Abstract: A two piece throttling valve is disclosed. The valve assembly includes a stationary outer housing with an inner removable operable assembly. In this configuration the piping (pump stack) does not have to disassembled to remove, clean or replace the internal valve pieces or the in-line screen. The inner assembly can be quickly removed for cleaning. The entire valve assembly is heated to reduce deposition of volatile process byproducts on the internal valve surfaces and reduce the cleaning frequency. A wedge plate is provided in the outer stationary valve housing to mate with a sloped bottom surface of the inner valve housing such that when the inner assembly is in position in the outer valve housing there is a tight fit between adjacent sealing surfaces around the valve bore. A single flat surface seal provides vacuum sealing between the inner assembly and outer housing. A dual valve stem (shaft) seal seals the valve shaft.