Freeze Fitting Procedure
ACM composite marine materials are capable of being freeze fitted using liquid nitrogen, the procedure for this process is as follows:
Select or manufacture a thin wall steel container which can be clad with insulating material around its outside diameter the container should be just large enough to hold the bearing and allow it to be completely immersed in the liquid nitrogen.
Place the bearing into the container then start to pour in the nitrogen. For the first few moments the nitrogen will boil off as soon as it contacts the steel surface. Once the steel surface has cooled sufficiently the nitrogen will start to fill the container.
Due to the extreme temperature differential the liquid nitrogen will continue to boil off for some time during this period it will be necessary to keep topping up the container ensuring the bearing is completely covered by the nitrogen.
When the boiling has subsided, the bearing should be left to stand in the nitrogen for a further period of time. This will be dependant upon the bearing size and can vary from a minimum of 10 minutes for small bearings, up to 45 minutes for large bearings.
When working with liquid nitrogen operators should ensure they are fully conversant with the necessary precautions for its handling and use, as prescribed by the liquid nitrogen supplier. The correct protective clothing and eye protection should be used at all times.
Liquid nitrogen is oxygen depleting and should not be used in confined spaces.
It should be noted that dry ice typically will not give sufficient shrinkage of the bearing to facilitate freeze fitting and additional mechanical force to press fit may also be required.
Contact our technical department for guidance when using dry ice.
