The lug type butterfly valves are mainly used in cases where the valve is at the end of a pipe as there will not be a second flange for securing the studs. Instead of the lugs, the cast on the valve with tapped holes that matches the bolt pattern for the pressure and size clarification of the flange. Bolts are passed via the flange hole and are threaded into the tapped holes of the lug. In most cases, the pressure rating of a butterfly valve mainly at the end of line service is directed by a safety factor of two as there is the absence of a companion flange for securing the assembly together. Some of the manufacturers offer a complete pressure rating so it is best for verifying the rating with the particular valve manufacturer. Most of the common butterfly valve types are available with elastomeric seal. Only for infrequent positioning like off and on service or cases where the valve is set in the position for a much longer period of time, these valves are good. Applications in which the butterfly valve is used frequently for throttling the fluid need a metallic seat for avoiding erosion of the elastomer. Several benefits are offered by butterfly valves which makes it suitable to use over other types of valves, most importantly bigger valves. These save valves save space, weight, and significantly reduces the cost. As there are a smaller number of moving parts, the maintenance cost is also less. Cavitation is also less as there are no pockets for trapping the fluids. Butterfly valve design offers much suitability for a large flow of liquids at low pressure and for handling slurries with a large number of suspended particles and solids. This makes them an ideal choice for mud pumps that often have lost circulation material, friction reducers, and other additives which aids during the drilling process.