What can be done to accommodate the significant expansion and contraction of polypropylene?
Polypropylene expands about eight times as much as steel. Allegheny has developed many innovative designs to accommodate this expansion. Long tanks have labyrinth seals or rubber and plastic expansion seals between sections. Where steel reinforcement is incorporated in the tank structure, it must be designed with sufficient clearance to permit the plastic tank to expand and contract. The wide variety of polypropylene fabrications in use today shows Allegheny s ability to control this problem. What is the life expectancy for polypropylene equipment? Life expectancy is related to service and operating parameters of the equipment. There are polypropylene tanks in sulfuric acid pickling operations for over twenty-five years. We expect similar life expectancy from hydrochloric acid pickling lines. With good maintenance procedures, nitric/hydrofluoric pickling tanks should have up to fifteen years of life.
