Abstract: An apparatus for dispensing an additive (70) into a stream (14) of well proppant includes a sealed housing (42), (44), (52) containing a first chamber (102), a second chamber (104), and an additive dispenser (64), (72) operably connected to a motor (92). The upper chamber (102) is adapted to contain the additive (70), and the lower chamber (104) communicated with the pressurized well proppant stream (14). The additive dispensing means (64), (72) is disposed between the upper chamber (102) and the lower chamber (104). Pressure equalizing tubes (98 and 99) within said housing (42), (44), (52) extend from the upper chamber (102) through the additive dispenser (64), (72) to the lower chamber (104) to equalize the fluid pressure existing in the lower chamber (104) with the fluid pressure existing in the upper chamber (102) during the dispensing of the additive ( 70) from the upper chamber (102) to the lower chamber (104).

Abstract: An apparatus for dispensing an additive (70) into a stream (14) of well proppant includes a sealed housing (42), (44), (52) containing a first chamber (102), a second chamber (104), and an additive dispenser (64), (72) operably connected to a motor (92). The upper chamber (102) is adapted to contain the additive (70), and the lower chamber (104) communicated with the pressurized well proppant stream (14). The additive dispensing means (64), (72) is disposed between the upper chamber (102) and the lower chamber (104). A pressure equalizing tube (98) within said housing (42), (44), (52) extends from the upper chamber (102) through the additive dispenser (64), (72) to the lower chamber (104) to equalize the fluid pressure existing in the lower chamber (104) with the fluid pressure existing in the upper chamber (102) during the dispensing of the additive (70) from the upper chamber (102) to the lower chamber (104).