Boiler

Depends on many things you have not told us.

Have you asked the furnace manufacturer? _{Why do I bother????????????????}

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RTFM psi.

Short answer: Important.

Long answer: Please provide more information.

Hi,

for safety; These doors are installed in heater and boiler walls. In the case of explosion the door will be raptured and will cause the combustion and explosion gases to be exited and avoid from destruction of heaters walls and other different parts.

for more detail you may review following article

http://www.inspection-for-industry.com/fired-process-heaters-safety.html

regards