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, HFR-715

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, but:

  1. What triggers the valve?
  2. Is there any limit to the height of the CLT?
  3. Could you have a silo tank in this position?

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 information.

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 PLACE.

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 changes).

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:

  1. 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 interrup

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