BG03 is a UK industry guidance document on Blowdown Systems for Industrial Steam Boilers. Produced jointly by the Combustion Engineering Association and the Safety Assessment Federation, it is aimed at the Owner, Operator, Engineer and Manager of a boiler plant to help them understand all aspects that affect the boilers and why blowing down is necessary, both from a practical operational performance view and for legal compliance.
The guidance document applies to blowdown arrangements for steam boilers including water tube boilers with a single main blowdown line.
The guide explains why blowdown is necessary for industrial steam boilers, covering continuous, intermittent (bottom), and other forms of blowdown, and it places strong emphasis on the hazards associated with handling hot, pressurised water and steam. A major theme is that poorly designed or poorly maintained blowdown arrangements can create serious safety risks, so the document sets out design principles and operational precautions intended to reduce those risks.
A substantial portion of the guidance addresses the legal and technical framework governing blowdown systems in the UK. It references key legislation, making clear that compliance involves both engineering judgement and statutory duties.
The document also provides practical design considerations for blowdown vessels, associated pipework, venting, outlets, fittings, multi-boiler installations, and vessel cooling. In addition, it covers general precautions, the safe use of brick or concrete pits, and the need for regular examination and maintenance, including inspection by a competent person under a written scheme of examination. The second edition specifically adds more information on the sizing of typical blowdown vessel inlets and outlets and updates.
Overall, BG03 serves as a safety-focused engineering guide for ensuring that boiler blowdown systems are correctly designed, operated, and maintained, with the aim of protecting personnel, equipment, and providing compliance.
You can download the full guide for free from the Combustion Engineering Association Website using the following link: https://cea.org.uk/wp-content/uploads/2025/07/CEA-BG03.pdf
And finally, if you need someone to design your steam boiler blowdown system to be compliant with BG03, Steam Main can help you.