Processing of stone, gravel and sand - AltaMachines and equipments for stone, gravel and sand processing are mainly used in building industry. The range of machines type is biggest in this branch. It starts from the largest high-capacity stationary aggregates, including medium types in semi-mobile design and ends with the smallest ones mostly as mobile units.mobile sand and gravel processing,mobile sand and gravel processing,Welch Sand & Gravel maintains a river recreational area with their .Welch Sand & Gravel, Inc. is a 50-year old family owned company serving the greater Cincinnati, Ohio region, including portions of Indiana and Kentucky. . A new ® ST3.8™ mobile screen is helping Welch Sand & Gravel efficiently process gravel from the Great Miami River in Hamilton. One-stop process.