Z-Max Butterfly Valves We use our advanced ceramic materials to make high performance Z-max butterfly valves for use in demanding processing environments such as chemical processing, paper and pulp manufacturing and in oil and gas extraction and refining. The standard range includes valves from 2 (DN50) to 10 (DN250) nominal bore. Our Z-max butterfly valves have a cast steel body, stainless steel shaft and an advanced ceramic protection sleeve comprising shrouds for the disc, liner and shaft. The sleeve is made of Nilcra Zirconia, a high performance ceramic material that is strong, tough and highly resistant to chemical reagents and abrasive slurries. It offers excellent resistant to cavitation, a major problem for process control valves.