[HayZee518]

you have a closed steam system with air bleeders at each radiator. one pipe goes in with a valve - on the other end a straight pipe goes into the floor and back to the boiler. water boils at 212 degrees to flash into steam so the pipes and radiators will be HOT! whether you throttle how much steam goes into the radiator it will always be 212 degrees or slightly more. when the steam travels through the radiator part of it will condense back into hot water and work its way back to the boiler. the disks in a steam valve are made of a fiber material not rubber as in your water system. you can remove the valve bonnet and stem and get at the stem washer. the seats inside are probably not removable and are made of brass.