STF flowpath selectors are a variation of the ST flowpath, with the single difference that the non-selected streams are returned to their own vents or sources rather than being dead-ended or trapped as they are in the standard ST configuration. This is ideal for reactor processes in which removal of substantial amounts of sample would upset the equilibrium within the reactor, or if the stream is toxic or noxious and must be isolated.
An STF valve together with a 6 port sampling valve and pneumatic or electric actuators comprise a complete sampling system for the automated analysis of up to 16 sample points. In step 1, the sample loop on the 6 port valve is loaded from stream 4. In step 2, the 6 port valve is switched, injecting the sample. In step 3, the STF valve is advanced to stream 1 and the 6 port is switched back to the load position, beginning the next cycle.
Step 1
Sample loop on is loaded from stream 4
Step 2
Sample loop contents injected onto the column
Step 3
The STF valve is advanced to stream 1, and the sample loop filled with contents from stream 1
