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Case Study How an Aluminium tape caused a complete plant stoppage?
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Background : Breakdown are always one of the biggest obstacles in smooth running of Plants and leading to financial impact also. If plant runs smoothly without any breakdown, profitability increases, and you know that much better than us. People follow 100s of maintenance practices to keep their plant running 24x7 without interruption and breakdown. But still sometimes few breakdowns happen in such a way that, they make us learn many new things and what to and what not to do during maintenance practices. This is one such case study, where the maintenance activities followed by many plants become the reason for Breakdown. How? We will see in coming paragraphs and Please do not laugh when I say this incident happened on 2020 Dhuleti. Yes, you heard it right, on Dhuleti and 2020. Sometimes I feel breakdown and holiday are synonymous. Majority of plant breakdown keeps on happening on Sunday or Holiday. Seems, it has become a trend.
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Incident Details: On a fine day of Dhuleti, when many of plant people were celebrating Holi with all the precautions and eating various sweets and snacks. A Call came from plant Shift engineer to his Manager from plant. Call was “Sir, Jaldi aaiye, Preheater Fan (2750 kW) band ho gaya hai, uski MV drive nahi chal rahi aur uski wajah se plant bhi band ho gaya (Sir, please come soon, Preheater fan (2750 kW) is stopped due to some issue in MV drive and due to that plant is also stopped)”. Whenever Maintenance engineer hear such things his heartbeat always goes up. He asked his shift engineer to check, while he is on his way to plant from township. He gathered his team and went to plant to check the breakdown and start plant immediately. After reaching the substation he found out condition of panel as below.
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Picture of Panel where flashover took place (1.1) Little flashover, as you can see in above picture near fuse, which caused the Preheater MVVFD drive to trip, ultimately causing complete stoppage. Meanwhile replacement of burn out fuses, busbar, etc was started. Manager also inquired how this flashover occurred. The engineer shown them the burn out culprit (shown in an image below)
Picture of the Culprit that caused flashover & Hence plant stoppage (1.2) www.systemprotection.in
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How did this Aluminium tape, which was there at bottom of panel for closing panel holes, went near to the fuse?
Root Cause: The panel was of MVVFD Drive for 3000 kW 6.6 kV Motor, and it has 4 nos fan of 3.7 kW for cooling. And they were used for cooling of drive and were blowing air from inside of panel to outside. Due to this a negative pressure was created. Now the Aluminium tape, which are normally used to close unused holes in panel, was pasted in this drive during at the time of commissioning. And if the tape glue quality is not good or if the tape is not pasted after removing dust from surface, Aluminium tape can come out from the surface after some months or year.
Precautions to be taken: So, whenever you are pasting Aluminium tape in any panel just see, what if this tape glue weakens and it come out, it should not come in contact with any power or control circuit, which can ultimately create a flashover and an unnecessary breakdown. You can still imagine how a 100 Rs Aluminium tape caused damage of lacs to this plant. So, we can learn from here. Always do “Hazard Identification & Risk assessment� (HIRA) while doing any work or any modification in Panels or System.
Now due to negative pressure, the Aluminium tape which loses it glue or not properly pasted, come up and encountered power fuse (in image 1.1) and ultimately caused breakdown. However, the breakdown was not major, and plant started was within 5-6 hours of accident.
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