Hydrogenation unit: operational error
Thread Content
In 2008, the facility began operations initially. Single-unit trial operation of the reaction feed pump. Back then, everyone was a beginner and worked very diligently. Before starting the pump, all interlocks were checked, the on-site procedures were in order, and all instruments that needed to be activated were indeed activated. The valve position of the control valve for the minimum flow line was checked, and it was found that this valve operates in a reverse manner; the instrumentation team was informed accordingly. Start the pump; the initial valve position of the minimum flow control valve is set to 40%, which means the set input value is 60%. After starting the pump, there was significant vibration and high outlet pressure; it was determined that the minimum flow valve was set too low, resulting in some pressure buildup. The operator on the outside instructed the operator on the inside to open the valves, and the operator on the inside was very careful, increasing the valve settings one by one: 59, 58, 57, 56, 55. Yet the vibration increased and the flow rate decreased. Later, the pump room started vibrating as well, which terrified the people on site; the equipment technicians rushed back in a panic, forcing the pumps to be shut down. Later, upon inspection, it was found that the control valve of the minimum flow line was of positive action, haha! As soon as we informed the instrumentation team, they immediately changed it from reactive to proactive. It’s no use not notifying us! Hehe!
Reply to 1# twinkler: We are also getting ready; the experience is worth learning from!
Before starting up, the outlet valve of the feed pump can be slightly opened, provided that the check valve at the pump outlet does not leak internally or leaks only slightly. For our 800,000-ton hydrogenation process, due to design issues (fewer pipe fixations), severe pipeline vibration occurred every time the minimum flow line was used. Later on, we only opened two outlet valves instead of using the minimum flow line; the outlet valves were opened promptly after starting the pump, and no problems have occurred since then.
New installations have many such problems; therefore, it is best to simulate and test all control circuits before commissioning to ensure that the control modes are correct. Otherwise, problems are likely to arise, especially since instrument technicians often do not understand the manufacturing process.
What is your process for single-unit trial operation? How does the medium move? Should a temporary pipeline be added to return from the pump outlet to the raw material tank?
With our high-pressure water injection system, too, the small pipelines that were used at the initial stage with the minimum flow setting were quite concerning; later on, it became normal when the opening degree of the valve for the minimum flow setting was set at 70. Last winter, we switched our high-pressure water pump to Pump B; at that time, the cooling water and engine oil of that pump were checked. Not long after pump B started operating, smoke was detected; it was urgently switched to pump A, at which point pump B became stuck and could no longer rotate. The reason is that the coolant line of the oil cooler in pump B froze, causing the oil temperature to rise and ultimately ruining the pump.