You could have many justifications for using ball valves for crude metering, custody transfer class . Where lack of valve sealing affects the accuracy, due to meter bypass or other parallel streams, ball valves as DBB valves (Double Block and Bleed) will allow to check their sealing. Using metal to metal seats, stainless steel hard plated ball, you’ll avoid the erosion problem by sand and hard particles carried by crude oil. You can keep the full performance for decades with no maintenance.