Intensive and in-depth investigations found the explosion that killed eight Rheinmetall Denel Munition (RDM) employees last year was caused by a world-first at any munitions facility – a particular type of electrostatic electricity.
“The September 2018 explosion on RDM’s Somerset West campus was in the N16 building used for blending large volumes of propellant from smaller sub-lots. At the time of the incident, sub-lots of single base propellant were being blended into a homogenous final lot. Propellant was safely blended at the N16 facility since it commenced operations in the 1980s without incident. All members of the team were fully trained and the team leader and supervisor both had extensive experience with the material and operations underway at the time of the incident,” according to an RDM statement.
“The investigation established that during mandatory routine testing of sub-lots in the course of the manufacturing process it was found one sub-lot did not meet the required quality standards. Due process was not followed and, instead, an attempt to rework the material was made by adding extra graphite to the propellant.
“Based on extensive testing, assessments, and elimination of other initially suspected causes, the most likely cause of the explosion was a build-up of electrostatic electricity in a suspended graphite cloud due to the triboelectric effect and a subsequent discharge which ignited airborne propellant in the blending drum.”
Investigation leader Rod Keyser said: “The investigation team concluded the cause was a combination of human error when excess graphite was added to the material and a highly complex electrostatic electricity risk very unlikely to have been foreseen, or expected to have been foreseen, by the individuals involved.
“This particular type of electrostatic electricity risk was, as far as the investigation team has been able to determine, a previously unidentified and unforeseen hazard across the industry internationally,” he said.
Recently appointed RDM chief executive Jan-Patrick Helmsen said: “Safety has always been and remains RDM’s first priority. This incident underscores how we can work together to ensure a safe working environment for all. As part of this, our five guiding lights are infrastructure, recruitment, training, procedures and management control and leadership.
“We embarked on an exercise to incorporate the learnings from the investigation into the health and safety management system implemented at the Somerset West site and, where applicable, across the organisation.”
Key learnings will be shared across the industry internationally, to ensure workplace safety is continually improved as industry knowledge regarding applicable hazards is developed. This includes an intensive programme of refresher training for employees addressing specific work procedures and general safety rules, underpinned by the principle that safety is always paramount, RDM said.
Additional management controls and oversight protocols are being implemented to provide additional tools and support to line managers and supervisors as they work to assist RDM with enforcement of safety rules and procedures. All systems are being reviewed to ensure RDM continues to utilise best practice and minimises the risk of unintended errors on the part of any persons and at any point in its processes which may impact on safety, according to the company. Based on risk assessments in consultation with the relevant regulators, improvements are continually made to the layout and design of workplaces to ensure employees are consistently safe.
On continued safety at the plant, Helmsen said: “RDM has, since the incident, undergone an inspection process of its facilities with the input of relevant regulators, which included an assessment of safety systems in place. The facilities have been determined as safe and operations have been authorised to recommence.
“Without question, our employees are our most important asset. They are core to everything we do and it will always be our utmost priority to ensure a safe working environment for them.”