Distillery Accident Analysis - Major sources of ignition and flammable releases and how to manage them safely

Distilling and blending spirits involves a multitude of different occupational risks, from barrel handling to slips and falls. One of the more unique hazards compared to other FMCG businesses is the processing and storage of flammable substances which can result in workers and members of the public being hurt. In order to generate a healthy and safe industry and maintain a positive reputation, it is vital that business leadership takes the necessary steps to manage risks and implement best practice.

Online research and verification of local news articles and publicly available information from government sources revealed the following distillery accidents in North America, UK, Australia and New Zealand causing fatality or severe burns requiring hospital treatment.

Not all accident and near miss data is publicly available for example in the UK if a dangerous occurrence is submitted to the Health and Safety Executive this is kept confidential unless a prohibition notice is issued and/or prosecution takes place. The system is similar with WorkSafe in Australia; therefore, the data set is likely to be missing many dangerous occurrences.

Root cause analysis of the accidents listed narrowed down the following five sources.

• Naked Flames

• Non ATEx Equipment

• Contractor Management

• Vessel and Pipe Joints

• Improper Relief Venting

All five of these hazards can be manged through technical controls or organisational procedures. Below I will expand upon each one with reference to relevant UK and Australian legislation.

Naked Flames

Open Flames should not be present in any distillery production areas where flammable substances are stored and processed. This is mandated by multiple overlapping UK health and safety legislation including the Dangerous Substances and Explosive Atmosphere Regulations 2002 originating from the European ATEX Directives 95 & 137. It should be noted that DSEAR applies even to self-employed owner/operators as the risk extends to private property and members of the public. The Australian equivalent is AS 1940 and I highly recommend all Australian distillers purchase a copy of this standard.

While there is the tradition of directly firing stills as a heating source that does not mean that an exposed source of ignition is present. Distilleries such as Bowmore in Scotland continue to use direct fire as the heating method imparts signature character through flavour chemistry changes such as Maillard reactions. The system at Bowmore is enclosed and protected by multiple layers of SIL rated process control devices reducing the possibility of fire or explosion in the unlikely event of an uncontrolled release of flammable alcohol to a negligible extent.

Non-Rated Equipment

Equipment and Protective Systems Intended for Use in Potentially Explosive Atmospheres Regulations 1996 (EPS) applies to the supply and use of all machinery and instrumentation in zoned hazardous areas. New equipment supplied for use in places where an explosive atmosphere may occur must meet the requirements of EPS whatever its source. In the UK this is covered by the ATEx certification in accordance with IEC 60079, though there are other routes of achieving safety such as process control engineering and intrinsically safe barriers. While commonly associated with electrical devices like motors, ATEx certification also extends to cable glanding and junction boxes as well as mechanical equipment like gearboxes and pumps.

Typical ATEx equipment markings for gaseous atmospheres

Not all ATEx ratings are equal, and it is vital to ensure that the equipment you are purchasing and/or already using is suitably rated for the hazardous area it will be installed/operating within. I would urge all distilleries to have someone who is suitably trained check the rating of equipment and not just take supplier recommendations at face value.

ATEx is not a recognised certification in Australia for onshore use due to the method of verification of equipment safety not fully meeting Australian legislation. ANZEx or IECex certified equipment should be procured instead if possible, or equipment can be inspected in accordance with AS 60079 by a qualified engineer and a certificate of safety conformance issued.

Contractor Management

Contractors are unlikely to be aware of the specific hazards present at every site even where pipework and vessels are labelled and a zoning map is on display. A Permit to Work (PTW) is a formal authorization for any work that could ignite flammable substances, ensuring all risks are assessed and mitigated before work begins.

Proper contractor management serves as a safety control with risk assessment and method statement documents detailing the specific work, associated hazards (e.g., sparks, heat), necessary precautions (like gas testing and flushing equipment), and emergency procedures particularly if other hazards are involved such as vessel entry. Implementing a formal PTW system is the best way to meet legal duties required of distilleries under regulations such as the Health and Safety at Work Act 1974 and The Occupational Health, Safety and Welfare Act 1986, and having a system in place is likely to come up on an insurance inspection visit.

Processes that are normally undertaken that can create explosive atmospheres should be isolated form works being carried out and equipment should be made safe before commencement though procedures such as Lockout/tagout and then inspected prior to return to service. PTW systems are great for managing other hazards such as working at height ensuring that potentially conflicting activities are coordinated and isolated properly and do not result in a dangerous situation as well as vetting contractors and ensuring the job is carried out as expected.

Vessel and pipe joints

So far, we have covered sources of ignition but to have a fire there must also be a combustible substance. Alongside overfilling that has not been mitigated against through layers of protection such as automatic shutdown interlocked to level sensors; failure of flanges, joints and unions is a frequent source of accidental flammable releases in distilleries.

Reporting of Injuries, Diseases and Dangerous Occurrences Regulations 2013 states that flammable releases over certain quantities should be reported as dangerous occurrences in the event of sudden, unintentional and uncontrolled release inside a building:

• of 100 kilograms or more of a flammable liquid. 

• of 10 kilograms or more of a flammable liquid at a temperature above its normal boiling point.

• of 10 kilograms or more of a flammable gas.

A loss of over 250L is also reportable to DEFRA if the spillage is not recovered. Suitable control measures should be in place to reduce the likelihood and consequences of flammable releases to a low overall level as determined by risk assessment e.g. vapour detection and routine valve and flange inspections.

The below table ranks the strength and durability of unions that are employed in distilleries and is just one consideration that should form part of the selection criteria when choosing a certain type of union over another for vessel and pipework fabrication.

Australia has a unique standard for the manufacture of tanks specifically for flammable and combustible liquids, AS1692, which includes recommendations for unions and fittings.

Relief Venting

Plant and machinery containing dangerous substances should be provided with adequate ventilation to prevent hazardous explosive atmospheres from occurring so far as reasonably practicable. For plant and machinery purchased from within the EU, this should be confirmed by the supplier in compliance with their duties under the Machinery Directive 2006/42/EC implemented in UK law by the Supply of Machinery (Safety) Regulations 2008 (SI 2008/1597).

Where the plant or machinery is manufactured by the employer or imported from outside the EU, the employer takes on the responsibility for ensuring its safe design and use. This includes installation modifications.

Many stills have pressure relief valves that are not suitably rated or not marked. This has led to vessels rupturing under explosive force when there was a blockage. Distilleries should check pipework is sufficiently sized and devices are suitably rated and have them maintained and inspected at regular intervals.

Overheating

A potential source of explosive atmospheres inside distilleries though not seen as the root cause of a serious accident in the data set is the uncontrolled release of flammable vapour from a condenser. Whether because of a loss of water pressure, operator error or sabotage this hazard is incredibly dangerous and should not be managed solely by standard operating procedure.

PUWER 1998 requires employers and others who control work equipment to ensure it is suitable, safe, maintained, and used only by competent, trained individuals. This includes specification and installation as well as measures like guards and emergency stops. Regulation 12 is particularly relevant to the storage and processing of flammable liquids, as it requires employers to ensure that people are not exposed to hazards arising from; equipment catching fire or overheating; the unintended or premature discharge of any liquid or vapour; the unintended or premature explosion of the work equipment or any substance used or stored in it.

In addition to manual condenser cooling control many stills also have manual heating control, requiring operators to turn down the heating applied as boiling is approached which may also cause a similar scenario to cooling failure leading to the still overboiling and venting hot vapourised alcohol. Where stills were not supplied with an automated shutdown one can be retrofitted to protect against the possibility of overheating in the future. This was done shortly after a near miss incident I experienced caused by equipment being tampered with during a tour, which would have led to a large vapour release without intervention.

Every distillery is different and the best way to identify and effectively control and manage the hazards on site to a safe and acceptable level is to carry out a hazardous operations risk assessment. By doing this as early as possible during construction or expansion significant costs can be saved later and the same is true for existing operations. Prioritising a site wide analysis of risk allows spend to be rationalised and budgeted to tackle the right things in the right way and may yield other efficiencies or quality improvements.

Head to the Checklist Tab to request your free DSEAR Safety Self Audit Checklist.