What pressure must the boiler be hydrostatically tested to after completion of boiler boiling out?

The hydrostatic test of a boiler is a critical procedure to ensure the integrity and safety of the boiler after the boiling-out process, which is used to clean the boiler and remove impurities. For this procedure, the boiler is typically tested at a pressure that is a certain percentage above its normal operating pressure to ensure that it can withstand the operating conditions it will encounter in service.

A hydrostatic test pressure of 150 psig is commonly specified for testing boilers after boiling out. This pressure is generally adequate to verify the sealing of all joints and the overall structural integrity of the boiler without causing damage to its components. By testing at this pressure, any potential leaks or weaknesses can be identified and addressed before the boiler is put into active service.

Choosing a pressure that is either too low would not sufficiently challenge the system to reveal defects, while a pressure that is too high could risk damaging the boiler or creating unsafe conditions. Thus, the selection of 150 psig is a standard practice that balances safety and effectiveness in identifying issues in the boiler's design or construction.