For attribution to a CS Energy spokesperson:
CS Energy is treating the incident that occurred on Unit C3 at Callide Power Station on 4 April with the utmost seriousness and has implemented a range of controls to ensure the safety of our people and plant.
Our recently appointed Chief Operating Officer (COO) Andrew Buswell has been on site and is leading the investigation and recovery works.
While no one was in the area at the time of the event and there were no injuries, we recognise the significance of what has occurred on the unit.
Following operational risk assessments, we have strengthened our safety controls including:
- restricting access around the boiler, especially when clinkers are deloading
- applying more rigorous metrics on our clinker management tool, and
- running more frequent clinkering deloads to prevent clinkers from reaching excessive size.
Our investigations and inspections are ongoing to fully assess what occurred on Unit C3 and the repairs required to safely return the unit to service.
Access to the area is being strictly controlled and we are mobilising to prepare the internals of the boiler for safe engineering access.
Alongside our internal technical investigation, we will be appointing an independent engineering consultant to lead an ICAM investigation (Incident, Cause, Analysis, Method). The ICAM investigation will also look at smaller clinker incidents that have occurred at Callide in the past to further inform us of root cause. From this we will develop an action plan that will be prioritised, with checks to make sure actions are closed out.
We are also working closely with Workplace Health and Safety Queensland (WHSQ) to support their investigation alongside our own. Any additional safety measures identified will be prioritised and implemented.
From our preliminary investigation we understand the following happened on Unit C3:
- On 4 April 2025, a significant clinker (hardened ash) detached from the boiler wall of Unit C3. It is common for clinkers to form at coal fired power stations. CS Energy has clinker management tools and practices in place to regularly detach clinkers from furnace tubes so they can fall to the bottom of the boiler for easy removal.
- On this occasion, when the clinker detached, it resulted in the release of steam from the ash conveyor water system. The released steam extinguished the flames of all four fuel pulverisers (mills), prompting an automatic unit trip, in accordance with the unit's safety design.
- The flame loss led to furnace pressure fluctuations—initially negative as the collapsing flame drew in unburnt fuel and air, followed by a positive pressure surge caused by the re-ignition of the accumulated fuel and the subsequent gas expansion. This pressure event dislodged insulation and cladding materials from the boiler walls, causing damage to adjacent platforms. Importantly, there was no loss of high-pressure steam or water.
Background
Clinker deloads are common practice in the management of clinkers at coal-fired power stations. By reducing the load, it reduces the pressure inside the boiler, allowing the clinker to detach from the side and fall to the bottom of the boiler for easy removal.
Callide Power Station is comprised of two power plants, Callide B and C, each with two generating units (B1 and B2, C3 and C4).
Callide B has a capacity of 700 megawatts (MW) and is 100 per cent owned by CS Energy.
Callide C has a capacity of 848 MW. CS Energy (through our subsidiary Callide Energy Pty Ltd) owns Callide C in a 50/50 joint venture (JV) with IG Power. CS Energy operates Callide C on behalf of the JV.