Some valves are so advanced that they can survive in the most demanding environments. One example is TTV's PTFE range of lugged Butterfly Valves
, which have been designed from years worth research and development with chemical manufacturers who produce aggressive fluids. Lugged butterfly valves are also very common in the chemical industry. The valves can be installed on either side of a pipe and allow maintenance one side without disturbing the rest of the system. This is especially important if there's still pressure in one part of the line.