Dairy Establishment Inspection Manual – Chapter 18
E. Meter Based Timing Systems

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Test 25: High Flow Alarm

Application:

To all HTST pasteurizers, HHST and aseptic processing systems using a Meter Based Timing System to replace a positive displacement Flow Control Device.

Frequency:

  1. Upon installation and at least once every 6 months thereafter.
  2. Whenever seal on the flow alarm is broken.

Criteria:

When flow rate equals or exceeds the value at which the holding time was measured, the Flow Diversion Device shall assume the diverted position, even though temperature of the milk in the holding tube is above pasteurization temperature.

Apparatus:

None.

Method:

Adjust the set point of the flow alarm so that the flow is diverted when the flow rate equals or exceeds the value at which holding time was measured.

Procedure:

  1. Operate the HTST, HHST pasteurizer or the aseptic processing equipment in forward flow, below the high flow alarm, using water above pasteurization temperature.
  2. Adjust set point on the alarm slowly downward until the frequency pen on the Flow Recorder indicates that an alarm condition has occurred.
  3. Observe that the Flow Diversion Device moved to the diverted position while water passing through the system remained above pasteurization temperature. Verify that the frequency pen on the Flow Recorder records the duration of the high flow condition.
  4. Record the set point of the flow alarm, the occurrence of flow diversion, and the temperature of water in the holding tube.

Corrective Action:

If the Flow Diversion Device does not move to the diverted position, when the frequency pen of the recorder indicates a diversion, a modification or repair of the control wiring is required.

Test 26: Loss of Signal Alarm

Application:

To all HTST pasteurizers, HHST and aseptic processing systems using a Magnetic Flow Meter System to replace a positive displacement Flow Control Device.

Frequency:

  1. Upon installation and at least once every 6 months thereafter.
  2. Whenever seal on the Flow Alarm is broken.
  3. Whenever alteration is made affecting the holding time, the velocity of the flow or the capacity of the holding tube.
  4. Whenever a check of the system indicates a speed-up.

Criteria:

Forward flow occurs only when flow rates are below the Flow Alarm set point and above (5% of the maximum) the Loss of Signal Alarm set point.

Apparatus:

None.

Method:

By observing the actions of the frequency pen on the Flow Recorder and the position of the Flow Diversion Device.

Procedure:

  1. Operate the HTST, HHST pasteurizer or aseptic processing system with the Flow Diversion Device in the forward flow position, at a flow rate below the Flow Alarm set point and above (5% of the maximum) the Loss of Signal Alarm set point, using water.
  2. Disrupt power to the magnetic flow meter or decrease the flow through the flow meter below the Low Flow Alarm set point.
  3. Observe that the frequency pen of the Flow Recorder records an alarm condition for the duration of the loss of signal or low flow condition, and that the Flow Diversion Device moves to the diverted flow position for the duration of this condition.
  4. Record the results.

Corrective Action:

If the valve does not divert or the pens do not move, adjustment of low flow alarm or modification or repair of control wiring is required.

Test 27: Flow Cut-in and Cut-out

Application:

To all HTST pasteurizers, HHST and aseptic processing systems using a Magnetic Flow Meter System to replace a positive displacement Flow Control Device.

Frequency:

  1. Upon installation and at least once every 6 months thereafter.
  2. Whenever seal on the flow alarm is broken.
  3. Whenever any alteration is made affecting the holding time, the velocity of the flow or the capacity of the holding tube.
  4. Whenever a check of the capacity indicates a speed-up.

Criteria:

Forward flow occurs only when flow rates are below the Flow Alarm set point and above the Loss of Signal Alarm set point.

Apparatus:

None.

Method:

By observing the Recorder readings along the action of the frequency pen on the Flow Recorder.

Procedure:

  1. Operate pasteurizer in forward flow, at a flow rate below the Flow Alarm set point and above Loss of Signal Alarm set point, using water above pasteurization temperature.
  2. Using the Flow Controller, increase flow rate slowly until the frequency pen on the Flow Recorder indicates an alarm condition (flow cut-out point). The Flow Diversion Device will also assume the diverted position.
  3. Observe the reading of flow rate from the Recorder, the instant flow cut-out occurs, as indicated by the frequency pen of the Flow Recorder.
  4. With the pasteurizer operating on water above the pasteurization temperature, with the Flow Diversion Device diverted because of excessive flow rate, slowly decrease flow rate until the frequency pen on the Flow Recorder indicates the start of a forward flow movement (flow cut-in point). Because of the time delay relay described in Test 28, the Flow Diversion Device will not move immediately to the forward flow position.
  5. Observe the reading from the Recorder, the instant flow cut-in occurs, as indicated by the frequency pen of the Flow Recorder.
  6. Record results.

Corrective Action:

If the cut-in or cut-out point occurs at a flow rate equal to or greater than the value at which holding time was measured, adjust the Flow Alarm to a lower set point and repeat the test.

Test 28: Time Delay Relay (Flow Recorder)

Application:

To all HTST pasteurizers using Magnetic Flow Meter System to replace a positive displacement Flow Control Device.

Frequency:

  1. Upon installation and at least once every 6 months thereafter.
  2. Whenever seal on the flow alarm is broken.
  3. Whenever any alteration is made affecting the holding time, the velocity of the flow or the capacity of the holding tube.
  4. Whenever a check of the capacity indicates a speed-up.

Criteria:

Following a flow cut-out, as described in the test for flow cut-in and cut-out (Test 27), forward flow shall not occur until all the product in the holding tube has been held at or above pasteurization temperature for at least the minimum holding time of the product with the longest required holding time (e.g. 15 seconds or 25 seconds for depending on the products).

Apparatus:

Stopwatch.

Method:

Set time delay equal to or greater than the minimum holding time.

Procedure:

  1. Operate pasteurizer in forward flow, at a flow rate below the Flow Alarm set point and above the Loss of Signal Alarm set point, using water above pasteurization temperature.
  2. Using the Flow Controller, increase flow rate slowly until the frequency pen on the Flow Recorder indicates an alarm condition, and the Flow Diversion Device moves to the diverted position. There shall be no time delay between the movements of the frequency pen and the Flow Diversion Device.
  3. With the pasteurizer operating on water above the pasteurization temperature, with the Flow Diversion Device diverted because of excessive flow rate, slowly decrease flow rate.
  4. Start the stopwatch the instant the frequency pen on the Flow Recorder indicates the end of the alarm condition.
  5. Stop the stopwatch the instant the Flow Diversion Device starts to move to the forward flow position. Record results.

Corrective Action:

If the time delay is less than the minimum holding time, increase the time setting on the time delay and repeat this test procedure.

Test 29: Thermal Limit Controller For Control-Sequence Logic

Thermal limit controllers used with HHST and aseptic processing systems that have the flow-diver­sion device located downstream from the regenerator and/or cooler shall be tested by one of the following applicable tests at the frequency specified.

Test 29.1: HHST Pasteurization and Aseptic Processing- Indirect Heating

Application:

To all HHST and aseptic processing systems pas­teurizers using indirect heating. When testing aseptic processing systems, the "product divert system" or "product divert valve" or "acceptable control system" may be substituted for the "flow-diversion device" when it is referenced in this test.

Frequency:

  1. Upon installation, and every 6 months thereafter.
  2. Whenever a seal has been broken.

Criteria:

The pasteurizer or aseptic processing equipment shall not operate in forward flow until the product surfaces downstream from the holding tube have been held at or above the required pasteurization temperature for the required time or, in the case of aseptic processing equipment, sterilized. On start-up, surfaces shall be exposed to fluid at pas­teurization or in the case of aseptic processing equipment, sterilization temperature for at least pas­teurization or sterilization time. If the product tempera­ture falls below the pasteurization or sterilization standard in the holding tube, forward flow shall not be re-achieved until the product surfaces downstream from the holding tube have been re-held at or above the required pasteurization temperature for the required time, or is the case of aseptic processing equipment, re-sterilized.

Apparatus:

  1. Constant tempera­ture water, oil or other suitable media bath.
  2. Test lamp from the pneumatic testing device as shown in figure 4.

Method:

The control-sequence logic of the thermal limit controller is determined by monitoring the electric signal from the thermal limit controller during a series of immersions and remov­als of the two sensing elements from a bath heated above the cut-in temperature.

Procedure:

  1. Heat a constant temperature water, oil or other suitable media bath a few degrees above the cut-in temperature on the thermal limit controller.
  2. Wire the test lamp in series with the signal from the thermal limit controller to the flow-diversion device. If some processors have time delays built into their control logic in excess of that required for public health reasons, bypass these timers or account for their effect in delaying forward flow.
  3. Immerse the holding tube sensing element in the bath, which is above the cut-in temperature. The test lamp should remain unlit, i.e. diverted flow. Leave the sensing element in the bath.
  4. Immerse the 2nd or more as required sensing element in the bath. The test lamp should light up, i.e. forward flow after a minimum time delay of 1 second for continuous flow pasteurization systems. For aseptic processing systems, no delay is required if the filed process includes a documented sterilization period.
  5. Remove the 2nd or more as required elements from the bath. The test lamp should remain lit, i.e. forward flow.
  6. Remove the holding tube sensing element from the bath. The test lamp should go out immediately, i.e. diverted flow, sterilization timer not timing.
  7. Re-immerse the sensing element of the holding tube in the bath. The test lamp should remain unlit, i.e. diverted flow. Record results.
  8. With all elements in the bath observe the sterilization timer. Start the watch when the test lamps light (cut-in temperature) turns on.
  9. Record the time. Compare the results to the Scheduled Process to verify that the time meets that specified by the Process Authority.
  10. Stop the watch when the sterilization timer has elapsed.
  11. Record this time.

Corrective Action:

If the control-sequence logic of the thermal limit con­troller does not follow the pattern set out in the procedures section, the instrument shall be rewired to conform to this logic.

Test 29.2: HHST Pasteurization and Aseptic Processing - Direct Heating

Application:

To all HHST pasteurizers and aseptic processing systems using direct contact heating. When testing aseptic processing systems, the "product divert system" or "product divert valve" or "acceptable control system" may be substituted for the "flow-diversion device" when it is referenced in this test.

Frequency:

  1. Upon installation, and every 6 months thereafter.
  2. Whenever a seal has been broken.

Criteria:

The pasteurizer or aseptic processing equipment shall not operate in forward flow until the product surfaces downstream from the holding tube have been held at or above the required pasteurization temperature for the required time or, in the case of aseptic processing equipment, sterilized. On start-up, surfaces shall be exposed to fluid at pas­teurization or in the case of aseptic processing equipment, sterilization temperature for at least pas­teurization or sterilization time. If the product tempera­ture falls below the pasteurization or sterilization standard in the holding tube, forward flow shall not be re-achieved until the product surfaces downstream from the holding tube have been re-held at or above the required pasteurization temperature for the required time, or is the case of aseptic processing equipment, re-sterilized.

Apparatus:

  1. Constant tempera­ture water, oil or other suitable media bath.
  2. Test lamp from the pneumatic testing device as shown in figure 4.

Method:

The control-sequence logic of the thermal limit controller is determined by monitoring the electric signal from the thermal limit controller during a series of immersions and remov­als of the three sensing elements from a bath heated above the cut-in temperature.

Procedure:

  1. Heat a water, oil or other suitable media bath to a constant temperature, a few degrees above the cut-in temperature on the ther­mal limit controller.
  2. Wire the test lamp in series with the signal from the thermal limit controller to the flow-diversion device. If some processors have time delays built into their control logic in excess of that required for public health reasons, bypass these timers or account for their effect in delaying forward flow. The pressure switches which must be closed to achieve forward flow must also be bypassed before performing this test.
  3. Immerse the sensing ele­ment from the flow-diversion device in the bath which is above the cut-in tempera­ture. The test lamp should remain un­lit, i.e. diverted flow. Remove this sensing element from the bath.
  4. Immerse the sensing ele­ment from the vacuum chamber in the bath. The test lamp should remain un­lit, i.e. diverted flow. Remove the sensing element from the bath.
  5. Immerse two sensing ele­ments, from the vacuum chamber and flow-diver­sion device in the bath. The test lamp should remain unlit, i.e. diverted flow. Leave the two sensing elements in the bath.
  6. Immerse the sensing ele­ment from the holding tube in the bath. The test lamp should light up, i.e. forward flow after a minimum time delay of 1 second for continuous flow pasteurization systems. For aseptic processing systems, no delay is required if the filed process includes a documented sterilization period.
  7. Remove one sensing ele­ment, the flow-diversion device, from the bath. The test lamp should remain lit, i.e. forward flow.
  8. Remove another sensing ele­ment, the vacuum chamber from the bath. The test lamp should remain lit, i.e. forward flow.
  9. Remove the last sensing ele­ment, the holding tube from the bath. The test lamp should go out immediately, i.e. diverted flow.
  10. Re-immerse the sensing ele­ment, holding tube in the bath. The test lamp should remain unlit, i.e. di­verted flow.
  11. Record results.
  12. Re-seal regulatory controls as necessary.

Corrective Action:

If the control-sequence logic of the thermal limit con­troller does not follow the pattern set out in the procedures section, the instrument shall be rewired to conform to this logic.

Test 30: Setting of Control Switches for Product Pressure in the Holding Tube

Application:

To all HHST pasteurizers and aseptic processing systems which are capable of operating with product in forward flow mode, with less than 518 Kpa (75 psig) pressure in the holding tube. When testing aseptic processing systems, the "product divert system" or "product divert valve" or "acceptable control system" may be substituted for the "flow-diversion device" when it is referenced in this test.

Frequency:

  1. Upon installation and at least once every 6 months thereafter.
  2. Whenever the pressure switch seal is broken.
  3. When­ever the operating temperature is changed.

Criteria:

The pasteurizer or aseptic processor shall not operate in forward flow unless the product pressure in the holding tube is at least 69 Kpa (10 psi) above the boiling pressure of the product.

Apparatus:

  1. Sanitary pressure gauge.
  2. Test lamp from the pneumatic testing device as shown in figure 4.

Method:

The pressure switch is checked and adjusted so as to prevent forward flow unless the product pressure in the holding tube is at least 69 Kpa (10 psi) above the boiling pressure of the product.

Procedure:

  1. From Figure 1-5, deter­mine the pressure switch setting necessary for the operating temperature (not the diversion temperature) being used in the process.
  2. Install the sanitary pressure gauge of known accuracy and the pressure switch sensing element on the pneumatic testing device.
  3. Remove the seal and cover to expose the adjustment mechan­ism on the pressure switch.
  4. Place the test lamp in series with the pressure switch contacts or use some other method to monitor the cut-in signal.
  5. Apply air pres­sure to the sensing element, and deter­mine the pressure gauge reading at the cut-in point of the switch which will light the test lamp. If the switch is short cir­cuited, the lamp will be lit before air pressure is applied.
  6. Determine that the cut-in pressure on the switch is equivalent to or greater than the required pressure from the figure below.
  7. Record results.
  8. Where adjustment is necessary, refer to manufacturer's instruc­tion.
  9. After adjustment, repeat the above proced­ure.
  10. When the results are satisfactory, seal the pressure switch setting.
  11. For each operating temper­ature on HHST pasteurizers using direct contact heating, the product pressure switch setting is determined from the figure below.

Note: The pressure setting shall be adjusted upward by the difference between local normal atmospheric pressure and at sea level.

Table 40 – Pressure Switch Settings
Figure - Pressure Switch Settings. Description follows.
Description of image - Pressure Switch Settings

This chart shows the operating temperatures of different pressure switch settings at sea level.

At temperatures of 191°Fahrenheit (F) to 210°Fahrenheit the pressure switch setting is 10 pounds per square inch gauge (PSIG) at sea level.

  • At 220°F the pressure switch setting is 13 PSIG at sea level.
  • At 230°F the pressure switch setting is 16 PSIG at sea level.
  • At 240°F the pressure switch setting is 20 PSIG at sea level.
  • At 250°F the pressure switch setting is 25 PSIG at sea level.
  • At 260°F the pressure switch setting is 31 PSIG at sea level.
  • At 270°F the pressure switch setting is 37 PSIG at sea level.
  • At 280°F the pressure switch setting is 45 PSIG at sea level.
  • At 290°F the pressure switch setting is 53 PSIG at sea level.
  • At 300°F the pressure switch setting is 62 PSIG at sea level.

Test 31: Setting of Control Switches for Differential Pressure across the Injector

Application:

To all HHST pas­teurizers and aseptic processing systems using direct contact heating. When testing aseptic processing systems, the "product divert system" or "product divert valve" or "acceptable control system" may be substituted for the "flow-diversion device" when it is referenced in this test.

Frequency:

  1. Upon installation and at least once every 6 months thereafter.
  2. Whenever the differential pressure controller seal is broken.

Criteria:

The pasteurizer or aseptic processor shall not operate in forward flow unless the product pressure drop across the injector is at least 69 Kpa (10 psi).

Apparatus:

  1. Sanitary pressure gauge.
  2. Test lamp from the pneumatic testing device as shown in figure 4.

Method:

Check the differential pressure switch and adjust it so as to prevent forward flow unless the differen­tial pressure across the injector is at least 69 Kpa (10 psi).

Procedure:

A. Calibration of the Injector Differential Pressure Controller Probes:

  1. Loosen the connection at both pressure sensors and allow for any liquid to drain through the loose connections. Both pointers, or digital displays, shall be within 3.5 Kpa (0.5 psi) of 0 Kpa (0 psi). If not, adjust the pointer(s), or digital display(s), to read 0 Kpa (0 psi).
  2. Remove both sensors and mount them in a tee, or connect them to a pneumatic testing device. Record any difference in the zero (0 Kpa (0 psi)) readings that may have occurred because of this change in elevation.
  3. Attach the tee and both sensors to a pneumatic testing device and adjust the air pressure to the normal operating pressure used at the injector. The pointer or digital display reading separation is to be within 6.9 Kpa (1 psi) of that observed before the pressure was applied. If this is not the case, the instrument requires adjustment or repair.
  4. When the results are satisfactory, record the test results and proceed as directed below.

B. Setting of the Injector Differential Pressure Controller Switch:

  1. Disconnect the sanitary pressure sensing element that is normally located after the steam injector from the pneumatic testing device and cap the resulting opening. Leave the pressure sensing element, which is installed prior to the steam injection, on the pneumatic testing device.
  2. Leave the other pressure sensing element open to the atmosphere, but at the same height as the sensing element connected to the pneumatic testing device.
  3. Wire the test lamp in series with the differential controller micro-switch or use the method provided by the instrument manufacturer to monitor the cut-in signal.
  4. Apply air pressure to the sensing element and determine, from the test lamp, the pressure gauge reading at the cut-in point of the differential pressure switch.
  5. The differential pressure cut-in on the controller shall be at least 69 Kpa (10 psi). Adjust if necessary. Refer to the manufacturer's instructions.
  6. After adjustment, repeat the test.
  7. Once results are satisfactory, seal the instrument and record the results.

Note: this test is to assure at least a 10 psi pressure loss of product at exit end of the steam injector. This assures complete condensation of the steam within the injector.

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