Explain about the Pot Bearing?

POT bearing was developed in 1959 as an alternative to heavy steel sliding bearings. It consists of a circular non-reinforced rubber-pad fully enclosed in a steel pot. The rubber is prevented from bulging by the pot walls and it acts similar to a fluid under high pressure. From the discussion on various bearings, it has been observed that most of the bearings have the limitation of either load or movement capacity. The load range and movement capacity of various types of bearings are given in Table.

TABLE: Load and Movement Ranges

The above bearings are adequate for smaller spans having the requirement of load and movement, within the range prescribed in the above table. But what to do for the larger spans having more load and more movements? In fact the problem of load can be solved by providing more bearing area or providing more number of bearings so that load is shared by many bearings. However this idea of 'sharing' can't be extended to movement because the number of ends can't be more than two.

Therefore, it is the requirement of movement which is more critical than the load requirement and we require some other type of bearing where the horizontal movement should not be the limiting factor. Since necessity is the mother of invention, a special category of bridge bearing was developed known as 'POT and PTFE'. PTFE is a short form of Poly Tetra Fluoro Ethylene.