If three boilers each have a pressure of 130 kPa, the pressure in the steam header will be:

The correct answer reflects the pressure in the steam header, which is directly related to the pressure of the individual boilers. Each boiler operates at a pressure of 130 kPa, and because these boilers are connected to the same steam header, the pressure in the header will also be 130 kPa.

Understanding that pressure is a measure of force per unit area, we recognize that the pressure indicated by the boilers is the absolute pressure acting within the system. Therefore, when assessing the steam header connected to multiple boilers, as long as there are no additional factors affecting the system (like pressure drops or restrictions), the steam header will reflect the same pressure as the individual boilers.

The other units mentioned in the incorrect options do not accurately represent the pressure when converted from kPa. Specifically, while both bar and kg/cm² can be related to pressure, they are substantially larger units compared to kPa. Similarly, 130 MPa represents an extreme pressure inappropriate for this case. Each of these units either lead to misunderstanding in pressure measurement or vastly inflate the context, making kPa the correct and relevant unit in this scenario.