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Operators of a Lannate® insecticide manufacturing process were attempting to clear a hydrate blockage in the methyl mercaptan feed line between the methyl mercaptan storage tank and the reaction section by pouring hot water on the outside of pipe to melt it. In order to prevent over-pressure of the line as the hydrate plug melted, isolation valves between the methyl mercaptan feed line and the vent gas header were temporarily cracked open. The pressure in the vent gas header began to rise but this was incorrectly assumed to be a consequence of liquid accumulation in the vent gas header to the downstream incinerators/vent gas scrubber, so the header was drained through a hose to an open floor drain. Almost 24,000 lb (10,900 kg) of highly toxic methyl mercaptan was released to the atmosphere inside the enclosed, unventilated manufacturing building via the drain.
Ask yourself and your crew:
- How can something like this happen here (e.g. on our site)?
- What safety measures (i.e. procedures, controls/barriers) do we have in place to mitigate the risk?
- How do we know the risk controls/barriers are working?
- What improvements or changes should we make to the procedures, controls/barriers or the way we work?
Original content courtesy of IChemE Safety Centre
