Abstract: Apparatus and method for dissolving chemical tablets for creating a variable rate of chemical dissolution in a stream of constant flow rate of untreated liquid, especially water. The apparatus includes a housing in which a container is placed. The container includes a sieve plate or perforated grid which separates the container into an upper chamber in which chemical tablets are stored and a lower mixing chamber. A collection reservoir is defined in an annular outside the container wall and inside of the housing. Several arrangements are illustrated by which a vortex of liquid is generated of controllable variable intensity in the lower or mixing chamber thereby creating uneven liquid pressure beneath the perforated grid as a function of radial distance. As a result, fluid passes aggressively through outer radial perforations or holes in the grid and which impinge on the chemical tablets stacked on the grid.

Abstract: A production swivel with passive control of dynamic seal gap width using internal swivel pressure. The swivel includes inner and outer housings with a middle housing which transfers, component deformation due to fluid pressure from the dynamic sealing interface to the static sealing interface. The outer housing and inner housing rotate together, but the outer housing is free to expand radially outward from the middle housing with increasing fluid pressure. A floating riser spool is pressure balanced at the connection to the inner housing and to a fixed swivel stack base. Swivels are stacked with a swivel connector/spool and upper and lower mounting rings cooperatively dimensioned so that access to seals can be obtained while the swivels remained stacked without the use of overhead cranes or other lifting points than the swivel being serviced.