ASME PTC 19.3 TW-2016 pdf download.Thermowells.
Thermowells are an integral part of the piping system and the process containment system, and as a result, they may be subject to requirements from the governing piping or pressure vessel code. 3-1 REFERENCE STANDARDS AND GOVERNING CODES (a) ASME B40.200, Section B40.9, on Thermowells for Thermometers and Elastic Temperature Sensors, discusses the selection, fabrication, and installation of thermowells, as well as providing some standardized designs. Complement- ing ASME B40.200, Section B40.9, PTC 19.3 TW is limited in scope to mechanical design of thermowells. (b) ASME Boiler and Pressure Vessel Code (BPVC) Section III Appendices, Nonmandatory Appendix N provides guidance on the flow-induced vibration of banks or arrays of tubes and on the excitation of structural vibrations by turbulence. Both of these topics are outside the scope of PTC 19.3 TW, which considers the vibration of single thermowells due to vortex shedding only. (c) Guidance on minimizing temperature measurement errors in thermowell applications is found in the latest edition ofPTC 19.3. Effects considered include heating ofthe thermowell by fluid impingement, errors due to thermal radiation and conduction along the thermowell, and heat transfer between the thermowell and the surrounding fluid. 3-2 SPECIFICATION OF THERMOWELLS Specification of a thermowell and the materials of construction are the sole responsibility of the designer of the system that incorporates the thermowell. Sole responsibility for ensuring compatibility of the process fluid with the system rests with the end user. Thermowells may be stated to be in conformance to this Standard, subject to the requirements of Section 9 of this Standard.
4-1 CONFIGURATIONS Figure 4-1-1 shows a schematic diagram of a thermowell, along with its characteristic dimensions. Typical thermowell attachment configurations include threaded, socket weld, weld-in, lap-joint (Van Stone), and integral- flanged as shown in Figs. 4-1-2, 4-1-3, and 4-1-4 (see also Table 4-1-1). These figures are representative of common practice but do not display all allowable attachment configurations. The selection of a specific attachment method is subject to the governing piping or pressure vessel code. Use of ball joints, spherical unions, or packing gland installations are not permissible in Performance Test Code applications. The dashed line in Fig. 4-1-1 indicates the support plane, which is an imaginary extension of the supporting- structure surface that passes through the shank of the thermowell. The unsupported length, L, is calculated as the distance from the tip of the thermowell to the intersection of the thermowell axis with this surface. For thermowells mounted on flanges or welded into weld adaptors, the support plane will be a flat plane. However, for thermowells mounted by direct welding into a pipe wall, the support plane will actually be a curved surface with the same curvature as the inner pipe wall. For this case, the support plane should be approximated as a plane located at a distance from the thermowell tip equal to the largest actual distance from the tip to any point on the true curved support surface. For thermowells welded to a flange or pipe wall at an angle, the support plane will not be normal to the thermowell axis. For nonstandard attachments, this Standard covers the design requirements of the thermowell only. The designer shall account for the support compliance of the attachment (refer to subsection 6-6), and the attachment method shall meet all the requirements of the governing piping or pressure vessel code.ASME PTC 19.3 TW pdf download.