Steam and water spray technologies

First invented and patented by Surdry in 1983, the SWS retort technology combines steam-air mixture with water spray to produce fast and even heating. The water is kept in the bottom of the chamber and recirculated by a high speed pump to the spray nozzles. The cooling is typically made by circulating the vessel water through a heat exchanger to where external cold water is fed. Retorts without heat exchanger are also available for investment cost reduction, although in this case the water is not easily recovered for reuse in successive cooling cycles.

The number of manifolds or tubes with spray nozzles is optionally increased to use pouches and trays, so preventing the “umbrella” effect of the top layers of pouches or trays by screening over the lower layers.

The technology first enabled the use of pouches and trays with even heating and cooling without full water immersion, thus reducing dramatically the steam and water consumption as well as the process cycle time.


  • Direct steam injection in combination with superheated top and side spray ensure good heat distribution and safe process repeatability with minimum cleaning.
  • Retort pressure is controlled by compressed air injection and with high accuracy within the recipe settings to ensure perfect container integrity.
  • Water spray provides fast and even cooling. The water may come from a cooling tower or water chiller and it may be reclaimed for reuse.
  • The amount of water in the vessel is small and is recirculated via a filter before reaching the spray nozzles. The flow is controlled by means of a flowmeter and the level via level control instruments. The water may remain in the vessel for consecutive cycles.