This standard specifies the minimum requirements for general purpose steam turbines. These requirements includes basic design, materials, related lubrication systems, control, auxiliary equipment and accessories. This standard includes only general purpose turbines. General purpose turbines are horizontal or vertical turbines which are used to drive equipment that can be usually spared and turbine is relative small in size (with respect to power),or is in non-critical service. These are generally used where steam conditions will not exceed a pressure of 48 bar (700psig) and a temperature of 400 degree centigrade.(750 degrees F) or where speed will not exceed 6,000 r/min. This standard does not cover special purpose turbines. This standard is based on API 611, fifth edition,2008, supplements and deletes various clauses of API 611.In addition some new clauses have been added.