the bottom of a reaction vessel it provides all of the functionality of a typical valve system but additionally it allows two probes to be inserted to monitor vessel reactions moreover the probes can be individually installed and removed without need to remove any of the valve system fixtures from the vessel and one or more of the probes can be exposed within the vessel the system 1 comprises the following main components 4 housing for base of the infra red probe 3 5 a probe connecting piece which is flanged to support continuation of the probes upwardly through a passageway to the top of the valve system 1 7 temperature sensor tip such as a pt100 rtd temperature sensor 8 tip of the infra red probe 3 which is exposed in the vessel 9 10 11 o rings and sleeve forming a circumferential seal around the probe tip 8 32 bolt and nuts connecting a top assembly with the valve body to the actuator 48 49 connecting piece and bolts for actuator 15 70 release screws for probes and connecting piece 5 71 temperature sensor conduit for pt100 rtd temperature sensor 7 terminated in connection head 6 the valve system 1 performs the conventional valve operations required for the bottom of a reaction vessel the configuration of the valve disc or u201c plug u201d 20 being sloped to avoid blind spots for vessel draining and flushing however the central stem 26 of the system 1 includes both the temperature sensor probe 7 and the infra red probe 8 they are fitted as illustrated into a confined space so that the system 1 can include the pneumatic actuator 15 of similar overall.