Dairy Establishment Inspection Manual – Chapter 17 - Higher Heat Shorter Time (H.H.S.T.) Processing and Extended Shelf-Life (ESL) Dairy Products
1.17.01 H.H.S.T. Flow Schematic

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The H.H.S.T. system, although similar to an H.T.S.T. pasteurizer, operates at higher temperatures (above 100°C) and pressures. It also uses a pasteurization or sterilization cycle to pasteurize or sterilize the entire system prior to commencing production.

The number of factors involved and any changes made to the processing system must be done with the full involvement of the process authority responsible for the scheduled process. Even slight modifications made to the H.H.S.T. system may have an impact on its operation and safety.

This task will evaluate the flow schematic of the H.H.S.T. processing system from the constant level tank to the finished product storage tank. Flow Schematic [Process and Instrumentation Diagram (P&ID)]

Plant management must have a flow schematic, outlining the H.H.S.T. system and its related components, which is maintained and kept in the plant's file. When equipment and/or pipelines are installed or changed, plant management must ensure that the flow schematic is updated. All components of the H.H.S.T. must be on the flow schematic (P&ID). No Cross Connections

A cross-connection is a direct connection allowing one material to contaminate another. There needs to be a complete segregation of incompatible products such as raw materials and pasteurized food products, cleaning products and food products (including potable water) and waste materials or utility materials and food products, as outlined under task Consideration also needs to be given to preventing inadvertent cross contamination of independent food products (e.g. soy beverages and milk) which may pose allergenic concerns.

For other applications (C.I.P. supply lines and return line circuits used for C.I.P. cleaning and Amini-washes on tanks, lines, pasteurizers or other equipment that may be washed while connected to product lines containing milk products or potable water and lines for final rinse), this segregation must be accomplished by the use of separate pipelines and vessels for incompatible products and establishing effective physical breaks at connection points by at least one of the following arrangements: physical disconnecting of pipelines, double block and bleed valve arrangements, double seat (mix proof) valves, aseptic barriers, or other equally effective systems. Refer to Appendix 19-10 for assessment of these applications.

Attention must also be paid to the design of the constant level tank and piping, and the Flow Diversion Device (FDD), as these are areas where potential cross-connections could exist if the design or installation is improper. The following sections namely, and to provide more details for the evaluation of these tasks.

A physical verification by the inspector must be done to check the accuracy of the schematic/P&ID and to ensure that no cross connections exist. Even if the plant does not have a schematic on file, an assessment for cross connections must be completed on the H.H.S.T. system.

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