Issues with the setup of the high-pressure isolation fluid system?
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This post was last edited by zzcqiang on 2017-8-23 at 12:24. There are many high-pressure orifice-type flowmeters in high-pressure hydrogenation units; some design institutes have designed high-pressure isolation fluid systems that include high-pressure oil injectors for the purpose of instrument maintenance. However, some design institutes do not install high-pressure isolation fluid systems due to considerations such as cost or safety. Let’s discuss what the appropriate approach is It is necessary to take into account both production maintenance and safe operation.
Have those who have used high-pressure oil injectors shared their experiences regarding the advantages and disadvantages of using them?
Our facility used high-pressure oil injectors (imported from abroad) for high-pressure hydrogenation (16 MPA). After some time, these injectors started to malfunction, which even led to a shutdown of the plant due to interlocks. The main problems were insufficient flow rate and blockages at various pressure measurement points. Replacing the oil injectors was costly, and regular lubricant topping up was also required – it was quite troublesome. Later, we switched to an isolation fluid system that allows for remote control, and the results have been very good. As far as I know, high-pressure hydrogenation mostly uses high-pressure oil injectors, and the performance of these methods is not very good; it is recommended to carry out modifications.
Could you share the better modification methods you used later on?
It’s quite simple: a tee fitting is added to the existing pipeline (1/4'' stainless steel pipe), and the new isolation fluid system is connected to each branch. This allows the original pipeline structure to remain unchanged; the installation is straightforward – the existing electric oil injection system can be discontinued, and the new system can be put into use. The new system uses instrument air as power, with controllable flow, and can also be controlled remotely via DCS. The new system sets the pressure level at 19.6 MPA, with a maximum of 30 MPA. The isolation fluid is ethylene glycol (pay attention to the water content, as hydrogenation catalysts cannot tolerate water). On-site irrigation can also be achieved. Significant costs were saved (the cost of each oiling head is around 5,000 yuan, plus lubricants, etc.).
Instrument air is available everywhere in the hydrogenation unit; it serves merely as a substitute for power to drive the injection of isolation fluid into the pressure guiding pipes. Instrument air does not enter the process pipelines, so there are no safety issues associated with it； Our factory has used nearly 20 sets of pneumatic isolation fluid systems.