The Flat Sand Valve is legacy metering technology, where the metering is performed by sliding a lever to open and close the abrasive port.  It is simple in design and relatively inexpensive, but has a few limitations.  Details as follows:

• Slide-plate metering design, controlled by lever
• 1 1/4″ (32 mm) ports
• Features side cleanout-inspection port
• Available with or without outlet nipple and Y-piece (Optional rubber lined nipple is available to extend nipple life.)
• The major limitations are:
  • Not recommended for use with metallic abrasives
  • The slide plate/lever design does not provide effective fine metering control.  Typically this results in over consumption of media.  For low-volume blasting using inexpensive media, this may not be an issue.

Note:  These limitations can be eliminated by replacing the FSV with a MicroValve 3.  No modifications required.  Alternatively, legacy pots with inlet-outlet controls and FSV technology can be completely modernized with either the MicroValve Retrofit Kit (for pressure-release technology) or the TeraValve Retrofit Kit (for pressure-hold technology).