Because flanges allow the assembly and maintenance of system components without the need for cutting and welding pipe, they play an important role in piping systems. However, the structural integrity and leak tightness of waterworks piping systems are only as strong as the weakest element, which often is the flange connection between various valves and fittings. Yet because piping systems are subject to many types of loads and are constructed of a variety of materials, understanding and predicting the rating and performance of those flange connections is difficult. This is further complicated by the fact that different sealing mechanisms such as gaskets, O-rings and mechanical seals can significantly affect the performance of the connections. As far as ratings, ASME B16.1 lists pressure ratings for Class 125 flanges from 50 to 200 psig depending on size, material and temperature.