For Ammonia or Freon service Teikoku offers two specially designed pump models - the Horizontal Type R and the Vertical Type RW.
Both pumps do not have any internal circulation and vaporizing media directly escapes from the pump cavity through the venting port connected to the rear bearing housing.

The fluid which escapes from the pump returns to the tank through the so-called recirculation line. This line shall be piped as per the layout and notes below. Teikoku strongly recommends this particular pipe design to avoid any gas from being trapped in any part of the reverse flow line. This also applies for the case, that the pump is frequently shut down and started again. It must be assured, that dissolved or flush gas can return to the suction tank even if the pump is not running.

Piping must continuously rise all the way to the return point. Avoid the dotted line piping.

Do not connect the reverse circulation line to liquid filled zone of the tank.

Orifice must be instaleld in a vertical line.

Do not install a check valve on the reverse circulation line.

The Teikoku data sheet will speicfy the available total head at the pump reverse flange at the required reverse flow rate. In other words, HR is the net pressure available to get the reverse circulation flow back to the suction tank.

Reverse line layout and sizing should be made in such matter, that the total flow loss HRL and the static head HRS will satisfy the equation, or

Teikoku must be advised of the estimated total loss, i.e. HRS + HRL in advance of final engineering work in order to investigate, whether the pump can generate enough pressure to return the flow to the suction tank.

Reverse piping is required for all pumps in parallel service.