New York Codes, Rules and Regulations
Title 1 - DEPARTMENT OF AGRICULTURE AND MARKETS
Appendices
Appendix 10
PASTEURIZATION EQUIPMENT AND
CONTROLS--TESTS
(cf. Part 3)
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 six Fahrenheit degrees or not more than four 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 and samples to be taken 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(C).
Application.--To all indicating thermometers used for measurement of product temperature during pasteurization.
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. 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) 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(C).
Application.--To all recording and recorder/controller thermometers used to record product 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. Test thermometer meeting specifications under Appendix 9.
2. Water or oil bath and agitator.
3. Suitable means of beating 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. 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, indicating thermometer reading.
6. Remove sensing element from bath at operating temperatures and immerse in melting ice for not less 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.
TEST 3. RECORDING THERMOMETERS--TIME ACCURACY
Reference.--Item 16p(C).
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(C).
Application.--To all recording and recorder/controller thermometers used to record product 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 product at a stabilized pasteurization temperature.
Procedure.--
1. While product 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(A).
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 stem(s) for ease of movement.
Procedures. --When a stem packing nut is used, tighten stem packing nut as much as possible. Operate system; place device in forward and diverted flow several times. Note freedom of action of valve system.
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 pomp 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 located on the valve bonnet cover plate. 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 product 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 product 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. INDICATING THERMOMETERS ON PIPELINES--THERMOMETRIC RESPONSE
Reference.--Item 16p(A).
Application.--To all indicating thermometers located on pipelines and used for determination of product temperatures during pasteurization.
Frequency.--Upon installation and once each 3 months thereafter.
Criteria.--Four seconds under specified conditions.
Apparatus.--Pipeline 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 bath will depend upon the scale range of the thermometer to be tested.
Procedure.--
1. Immerse indicating thermometer in water 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 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 a pasteurization temperature 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 had 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 (72° C) and 166° F (75° C).
Corrective Action.--If the response time should exceed 4 seconds, the thermometer should be replaced or returned for repair.
TEST 7. RECORDER/CONTROLLER--THERMOMETRIC RESPONSE
Reference.--Item 16p(A).
Application.--To all recorder/controllers used in connection with continuous flow pasteurizers.
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 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 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 No. 8), either while in normal operation or by using a water bath.
3. Remove sensing element and allow to cool to room temperature.
4. Heat water 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 water 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 8. PRODUCT-FLOW CONTROLS--PRODUCT TEMPERATURES AT CUT-IN AND CUT-OUT
References.--Items 16p(A), 16p(C)
Product--flow controls shall be tested for product temperature at cut-in and cut-out by one of the following applicable tests at the frequency prescribed:
Application. --All recorder/controllers used in connection with HTST pasteurizers.
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.--
1. Cut-in temperature.
a. While the product 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 product at a rate not exceeding 1° F (0.5° C) every 30 seconds.
b. 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.
c. Record the indicating thermometer reading on the recorder chart; inscribe initials. The regulatory agency shall record test findings.
2. Cut-out temperature.
a. After the cut-in temperature has been determined and while the product 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.
b. 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.
TEST 9. SETTING OF CONTROL SWITCHES--REGENERATOR PRESSURE
Reference.--Item 16p(B).
1. PRESSURE SWITCHES.--Used to control operation of booster pumps.
Application.--To all pressure switches controlling the operation 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 product 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 2inch-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 so 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 product 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 a. preceding. 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 product 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 product at 40° F (5° 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 product 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 product and pasteurized product 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 systems.
Frequency. --Upon installation, each 3 months thereafter, and whenever the differential pressure controller is adjusted or repaired.
Criteria. --The booster pump shall not operate 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.
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. CONTINUOUS FLOW HOLDERS--HOLDING TIME
Reference.--Item 16p(A).
Application. --To all HTST pasteurizers employing a holding time of 15 seconds or longer.
Frequency. --Upon installation and semiannually 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.
Criteria.--Every particle of product shall be held for at least 15 seconds in both the forward- and diverted-flow positions.
Apparatus.--Electrical conductivity measuring device, Appendix 10(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 product is desired, the conductivity test is made with water. The results found with water are converted to the product flow time by formulation since a pump may not deliver the same amount of product as it does water.
Procedure.--
1. 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.
2. 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.
3. 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.
4. Operate the pasteurizer using water at pasteurization temperature, with flow-diversion device in forward-flow position.
5. Quickly inject 50 ml. of saturated sodium chloride solution into the holder inlet.
6. 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.
7. Stop the stopwatch with the first movement of the indicator of a change in conductivity.
8. Record results.
9. 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.
10. Repeat steps 4. through 9. for testing time on water in diverted flow.
11. With the pump at the same speed and equipment adjusted as in 1. 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.)
12. Repeat procedure 11. using milk.
13. 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.
14. 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(A), section 3.25(b)(6)(ii) of this Title.
