Regarding whether temperature protection sleeves are needed for process pipelines
Thread Content
I was previously involved in many designs related to the chlor-alkali industry; now that I’m working in the petrochemical industry, I believe the principles of instrument design are similar, though the requirements in the petrochemical industry are stricter. However, I have always had doubts regarding the issue of temperature sleeves in the petrochemical industry; I searched through all the materials I had at my disposal but could not find any information indicating that temperature sleeves are necessary on pipes in this industry. Firstly, I admit that installing temperature sleeves on the pipes complies with the regulations of the instrumentation field, which state that process pipes are closed systems before being connected to instruments. Secondly, installing instrument sleeves on the pipes allows for the online replacement of temperature instruments. Thirdly, this approach is better from a safety perspective. But I think: (1) the possibility that the temperature gauge is broken is low, and it is inspected every year; even turning off the valve allows for replacement ； (2) I have no issue with installing pipe temperature sleeves for flammable, explosive, toxic, and other such media, but is it necessary to add them even for things like air and circulating water? (3) Generally, temperature measuring instruments come equipped with sleeves 12, 16, or even finer protective tubes; if the material of these protective tubes is suitable for handling the substance, why add another sleeve? (4) As far as I know, the cost of one sleeve is not lower than that of a bimetallic element, and 100 such sleeves would cost fifty to sixty thousand – so why go to the extra expense? I mention these things in order to ask the process designers here: under what circumstances do you require instruments to be equipped with protective pipes for the pipelines/equipment?
As you said, whether a thermometer sleeve is necessary isn’t something that is required in all petrochemical operations; I don’t recall any such requirement existing. In the petrochemical plants I’ve been involved with, some use sleeves while others do not. Personally, I think that in fact it should be determined based on operating conditions and costs: for example, in cases where online replacement is required, or when high reliability in temperature control is necessary. . . It should be added; otherwise, it can be added or not, depending on individual circumstances.
In environments with high-pressure corrosive effects and conditions prone to wear, protective sleeves are generally installed. . .
It is not mandatory, but based on experience, an outer sleeve is needed when the pressure is 4 MPa or higher. The pressure resistance of prefabricated sleeves is insufficient; moreover, prefabricated sleeves can also be removed online
Our devices are equipped with tube sleeves, but that’s only to prevent wear; we’ve never seen it used for any other purpose! ! :)