I found a door with a pair of hinges that look like most ordinary door hinges but don't let the door to be taken off the doorpost. They seem to have a pivot that passes through the whole height of a hinge and has thick flat cylinders on each end - each has diameter of about 8 millimeters and height of about 3 millimeters.
I decided those were nuts that could be unscrewed and tried to grab them with pliers and turn counter-clockwise, but they don't seem to react, I only scratched them.
Detaching those hinges from both the door and the doorpost is not an option - I need to take them apart to apply graphite grease to them.
How do I take those hinges apart?