section length of a thermocouple is approximately 20 mm, that of a thermal resistor and bimetallic thermometer is about 40 mm, while the sensitive section length of a pressure-type thermometer is equal to the length of its temperature sensing element. Under normal circumstances, the fluid flow velocity should not exceed 8 m/s, and the gas flow velocity should not exceed 40 m/s. Moreover, when the pipe diameter is greater than DN250, the immersion length of the temperature sleeve within the pipe can range from 120 mm to 150 mm.

This is the content I have organized in WORD. Do you still have any questions after reading it?

This post was last edited by sdlymtf on 2022-10-18 at 16:50. It’s too detailed; I’ve learned a lot from it. I’ll take some time to think about it carefully~~