Process Area Activity – [I See Now-27] Heat Transfer Oil Injection

Thread Content

Let me share with you an incident that occurred due to a problem related to the manufacturing process. In 2013, a new facility was built at the plant; the heat transfer oil system is used for heating the oil. This system includes a steam generator – the heat transfer oil heats the water in the boiler to produce steam, functioning essentially as a heat exchanger. The tube side uses heat transfer oil, while the shell side uses water; steam is generated at the top of the water in the shell side of the heating furnace. In the heat transfer oil system, it is necessary to ensure that every pipeline is properly heated, so the steam generator is also heated (the other components are the reboilers at the bottom of each tower). Two heat transfer oil pumps were started up, and there was a temperature rise in the pipeline leading to the steam generator; the pipeline coming out of the steam generator also experienced a temperature increase (though it was lower than that at the inlet). We had a total of three heat transfer oil pumps, with two in operation and one as a backup. To ensure that the heat transfer oil in the pipelines of all three pumps reached the desired temperature, the pumps were switched back and forth at certain points (the switching procedure involved starting the backup pump and shutting down one of the operating pumps). It seems that the oil was heated up to over 200°C. It was morning on that day, and I was present at the site. Suddenly, oil started spraying from the high-level oil tank in the heat transfer oil system. This tank was installed at the highest point of the facility (on the third platform), and the spraying of oil caused most of the facility to collapse from top to bottom. The entire facility was filled with heat transfer oil, which flowed into the drainage ditches located within the enclosures on each floor; it was only after reaching these ditches that the oil separated into rainwater and sewage pipelines. At that time, the drainage ditches around the facility were full, and since they were connected to the rainwater pipeline system, the facility staff quickly used materials to block those outlets and rerouted the flow to the sewage pipeline system. Others used empty heat transfer oil tanks to collect the clean oil from the ditches and used it to wipe down the equipment that had been exposed to the oil, as well as the floor of the facility. In short, it took several days to deal with this situation. I’m glad that the heat transfer oil that was sprayed out didn’t cause a fire; it was only some heat transfer oil that was lost. Post-incident analysis: It was also during the day that it was decided to switch the heat transfer oil pumps; for a short period of time, all three heat transfer oil pumps were operating simultaneously. The heat transfer oil flowing through the \"tube side\" of our steam generator had a spiral shape. Due to the higher flow rate of the three pumps being used at that time, this caused the heat transfer oil in the steam generator’s tube side to become unobstructed (reason: the higher the temperature of the heat transfer oil, the lower its viscosity; therefore, the problem did not occur when the pumps were switched at lower temperatures, but rather at a high temperature of over 200°C, which led to complete unobstruction of the steam generator). The water and light components inside the steam generator, which prevented the oil from being heated thoroughly, were ejected rapidly into the upper oil tank, thereby carrying away a large amount of heat transfer oil. Previously, the temperature at the outlet of the steam generator was also high (probably over 100 degrees), slightly lower than that at the inlet. It is thought that the presence of boiler water in the \"shell side\" of the steam generator provides a cooling effect, which is why the outlet temperature is lower than the inlet temperature. That’s all for now; I’m not sure if it’s clear enough. So even those working in process development still need to become more familiar with the equipment; by understanding it in advance, things become clear.