Abstract: Disclosed is an apparatus including a probe adapted for removal through an aperture in the side wall of a high pressure chamber. The probe is supported at one end of a rod that is coaxially received within a sleeve. A plate at the free end of the rod forms a sealed connection between the rod and the sleeve. The sleeve extends within a tube attached at one end to the high pressure chamber in an enclosing relation with the aperture therein. The tube is divided along its length and secured by flanges to a valve used to selectively block the flow of media from the high pressure chamber after the sleeve is withdrawn along the tube beyond the valve. Screw threads on the external surface of the sleeve mate with internal screw threads formed in a screw head that is supported by the end of the tube to displace the sleeve therealong.