Water can be a hazard in process plants. When water is mixed with some materials, typically gases but also liquids, it can form a crystaline, ice-like solid. This solid is called a hydrate. When a hydrate forms, it can plug piping, instrument connections, valves, and other equipment, which causes process upsets that may be hazardous. Hydrogen sulfide, acetylene, methyl mercaptan, chlorine, vinyl fluoride, carbon dioxide, ethylene, methane, ethane, natural gas, and other hydrocarbon gases can form hydrates.
