When should a non-return valve be opened when putting a boiler online?

A non-return valve, also known as a check valve, plays a crucial role in maintaining the integrity of the boiler and the associated piping system. Opening the valve at the right pressure is essential to ensure that the boiler can operate efficiently and safely while preventing the backflow of water or steam into the boiler.

When the boiler pressure builds to 10 to 25 psi below the header pressure, it is the ideal time to open the non-return valve. This timing helps to ensure that the boiler is positively pressurized, which minimizes the risk of backflow and allows steam or water to flow efficiently from the boiler to the header. By waiting until the pressure is close to the header pressure, it ensures that the boiler can dispatch steam or water without interruptions or complications that could arise if the non-return valve were to open prematurely.

Opening the valve too early could lead to issues such as water hammer or backflow, which can be damaging to the system. Therefore, monitoring the pressure and waiting until it reaches the appropriate levels is a best practice in boiler operations and greatly contributes to a safe and effective start-up procedure.