Butterfly valves can be used for on/off service and throtting/balancing. They are superior in "versatility" as compared to a gate or globe valve. Butterfly valves have a wider range of chemical resistance due to the trim options and choice of elastometric liners. Butterfly valves offer 1/4 turn open to close. Gates and globes require multiple turns to open and close. Ease of opening or closing means that butterfly valves can employ less expensive operators. A butterfly valve is generally 40% the cost of an iron gate equaling, not only low initial cost but low installation costs as well!