A hollow metal door on my facility will not open at certain times of the day. Why is that?
This is a condition called “Thermal Bow”. This is a temporary condition which may occur in metal doors due to the inside/outside temperature differential. This is more common when the direct rays of the sun are on a door surface. The quickest and easiest solution is to paint the door a light color, which will help deflect the heat away from the door.
