Abstract: Apparatus for freezing liquid in a fluid conducting pipe comprises a freeze jacket having two halves for releasably surrounding a section of pipe. Each jacket half includes outwardly extending flanges in abutting relationship when the jacket halves surround the section of pipe, and structure is provided on the flanges for releasably securing the two jacket halves together around the pipe. The jacket has an internal cylindrical freeze cavity adjacent the pipe and this cavity receives and retains a supply of liquid nitrogen. The cylindrical freeze cavity is defined in part by an inner two-part fixedly secured cylindrical sleeve, one half of the sleeve being associated with each half of the jacket. Insulation is positioned on the outside of each fixed sleeve half between that sleeve and an outer removable cover. Removal of the cover enables internal structural repairs and exposes the insulation for removal and replacement with new insulation.