To ensure safe and reliable shut-off even at low temperatures below -100°C, Hartmann has developed various ball valve designs with construction features and materials suitable for cryogenic applications. Soft-seated valves often reach their limits in the main seal between the ball and the housing (seat) because the soft material contracts due to the cold and can consequently become hard or brittle. Metal-seated ball valves, however, are almost dimensionally stable, so a standard spring-loading is sufficient to compensate for dimensional changes caused by low temperatures.
The medium ethylene, an important raw material for the chemical industry used, among other things, in the production of polyethylene, ethylene oxide, or styrene, requires very specialized valves. Ethylene is often conveyed at high pressures.
Hartmann ball valves, deployed in various plants worldwide, feature a purely metallic sealing system and incorporate suitable high-quality coatings. The special processing of the coated parts ensures that the valves are gas-tight even at high ethylene pressures of 210 bar. In some plants, ethylene is present at -110°C. In these cases, appropriately low-temperature-suitable materials are used. To ensure sealing via the operating stem, a stem extension is integrated, which pulls the actual seal out of the “cold zone.”
Due to the high flammability of ethylene, Hartmann ball valves are supplied as Fire Safe certified valves. Additionally, an anti-static discharge within the valve must be ensured, which is already standard in all Hartmann valves.
