Retriever and Valve
Retriever tool and a service valve together are retriever tool kit.
Its scope is used to insert/retrieve monitoring devices in a plant under pressure without any loss of pressure and/or leakage of fluid. It could be used even in horizontal/vertical position. Due to its internal construction, the retriever tool allows the insertion and extraction of the probe applying only the force necessary to overcome the weight of the moving part. It works, in fact, by balancing the internal pressure so that no forces are exercised on the retriever.
Service valve connects retriever tool and access fitting during operation; its duty is to shut off the access fitting while the insertion or the extraction of the probe is realized. It is ball type, full opening port. Both retriever tool and service valve have an appropriate set of seals to avoid any leakage problem.