§ 59.216b. High temperature short-time (HTST) continuous flow
(a) Indicating thermometers and recorder/controller instruments. All indicating thermometers and recorder/controller instruments and devices used in connection with the high-temperature, short-time, continuous-flow pasteurization of milk or milk products shall comply with the applicable specifications set forth in Appendix H of the PMO.
(b) Automatic milk controller. Each high-temperature, short-time, continuous-flow pasteurization system shall be equipped with an automatic milk-flow control of the diversion type, which complies with paragraphs (1) and (2).
(1) Automatic milkflow controls shall mean those safety devices which control the flow of milk in relation to the temperature of the milk, heating medium, pressure, vacuum, or other auxiliary equipment. Milk-flow controls shall not be considered as part of the temperature control equipment. Milk-flow controls shall be of the flow-diversion type which automatically causes the diversion of the milk in response to a sublegal pasteurization temperature. At sublegal temperatures, flow-diversion devices return the milk to the raw milk side of the heating system continuously until legal pasteurization temperatures are obtained; at which time, the device restores forward flow through the pasteurizer.
(2) All flow-diversion devices used in continuous pasteurizers shall comply with the following or equally satisfactory specifications:
(i) Forward flow of subtemperature milk due to the omission or looseness of the connecting clip shall be prevented by:
(A) Making the valve and its actuating mechanism integral;
(B) Where there is a connecting device, by making it impossible to assemble the valve and its actuating mechanism except in such a manner that it will function properly;
(C) Where there is a connecting device which may be omitted or shaken loose, by providing for pushing, instead of pulling the valve to the diverted position;
(D) By providing that the pump will shut down when the milk is below the pasteurization temperature and the valve is not in the fully-diverted position; or
(E) By any other equally satisfactory means.
(ii) When a packing gland is used to prevent leakage around the actuating stem, it shall be impossible to tighten the stem packing nut to such an extent as to prevent the valve from assuming the fully-diverted position.
(iii) A leak escape shall be installed on the forward-flow side of the valve seat. However, when back pressure is exerted on the forward-flow side of the valve seat while the milkflow is being diverted, the leak escape should lie between two valve seats or between two portions of the same seat, one upstream and the other downstream from the leak escape. The leak escape shall be designed and installed to discharge all leakage to the outside or to the constant-level tank through a line separate from the diversion line; provided that when leakage is discharged to the constant-level tank, a sight glass shall be installed in the leak escape line in a vertical position to provide a visual means of leak detection.
(iv) The closure of the forward-flow seat shall be sufficiently tight so that leakage past it will not exceed the capacity of the leak escape device, as evidenced when the forward-flow line is disconnected; and, in order that proper seating may not be disturbed, the length of the connecting rod shall not be adjustable by the user.
(v) The flow-diversion device shall be so designed and installed that failure of the primary motivating power shall automatically divert the flow of milk.
(vi) The flow-diversion device shall be located downstream from the holder. The flow-control sensor shall be located in the milk line not more than 18 inches upstream from the flow-control device.
(vii) In the case of higher-heat, shorter-time (HHST) pasteurizing systems utilizing the temperature of 191°F (89°C) and above and holding times of one second and less, the flow-diversion device may be located downstream from the regenerator or cooler section; provided that when the flow-diversion device is located downstream from the regenerator or cooler section, the flow-diversion device shall be automatically prevented from assuming the forward-flow position until all product-contact surfaces between the holding tube and flow-diversion device have been held at or above the required pasteurization temperature continuously and simultaneously for at least the required pasteurization time as defined in § 59.1 (relating to definitions).
(viii) The pipeline from the diversion port of the flow-diversion device shall be self-draining and open to the atmosphere and shall be free of restrictions or valves, unless such restrictions or valves are so designed that stoppage of the diversion line cannot occur.
(ix) When it is used, the pipeline from the leak detection port of the flow-diversion device shall be self-draining, and shall be free of restrictions or valves, unless such restrictions or valves are so designed that stoppage of the leak detector line cannot occur.
(c) Milk-flow controller instrumentation. The following requirements shall be met with respect to the instrumentation of the milk-flow controller:
(1) The thermal limit controller shall be set and sealed so that forward flow of product cannot start unless the temperature at the controller sensor is above the required pasteurization temperature nor continue during descending temperatures when the temperature is below the required pasteurization temperature. The seal shall be applied by the regulatory agency after testing and shall not be removed without immediately notifying the regulatory agency. The system shall be so designed that no milk can be by-passed around the controller sensor, which shall not be removed from its proper position during the pasteurization process. The cut-in and cut-out milk temperatures, as shown by the indicating thermometer, shall be determined at the beginning of each days operation and entered upon the recorder chart daily by the plant operator.
(2) In the case of HHST pasteurization systems, utilizing the temperatures of 191°F (89°C) and above and holding times of one second or less, with the flow-diversion device located downstream from the regenerator or cooler section; additional temperature controllers and timers shall be interwired with the thermal limit controller, and the control system shall be set and sealed so that forward flow of product cannot start until all product-contact surfaces between the holding tube and flow-diversion device have been held at or above the required pasteurization temperature continuously and simultaneously for at least the required pasteurization time. The control system shall also be set and sealed so that forward flow cannot continue when the temperature of the product in the holding tube is below the required pasteurization temperature. The seal shall be applied by the regulatory agency after test and shall not be removed without immediately notifying the regulatory agency. The system shall be so designed that no product can be by-passed around the control sensors, which shall not be removed from their proper position during the pasteurization process. For these HHST systems, daily measurement by the operator of the cut-in and cut-out temperature is not required.
(3) Manual switches for the control of pumps, homogenizers, or other devices which produce flow through the holder shall be wired so that the circuit is completed only when the milk is above the required pasteurization temperature or when the diversion devise is in the fully-diverted position.
(d) Holding tube.
(1) Holders shall be designed to provide for the holding of every particle of milk or milk product for at least the time required for pasteurization.
(2) The holder shall be so designed that the simultaneous temperature difference between the hottest and coldest milk in any cross section of flow at any time during the holding period will not be greater than 1°F (0.5°C). This requirement may be assumed to have been satisfied without test in tubular holders of seven inches or smaller diameter which are free of any fittings through which the milk may not be thoroughly swept.
(3) No device shall be permitted for short circuiting a portion of the holder to compensate for changes in rate of milk flow. Holding tubes shall be installed so that sections of pipe cannot be left out, resulting in a shortened holding time.
(4) The holding tube shall be arranged to have a continuously upward slope in the direction of flow or not less than 0.25 inches a foot.
(5) Supports for tubes shall be provided to maintain all parts of holding tubes in a fixed position, free from any lateral or vertical movement.
(6) The holder shall be so designed that no portion between the inlet and the flow-control temperature sensor is heated.
(7) The holding time for the HHST processes shall be determined from the pumping rate rather than by the salt conductivity test because of the short holding tube. The holding tube length shall be such that the fastest flowing particle of any product will not traverse the holding tube in less than the required holding time. Since laminar flow can occur in the holding tube during pasteurization of high-viscosity products, holding tube lengths are calculated as twice the length required to hold the average flow for the standard time.
(8) With the steam injection process, a pressure limit indicator is needed in the holding tube to keep the heated product in the liquid phase. The instrument must have a pressure switch so that the flow-diversion device will move to the divert position if the product falls below a prescribed value. For operating temperatures between 191°F (89°C) and 212°F (100°C), the pressure switch shall be set at ten pounds per square inch (psi). For units which have operating temperatures above 212°F (100°C), the pressure switch shall be set at a pressure ten psi the boiling pressure of the product at its maximum temperature in the holding tube.
(9) With the steam injection process, a differential pressure limit indicator across the injector is needed to ensure adequate isolation of the injection chamber. The instrument must have a differential pressure switch so that the flow diversion device will move to the divert position if the pressure differential across the injector falls below ten psi.
(e) Indicating and recording thermometers.
(1) All indicating thermometers shall be located as near as possible to the temperature sensor of the recorder/controller but may be located a short distance upstream from the latter where milk between the two thermometers does not differ significantly in temperature.
(2) The temperature shown by the recorder/controller shall be checked daily by the plant operator against the temperature shown by the indicating thermometer. Readings shall be recorded on the chart. The recorder/controller shall be adjusted to read no higher than the indicating thermometer.
(3) The recorder/controller charts shall comply with the applicable provisions of § 59.216d (relating to temperature-recording charts equipment tests and examinations).
(f) Flow-promoting devices.
(1) The pump or pumps and other equipment which may produce flow through the holder shall be located up-stream from the holder, provided that pumps and other flow-promoting devices may be located downstream from the holder if means are provided to eliminate negative pressure between the holder and the inlet to such equipment. When vacuum equipment is located downstream from the holder, an effective vacuum breaker plus an automatic means of preventing negative pressure in the line between the flow-diversion device and the vacuum chamber will be acceptable.
(2) The speed of pumps or other flow-promoting devices governing the rate of flow through the holder shall be so controlled as to insure the holding of every particle of milk for at least the time required as defined in § 59.1 for the milk or milk products and the process used. In all cases, the motor shall be connected to the metering pump by means of common drive shaft or by means of gears, pulleys, or a variable-speed drive with the gear box, the pulley box, or the setting of the variable speed protected in such a manner that the holding time cannot be shortened without detection by the Department. This shall be accomplished by the application of a suitable seal after tests by the Department and such seal shall not be broken without immediately notifying the Department. This paragraph applies to all homogenizers used as timing pumps. Variable speed drives used in connection with the metering pump shall be so constructed that wearing or stretching of the belt results in a slowdown, rather than a speedup of the pump. The metering or timing pump shall be of the positive displacement type.
(3) The holding time shall be taken to mean the flow time of the fastest particle of milk, at or above the required pasteurization throughout the holder section. Tests for holding time shall be made when all equipment and devices are operated and adjusted to provide for maximum flow. When a homogenizer is located upstream from the holder, the holding time shall be determined with the homogenizer in operation with no pressure on the homogenizer valves. Where bypass lines are provided either upstream or downstream from the metering pump, the holding time shall be tested with both the regular and bypass line open, unless the bypass valve is so designed that both lines cannot be open at the same time. The holding time shall be tested during both forward and diverted flow. If necessary to lengthen the holding time during diverted flow, an identifiable restriction may be placed in the vertical portion of the diversion pipeline. When vacuum equipment is located downstream from the holder, the holding time shall be tested with the metering pump operating at maximum flow and the vacuum equipment adjusted to provide for the maximum vacuum. The holding time shall be tested in both forward and diverted flow by the Department.
(g) Heating by direct addition of steam. When culinary steam is introduced directly into milk or milk products as the means of terminal heating to achieve pasteurization temperature, the steam injector shall be designed, installed, and operated to comply with the following or equally satisfactory specifications:
(1) The product and steam flows shall be isolated from pressure fluctuations inside the injection chamber.
(2) The product pressure in the holding tube shall be of sufficient magnitude to condense the steam and keep the product in the liquid phase. A minimum product pressure in the holding tube of ten psi for operating temperatures from 191°F (89°C) to 212°F (100°C) is satisfactory. For units which have operating temperatures above 212°F (100°C), the pressure of the product in the holding tube must be at least ten psi above the boiling pressure of the product at its maximum temperature in the holding tube.
(3) The process should be as free as possible for noncondensable gases that may evolve from the product or be carried in the steam supply. The steam boiler shall be provided with a deaerator.
(h) Prevention of product adulteration with added water.
(1) When culinary steam is introduced directly into the milk or milk product downstream from the flow-diversion device, means shall be provided to preclude the addition of steam to the product unless the flow-diversion device is in the forward-flow position. The requirements of this paragraph may be satisfied by the use of an automatic steam control valve with temperature sensor located downstream from the steam inlet, or by the use of an automatic solenoid valve installed in the steam line and so wired through the flow-diversion device controls that steam cannot flow unless the flow-diversion device is in the forward-flow position.
(2) When culinary steam is introduced directly into the milk or product, automatic means shall be provided to maintain a proper temperature differential between incoming and outgoing milk to preclude dilution with water.
(3) When a water feed line is connected to a vacuum condenser and the vacuum condenser is not separated from the vacuum chamber by a physical barrier, means shall be provided to preclude the backup and overflow of water from the vacuum condenser to the vacuum chamber. This paragraph may be satisfied by the use of a safety shutoff valve, located on the water feed line to the vacuum condenser, automatically actuated by a control which will shut off the inflowing water. This valve may be actuated by water, air, or electricity and shall be so designed that failure of the primary motivating power will automatically stop the flow of water into the vacuum condenser.
This section cited in 7 Pa. Code § 59.216c (relating to pasteurizers employing regenerative heating).
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