Milk Separator

Milk separation

Milk Separator


Milk Separator Operation:
Do not underestimate the impact on the dairy business from a milk separator not operating to its optimum.
A high volume milk separator not running to its optimum can easily cost a business well in excess of £250,000 per annum. (further explained below)

This alone should ensure that your cream separator is well maintained.

Cream fat separation from milk can be either partial or full cream separation.

The fat % of the cream would normally be 40% for buttermaking

The milk separator is one of the most important pieces of equipment in a dairy factory and its impact on dairy profitability and skimmed milk powder specifications and process losses is often underestimated by dairy manufacturers.
The dairy separator is a high speed centrifuge which needs to be properly operated, maintained and serviced to give reliable and efficient service.
A milk separator can contribute up to 25% of your waste water losses and increasing the cost of dairy waste water treatment and disposal.

A well maintained efficient milk separator will give skim fats of 0.05% consistently resulting in a good cream yield.
e.g. if a separator is running badly then it may give a higher cream fat % in the skimmed milk which will not attract a premium compared to selling it as cream. It may also cause the skimmed milk at the very least to be inconsistent in fat content and at worst out of specification by being over 1.5% fat in skimmed milk powder.
If a dairy separator is running at 30,000 litres per hour then during a 20 hour run it will seperate 600,000 litres resulting in an estimated 60,000 litres of cream at 40% milk fat and 540,000 litres of skimmed milk. If the separator is not optimised then an additional est 0.05% fat or more can be lost to the skim. 540,000 litres of skimmed milk x 0.05% means a loss of an estimated £350,000 / annum in cream revenue (est 2019 cream prices).

Tip for production Managers
ALL dairy manufacturers should be able to achieve a fat in skimmed milk powder of 0.7% - 0.8% and anything above this should be investigated as a priority as it is an indication of poor performance.


Cross reference the liquid skim fats off the separator with the skimmed milk powder fats. The reference test for milk fats is the manual gerber test and this is often not carried out correctly and giving low readings. The way to eliminate these errors is for the production manager to monitor skimmed milk powder fats.Samples are only taken during the efficient running of the separator (when it is fully up to speed) The performance of the dairy separator can easily be monitored using the separator amps. The historical trend graph should be adjusted to show the load on the separator over time.. The separator amps will rise during a partial de-sludge or full desludge and due to the loss of bowl speed when the bowl drops and sediment is ejected.If the partial desludge or full desludge is set too long or too frequently then the amps will clearly show this. The amps will also indicarte if there is a separator service / bearings or balance issue as the amps will be erratic indicating vibration.

The milk separator may be over desludging resulting in intermittent high skim fats / high losses which will not show up well in the skim silo / skim samples. This is because over time the intermittent bad samples are lost in the volume of the skim silo and are not picked up during samoling direct from the separator as this is only done when the bowl is up to speed and does not take account of too long and too frequent de-sludger. (poorly set parameters)

The milk separator can contribute up to 25% or more of losses to waste water. This makes it critical for managers to monitor performance through milk powder samples fat results and not through liquid skim fat results.

For a rapid assessment / 1 day scan of your operational efficiency then please contact us

Requirements: Prior to separation the milk is preheated and after separation it is heat treated usually using High Temperature Short Time (HTST) Pasteurization. The temperature must not be less than 72.4 deg Celsius for 15 seconds and preferably 26 seconds.

Record keeping: It is a legal requirement in most countries to keep signed records of pasteurisation for at least 2 years.

Cold milk separators are available but the skimming efficiency should be compared with that of a warm milk separator and potential for increased process losses.

Cold milk separation is carried out at about 10 degrees C. One of the advantages of cold separation is that Thermoduric and Thermophillic spores will not germinate and multipy over a long production run. This would be important for some manufactures but for others it may not be a major issue due to either consistent all year round good milk quality or the use of microfiltration or bactofugation. The ideal is to have consistent clean milk but this can not be guaranteed so the next best step without affecting milk separator efficiency adversely is to microfilter or use a bactofuge. Manuafacturers should estimate the operational costs and process losses vs benefits of the options.

Pre start checks:

    The operator should ensure sufficient utilities and product, are available such as;
  • Air (oil free, dry and filtered - moist air causes damage to instrumentation.
  • Steam
  • Mains water
  • Chilled water.
  • Soft water.
  • Milk
  • Plant preparation
  • Ensure all plant and pipes are clean.
  • Set up the routes to and from silos / milk and cream tanks.
  • Ensure the Heat Exchanger has a valid leak test certificate.
  • Start separator and bactofuge followed by the pasteuriser.
  • Settle the plant down on water, test the pasteuriser divert is operating at 72.4 degrees C.
  • Ensure Separator and Bactofuge de-sludge and partial de-sludge are operating correctly - critical for efficiency.
  • In an automated system the CIP age is automatically logged and if “Maximum CIP age” is exceeded the pasteurizer looses status “Clean” and is changed to status “Not clean”.
  • An initial sterilisation step (85c for 10 minutes) is carried out prior to introducing milk to the pasteuriser.
  • The heating section must never be active if the flow is below “Minimum flow before start heating" as this may cause product burn on.
  • When introducing milk to the plant there is usually a water push from the silo to the pasteuriser balance tank and to the finished product tanks and this can be done manually or incorporated into an automatic system.
  • The balance tank level is normally level or float controlled.
  • Operation: The volume, age, quality (Microbial, Fat and SNF and temperature) of milk in the storage tanks must be recorded by the operator at the start and then at frequent intervals. (automated systems will include this data)
  • The water in the lines is pushed to drain by a predetermined time / volume and ideally incorporating turbidity sensors.
  • The operator should complete the milk / whey pasteurization log sheet every hour and sign the divert check prior to commencing on product.
  • Frequent samples of the skimmed milk should be taken direct from the separator during normal running (not immediately after a de-sludge). Silo samples should be taken every hour and tested for fat
  • End of production: Production ends when the pre-set production volume is reached or the operator manually stops the production. The production ends with a water push to the receiving tanks.

    During operation: Monitor how long the separator and Bactofuge take to recover their revolutions after a partial de-sludge and full desludge and correlate this data with the amperage and the fat in skim (if producing skimmed milk) and this will maximise the yield through ensuring optimum operation. A good separator will consistently give skim fat of 0.05% or less ensuring that the fat in powder is less than 1%. In some plants the separators feed the skimmed milk directly to the evaporator and this may give rise to unacceptable fluctuations in skim fat, using a large buffer skim silo ensures that any small lapses in efficiency due to too high a desludge time etc resulting in slugs of high fat skim are balanced out to give a consistent low fat result rather than dried as a high fat slug.

    Bactofugation is the removal of microbes by centrifugal force.

    Bactofugation can remove up to 99.8 % of all sporeforming bacteria but to get this efficiency will likely require double bactofugation

    The cream is separated prior to bactofugation and high temperature pasteurised before being returned to the milk if producing a standardised product or sent to the cream tanks if producing skimmed milk.

    The latest bactofuges incorporate a recirculation loop for the bactofugate to minimise on product losses.

Milk Separator Service:

The milk Separator should be serviced at lease annually depending on the running hours

Follow the manufacturers service instructionsdp>

If the separator is showing signs of unbalance or vibration then this should be investigated with urgency as a centrifugla separator operating out of balance can cause serious damage.

Excess vibration or inefficient separation deserves immediate attention as it is a clear indication that there is something amiss.

Milk Cream Separator being serviced
  • Ensure the area is clean and clear
  • Ensure that you have the correct tools, instruction manual and safety gear
  • Place the bowl on the provided heavy rubber mat to avoid damage
  • Place components on a pallet with a cardboard or other clean / acceptable soft material to avoid damage to components
  • Strip the plate pack ensuring that you know how to reassemble it
  • Inspect and clean all components
Milk Separator Service

Milk Standardiser

Milk Standardizer

Milk Bactofuge

Milk Pasteuriser

Cream Standardiser

Cream Pasteuriser

For more information or to discuss your requirements please contact us

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John Watson
Office: +44 1224 861 507
Mobile: +44 7931 776 499
jw@dairyconsultant.co.uk

We are a longstanding member of the Society of Dairy Technology and have Fellowship of the Institute of Food Science and Technology.
Member of the Society of Dairy Technology and have Fellowship of the Institute of Food Science and Technology IOD

 

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