safety wrong material.ppt

8/10/2019 Safety Wrong material.ppt

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Wrong material in the wrong tank:A fatal reactive chemistry incident

02nd March 2011

Safety Moment


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This safety moment describes a fatal incidentin which the incorrect material from a tank truckwas unloaded into a storage tank

This incident occurred on June 4, 1999 around 3.30 amin Whitehall Leather Company, Michigan USA, andwas investigated by the United States NationalTransportation Safety Board (NTSB)

The material from the truck reacted with the material in

the storage tank to produce highly toxic HydrogenSulfide (H 2S) gas

Two personnel were exposed to the toxic gas


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The company operated a location that had severalchemicals stored in tanks at various locations in the plant

Water solutions of sodium hydrosulfide and ferrous sulfatewere among the chemicals received by truck and unloadedinto storage tanks

Plant procedure was to off load chemicals from the tankerwith the assistance of Shift Supervisor

Shift Supervisor was expecting a delivery of FerrousSulfate

Incident Background


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A tank truck containing Sodium Hydrosulfide arrived at theplant

The Shift Supervisor escorted the driver to the Ferrous

Sulfate tank and authorized him to off load withoutinspecting the truckers paperwork and left the unloadingarea

The driver connected the piping to the tank and beganoffloading Sodium Hydrosulfide through a connectionmarked Ferrous Sulfate

Incident Background


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Incident Scene

Unloading arrangement


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Incident Scene

Unloading connection


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Plant Layout

The truck of SodiumHydrosulfide wassupposed to be unloadedto these tanks

It was actually hooked upand unloaded to theFerrous Sulfate tanks atthis location


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What happened ?

The unloading of Sodium Hydrosulfide in the Ferrous

Sulfate tank lead to a reaction which produced HydrogenSulfide (H 2S), a colorless gas which is highly toxic at800ppm

An employee noticed an unusual odor and lostconsciousness

The operator regained consciousness after 10 minutes tonotify other employees to raise an emergency

The truck driver was found unconscious and later

pronounced dead at the scene due to exposure to H 2S gas


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Plant Layout

The truck driverwas foundunconscious atthis location anddied fromHydrogen Sulfideexposure

An operatorpassed out at thislocation, butfortunatelyrecovered in timeto get help


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The Shift Supervisor assumed the contents of thedelivery based on experience and what he wasexpecting to receive

The Standard Operating Procedure for unloading ofchemicals was not followed

No plant employee observed the off-loading and therewas no method of communication at the unloading area

Sampling procedure of the chemicals was also notadopted in the unloading area

Why did this happen ?


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Lessons Learnt

A Standard Operating Procedure for unloading chemicalsin storage tanks was developed and a unloading checksheet was also maintained in every shift

Company designated two authorized personnel to assistthe driver in unloading of bulk shipments

Company also placed barrier gates at the entrances to

the bulk chemical unloading areas

An emergency remote alarm button was installed at eachmaterial transfer location


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safety wrong material.ppt

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