New York Codes, Rules and Regulations
Title 1 - DEPARTMENT OF AGRICULTURE AND MARKETS
Appendices
Appendix 4

Current through Register Vol. 45, No. 52, December 27, 2023

PASTEURIZATION EQUIPMENT AND CONTROLS-TESTS

(cf. Part 2)

I. Testing Apparatus Specifications

TEST THERMOMETER

Type. -Mercury-actuated; readily cleanable; plain front, enameled back; length 12 inches, immersion point to be etched on stem, mercury to stand in contraction chamber at 32°F (0°C).

Scale Range.-At least 12°F (7°C) below and 12°F (7°C) above the pasteurization temperature at which the operating thermometer is used, with extensions of scale on either side permitted, protected against damage at 300°F (149°C).

Temperature Represented by Smallest Scale Division.-0.2°F (0.1°C).

Number of Degrees per Inch of Scale.-Not more than 6 Fahrenheit degrees or not more than 4 Celsius degrees.

Accuracy.-Within 0.2°F (0.1°C) plus or minus, throughout specified scale range. The accuracy shall be checked against a thermometer which has been tested by the National Bureau of Standards.

Bulb.-Corning normal or equally suitable thermometric glass.

Case.-Suitable to provide protection during transit and periods when not in use.

GENERAL PURPOSE THERMOMETER

Type.-Pocket type; mercury-actuated.

Magnification of Mercury Column.-To apparent width of not less than 0.0625 of an inch.

Scale Range. -30°F (-1°C) to 212°F (100°C), with extension on either side permitted. Protected against damage at 220°F (105°C).

Temperature Represented by Smallest Scale Division.-2°F (1°C).

Number of Degrees per Inch of Scale.-Not more than 52 Fahrenheit degrees or not more than 29 Celsius degrees.

Accuracy. -Within 2°F (1°C) plus or minus, throughout the specified scale range. Checked periodically against a known accurate thermometer.

Case.-Metal, provided with a fountain pen clip.

Bulb.-Corning normal or equally suitable thermometric glass.

ELECTRICAL CONDUCTIVITY MEASURING DEVICES

Type.-Wheatstone bridge, Galvanometer, Milliammeter; manual or automatic.

Conductivity.-Capable of detecting change produced by the addition of 10 ppm of sodium chloride, in water of 100 ppm of hardness.

Electrodes.-Standard.

Automatic Instruments.-Electric clock, time divisions not less than 0.2 of a second.

STOPWATCH

Type.-Pocket type, open face, hand indicating fractional seconds.

Accuracy.-Accurate to 0.2 of a second.

Hands.-Sweep hand, one complete turn every 60 seconds or less.

Scale.-Divisions of not over 0.2 of a second.

Crown.-Depression of crown starts, stops, and resets to zero.

II. Test Procedures

Equipment and field tests to be performed by the regulatory agency are listed and suitably referenced below. The results of tests shall be recorded on suitable forms and filed as the regulatory agency shall direct.

TEST 1. INDICATING THERMOMETERS-TEMPERATURE ACCURACY

Reference.-Item 16p(D).

Application.-To all indicating thermometers used for measurement of milk temperature during pasteurization, including airspace thermometers.

Frequency.-Upon installation and once each 3 months thereafter.

Criteria.-Within 0.5°F (0.25°C) for pasteurization thermometers and 1°F (0.5°C) for airspace thermometers plus or minus, in a specified scale range.

Apparatus.-1. Test thermometer meeting specifications under Appendix 4, Part I.

2. Water or oil bath and agitator.

3. Suitable means of heating water or oil bath.

Method.-Both thermometers exposed to a water or oil medium of uniform temperature. Indicating thermometer reading is compared to the reading of the test thermometer.

Procedure.-1. Prepare 10 gallons of water in a milk can or a quantity of oil in an oil bath by raising the temperature of the water or oil to within a range of 3°F (2°C) of the appropriate pasteurization temperature or airspace temperature.

2. Remove heat source, agitate water or oil bath rapidly.

3. Continue agitation. Insert indicating test thermometer to indicated immersion point during the test.

4. Compare both thermometer readings at the temperature reading within the test range.

5. Repeat comparison of readings.

6. Record thermometer readings, thermometer identification, or location.

Corrective Action.-Do not run test if mercury column has been split or capillary tube is broken as thermometer should be returned to the factory for repair. When the indicating thermometer differs from the test thermometer by more than 0.5°F (0.25°C) and the airspace thermometer by more than 1°F (0.5°C), the scale plate of the indicating thermometer should be adjusted to agree with the test thermometer. Retest the thermometer after adjustment.

TEST 2. RECORDING THERMOMETERS-TEMPERATURE ACCURACY

Reference.-Item 16p(D).

Application.-To all recording and recorder/controller thermometers used to record milk temperatures during pasteurization.

Frequency. -Upon installation, at least once each 3 months and whenever recording pen-arm setting requires frequent adjustment.

Criteria.-Within 1°F (0.5°C) plus or minus, in specified scale range.

Apparatus. -Pasteurizer indicating thermometer previously tested against a known accurate thermometer, three 10-gallon milk cans, or suitable vats or containers, agitator, suitable means of heating water baths, and ice.

Method.-The testing of a recording thermometer for temperature accuracy involves the determination of whether or not the temperature pen-arm will return to within 1°F (0.5°C) of its previous setting after exposure to boiling water and melting ice.

Procedure.-1. Adjust the recording pen to read exactly as the previously tested indicating thermometer in the temperature range for the pasteurization process being used after a stabilization period of 5 minutes at a constant temperature. The water bath shall be rapidly agitated throughout the stabilization period.

2. Prepare one water bath by heating to the boiling point. Maintain temperature. Prepare a second container with melting ice. Place water baths within working distance of the recorder sensing element.

3. Immerse the sensing element of recorder in boiling water for not less than 5 minutes.

4. Have a can of water adjusted to a temperature within the testing range for the pasteurization process being used.

5. Remove the sensing element from the boiling water and immerse in water at a temperature within the testing range for the pasteurization process being used. Allow a 5-minute stabilization period for both indicating and recording thermometers. Compare readings of 1°F (0.5°C) plus or minus, indicator thermometer reading.

6. Remove sensing element from bath at operating temperatures and immerse in melting ice for not lean than 5 minutes.

7. Remove sensing element from ice water and immerse in water at a temperature within the testing range for the pasteurization process being used. Allow a 5-minute stabilization period for both indicating and recording thermometers. Compare readings of 1°F (0.5°C) plus or minus, indicator thermometer reading.

8. Record results.

Corrective Action.-If the pen does not return to 1°F (0.5°C) plus or minus of indicating thermometer reading, the recording thermometer should be repaired.

Note.-When this test is performed on recorder/controllers used with HHST pasteurization systems, an oil bath shall be substituted for the boiling water in step 3. above. The temperature of the oil bath shall be such that the temperature sensing element of the recorder/controller system is raised to a temperature above that which the recorder/controller is capable of sensing.

TEST 3. RECORDING THERMOMETERS-TIME ACCURACY

Reference.-Item 16p(D).

Application.-To all recording and recorder/controller thermometers used to record time of pasteurization.

Frequency.-Upon installation and at least once each 3 months thereafter.

Criteria. -The recorded time of pasteurization shall not exceed the true elapsed time.

Apparatus.-1. A watch graduated at intervals not to exceed 1 minute, and accurate to within 5 minutes in 24 hours.

2. A pair of dividers, or any other suitable device for measuring short distances.

Method.-Comparison of the recorded time over a period of not less than 30 minutes with a watch of known accuracy. For recorders utilizing electric clocks, check cycle on face plate of clock with known cycle; observe that clock is in operating condition.

Procedure.-1. Determine if chart is appropriate to recorder.

2. Inscribe reference mark at the pen point on the recorder chart at the start of the holding period and record the time.

3. At the end of 30 minutes by the watch, inscribe a second reference mark at the pen point position on the chart.

4. Determine the distance between the two reference marks and compare the distance with the time-scale divisions on the record chart at the same temperature.

5. For electric clocks, remove face plate, compare cycle specification on face plate with the current cycle utilized.

6. Enter finding on chart and initial. Record results.

Corrective Action.-If recorded time is incorrect, the clock should be adjusted or repaired.

TEST 4. RECORDING THERMOMETERS-CHECK AGAINST INDICATING THERMOMETER

Reference.-Item 16p(D).

Application.-To all recording and recorder/controller thermometers used to record milk temperatures during pasteurization.

Frequency.-At least once each 3 months by regulatory agency; daily by plant operator.

Criteria.-Recording thermometer shall not read higher than corresponding indicating thermometer.

Apparatus.-No supplementary materials required.

Method. -This test requires only that the reading of the recording thermometer be compared with that of the indicating thermometer at a time when both are exposed to milk at a stabilized pasteurization temperature.

Procedure.-1. While milk is at a stabilized pasteurization temperature, read indicating thermometer.

2. Immediately inscribe on the recording-thermometer chart a line intersecting the recorded temperature arc at the pen location; record on the chart the indicating thermometer temperature; initial.

3. Record results.

Corrective Action. -If recording thermometer reads higher than indicating thermometer, the pen should be adjusted by the operator.

TEST 5. FLOW-DIVERSION DEVICE-PROPER ASSEMBLY AND FUNCTION

Reference.-Item 16p(D).

Application.-To all flow-diversion devices used with continuous-flow pasteurizers.

Frequency.-Upon installation and at least once each 3 months thereafter.

Criteria.-The flow-diversion device shall function correctly in operating situations and shall de-energize the metering pump in the event of malfunction or incorrect assembly.

1. LEAKAGE PAST VALVE SEAT(S)

Apparatus.-Suitable tools for disassembly of flow-diversion device and sanitary piping.

Method. -Observe the valve seat(s) of the flow-diversion device for leakage.

Procedure.-With the system operating with water, place the flow- diversion device in diverted-flow position. Disconnect the forward flow piping; observe the valve seat for leakage. Check leak escape ports to see if they are open.

Corrective action.-If leakage is noted, device must be dismantled and defective gaskets replaced or other suitable repairs made.

2. OPERATION OF VALVE STEM(S)

Apparatus.-Suitable tools for disassembly of flow-diversion device and sanitary piping.

Method.-Observe flow-diversion device valve stem(s) for ease of movement.

Procedures.-When a stem packing nut is used, tighten stem packing nut as much at possible. Operate system; place device in forward and diverted flow several times. Note freedom of action of valve stem.

Corrective action. -If valve action is sluggish, suitable adjustment or repair shall be made to permit stem to act freely in all positions, with packing nut, when used, fully tightened.

3. DEVICE ASSEMBLY, SINGLE STEM DEVICE

Apparatus.-Sanitary fitting wrench.

Method.-Observe function of metering pump when flow-diversion device is improperly assembled.

Procedures.-a. With HTST system in operation, unscrew by one-half turn, the 13H hex nut which holds the top of the valve to the valve body. This should de-energize the metering pump. This test should be run with no piping connected to the forward flow port of the device since there can be sufficient force from the piping to keep the forward flow port tightly clamped even though the hex nut is loosened.

b. With the HTST system in operation and the flow-diversion device in the diverted position, remove the connecting key located at the base of the valve stem. The metering pump should be de-energized.

Corrective action.-If metering pump fails to respond as indicated, immediate checks of the device assembly and wiring are required to locate and correct the cause.

4. DEVICE ASSEMBLY, DUAL STEM DEVICE

Apparatus.-None.

Method.-Observe function of metering pump when flow-diversion device is improperly assembled.

Procedures. -a. With the device in diverted-flow position, remove one actuator clamp.

b. Move the device to the forward-flow position and disconnect stem from actuator.

c. Move the device to the diverted-flow position and turn on the metering pump. The metering pump should not run.

d. Reassemble the device by moving it to the forward-flow position and reconnecting the stem to the actuator.

e. Move the device to the diverted-flow position and replace the actuator clamp.

f. Repeat the procedure for the other actuator.

Corrective action. -If metering pump fails to respond as indicated, an immediate check of the device assembly and wiring are required to locate and correct the cause.

5. MANUAL DIVERSION (when booster pump is installed in the HTST system)

Apparatus.-None.

Method.-Observe the response of the system to manual diversion.

Procedure.-With the HTST system in operation and the flow-diversion device in the forward-flow position, press the manual diversion button. This should (a) cause the valve to assume the divert position, and (b) de-energize the booster pump; the pressure differential between raw and pasteurized milk in the regenerator should be maintained.

Corrective Action.-If (a) and (b) above do not occur as described or the necessary pressure differential between raw and pasteurized milk is not maintained, the assembly and wiring of the HTST system must be immediately reviewed and the indicated deficiencies corrected.

6. RESPONSE TIME

Apparatus.-Stopwatch. The stopwatch should be used to determine that the response time interval does not exceed 1 second.

Method.-Determine the elapsed time between the instant of the activation of the control mechanism at cut-out temperature on declining temperature and the instant the flow-diversion device takes the fully diverted-flow position.

Procedure.-a. With water or oil bath at a temperature above cut-out temperature, allow the water or oil to cool gradually. At the moment the cut-out mechanism is activated, start the watch and the moment the flow-diversion device takes the fully-diverted position, stop the watch.

b. Record results.

Corrective Action. -Should response time exceed 1 second, immediate corrective action must be taken.

7. TIME DELAY INTERLOCK WITH METERING PUMP.

Application.-To dual stem flow-diversion devices with a manual forward-flow switch.

Apparatus.-None.

Method.-Determine that the device does not assume a manually induced forward-flow position while the metering pump is running.

Procedures.-With the system running in forward flow, move the control switch to the "Inspect" position and observe that the following events automatically occur in sequence:

a. The device immediately moves to the diverted-flow position and the metering pump is turned off.

b. The device remains in the diverted-flow position while the metering pump is running down.

c. After the metering pump stops turning, the device assumes the forward-flow position.

d. Repeat the above procedure by moving the control switch to the cleaned-in-place (CIP) position.

e. Record test results and seal the control enclosure.

Corrective action. -If the above sequence of events does not occur, either a timer adjustment or wiring change is required.

TEST 6. LEAK PROTECTOR VALVE

Reference.-Item 16p(D).

Application.-To all pasteurizer inlet and outlet valves.

Frequency.-Upon installation and at least once each 3 months thereafter.

Criteria.-No leakage of milk past the valve seat in any closed position.

Apparatus.-No supplementary materials required.

Method.-By observing when the piping is disconnected from the valve outlet whether or not leakage past the valve seat occurs when milk pressure is exerted against the upstream face of the valve.

Procedure.-1. During normal operation, while milk pressure is exerted against the valve inlet, fully close the valve and disconnect the outlet piping.

(Caution: Care must be taken to avoid contamination of the valves or the piping.)

2. Observe whether or not any milk is leaking past the valve seat into the valve outlet.

3. In the case of plug-type valves, turn the valve to the just-closed position, and examine for leakage into the valve outlet.

4. Reconnect the outlet piping.

5. Record identity of the valve, and findings, for office record.

Corrective Action. -If leakage past the valve seat should occur in any closed position, the valve plug should be reground, gaskets replaced, springs replaced or other necessary steps be taken to prevent leakage.

TEST 7. INDICATING THERMOMETERS ON PIPELINES-THERMOMETRIC RESPONSE

Reference.-Item 16p(D).

Application.-To all indicating thermometers located on pipelines and used for determination of milk temperatures during pasteurization.

Frequency.-Upon installation and once each 3 months thereafter.

Criteria.-Four seconds under specified conditions.

Apparatus.-Test thermometer, stopwatch, water bath (10-gallon can), agitator, heat supply, and indicating thermometer from pasteurizer.

Method.-By measuring the time required for the reading of the thermometer being tested to increase 12°F (7°C) through a specified temperature range (temperature range must include pasteurization temperature). The temperature used in the water or oil bath will depend upon the scale range of the thermometer to be tested.

Procedure.-1. Immerse indicating thermometer in water or oil bath heated to a temperature at least 19°F (11°C) higher than minimum scale reading on indicating thermometer. Bath temperature should be higher than maximum pasteurization temperature for which thermometer is used.

2. Immerse indicating thermometer in bucket of cold water for several seconds to cool it.

Note.-Continuous agitation of water baths during the performance of steps 3, 4, and 5 is required. Elapsed time between end of step 1, and beginning of step 3 should not exceed 15 seconds so hot water bath does not cool significantly.

3. Insert indicating thermometer in hot water or oil bath to proper bulb immersion depth.

4. Start stopwatch when indicating thermometer reads 19°F (11°C) below bath temperature.

5. Stop stopwatch when indicating thermometer reads 7°F (4°C) below bath temperature.

6. Record thermometric response time for office record.

Example. -On a thermometer with a range of 150°F to 175°F (66°C to 80°C) used at pasteurization temperatures of 161°F and 166°F (72°C and 75°C), a water bath of 170°F (77°C) could be used. 19°F (11°C) below 170°F (77°C) would be 151°F (66°C); 7°F (4°C) below 170°F (77°C) would be 163°F (73°C). Hence, after immersing the thermometer which has been previously cooled, in the 170°F (77°C) bath, the stopwatch is started when the thermometer reads 151°F (66°C) and stopped when it reads 163°F (73°C).

Note.-The test included the pasteurization temperature of 161°F and 166°F (72°C and 75°C).

Corrective Action.-If the response time should exceed 4 seconds, the thermometer should be replaced or returned for repair.

TEST 8. RECORDER/CONTROLLER-THERMOMETRIC RESPONSE

Reference.-Item 16p(B).

Application.-To all recorder/controllers used in connection with continuous-flow pasteurizers except those in which the flow-diversion device is located at the end of the cooler section.

Frequency.-Upon installation and at least once each 3 months thereafter.

Criteria.-Five seconds, under specified conditions.

Apparatus.-Previously tested indicating thermometer on pasteurizers), stopwatch, water or oil bath (10-gallon milk can), agitator, heat supply.

Method.-Measure the time interval between the instant when the recording thermometer reads 12°F (7°C) below the cut-in temperature and the moment of cut-in by the controller. This measurement is made when the sensing element is immersed in a rapidly agitated water or oil bath maintained at exactly 7°F (4°C) above the cut-in temperature.

Procedure. -1. Check and, if necessary, adjust the pen-arm setting of the recording thermometer in the proper reference arc to agree with the indicating thermometer reading at pasteurization temperature.

2. Determine the cut-in temperature of controller (Test 10), either while in normal operation or by using a water or oil bath.

3. Remove sensing element and allow to cool to room temperature.

4 Heat water or oil bath to exactly 7°F (4°C) above the cut-in temperature while vigorously agitating bath to insure uniform temperature.

5. Immerse recorder/controller bulb in bath. Continue agitation during items 6. and 7. below.

6. Start stopwatch when the recording thermometer reaches a temperature of 12°F (7°C) below the cut-in temperature.

7. Stop stopwatch when the controller cuts in.

8. Record thermometric response time for office record.

Corrective Action.-If the response should exceed 5 seconds, the recorder/controller should be repaired.

TEST 9. SETTING OF CONTROL SWITCHES-REGENERATOR PRESSURE

Reference.-Item 16p(D).

1. PRESSURE SWITCHES.-Used to control operation of booster pumps.

Application.-To all pressure switches controlling the operations of booster pumps on HTST pasteurizer systems employing regenerators.

Frequency. -Upon installation, each 3 months thereafter, after any change in the booster pump or the switch circuit, and/or whenever the pressure switch seal is broken.

Criteria.-The pump shall not operate unless there is at least a 1-pound pressure differential on the pasteurized milk side of the regenerator.

Apparatus. -Sanitary pressure gauge and pneumatic testing device, for checking and adjusting pressure switch settings.

A simple inexpensive pneumatic testing device may be made from a discarded 2 inch-7BX sanitary tee, with two additional 13H nuts, one of which is provided with a 16A cap, drilled and tapped for a 1/2-inch galvanized iron nipple for the air connection. A hose connection is made to a compressed air source in the plant by means of a snap-on fitting. The air pressure can be controlled by an inexpensive pressure reducing valve (range 0-60 psig) followed by a 1/2-inch globe type bleeder valve connected into the side outlet of a 1/2-inch tee installed between the pressure reducing valve and the testing device. The pressure switch to be tested is disconnected from the pasteurizer and connected to another of the outlets of the sanitary tee, and the pressure gauge is connected to the third outlet of the sanitary tee. By careful manipulation of the air pressure reducing valve and the air bleeder valve, the air pressure in the testing device may be regulated slowly and precisely. (In operating the device, care should be taken to avoid exposing the pressure switch and the sanitary pressure gauge to excessive pressure which might damage them. This can be done by first closing off the air pressure regulating valve and opening fully the bleeder valve; these may then be manipulated slowly to bring the air pressure in the testing device within the desired range.) A test light of proper voltage can be placed in series with the pressure switch contact and in parallel with the electrical load (booster pump starter) so the actuation point may be readily determined.

Method. -Check and make adjustment of pressure switch so as to prevent the operation of the booster pump unless the pressure on the pasteurized milk side of the regenerator is greater by at least 1 psi than any pressure that may be generated on the raw side.

Procedure.-(a) Determine maximum pressure of booster pump.

(1.) Install sanitary pressure gauge in tee at discharge of booster pump.

(2.) Operate the pasteurizer with water, with the flow-diversion device in forward-flow position, the metering pump operating at minimum speed possible, and the booster pump operating at its rated speed. If vacuum equipment is located between the raw outlet from the regenerator and the metering pump, it should be bypassed while this determination is made.

(3.) Note maximum pressure indicated by pressure gauge under these conditions.

(b) Check and set the pressure switch.

(1.) Install a sanitary pressure gauge of known accuracy on the pneumatic testing device to which the pressure switch sensing element should also be connected.

(2.) Remove the seal and cover to expose adjustment mechanism on pressure switch.

(3.) Operate the testing device and determine the pressure gauge reading at the cut-in point of the pressure switch which will light the test lamp. (If the switch is short circuited, the lamp will be lighted before air pressure is applied.)

(4.) The cut-in point should be adjusted, if necessary, so as to occur at a pressure gauge reading at least 1 psi greater than the maximum booster pump operating pressure, as determined under section a. of this method. Where adjustment is necessary, refer to manufacturer's instructions for adjusting procedure. After adjustment, recheck actuation point and readjust if necessary.

(5.) Replace cover and seal the pressure switch and restore sensing element to original location.

(6.) Record test results for the office record.

2. TIME DELAY SWITCHES.-Used to control operation of booster pumps.

Application.-To all time-delay switches controlling operation of booster pumps.

Frequency.-Upon installation, after any change in the pump or relay circuit and whenever seal is broken.

Criteria.-The booster pump shall not operate until the pasteurized milk has achieved a pressure at least 1 pound greater than the maximum pressure developed by the booster pump.

Apparatus.-Accurate stopwatch, graduated at intervals not to exceed 0.2 of 1 second, pressure gauge or manometer.

Method.-Reference: Dashiell, W. N., Use of Time Delay Relay To Control Booster Pump Operation. Journal of Milk and Food Technology, 21:7. July 1958.

Procedure.-a. Operate pasteurizers with water with the flow-diversion device in forward-flow position, metering pump operating at minimum speed, booster pump at rated speed. Vacuum equipment not operating or bypassed.

b. Determine the maximum pressure developed at the discharge of the booster pump. Following the determination of the height of the liquid level, add at least 3 feet to provide the 1-pound pressure differential equivalent of 0.7 feet of water column to compensate for difference in the specific gravity between water at 161°F (72°C) and raw milk at 40°F (4°C). The pasteurized liquid level must rise to the computed elevation, above the outlet level of the booster pump and be vented to the atmosphere at this or higher level.

c. Time the interval from the moment the forward flow is established until the pasteurized liquid level rises to the required elevation. The time measurement shall be made at the beginning of a run when no water is in the pasteurized product line. The booster pump shall not be operating.

d. The time delay relay shall be installed in the circuit, interlocked with the metering pump, forward-flow of the flow-diversion device and the booster pump. Adjust the time delay setting to provide the time interval. Check the setting several times. Seal the time delay relay.

e. Record for permanent office record.

Corrective Action. -Adjust pasteurized milk pipe to proper elevation. If time delay relay is not accurate, return for repair.

3. PRESSURE GAUGES.-Used with booster pump operations

Application.-To all required pressure gauges used to measure relative raw milk and pasteurized milk pressure in HTST regenerators.

Frequency. -Upon installation, each 3 months thereafter, and whenever the gauges are adjusted or repaired.

Criteria.-Required pressure gauges shall be accurate.

Apparatus. -Identical testing device used to check proper operation of pressure switch (Test 9, 1).

A pressure gauge of known accuracy is connected to one outlet of the test apparatus. The gauge being checked is connected to the second outlet of the sanitary tee. Air is bled into the system through the third outlet and comparative readings made. Record test results for office record.

Corrective Action. -Inaccurate gauges should be returned to the factory for repair. It is not recommended that the plant operator attempt the adjustment of pressure gauges.

4. DIFFERENTIAL PRESSURE CONTROLLER

Application.-To all differential pressure controllers used to control operation of booster pumps on HTST and HHST systems, or used to control operation of flow-diversion devices on HHST systems when no vacuum breaker is located downstream from the holding tube.

Frequency. -Upon installation, each 3 months thereafter, and whenever the differential pressure controller is adjusted or repaired.

Criteria.-The booster pump shall not operate or the pasteurizer shall not operate in forward flow unless the product pressure in the pasteurized side of the regenerator is at least 1 psi greater than the product pressure in the raw side of the regenerator. When the differential pressure controller is used to control the flow-diversion device on HHST systems, and improper pressures occur in the regenerator, the flow-diversion device shall move to the diverted-flow position and remain in diverted flow until proper pressures are reestablished in the re-generator and 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 section 2.2(a) of this Title.

Apparatus.-A sanitary pressure gauge and a pneumatic testing device described under PRESSURE SWITCHES (Test 9,1) above can be used for checking and adjusting the differential pressure switch setting.

Method. -The differential pressure switch is checked and adjusted to prevent operation of the booster pump, or prevent forward flow, unless the product pressure in the pasteurized side of the regenerator is at least 1 psi greater than the pressure in the raw side of the regenerator.

Procedures.-a. Loosen the process connection at both pressure sensors and wait for any liquid to drain through the loose connections. Both pointers should be within 0.5 psi of 0 psig. If not, adjust pointer(s) to read 0 pounds psig.

b. Remove both sensors from the process and mount them in a tee, either at the discharge of the booster pump, or connected to the pneumatic testing device. Note the separation between the two pointers. The change in elevations of the sensors will have caused some change in the zero readings. Turn on the booster pump switch and depress the test push button to operate the booster pump. If the pneumatic testing device is used in lieu of the booster pump, adjust air pressure to the normal operating pressure of the booster pump. Note that the pointer separation is within 1 psi of that observed before pressure was applied. If not, the instrument requires adjustment or repair.

c. Return the pressure sensors to their normal process locations and turn off the booster pump switch. Manually move and hold the white pointer (raw side of the regenerator) at the normal operating pressure of the booster pump. Press the test push button while manually moving the orange pointer (pasteurized side of the regenerator) upscale until the pilot light turns on, then slowly move the orange pointer downscale until the pilot light turns off. The pilot light should not turn on until the orange pointer is at least 2 psi higher than the white pointer, and the pilot light should turn off when the orange pointer is no less than 2 psi higher than the white pointer. If necessary, adjust the differential setting. The 2 psi differential represents the sum of the 1 psi differential required between raw and pasteurized product in the regenerator, plus the 1 psi imprecision permitted between the two pressure sensors.

d. Seal the instrument and record test results for the office record.

TEST 10. MILK-FLOW CONTROLS-MILK TEMPERATURES AT CUT-IN AND CUT-OUT

References.-Item 16p(B), 16p(D).

Milk-flow controls shall be tested for milk temperature at cut-in and cut-out by one of the following applicable tests at the frequency prescribed:

1. Application.-All recorder/controllers used in connection with HTST pasteurizers except those in which the flow-diversion device is located at the end of the cooler section.

Frequency.-Upon installation and quarterly by the regulatory agency; daily by the plant operator.

Criteria.-No forward flow until pasteurization temperature has been reached. Flow diverted before temperature drops below minimum pasteurization temperature.

Apparatus.-No supplemental materials needed.

Method.-By observing the actual temperature of the indicating thermometer at the instant forward flow starts (cut-in) and stops (cut-out).

Procedure.-a. Cut-in temperature.

(1.) While milk or water is completely flooding the sensing element of the recorder/controller and the indicating thermometer, increase the heat gradually so as to raise the temperature of the water or milk at a rate not exceeding 1°F (0.5°C) every 30 seconds.

(2.) Observe the indicating thermometer reading at the moment the forward flow starts (i.e., flow-diversion device moves). Observe that the frequency pen reading is synchronized with the recording pen on the same reference arc.

(3.) Record the indicating thermometer reading on the recorder chart: inscribe initials. The regulatory agency shall record test findings.

b. Cut-out temperature.

(1.) After the cut-in temperature has been determined and while the milk or water is above the cut-in temperature, allow the water to cool slowly at a rate not exceeding 1°F (0.5°C) per 30 seconds. Observe indicating thermometer reading at the instant forward flow stops.

(2.) Record the indicating thermometer reading on the recorder chart.

Corrective Action.-Should the reading be below the minimum pasteurization temperature, the cut-in and cut-out mechanism and/or the differential temperature mechanism should be adjusted to obtain proper cut- in and cut-out temperatures by repeated tests. When compliance is achieved, seal the controller mechanism.

2. Application.-All HHST pasteurizers using indirect heating.

Frequency.-Upon installation, and every 3 months thereafter; whenever the thermal controller seal is broken.

Criteria.-The pasteurizer shall not operate in forward flow unless pasteurization temperature has been achieved. The product flow shall be diverted at a temperature no lower than the chosen pasteurization standard.

Apparatus.-No supplemental materials needed.

Method.-The cut-in and cut-out temperatures are determined by observing the actual temperature in the constant temperature bath at which the two sensing elements signal for forward flow (cut-in) and diverted flow (cut-out).

Procedures.-a. Wire the test lamp in series with the control contacts of the sensing element (holding tube). Immerse this sensing element in the constant temperature bath. Raise the bath temperature at a rate not exceeding 1°F (0.5°C) every 30 seconds. Observe the temperature reading at the cut-in temperature. Record the temperature for the office record.

b. After the cut-in temperature has been determined and while the bath is above the cut-in temperature, allow the bath to cool slowly at a rate not exceeding 1°F (0.5°C) per 30 seconds. Observe the temperature reading on the controller when the test lamp goes out (cut-out temperature). Determine that the cut-out temperature on the thermal limit controller is equivalent to or greater than the chosen pasteurization standard. Where adjustment is necessary, refer to manufacturer's instructions. After adjustment, repeat the procedure above and when the results are satisfactory, record results for the office records.

c. Repeat the procedure for the other sensing element, (flow-diversion device). When proper cut-out temperature has been verified for both sensing elements, seal the controller system.

3. Application.-All HHST pasteurizers using direct contact heating.

Frequency.-Upon installation, and every 3 months thereafter; whenever the thermal limit controller seal is broken.

Criteria.-The pasteurizer shall not operate in forward flow unless pasteurization temperature has been achieved. The product flow shall be diverted at a temperature no lower than the chosen pasteurization standard.

Apparatus.-No supplemental materials needed.

Method.-The cut-in and cut-out temperatures are determined by observing the actual temperature in the constant temperature bath at which each of the three sensing elements signals for forward flow (cut-in) and diverted flow (cut-out).

Procedures.-a. Wire the test lamp in series with the control contacts of the sensing element (the holding tube). Immerse this sensing element in the constant temperature bath. Raise the bath temperature at a rate not exceeding 1°F (0.5°C) every 30 seconds. Observe the temperature reading on the controller when the test lamp lights (cut-in temperature). Record the temperature for the office record.

b. After the cut-in temperature has been determined and while the bath is above the cut-in temperature, allow the bath to cool slowly at a rate not exceeding 1°F (0.5°C) per 30 seconds. Observe the temperature reading on the controller when the test lamp goes out (cutout temperature). Determine that the cut-out temperature on the thermal limit controller is equivalent to or greater than the chosen pasteurization standard. Where adjustment is necessary, refer to manufacturer's instructions. After adjustment, repeat the procedure above and when the results are satisfactory, record results for the office record.

c. Repeat the procedure for the other two sensing elements, i.e., the vacuum chamber and flow-diversion device. Rewire the test lamp in series with the control contacts from each sensing element, respectively. When proper cut-out temperatures have been verified for all three sensing elements, seal the controller system.

TEST 11. CONTINUOUS FLOW HOLDERS-HOLDING TIME

Reference.-Item 16p(B).

Continuous flow holders shall be tested for holding times by one of the applicable tests.

1. Application.-To all HTST pasteurizers employing a holding time of 15 seconds or longer.

Frequency.-As set forth in application 2 below.

Criteria.-Every particle of milk shall be held for at least 15 seconds in both the forward- and diverted-flow positions.

Apparatus.-Electrical conductivity measuring device, Appendix 4 (I.) capable of detecting change in conductivity, equipped with standard electrodes; table salt (sodium chloride), 50 ml. syringe; stopwatch; suitable container for salt solution.

Method.-The holding time is determined by timing the interval for an added trace substance to pass through the holder. Although the time interval of the fastest particle of milk is desired, the conductivity test is made with water. The results found with water are converted to the milk flow time by formulation since a pump may not deliver the same amount of milk as it does water.

Procedure.-a. Examine the entire system to insure that all flow promoting equipment is operating at maximum capacity and all flow impeding equipment is so adjusted or bypassed as to provide the minimum of resistance to the flow. There shall be no leakage on the suction side of the timing pump.

b. Adjust variable speed pump to its maximum capacity (preferably with a new belt and full size impellers). Check homogenizers for seals and/or gears or pulley identification.

c. Install one electrode at the inlet to the holder and the other electrode in the holder outlet. Close the circuit to the electrode located at the inlet to the holder.

d. Operate the pasteurizer using water at pasteurization temperature, with flow-diversion device in forward-flow position.

e. Quickly inject 50 ml. of saturated sodium chloride solution into the holder inlet.

f. Start the stopwatch with the first movement of the indicator of a change in conductivity. Open the circuit to the inlet electrode and close the circuit to the electrode at the outlet of the holder.

g. Stop the stopwatch with the first movement of the indicator of a change in conductivity.

h. Record results

i. Repeat the test six or more times, until six successive results are within 0 5 seconds of each other. The average of these six tests is the holding time for water in forward flow. When consistent readings cannot be obtained, purge the equipment, check instruments and connections, and check for air leakage on suction side. Repeat tests. Should consistent readings not be obtained, use the fastest time as the holding time for water.

j. Repeat steps d. through i. for testing time on water in diverted flow.

k. With the pump at the same speed and equipment adjusted as in a. above, time the filling of a 10-gallon can with a measured weight of water using the discharge outlet with the same head pressure as in normal operation. Average the time of several trials. (Since flow rates of the large capacity units make it very difficult to check by filling a 10-gallon can, it is suggested that a calibrated tank of considerable size be used.)

l. Repeat procedure k. using milk.

m. Compute the holding time for milk from the following formula by weight, using the average specific gravity. Compute separately for forward flow and diverted flow.

Holding time for milk=(1.032(TMw)/Ww) (by weight), in which-

1.032 = specific gravity for milk;

T = average holding time for water;

Mw = average time required to deliver a measured weight of milk.

Ww = average time required to deliver an equal weight of water.

n. Record results for office record.

Corrective Action.-When the computed holding time for milk is less than that required either in forward flow or diverted flow, the speed of the timing pump shall be reduced or adjustment made in the holding tube, and the timing test repeated until satisfactory holding time is achieved. Should an orifice be used to correct the holding time in diverted flow, there should be no excessive pressure exerted on the underside of the valve seat of the flow-diversion device. Governors shall be sealed on motors that do not provide a constant speed as provided in Item 16p(B) § 2.46 b.6.ii.

2. Application. -To all HHST pasteurizers using indirect heating.

Frequency.-Upon installation and quarterly thereafter, whenever seal on speed setting is broken: any alteration is made affecting the holding time, the velocity of the flow (such as replacement of pump, motor, belt, drive or driven pulleys, or decrease in number of HTST plates) or the capacity of holding tube: or whenever a check of the capacity indicates a speedup. Except that semiannually two canfill measurements may be substituted for electrical conductivity measurements. The canfill measurements shall be conducted as provided in Item k. of Test 11 of this Appendix.

Criteria.-Every particle of product shall be held for the minimum holding time in both the forward-and diverted-flow positions.

Apparatus.-No supplemental materials needed.

Method.-Fully developed laminar flow is assumed and holding tube length is calculated. An experimental determination of pumping rate is required; this is accomplished by determining the time required for the pasteurizer to fill a vessel of known volume, converting these data by division to obtain flow rate in gallons per second, and multiplying this value by the proper number in Table 8 of this paragraph to obtain the required length of holding tube. Holding tube lengths for HHST pasteurizers with indirect heating for a pumping rate of 1 gallon/second are:

TABLE 8

Procedures. -a. Examine the entire system to ensure that all flow promoting equipment is operating at maximum capacity and all flow impeding equipment is so adjusted or bypassed to provide the minimum of resistance to the flow. This means that in-line filters must be removed, booster pumps must be in operation, and vacuum equipment in the system must be operating at a maximum vacuum. Also, before the tests are begun, the pasteurizer should be operated at maximum flow for a sufficient time to purge air from the system (about 15 minutes) and pipe connections on the suction side of the metering pump should be made tight enough to exclude entrance of air. With the pasteurizer operating with water, adjust the metering pump to its maximum capacity, preferably with a new belt and full-size impellers.

b. Determine that no flow exists in the diverted line, and measure the time required to deliver a known volume of water at the forward-flow discharge line. Repeat the test at least once to determine that the measurements are consistent.

c. Repeat the steps in paragraphs a. and b. of this procedure in diverted flow by collecting the effluent at the discharge of the divert line.

d. Select the greatest flow rate (shortest delivery time for the known volume) and calculate the flow rate in gallons per second by dividing the known volume by the time required to collect the known volume. Multiply this value with the appropriate value in Table 8 to determine the required holding tube length.

e. Determine the number and type of fittings in the holding tube and convert these to equivalent lengths of straight pipe with the use of Table 9 of this paragraph. Determine the total length of the holding tube by adding the equivalent lengths of the fittings to the measured straight lengths of pipe. Record the number and type of fittings, the number and length of straight pipes, and the holding tube configuration for the office record. If the temperature sensor is located at the beginning of the holding tube, the holding tube shall be protected against heat loss by material that is impervious to water.

TABLE 9 Centerline Distances of 3-A Fittings

Alternate procedure. -For pasteurizers of large capacity, the method of measuring flow rate at the discharge of the pasteurizer is inconvenient, and the following alternate test procedure may be used. Remove the divert line from the raw-product supply tank, and turn off the product pump feeding the raw-product supply task. Suspend a sanitary dip stick in the raw-product supply tank, and operate the pasteurizer at maximum capacity. Record the time required for the water level to move between two graduations on the dip stick. The volume of water is calculated from the dimensions of the raw-product supply tank and the drop in water level. Flow rate is determined as follows: Divide the volume of water removed from the raw-product supply tank by the time required to remove it.

Corrective action. -If the length of the holding tube is shorter than the calculated length, reseal the metering pump at a slower maximum speed, or lengthen the holding tube, or both, and repeat the above determination.

3. Application.-To all HHST pasteurizers using direct contact heating.

Frequency.-When installed and semiannually thereafter; whenever seal on the speed setting is broken; whenever any alteration is made affecting the holding time, the velocity of the flow, e.g., replacement of pump, motor, belt, driver or driven pulley, or decrease in the number of heat exchange plates, or the capacity of the holding tube; whenever a check of the capacity indicates a speedup.

Apparatus.-No supplemental materials needed.

Criteria.-Every particle of product shall be held for the minimum holding time in both forward- and diverted-flow positions.

Method.-Fully developed laminar flow and a temperature increase by steam injection of 120°F (67C) are assumed, the temperature-time standard is chosen by the processor, and the required holding tube length is calculated from an experimental determination of pumping rate.

Procedures. -a. Examine the entire system to ensure that all flow promoting equipment is operating at a maximum capacity and all flow impeding equipment is so adjusted or bypassed as so provide the minimum resistance to the flow. Remove in-line filters, make certain booster pumps are operating and that vacuum equipment in the system is operating at maximum vacuum. Also, before the tests are begun, operate the pasteurizer at maximum flow for a sufficient time to purge the air from the system (about 15 minutes) and tighten pipe connections on the suction side of the metering pump to exclude entrance of air. With the pasteurizer operating on water, adjust the metering pump to its maximum capacity. Determine that no flow exists in the diverted line, and measure the time required to deliver a known volume of water at the discharge of the pasteurizer in forward flow. Repeat the test at least twice to determine that the measurements are consistent.

b. Repeat the last step (a. above) in diverted flow by collecting the effluent at the discharge of the divert line. Select the greatest flow rate, the shortest delivery time for the known volume, and calculate the flow rate in gallons per second by dividing the known volume by the time required to collect the known volume. Multiply this value, gallons per second, with the appropriate value in Table 10 of this paragraph to determine the required holding tube length. Holding tube lengths for direct contact heating pasteurizers with a pumping rate of 1 gallon/second are:

TABLE 10

c. Determine the number and type of fittings in the holding tube, and convert these to equivalent lengths of straight pipe with the use of Table 9.

Determine the total length of the holding tube by adding the equivalent lengths of the fittings to the measured lengths of straight pipe. If the actual holding tube length is equivalent to or greater than the required holding tube length, record the number and type of fittings, the number and length of straight pipes, and the holding tube configuration, for the office record. Make sure that the holding tube slopes upward at least 0.25 inch per foot. The holding tube shall also be protected against heat loss with insulation that is impervious to water if the temperature sensor is located at the beginning of the holding tube.

Alternate procedure. -For pasteurizers of large capacity, the method of measuring flow rate at the discharge of the pasteurizer is inconvenient, and the following alternate test procedure may be used. Remove the divert line from the raw product supply tank, and turn off the product pump feeding the raw-product supply tank. Suspend a sanitary dip stick in the raw-product supply tank, and operate the pasteurizer at maximum capacity. Record the time required for the water level to move between two graduations on the dip stick. Calculate the volume of water from the dimensions of the raw-product supply tank and the drop in water level. Determine flow rate as follows: Divide the volume of water, in gallons, removed from the raw-product supply tank by the time, in seconds, required to remove it. Then use Table 10 to calculate the required holding tube length.

Corrective action. -If the length of the holding tube is shorter than the calculated length, reseal the metering pump at a slower maximum speed, or lengthen the holding tube, or both, and repeat the procedure.

TEST 12. THERMAL LIMIT CONTROLLER FOR CONTROL-SEQUENCE LOGIC

References.-Items 16p(B), 16p(D).

Thermal limit controllers used with HHST 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.

1. Application. -To all HHST pasteurizers using indirect heating.

Frequency.-Upon installation, and every 3 months thereafter.

Criteria.-The pasteurizer shall not operate in forward flow until the product surfaces downstream from the holding tube have been sanitized on start up; surfaces shall be exposed to fluid at pasteurization temperature for at least pasteurization time. If the product temperature falls below the pasteurization standard in the holding tube, forward flow shall not be reachieved until the product surfaces downstream from the holding tube have been resanitized.

Apparatus.-A constant temperature bath of water or oil and the test lamp from the pneumatic testing device described in Test 9, 1 can be used to check the control-sequence logic of the thermal limit controller.

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.

Procedures. -a. Heat a constant temperature water or oil bath a few degrees above the cut-in temperature on the thermal limit controller. 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.

b. Immerse the sensing element of the flow-diversion device in the bath, which is above the cut-in temperature. The test lamp should remain unlighted, i.e., diverted flow. Leave the sensing element in the bath

c. 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 second.

d. Remove the sensing element of the flow-diversion device from the bath. the test lamp should remain lighted, i.e., forward flow.

e. Remove the holding tube sensing element from the bath The test lamp should go out immediately, i.e., diverted flow.

f. Reimmerse the sensing element of the holding tube in the bath. The test lamp should remain unlighted, i.e., diverted flow.

Corrective action. -If the control sequence logic of the thermal unit controller does not follow this pattern, the instrument shall be required to conform to this logic.

2. Application.-To all HHST pasteurizers using direct contact heating.

Frequency.-Upon installation, and every 3 months thereafter.

Criteria.-The pasteurizer shall not operate in forward flow until the product surfaces downstream from the holding tube have been sanitized on start up; surfaces shall be exposed to fluid at pasteurization temperature for at least pasteurization time. If the product temperature falls below the pasteurization standard in the holding tube, forward flow shall not be reachieved until the product surfaces downstream from the holding tube have been resanitized.

Apparatus.-A constant temperature bath of water or oil and the test lamp from the pneumatic testing device described in Test 9, 1 can be used to check the control-sequence logic of the thermal limit controller.

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.

Procedures.-a. Heat a water or oil bath to a constant temperature, a few degrees above the cut-in temperature on the thermal limit controller. 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. Before performing this test, make sure the pressure switches which must be closed to achieve forward flow, have also been bypassed.

b. Immerse the sensing element from the flow-diversion device, in the bath, which is above the cut-in temperature. The test lamp should remain unlighted, i.e., diverted flow. Remove this sensing element from the bath.

c. Immerse the sensing element from the vacuum chamber, in the bath. The test lamp should remain unlighted, i.e., diverted flow. Remove the sensing element from the bath.

d. Immerse two sensing elements, from the vacuum chamber and flow-diversion device, in the bath. The test lamp should remain unlighted, i.e., diverted flow. Leave the two sensing elements in the bath.

e. Immerse the third sensing clement, 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.

f. Remove one sensing element, the flow-diversion device, from the bath. The test lamp should remain lighted, i.e., forward flow.

g. Remove another sensing element, the vacuum chamber, from the bath. The test lamp should remain lighted, i.e., forward flow.

h. Remove the last sensing element, the holding tube, from the bath. The test lamp should go out, i.e., diverted flow, immediately.

i. Reimmerse the sensing element, holding tube, in the bath. The test lamp should remain unlighted, i.e., diverted flow.

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 13. SETTING OF CONTROL SWITCHES FOR PRODUCT PRESSURE IN THE HOLDING TUBE

Reference.-Item 16p(B).

Application.-To all HHST pasteurizers using direct contact heating.

Frequency.-Upon installation, and every 3 months thereafter; whenever the pressure switch seal is broken; and whenever the operating temperature is changed.

Criteria.-The pasteurizer shall not operate in forward flow unless the product pressure in the holding tube is at least 10 psi above the boiling pressure of the product.

Apparatus.-A sanitary pressure gauge and a pneumatic testing device described in Test 9,1 can be used for checking and adjusting the pressure switch setting.

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 10 psi above the boiling pressure of the product.

Procedure. -From Figure 31 determine the pressure switch setting necessary for the operating temperature (not the diversion temperature) being used in the process. Install the sanitary pressure gauge of known accuracy and the pressure switch sensing element on the pneumatic testing device. Remove the seal and cover to expose the adjustment mechanism on the pressure switch. Place the test lamp in series with the pressure switch contacts or use some other method to monitor the cut-in signal. 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 lighted before air pressure is applied. Determine that the cut-in pressure on the switch is equivalent to or greater than the required pressure from Figure 31. Where adjustment is necessary, refer to manufacturer's instruction. After adjustment, repeat the procedure set out in this paragraph. When the results are satisfactory, seal the pressure switch setting and record the results for the office record. For each operating temperature on HHST pasteurizers using direct contact heating, the product pressure switch setting is as follows:

Click to view image

TEST 14. SETTING OF CONTROL SWITCHES FOR DIFFERENTIAL PRESSURE ACROSS THE INJECTOR

Application.-To all HHST pasteurizers using direct contact heating.

Frequency.-Upon installation and every 3 months thereafter; whenever the differential pressure controller seal is broken.

Criteria.-The pasteurizer shall not operate in forward flow unless the product pressure drop across the injector is at least 10 psi.

Apparatus.-A sanitary pressure gauge and a pneumatic testing device described in Test 9,1 can be used for checking and adjusting the differential pressure controller.

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 10 psi.

Procedure.-Remove both pressure sensing elements from their original locations on the pasteurizer, install the sanitary pressure gauge of known accuracy and the pressure sensing element that is installed prior to steam injection on the pneumatic testing device. 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. Wire the test lamp in series with the microswitch of the differential pressure controller or use the method provided by the instrument manufacturer to monitor the cut-in signal. Apply air pressure to the sensing element and determine the pressure gauge reading at the cut-in point of the differential pressure switch that will light the test lamp. Determine that the differential pressure cut-in on the controller is at least 10 psi. Where adjustment is necessary, refer to manufacturer's instructions. After adjustment, repeat the procedure set forth in this paragraph. When the results are satisfactory, seal the instrument and record the results for the office record.