A Labour Department report shows that the refrigerant gas used at the Icepak Tamahere coolstores was a highly explosive propane-ethane mix known as HyChill-50 of HR22/502.
The Department of Labour (DoL) is still investigating the April 5 explosion and fire, which killed firefighter Derek Lovell and injured seven others. But Tamahere Forum has obtained an initial incident report after requesting it under the Official Information Act.
The incident report, required to be completed for all significant events involving hazardous substances under the Hazardous Substances and New Organisms Act (HSNO), is dated April 6, the second day of the fire which went on to burn for five more days.
The report shows that initially the DoL believed the refrigerant used was HR12 but in an email to Tamahere Forum a spokesman said “we now know that the product was HR22/502.” The report has been corrected to show the actual refrigerant used. It is a mix of 95% propane and 5% ethane.
The DoL’s incident report is here: labour-dept-icepak-coolstore-fire-incident-report
The refrigerant is manufactured by Australian company HyChill, which says on its website that “HyChill HR22/502 is the natural organic solution for low temperature refrigeration and air-conditioning systems previously charged with HCFC R22 or CFC R502.”
The gas is considered more environmentally friendly than the gases it replaces because it is far less ozone depleting and makes a negligible contribution to global warming.
“An air conditioner or refrigeration system charged with HR22/502 uses up to 20% less power than HCFC-based refrigerants. Because hydrocarbon refrigerant is more efficient, it can cool a room down to the temperature set by the thermostat in less time. In hot weather, this can result in substantial energy savings,” says HyChill.
HyChills Material Safety Data Sheet for HR22/502 notes that it is “highly flammable at normal temperatures and pressures.” It is flammable when only 1.9% of the gas is in the air.
“Containers of HR22/502 are explosive hazards, when exposed to excessive heat,” the data sheet notes. The data sheet is here: hr22-502-data-sheet
There is a significant movement toward so-called natural refrigerants because of their greater environmentally friendly nature but they are also easily ignited by a spark, heat or flames. The risks are clearly set out in HyChill’s emergency procedures document here: hychill-gas-emergency-procedures
Icepak acknowledged some time after the fire that it was using propane at Tamahere but without the the required safety certification.
The company had gained resource consents on the basis it would use non-flammable freon gas.
Icepak was trialling propane at its Waharoa coolstore and had got a $60,800 grant from the Energy Efficiency Conservation Authority to cover the costs of using the refrigerant including safety equipment and gas sensors.
It is unknown whether it had also put new safety measures at Tamahere, which would need to have included isolation of electrical switches and other possible ignition points. The plant would also have needed gas sensors, alarms and warning signs that would have alerted firefighters to the presence of the dangerous gas.
Locals recall that on the morning of the day the fire broke out there was a power failure. Physicist and engineer Dr Evan Bydder advises that there are a number of ways in which the electrical problems could have been related to the explosion and fire.
They include that the power drop-outs and brown outs experienced that day could have been caused by an electrical fault at Icepak, for example a refrigeration compressor motor failing, stalling, catching fire or burning out. Alternatively, a brown-out occurring elsewhere could have caused a motor at the plant to stall and eventually over heat.
Another possibility is that the power interruption could have dropped off some loads and caused the voltage at Icepak to lift, partially saturating the stator of the motors causing excessive current draw, overheating and fire.
Firefighters who had no idea the flammable gas was in the plant could also have provided a spark to ignite leaking gas by axing their way into the coolstore or using their walky talkies.
A number of investigations are looking at such matters including by the DoL, the Fire Service, insurance companies and the Coroner.