What is typically inside the boiler during a hydrostatic test?

During a hydrostatic test, clean water is typically used as the testing medium inside the boiler. This process is crucial for identifying any leaks and ensuring the integrity of the boiler's structure under high-pressure conditions. Water is chosen because it is incompressible, which allows for an effective assessment of the boiler's ability to withstand pressure without any risk of explosion, as would be the case with gases.

Using clean water also minimizes the risk of contamination or damage to the boiler components since it does not introduce harmful substances. Additionally, water can easily be added or drained from the system, making it practical for testing purposes. The hydrostatic test usually involves filling the boiler completely with water, pressurizing it well beyond its operating pressure, and observing for any leaks or weaknesses in the construction.