Which type of safety valve mounting is not allowed according to the Heating Boiler Code?

Mounting a safety valve to an internal pipe in the boiler is not allowed according to the Heating Boiler Code because it can compromise the valve's functionality and effectiveness. Safety valves are designed to release excess pressure to prevent catastrophic failures, and if they are mounted internally, it can hinder their operation. Ideally, safety valves should be mounted in a way that allows for the free venting of steam or fluid to the atmosphere without any obstruction. By placing the valve externally or on top of the boiler, you ensure that it operates correctly under high-pressure situations, where quick response times are crucial for safety. Additionally, keeping the safety valve external enhances maintenance access, which is important for regular safety checks and ensuring the valve is operational when needed.