HOME SEPARATION.

New Zealand Journal of Agriculture, Volume VI, Issue 3, 15 March 1913, Page 290

HOME SEPARATION.

THE SEPARATOR.

G. M. Valentine.

The . Principle of Separation.

To get the best results from machinery of any description it is essential that the operator should understand the principle upon which it is worked. In the case of . the cream-separator it is the law of gravity as applied by centrifugal forcein other words, the law which compels any weight to fly to the extreme limits of the circle within which it is •confined when rapidly revolved. The inflowing stream of whole milk first strikes the bottom of the bowl, which is running at. high speed. It is immediately thrown to the outer wall and is then forced upwards to the skim-milk and cream outlets near the top of the bowl. The skim-milk, being the heavier, is thrown to the outside, while the lighter cream collects nearer the centre. In the old type of- hollow-bowl separator this action could be clearly seen. After a long run the bowl would often have a pyramid- of very rich cream suspended in the centre. Generally speaking, however, there is no clearly defined line between the cream and skim-milkrather a gradual shading from very rich cream in the centre to practically pure skim-milk on the outside. First the skim-milk escapes through the outlets provided to the skimmilk covers, while the cream rises to an outlet on or near the top of the -bowl, where it escapes to the cream-covers. The higher the speed •of any bowl of a given diameter the cleaner the skimming, due to the increased centrifugal force exerted on the milk, and the smaller the diameter of the bowl, the higher must be the speed. Speed is perhaps the most important point, and is, I believe, the most neglected. The richness of the cream delivered is regulated by a screw, which acts ■either on the cream or skim-milk outlets. In the former case the further the screw is turned in the nearer it is to the centre of the bowl, the amount of skim-milk which escapes with the cream being thereby less and the cream richer. According to the same rule, if we turn the screw out we get a thinner cream. In the latter case, the further the screw is turned in the smaller does it make the skim-milk outlet, thereby forcing more skim-milk out with . the cream and causing later the cream to be thinner. To turn the screw out in this case will give us a thicker cream.

A poor separator makes a discontented supplier, and a discontented supplier is a thorn in the flesh of the factory-manager. ~ It is a source of continuous loss to its owner and to the factory he supplies. The patron of a whole-milk factory is credited with the whole of the fat contained in the milk, and the losses in separation are borne by the factory. With home separation the loss is borne by the supplier, and, as the latter is not generally so well equipped for getting the best results, the loss is proportionately heavier. Farrington says, “ Under ordinary factory conditions few separators will deliver skim-milk containing less than one-tenth of 1 per cent, of fat when the sample is taken from the whole day’s run. This must be considered a most satisfactory separation.” (“ Testing Milk and its Products,” page 88.) This conclusion is arrived at by gravimetric analyses of samples of skim-milk. The Babcock test does not claim to show the actual fatcontent of skim-milk, but, according to the same authority, 0-05 of 1 per cent, must be added to the reading contained by that method to get the correct amount (page 91). This is due to the fact that the finer fats, which are not recoverable during separation, are equally difficult to get into the neck of the bottle in testing. Allowing that 0-1 per cent, is good skimming under average factory conditions,' it is probable that there is an actual, loss of at least 0-15 of 1 per cent, under the varied conditions obtaining where home separation is adopted. The writer has tested samples of skim-milk . showing a fat-content of 0-17 by Babcock’s test, or, say, 0-22 per cent, by gravimetric analysis. How this works out in money value may be shown thus, taking 0-15 as average skimming: 1,000 lb. of milk testing 4 per cent, contains 40 lb. of butter-fat. Allowing that this produces 100 lb. of cream and 900 lb. of skim-milk containing 0-15 per cent, of fat, the loss is = 1-35 lb. of fat, equal to 3-375 per cent, of the total butter-fat contained in the milk — i.e. 1 3 --* = 3-375 per cent. , This in a herd of fifty cows yielding 200 lb. of fat per year each represents a loss of £l6 17s. 6d., at Is. per pound for butter-fat. A portion of this loss is, however, unavoidable. Where whole milk is delivered to a factory the loss is made by the dairy company, whereas where the farmer skims his milk it is he who suffers the loss. What, the loss is when separating is carelessly done can only be guessed, but these figures will serve to show the absolute necessity of exercising the greatest care both in the selection of a machine and in the subsequent use of it. The first question asked of a separator salesman is, “ Does it turn easy ? ” The first one should be, “Does it skim clean?” Clean skimming, accessibility for cleaning, durability, and light drive are of prime importance.

Time of Separating.

The best results are obtained when milking and skimming proceed simultaneously, and when this is possible the separator should be of such a size that a start can be made as soon as milking is well under way, always provided that the number of milkers employed is such that the milk will not be left standing long . enough to become cold while waiting for enough to be milked to keep the machine going. Neither must the separator be run so long that the accumulation of dirt in the bowl will interfere with clean skimmingsay, an hour and a half. If the milk has to be left until milking is finished, a feed-tank with a false bottom should be provided, so that the temperature can be raised with hot water. In this case the bigger the machine the better.

How to set up Machine.

Having chosen a machine, carefully read the directions. Set it on a firm base, preferably of concrete or a block of wood set into the floor. , Leave a space of about 1 in. between the block and the base of the machine by means of a reel at each screw-bob. This prevents oil, &c., from accumulating under the machine, and allows of washing. See that the frame is perfectly level after it is screwed down. Thoroughly oil all bearings. Use only a high-grade oil made specially for this purpose, as on this , chiefly depends the ease in driving, and the life of the machine. Carefully wash and scald the bowl and all tinware, to remove the grease with which they are smeared ; then put the machine together again, with all parts in their proper place, and you are ready to start separating. Avoid sudden jerks in starting, or you will run the risk of snapping the ratchet-pawl in the handle, which is very hard and brittle. Raise speed slowly, taking care in the hand-machine to apply -an even pressure on the handle. A heavy push on the down stroke will only cause irregular running of the bowl, and will tend to wear the bearings and gearing unevenly. The separator must be run at the speed given by the maker, but it is better to err on the side of overspeed rather than underspeed. The hum of the machine gives an indication when the speed is right, but this must not be relied on. A metronome placed where it can be seen and heard, and set to the speed of the handle, is the best means of counting. Satisfactory results will not be attained when stops have to be made to fill up the milkcistern. Slow speed will give more cream of a lower test, and will cause a big loss of fat in the skim-milk. Excessive speed will give less cream of a higher test, and ensure a more perfect separation. Take care that the speed is up before turning on the milk, and. see that it is maintained when the extra , weight caused by . the milk in the bowl is felt. With the increasing use of the milking-machine the power-driven

home separator has also become more common, and, if intelligently used, .should give better results than the hand machine, as a more even speed can be obtained. Where the motive power is steam, turbine machines are most popular, and in good hands do very good work. With an oil-engine plant a hand-power machine, with fast-and-loose pulley attachment, a friction-clutch, or governor-pulley, is usually found, all of which are more or less satisfactory, but require careful watching to see that the belts or clutches are not slipping. It is absolutely necessary to try the speed of the machine at intervals during each separating. This can be easily done by counting the number of revolutions of the driving-shaft on the separator.

Treatment of Separator.

Return the first two or three gallons of skim-milk to the feed-tank, as it has always a fairly large percentage of butter-fat left in it. While the best temperature for separating is the natural heat of the milk as it comes straight from the cow, good results will be obtained with fresh milk not colder than 86° Fahr. If the milk from one milking is left over till the next, it will be necessary to heat it to 96° Fahr, before separating, and it will be all the better if held at this temperature for a few minutes to ensure a thorough heating of the fat-globules. Cold milk will give less cream with a higher test, but will mean a very serious loss of fat in the skim-milk. This is caused by the increased viscosity, or stickiness, of the cold milk, which prevents a clean separation of the fat. The amount of milk fed into the bowl is regulated by a float, which will act well with the tank supplied with the machine ; but if a larger tank is required the pressure on the float will be greater, and, care must be taken not to feed the machine too fast, as this will result in a thin cream and loss in the skim-milk. Underfeeding is also to be avoided. An uneven feed will cause an accumulation of thick cream in the bowl, and a consequent loss in skimming. Maintain a uniform feed, speed, and temperature throughout, the run, and flush out at the finish with . a gallon of skim-milk or clean warm water, to force all the cream out of the bowl. Wash the separator immediately after separating is finished, and do not forget to keep the frame sweet and clean as well as the bowl and tinware. Set the machine to deliver a cream containing not less than 40 per cent, of butter-fat, but do not be surprised if the test should vary a few points either above or below that from time to time, without altering the cream-screw.. The test will be higher if the machine is run overspeed, the milk too cold, the feed not sufficient or irregular, and the cows are going off in milk, &c. Thin cream will result from slow speed, overfeeding, fresh cows, cold

weather affecting cows, too much flushing of. the bowl, and the machine running rough, &c. A separator which is in good order should run with a smooth musical hum, and without vibration, and should deliver the cream and skim-milk in a steady stream. Vibration and noise are signs of something wrong, and should be seen to at -once. The more common troubles frame not being level, bowl-spindle bent, a broken spring in the top bearing throwing the bowl out of plumb, bearings worn and having too much play. A frequent cause of trouble in disc machines is through the discs getting worn with use, and fitting loosely on the centre pillar, thus causing vibration. This can be overcome by putting an extra disc in the bowl. A separator set to ’ deliver a 40-per-cent. cream in spring with fresh cows will give a much richer cream in the autumn, all other conditions being equal, and will require to be altered a little. A sample of skimmilk should be tested frequently. This can best be done by punching a small hole in the shoot, if one is used, and catching the drip. If there is no shoot, a large jug, or billy, can be held under the skimmilk spout at frequent intervals during the whole run, and a sample taken from it after it has been thoroughly mixed. The fact that no cream rises on a sample of skim-milk is no proof that it contains no butter-fat. The argument that “ the calves and pigs get it anyhow ” is, after all, only an excuse for bad work. The old saying that “if a thing is worth doing at all it is worth doing well ” still holds good. If you are going to separate your own milk, do it as it should be done. You will be surprised how interesting it will become. By all means rear good calves and pigs, but make a business proposition of that also, and remember that butter-fat at Is. per pound is rather expensive-pig-feed.

Green Maize. The dairy-farmers of the South Island are coming to appreciate the value of green maize for their milking-cattle. In the North maize is the chief -means of maintaining milk-production when grass dies off. The climate of the North is naturally more suitable for the cultivation of maize, but even in the South maize for green fodder succeeds in average seasons. The experimental farms and the co-operative field plots have effected useful work in popularizing the cultivation of this plant. Quite recently a. party of farmers inspected a heavy crop of maize near Christchurchgrown in a series of field-plot demonstrations. The party was highly gratified at the result. . The South Island Fields Instructor, Mr. A. Macpherson, expresses his great appreciation of the help he receives from the cordial concurrence of the farmers who undertake these trials.