Installation and application of pressure/differential pressure instruments and transmitters in hydrogenation plants

Hydrogenation process is a crude oil processing process that has been adopted in large quantities in the petrochemical industry in recent years. The hydrogenation unit is a pro-hydrogen working condition, in which the oil and hydrogen media are flammable and explosive, especially the hydrogen has a high explosion level. The high operating pressure and temperature of diesel hydrogenation, wax oil hydrogenation, residue hydrogenation and other hydrogenation units can easily lead to leakage of pipelines and equipment, with very serious consequences. When the hydrogenation unit is cold before start-up to the hot state during normal production or from the hot state during normal production to the cold state during shutdown, the process piping will produce large displacement and the height of the process equipment will change, and these changes will pull the instrumentation pilot lines and measuring instruments connected to it. Therefore, the working condition of hydrogenation unit has a great influence on the instrument lead pressure pipeline and installation. If the instrument lead pressure pipeline and installation connection cannot eliminate these adverse effects automatically, the lead pressure pipeline will break and the instrument process interface will be pulled apart, leading to leakage, which will not only affect the normal production, but also lead to the leakage of high pressure and high temperature medium that will hurt people and explode in case of fire. The actual working condition on site also proves this point, some hydrogenation devices have broken the lead pressure pipe and the interface of the pipe and valve parts are pulled apart; more common is the installation of flow measurement orifice plate on the high temperature and high pressure pipeline, the root of the lead pressure pipe and the process interface of the differential pressure transmitter are prone to leakage.

The instrumentation lead pipe is connected to the process piping or equipment and is in direct contact with the medium, which is one of the most used, complicated working conditions, high technical requirements and complicated design solutions in the instrumentation installation. The high-pressure hydrogenation unit is characterized by high hydrogen, high pressure, high temperature and high H2S corrosion, so the selection of instrumentation leadpipe specification, material and installation method is especially important for the long-cycle safe operation of the instrumentation and the unit.

The high temperature process pipeline and equipment of hydrogenation unit, from the cold state before start-up to the hot state after start-up, lead to large displacement of process pipeline and large change of process equipment height due to thermal expansion and contraction.