[Weekly Topic] Moving Equipment: Share something that happened around you this week (Updated in September)
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This post was last edited by lizhenpeng on 2011-9-19 09:40 / `* H0 W" `2 I& W( C Revised format: Talk about something that happened at work this week T6 |, y* l/ ?8 n3 C1 T Participation method: Share real stories related to technology, maintenance, etc. that occurred at work this week. (Share the technical problems you encounter at work, along with the methods you used to solve them, so that others can benefit from your experience. You can also discuss any difficulties or challenges you face, and everyone can help find solutions together. If it’s hard to explain in words, you can upload actual images for everyone to analyze.) 3 ^' e- A5 Z0 \) s# ?. |" \: A Requirements for participation: The topics must have occurred this week and be related to this section. A normal reply would be about wealth at 8 o’clock; if possible, a detailed description of wealth from 10 o’clock to 35 o’clock would be good.
1. Course of the equipment accident: After the unit was restarted following major maintenance, operators noticed that a large amount of ammonium methylate was spraying out from the high-pressure end sleeve of the plunger of the high-pressure methamine pump, making it impossible for anyone to approach the area. The operator stopped the process, and thanks to prompt action, no major accident occurred. Subsequently, the process engineers cleaned it thoroughly and handed it over for maintenance. 2 Analysis of the cause of the failure: By considering the inspection results of the O-rings in the bases of all the main packing boxes of this equipment, as well as the maintenance work carried out on it during this major repair, thorough analysis and discussion led to the following determination of the cause of the leakage: It was found that the broken and damaged O-rings in the bases of the packing boxes of the urea high-pressure methanamine pump were the direct cause of the methanamide leakage ； Upon rechecking all the O-rings at the bases of the main packing boxes on this machine, it was found that the O-rings used in installation have a specification of Φ130×5.5 mm, whereas the required specification for those O-rings is Φ130×5 mm. An examination of the entire overhaul process revealed that the maintenance personnel used an O-ring with dimensions of ø130×5.5 mm by mistake during installation; this resulted in insufficient pressure resistance of the O-ring, which was the fundamental cause of the leakage in the packing box of the urea high-pressure methanamine ammonia pump.
On September 11, a minor issue was addressed by shutting down the propylene compressor due to a leak in the pipeline of the purification process; however, after restarting the compressor, it was found that the vibration at its low-pressure end was above the acceptable level, with the highest value reaching 75. The vibration levels remain around this alarm threshold, so the compressor can only be operated under monitoring.
1. Phenomenon: After the propylene compressor stops, reverse rotation occurs, with the speed reaching 1000 revolutions per second. This ultimately leads to damage to the dry gas seal. 2. Reason: The compressor has a high compression ratio, the outlet pipeline is too long, and the diameter of the outlet pipeline is large. The dry gas seal is a single-unit design. 3. Technical upgrade: Replace the dry gas seal with a two-way seal. Add a return line from the outlet pipeline to the compressor inlet. 4. The technical improvement has yielded excellent results; please refer to it in case of similar issues with compressors.
Reply to 4# Orca: It should be a one-way channel, right? Your compressor doesn’t have any backflow, but it still must have an outlet for venting, right? It’s better to have backflow so as to avoid waste. Doesn’t your compressor’s outlet have a check valve? Or isn’t it sealing properly? In my opinion, the most important thing is to prevent the compressor from running in reverse; this not only affects the sealing but also has a significant impact on the compressor itself. I don’t know what the rated speed of the compressor at your place is; I’ve seen cases where the speed suddenly changes from a few hundred to over 5000 of the rated speed
Reply to 1# lizhenpeng: The facility has two pumps, each of which has automatic start/stop functions via the DCS. However, there are no check valves at the pump outlets; instead, butterfly valves are installed there. Is it safe to start or shut down these pumps using the DCS in such a situation?
Reply to 2# YTH-Gavin: I have a question – is the diameter of an O-ring with a size of 5.5 smaller than that of one with a size of 5.0?
In the facility where we are working, the propylene compressor is of the RWBⅡ 1080E type. In this compressor system, there is a balance line connecting the propylene condenser and the propylene storage tank, and another balance line connecting the oil return device and the propylene subcooler. What is the purpose of these balance lines? Thank you
When testing the dry gas seal of a pump, the outlet flare valve is closed (the pump is not started); if the nitrogen pressure cannot be maintained, could it be that the mechanical seal is damaged?