Process Safety Moments from CCPS

Date: June 2010Issue Number: 001AIChE © 2010. All rights reserved. Reproduction for non-commercial, educational purposes is encouraged. However, reproduction for the purpose of resale by anyone other than CCPS is strictly prohibited.

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

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Process Safety Moments

It is sincerely hoped that the information presented in this work will lead to even more innovation and advancement for the entire industry; however, neither the American Institute of Chemical Engineers, its consultants, CCPS Technical Steering Committee and Subcommittee members, their employers, their employers' officers and directors, the presenter of this work, the creators of this work, their employers, nor their employers' officers and directors, warrant or represent, expressly or by implication, the correctness or accuracy of the content of the information presented in these Guidelines. As between (1) American Institute of Chemical Engineers, its consultants, CCPS Technical Steering Committee and Subcommittee members, their employers, their employers' officers and directors , and (2) the user/viewer of this work, the user/viewer accepts any legal liability or responsibility whatsoever for the consequence of its use or misuse.

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What happened?A company operated a location that had several chemicals

stored in tanks in various places in the plant.

Plant procedure was for the shift supervisor to authorize the tanker driver to off load chemicals.

Water solutions of sodium hydrosulfide and ferrous sulfate were among the chemicals received by truck and unloaded into storage tanks.

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Plant LayoutThe truck of sodium

hydrosulfide was supposed to be unloaded to these tanks

It was actually hooked up and unloaded to the ferrous sulfate tanks at this location

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What happened?Shift supervisor was expecting a delivery of Ferrous Sulfate.

A tank truck containing Sodium Hydrosulfide arrived at the plant.

The driver had never been to the plant before.

The Shift Supervisor escorted the driver to the Ferrous Sulfate tank and authorized him to off load without inspecting the trucker’s paperwork.

The driver connected to the tank and began offloading Sodium Hydrosulfide through a connection marked “Ferrous Sulfate”.

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Incident Scene

Unloading arrangement

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Incident Scene

Unloading connection

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What happened?The two chemicals (sodium hydrosulfide and ferrous sulfate)

react and produce hydrogen sulfide (H2S), a colorless gas which is highly toxic at 800ppm.

An operator noticed an unusual odor and passed out.

The operator recovered sufficiently to notify others to call 911.

The truck driver was found unconscious and later pronounced dead at the scene.

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Plant LayoutThe truck driver was

found unconscious at this location and died from hydrogen sulfide exposure

An operator passed out at this location, but fortunately recovered in time to get help.

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Why did this happen ? The Shift Supervisor assumed the contents of the delivery

based on experience, and what he was expecting to receive.

Plant procedure for oversight of the delivery of chemicals was not followed.

The truck receiving and unloading procedure was not written.

No plant employee observed the off-loading.

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Why did this happen ?There was no method of communication at the unloading area.

Piping at the off-loading point was properly labeled (ferrous sulfate) but did not match the material listed on the shipping papers (sodium hydrosulfide).

Nobody checked that the material in the truck was the same as the material marked on the piping where the truck was connected.

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Can this happen at your plant?Do you have a written procedure for receiving chemicals?

Does it include safety instructions and a step to verify that the correct materials are being unloaded to the correct tanks?

How do you confirm that tank trucks, railroad tank cars, or other containers being unloaded actually contain the material that you think they contain?

Do you know the consequences of improperly mixing two of the materials you receive by truck or other bulk container by pumping one of them into the wrong tank?

Are you certain that tank vents are directed to a safe place so people will not be exposed to vapors vented from the tank?

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Can this happen at your plant?Are unloading connections and piping clearly labeled with the

material name and flow direction?

Is the unloading connection secured to prevent unauthorized off-loading?

If your plant allows truck drivers to unload materials, how do you know that they are properly qualified, and understand your plant’s safety rules and procedures?

What is your plant’s procedure for how to deal with the arrival of a shipment of any chemical at an unexpected time?

Can you communicate to get help if there is an emergency at the places where you unload or transfer chemicals?

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Points to discussIf the Supervisor was too busy, what should have been done?

How well trained on chemical hazards can you expect a truck driver to be? In particular, think about potential reactions with other chemicals in YOUR

plant.

How are chemical deliveries managed at your plant?

How is this kind of incident addressed in your Process Hazard Analyses (PHA)?

How are the hazards and necessary controls communicated to the operators and other plant staff following the PHA?

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Points to discussWhat safeguards could be implemented to prevent a

reoccurrence?

Should we make further improvements to prevent a similar event?

Do you know of any incidents in your plant or somewhere else in your company which were similar to this one? An incident which resulted in a serious incident, chemical reaction,

material release, injury, or other significant consequence? A “near miss” incident which did not have any consequence other than

material contamination or financial loss?

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For more information:References:

CCPS Process Safety Beacon, March 2009 (“Read only” copy available for download at www.sache.org)

United States National Transportation Safety Board (NTSB) Hazardous Materials Accident Brief, Accident No. DCA99MZ006, Whitehall, Michigan, June 4, 1999.

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Get more information:CCPS books and resources on reactive chemistry hazards:

Essential Practices for Managing Chemical Reactivity Hazards (2003)Individual Hardcopy BookCCPS Electronic Library (Knovel)

Guidelines for Process Safety Fundamentals in General Plant Operations (1995)Individual Hardcopy BookCCPS Electronic Library (Knovel)

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CCPS Web Site: www.aiche.org/ccps