Proppant dispensing system with knife-edge gate

A system for dispensing proppant, comprising:

• a conveyor having a belt that is endless and rotatable;
• a hopper positioned over the belt for discharge of proppant onto the belt, the hopper having a top opening that tapers downwardly to a discharge opening located at a bottom of the hopper,
• the hopper having at least one sidewall with a side opening therethrough,
• the side opening rising along the sidewall to an elevation above the discharge opening;
• a pair of opposed channels mounted on the system to taper downwardly along the at least one sidewall proximate the side opening;
• a plate that is slidingly engaged within the pair of opposed channels to cover the side opening over a selected area of the side opening above the belt, the plate having a straight bottom edge;
• and
• a clamp assembly configured to hold the plate at a fixed position with regard to the side opening with the straight bottom edge of the plate being retained at a fixed height when clamped above the belt such that
• when the belt is rotating and proppant is discharging from the discharge opening and the side opening onto the belt, the proppant forms a ribbon of uniform thickness that is useful in volumetric rate calculations.