CSB Final Report - YENKIN LP Pressure Vessel explosion - ONE DEAD, Massive Damage 3

[MJCronin]

https://www.csb.gov/yenkin-majestic-resin-plant-vapor-cloud-explosion-and-fire/

An April 8, 2021, explosion and fire erupted at the Yenkin-Majestic paint and OPC Polymers Corporation. One employee was fatally injured and eight were transported to area hospitals for injuries. The blast shook neighboring buildings and at least one nearby business sustained damage.

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In my opinion, this report touches on the most dangerous "festering sore" in the Process Chemical Industry ...
and by that I mean the usage of pressurized vessels that are neither storage tanks nor Code Regulated and Designed Pressure Vessels.

The fact that the Yenkin Resin facilities were being operated by a group of clueless MBAs in clown shoes, only made the explosion more certain

MJCronin
Sr. Process Engineer

 

[georgeverghese]

Read some of this report and some comments :
a) There is no overpressure control valve on this kettle that vents off excess pressure to the catch pot. This should have been set at some pressure above 4psig but well below RD set pressure, say 6-7psig. And there is no automatic emergency depressure blowdown valve either which would activate on confirmed gas detection around kettle 3.

b) I find it difficult to see why this solvent (hydrotreated light straight run naphtha with an IBP of 69degF) was added to the kettle while the kettle contents were still very hot at 420degF or so. Such action would have almost completely vaporised this relatively low boiling point solvent, then overloading the bubble cap vent absorber column. Using this solvent to hasten the cooling is bad practice to me, since it needlessly overloads the bubble cap column. It should only be used to control viscosity and density. Instead wait for the cooling coils to cool contents down. Why the hurry to chill the contents rapidly with cold solvent ? This was the primary source of the uncontrolled overpressure. The stopped agitator just made things worse. Think this should be done only when kettle contents are much cooler, after confirming that the agitator is still running.

c)Footnote b on page 32 of the CSB report says a total of 47 rupture disks were purchased for this kettle 3 from 1997 to 2019. So either the RDs' were not adequate to withstand these high temperatures, or there have been numerous overpressure events that lead to RD rupture. Clear sign of regular misoperation and inadequate penultimate overpressure automatic control measures.

 

[Rubje]

@georgeverghese

In response to your last comment c, it seems they should had stayed at the original design pressure of 40 psig since cleary it reached 15 psig quite often. This is just speculation but it seems they "derated" the vessel to 15 psig in order to get out of doing the API 510 inspection and conforming to ASME VIII requirements.

That is why i like how the report mentions ASME VIII and API 510 should address requirements for vessels below 15 psig. I'm not saying they should follow the same exact rules but when you have a cutoff at 15 psig many facilities just simply ignore the vessel and don't have a coherent engineering practice they use for repairs, inspections etc.

 

[georgeverghese]

Think these kettles should have a minimum upper design pressure of some 10% above the initial bubble point pressure (or say no more than the 10% volume vaporised fraction) of this hydrotreated LSR naphtha solvent at the max normal operating temperature of the kettle's contents.