When isolations go wrong, Slides of Business

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Health and SafetyExecutive

When Isolations go

WRONG

Andrew Hall HID CI 1G HM Specialist Inspector (Mechanical)

Case 1: North West Aerosols

13th December 2005 – Fire at North West Aerosols Ltd, Liverpool 1 Fatality3 severelyinjured

The ISOLATION

Gas house 1 had been isolated from the LPGsupply to use compressed air for filling aerosols

The LPG manifold connections used to supplyLPG to the filling lines were only isolated by apneumatically operated control valve

The only other valve on the line was a manuallyoperated ball valve that had been left open

The LPG supply manifold pipe work had not beenblanked off as per BAMA recommendations (selfseal, quick release couplings) representing goodpractice

Unblanked LPG Supply Manifold

Internal Plant Fire Damage

Causes

MAH’s are prevented by layers of protection -Some were in place but others were not:

Gas detection was thought to be non-functional

Control valves were defeated - (HS(G) 253recommends that control valves are not generallysuitable for isolations)

No end caps on manifold

Manually operated valve left open

Line change-over procedures were not followed

No specific isolation procedure

Further CONSEQUENCES

North West Aerosols ceased trading

Criminal Prosecution returned ‘Guilty Verdict’

Crown Court made financial checks andimposed a nominal penalty

Judge indicated a £250,000 fine for thecompany had it still been trading

Loss of Reputation

Civil Litigation

Legal Aspects^ •

The Health and Safety at Work etc Act 1974 Section 2 (1) says: "It shall be the duty of every employer to ensure, so far as is reasonably practicable, the health, safety and welfare at work of all his employees.“

Section (2) (a) says: "The provision and maintenance of plant and systems of work that are, so far as is reasonably practicable, safe without risks to health"

Case 2: Methanol LoC 20 - 35te^ •

Loss of Containment of 20 to 35 te ofMethanol when filling tank - ship to shore

This incident had the potential to be aCOMAH major accident

½” drain valve had been left open andunplugged after maintenance work to fit aROSOV and new valve on a thermal reliefline

Open ½ “ Drain Valve

½” drain valve

Causes

Human error, inadequate management systems andinadequate safe system of work

Work authorisation was poorly completed, with no detailsof valves to be replaced, tank isolations, reference todrawings P&ID’s

Method statement for work raised without training - It did not identify the isolation of valves or checks to return thesystem to a safe condition

The completed permit was not signed off as beingcompleted. Despite the permit remaining open for work tobe carried out on the tank, the site permitted the filling ofthe tank from the ship

Case 3: Chlorine Gas LoC Overview

Chlorine gas was introduced into a plant during a routineshort duration plant shutdown

The chlorine entered ducting and entered the workshop viaa fan housing

This resulted in a chlorine release into the workshop

The chlorine gas also reacted with hydrocarboncontamination within the ducting that resulted in a local fire

The level of gas present adjacent to the housing wasthought to be substantial enough to cause fatal injury to any unprotected individual.

The Incident in Detail

Chlorine gas supply was not isolated effectively

The power operated shutoff valve used to isolate thechlorine gas was passing and the manually operatedisolation valve was left open

Chlorine gas entered the towers main extraction system,built up and migrated to the adjoining extraction system ofthe steel dissolver vessel because the tower extractsystem wasn’t running

The Chlorine gas (heavier than air) flowed down thedissolver extract duct (only intended for hydrogen and air)and collected at the fan housing at ground level

The Incident^ •

The gas vented into the plant from the fanhousing

ALSO •

The gas exothermically reacted withhydrocarbon deposits in the ducting causing asmall fire

Estimated LoC was 50kg/hr Chlorine Gas overa 21 minute period