Hello,
If your bings have a dome shaped top, the diaphragm has two notches, ont on the piston side, one on the body side which ensure you do not mess the orientation.
If your bings are the flat domed one, you "normally" can't mess the orientation because the diaphragms are not replaceable ... But if you are careful this can be done and, thus, you need to take extra care to respect the proper orientation of the piston in the body...
Hope this helps