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U.S. Department of Health and Human Services


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M-I-85-8: Questions and Answers from HTST Training Course





                              200 ~C~ Street, S.W.
                              Washington, D.C. 20204
                              August 6, 1985
TO:       All Regional Food and Drug Directors
          Attn: Regional Milk Specialists
FROM:     Milk Safety Branch (HFF-346)
SUBJECT:  Questions and Answers from HTST Training Course
Enclosed are copies of questions and answers presented as a result of a
HTST Training Course in Region VII.
Copies are enclosed for distribution to the State milk sanitation regulatory
agencies and State milk rating officers in your Region.
                         Robert L. Sanders
                         Deputy Chief, Milk Safety Branch
                         Division of Cooperative Programs
                         Center for Food Safety and
                           Applied Nutrution
From:     Milk Safety Branch, HFF-346
Subject:  Questions/issues from HTST Training Course, M-I-85-8
To:       R.W. Wilson, Senior Regional Milk Specialist, Region VII,
          This is in response to your recent memo concerning the
          above subject:
1.Q. Constant Level Tank (CLT) - being higher than the bottom of the
     press with an automatic valve which dumps to the floor, thus
     allowing the regenerator to drain.  This does not sound bad at first,
               a.   What triggers the valve?
               b.   Is there any limit to the height of the CLT?
               c.   Could you have a silo tank in this position?
     A.   The PMO, Section 7, Item 16p(D), requires that all milk to
          milk regenerators be constructed, installed and operated so
          that the pasteurized or aseptic product in the regenerator
          will be under greater pressure than the raw milk in the
          regenerator at all times.  We are not aware of any system
          or method of accomplishing this other than the use of a
          constant level tank, designed and located in such a manner
          that the overflow of its top rim is lower than the lowest
          milk level in the regenerator.  We cannot visualize the use
          of valves to accomplish this required pressure differential at
          all times.
2.Q. Amount of Product - The Pasteurized Milk Ordinance requires the
     "Amount and Name of Pasteurized Milk or Milk Product
     Represented by Each Batch or Run on Pasteurized Milk or Milk
     Product Represented by Each Batch or Run on the Chart."  In the
     past, I have not asked for or insisted that the "Amount of Product:
     to be on the HTST chart?
     A.   The PMO Section 7, Item 16p(E), specifies that temperature
          recording charts have the "Amounts and name of
          pasteurized milk or milk product represented by each batch
          or run on the chart."  From recent incidents in investigating
          food borne outbreaks related to dairy products, the amounts
          of product processed has been essential to the investigation.
          Should the occasion ever arise when a dairy plant or
          regulatory agency be required to produce recording
          thermometer charts as evidence, it is essential that the
          charts be accurate, legible, and complete with all required
3.Q. Do we have to time the Taylor Magnetic flowmeter in the forward
     (above legal cut-in temperature) and diverted (below legal cut-out
     temperature positions?
     A.   Yes.  It is necessary to time the Taylor as well as all other
          reviewed magnetic flowmeter systems in the legal and sub-
          legal temperature positions.
4.Q. Centrifugal Pump - a regulatory agency reported that the
     centrifugal pump on the Taylor Magnetic Flow Meter unit does not
     stop in any position of the flow diversion valve.  This is not so
     with the Foxboro units in the state.  They indicated that, with the
     valve controls in the "inspect" positions, the pump continued to
     operate.  This condition was also true during the tests required to
     shut the metering pump off.
     A.   There would appear to be some improper wiring in the
          "Taylor" system.  The Certifugal pump is a flow promoting
          device and in accordance with Item 16P, (B), 2, C,(3).
          "Manual switches for the control of pumps, homogenizers
          or other devices which produce flow through the holder,
          shall be wired so that the circuit is completed only when the
          milk is above the required pasteurization temperature as
          defined in Definition S of this Ordinance for the milk or
          milk product and the process used, or when the diversion
          device is in the fully-diverted position."
5.Q. Is there a need for a vacuum breaker downstream from a dual stem
     flow diversion valve and upstream from the positive shut-off valve
     when a vacuum chamber is downstream from the flow diversion is
     in the fully-diverted position."
     A.   The vacuum breaker upstream from the positive shut off
          valve, although preferable, would not be mandatory
          providing the leak escape port is open to the floor and not
          connected back to the raw milk balance tank.  In our
          opinion, where the leak escape port is connected to the
          balance tank with a sanitary line, the downstream side of
          the FDV is not otherwise protected.  The least thing that
          could happen would be to siphon vapor from the raw milk
          balance tank and the most that could happen would be to
          siphon raw milk.
6.Q. What requirements must be met in order to operate a homogenizer
     (used as a timing pump) during the C.I.P. cycle, with a dual stem
     flow diversion device?
     A.   In order to effectively clean the dual stem flow diversion
          devices, it is necessary to "pulse" or move the device from
          diverted to forward position several times during the pre
          rinse, washing and post rinse cycles.  The original review
          by MSB and Engineering Branch (EB) specified that the
          timing pump could not operate during the CIP cycle.
          However, as the popularity of the dual stem device has
          increased there has also been an increased interest in using
          homogenizers as timing devices on HTST system, it is
          necessary to run the homogenizer as timing devices on
          HTST systems.
          This has caused a slight problem in that, if the homogenizer
          is to be cleaned as a part of the HTST system, it is
          necessary to run the homogenizer during CLEANED IN
          In resolution of this problem, MSB and E.B., have agreed
          that the intent of the PMO would be satisfied and the timing
          pump (HOMO) could be run during CIP provided the flow
          diversion device were kept in the diverted flow positions for
          a predetermined time (10 minutes).  This would prevent the
          inadvertent turning of the switch to CIP and then back to
          product run, thereby induction forward flow at sub-legal
          temperatures.  Wiring diagrams were submitted and
          reviewed to provide for these conditions (see copies of the
          appropriate M-b memorandums for details of these
7.Q. Under what condition can a two speed raw product booster pump
     be used in an HTST system?
     A.   A two speed row product booster pump can be operated
          during product flow at the low speed and at the high speed
          during CIP under the following conditions:
          a.   The high speed pump must be interlocked with an
               automatic CIP system so that once the CIP system is
               energized it will continue through its cycle without