These design requirements are applicable to valves suitable for use in controlling a coal/ash-solvent slurry under pressure letdown conditions in a coal liquefaction process. The valves are in the main flow downstream of the reactor vessel. The slurry also contains dissolved gases, including hydrogen, hydrogen sulfide and hydrocarbons. This valve must operate on a coal/ash-solvent slurry at 500 to 850/sup 0/F and with letdown pressures from 2000 to 4000 psig to atmospheric. The design and construction of the valves shall comply with commercial standards as defined in ANSI B16.34-1977. It should be noted that the valves will be used in piping systems that conform to the ASME Boiler and Pressure Vessel Code and the ANSI Code for Pressure Piping. Therefore, the valves are also subject to any limitations of those codes. In case of a conflict between requirements in these codes, the more stringent (i.e., more conservative) requirement shall apply. The valves shall be designed to be remote operating-type valves.