Questions about thermometer sleeves
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For the first project I took on, someone else prepared the instrument specifications; when filling in information regarding the thermometer, we were asked by our process team to provide the flow rate in the pipeline. At that time, I didn’t know anything about it, nor did I understand why the flow rate was needed. While reviewing the specifications recently, I came across this information; I also checked the documents related to previous projects, and those specifications for thermometers in those projects did not include any details regarding flow rate. Moreover, the descriptions in the specifications were quite vague. I’d like to ask everyone, is there a specific figure for this?
Most thermometer casings are made of 316 material; even an adult man standing on them will not cause any damage. If this flow rate is indeed in an extremely unusual range, the process will let you know. Have the thermometer manufacturer do the calculation. Thickened treatment.
This can be calculated using the vibration frequency formula; if the flow velocity is too high, the wall thickness of the casing can be made thicker
I’ve found this formula and I’ve also done the calculations; it’s as mentioned in the guidelines – at what flow rate is it necessary to carry out these calculations? Is there a specific value?
There is no fixed value; it also depends on factors such as the medium, flow rate, and the length of the temperature sensing section inserted into the pipe
Vibration calculations should be performed on the thermometer sleeves in the following situations: 1. Pumps or compressors’ outlet pipes. 2. Gas pipelines with a temperature of 200°C and a pressure higher than 1.6 MPa. 3. Steam and steam condensate pipes. 4. Pipes with a diameter larger than DN300. 5. Long-distance transmission pipelines. 6. Pipelines where water hammer or flashing may occur. 7. In situations where there is a potential risk after the sleeve breaks, such as in oxygen pipelines.
Thank you, it’s very detailed. May I ask where this requirement comes from?
This post was last edited by sun_fm on 2022-1-17 at 10:28. The vibration calculation of thermometer sleeves is related not only to process parameters but also to factors such as the processing method, thickness, shape, insertion depth, and material of the sleeves. According to HGT20507 and SHT3005, 1: For sleeves, integral drilled conical protection tubes are generally used. The diameter of such tubes is determined in accordance with the company’s regulations; for example, our company requires flange connections of DN40, with integral conical shapes, and the material of the protection tube must be at least grade 316. The sleeve dimensions are Φ26.5/18–Φ8 (with an armored core of Φ6). Under normal circumstances, the vibration calculations meet the requirements. 2. In 4.1.4.3 of HGT20507, vibration calculations for the protection tube are advisable in situations where the temperature, pressure, and flow rate of the process fluid are high. 3. In 5.3.11.f of SHT3005, in situations where the temperature, pressure, and flow rate of the process fluid are high or the pipe diameter is large, the vibration frequency and compliance calculations for the thermometer sleeve shall be carried out in accordance with the ASME PTC 19.3 TW standard. 4. My previous approach was to select the suitable casings and have the casing manufacturers carry out the calculations. 5. As for cases where vibration calculations are required, these are based on points 2 and 3; the original text comes from a sample document by HGT (similar to a standardized format)
This is a summary of experience; according to the standards, it should be the 8th floor. Additional note: Excessive vibration can be addressed by bolding, adding support rings, or reinforcing the structure. There are relevant software such as Wika or EDGE for performing the calculations directly.