Almost all door closers will have the above two adjustment hydraulic valves but some have additional features which can be adjusted similarly.
Fire door closers adjustment.
Clockwise gives the closer more closing power which also makes the door harder to open and turning the screw counter clockwise will give the door less closing strength and makes the door easier to open.
It is used to adjust the spring strength force to close the door.
Other door closer adjustments.
Door closers consist of a pneumatic cylinder which controls the speed of the door and a bracket which holds the cylinder to the door.
How to adjust a commercial door closer.
Spring adjustment is located on the end of the spring tube 5 32 allen wrench.
The back check valve if featured will usually be set apart from the first two discussed and may be marked with a b or bc.