Vacuum systems for mechanical milking. How to choose a milking machine for cows? Selection by pump type

16.05.2020

Igor Nikolaev

Reading time: 3 minutes

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The devices greatly facilitate manual labor when milking large and small cattle. The design of the equipment is simple, it is easy to use. No special skills are required. The principle of operation of all milking machines is vacuum. When choosing an apparatus, always take into account the number of livestock, milking speed, specifications. If a farmer has a mini milk processing plant, then milking machines are purchased with a milk line through which the raw materials go to the processing site.

Drawing of a milking machine for cows

The milking machine for cows consists of a stationary and mounted part. For milking at home, mobile equipment is used. For his movement support frame on wheels. There are two of them, with wide or narrow tires. Legs are provided for stability.

It is preferable to choose wheels with wide tires so that the throughput of the installation is higher.

The milking machine set includes the following modules:

electric motor: powered by 220 V; in some installations, a gasoline engine is provided: the equipment does not depend on the network; it is used for milking in pastures;
pump;
vacuum line hoses;
vacuum gauge;
vacuum regulator;
container for collecting milk with a lid; on the lid is check valve, a pulsator and a receiver are attached to it;
pulsator;
receiver;
collector;
vacuum and milk nozzles;
milking glasses.

Manufacturers complete the equipment with additional spare parts: teat rubber, milk and vacuum nozzles, equipment cleaner, brushes for cleaning hoses, cups and nozzles. When answering the question of how to choose, they pay attention to the type of pump, the presence or absence of certain components in the installation, the quality of milking.

Selection by pump type

The milking equipment is powered by an electric motor. It requires a voltage of 220 V. Power from 550 W to 750 W. The pump is a vacuum dry type or an oil pump. For the operator, a dry type vacuum pump is more convenient. It does not require maintenance, maintenance is reduced to an annual preventive examination.

The oil pump must be checked every 3 months: lubricate parts, determine the condition of the gasket or leather cuff. An oil pump is more convenient for cows. It is not as noisy as a dry type pump. Animals get used to it quickly.

If you choose between oil or dry equipment, then they lean towards a dry type vacuum pump, but with a silencer.

A vacuum pressure is created in the system. It is measured with a vacuum gauge. The optimum pressure is 50 kPa. To adjust, reduce or increase the pressure, a regulator is provided. These components must be mandatory in the milking machine. At low pressure, milking will be ineffective. At high pressure, the equipment may become unusable.

Milking machine pump

The presence of a pulsator

Pay attention to the presence of a pulsator in the installation. The process of taking milk takes place in a certain mode. In order to make it comfortable for the animal, milking is technologically brought closer to the natural feeding of a calf. He grabs the nipple, sucks out the milk. While the calf is swallowing milk, the nipple remains dormant. The calf makes 64 sucking movements per minute and gives the cow a rest.

A similar mode of milking creates a pulsator. He delivers vacuum in batches to the teat cups. The number of pulses is adjustable. Some models do not have a pulsator. It is replaced by a pump. The number of pulsations depends on the frequency of the piston or other moving elements. Impulses cannot be adjusted.

For the farmer, equipment without a pulsator is preferable. It costs less. For a cow, milking will be more comfortable with a pulsator.

Choice of teat cups

Attached equipment for milking consists of a collector, milk and vacuum nozzles, teat cups. The equipment is fixed on the teats of the cow's udder. In order to make the animal more comfortable, they choose devices with special devices that help to keep it on the udder.

The milking cups consist of a metal body and a teat rubber. There is a cavity between them. Vacuum enters or exits. The pulsator supplies air into the cavity, the rubber is compressed, captures the nipple - this is 1 so of milking. The pulsator takes in air, the rubber cuff goes to the walls of the glass, gradually releasing the nipple. At this time, milk is expressed - this is the 2nd cycle of milking. If the pressure in the udder, in the glass and in the milk tube is the same, then the cow's nipple is at rest - this is the 3rd cycle of milking. For an animal, this mode of milk intake is more familiar, but the equipment is more expensive.

Glasses are made of stainless steel or aluminum. A device made of aluminum is lighter, but made of steel is stronger. The nipple cuff is made of food grade rubber or silicone. Silicone for a cow is more comfortable, it is softer. Be sure to provide lining on the glasses so that the metal does not injure the udder of the cow. Some glasses have transparent plastic inserts. Through them determine the amount of milk that a cow gives. If milk does not flow into the glasses, milking is over.

Manufacturers offer milking machines for cows, heifers, goats. This is different models. The glasses are not the same size. Tall cups are for dairy cows with well developed udders and long teats. They are not recommended for heifers or for goats whose teats are shorter than those of cows. During milking, the glasses rise. They can come into contact with the udder and rub the skin.

Synchronous or asynchronous milking?

The collector is a device through which vacuum is supplied and milk passes. It contains a valve. When it is pressed, the milking machine turns on, the vacuum begins to flow into the glasses. They are put on alternately on the udder and milking begins.

In manual milking, milk is expressed first from the back two udder lobes, then from the front two lobes. For a cow, this method of milking is familiar. In order to preserve the method of manual milking with hardware milk sampling, asynchronous operation of the glasses is used. At the same time, vacuum comes from the collector first to the 2 rear udder lobes, and then to the front ones. The rear lobes are more developed in the cow, so the milking process begins with them.

With synchronous milking, all 4 cups work simultaneously. This is unnatural for the animal, but the speed of milking increases. In this case, the cow may not give all the milk, it is required to additionally milk it with your hands. The farmer decides on his own how to milk, chooses a synchronous or asynchronous milking machine for cows, but it must be borne in mind that the “manual milking” method is more convenient for the animal.

For one or two cows?

The milking equipment may have one or two milking machines. The process of taking milk from 1 cow is 6-8 minutes. If the farm has no more than 5 heads, then they purchase equipment with 1 set: 4 cups, 1 collector. Milking will end in 30-40 minutes.

For a herd of up to 30 cows, milking machines with 2 milking sets are purchased. They allow you to take milk from 2 cows at the same time. Milking will end in an hour and a half. In this case, milk is collected in 1 or 2 cans.

To speed up the process, they purchase stationary installations that operate from the remote control. Cows enter the boxes. They are equipped with milking machines. The operator puts the cups on the teats of the udder, the milk goes through the pipeline for processing or into the refrigerator. On large farms, milking parlors are equipped. They provide for a certain order of entry and exit of animals from the hall so that they do not collide, and the operator does not confuse cows with full and empty udders.

The invention relates to agriculture, in particular to vacuum plants for milking machines. The installation contains a pump, discharge and suction pipes, a circular collector, a suction pipeline, a jet, a liquid tank, and an electric motor. To increase the efficiency of the pump, the coolant is sucked through the pipeline through the jet and enters the circular manifold. With the help of a circular collector, it is evenly distributed over the entire volume of the suction pipe. This will cool the pump more efficiently and reduce fluid consumption, increase the pump capacity and the amount of vacuum created, which increases the efficiency of the milking machines. 3 ill.

The invention relates to agriculture, in particular to vacuum plants for milking machines 6, 1981, which is designed for machine milking in milking machines. However, the use of air cooling and a lubricating fluid supply system do not give the desired effect. Vacuum pumps are known in which the working part of the rotors is made of textolite, for example, the PTK brand. However, as experimental studies have shown, when the pump is operating, the textolite does not withstand heating temperatures above + 90 ° C. (Volkov I.E. Research and development of a milking machine with an individual vacuum source. Diss. Candidate of Technical Sciences., Kazan Agricultural Institute. - Kazan, 1974 ). However, the use of air cooling does not give the desired effect. Therefore, for cooling, it is advisable to inject a liquid-air mixture. The purpose of the invention is to increase the efficiency of a vacuum installation by ensuring a dosed supply of coolant and its uniform distribution in the working chamber. This is achieved by the fact that the suction cavity of the pump is equipped with a system for supplying coolant mixed with a gas flow .Figures 1 and 2 show the proposed vacuum installation, and figure 3 shows a circular collector. The vacuum installation consists of a pump 1, discharge 2 and suction pipes 3, circular collector 4, suction pipe 5, jet 6, liquid tank 7 and an electric motor 8. The principle of operation of the vacuum unit is as follows. When the pump 1 is operating, under the action of the vacuum created by it, liquid is sucked in in a dosed manner through the suction pipe 5 through the jet 6 from the liquid tank 7. Then it enters the circular collector 4, with the help of which it is evenly distributed over the entire volume of the suction pipe 3. The uniform supply of liquid mixed with the gas flow in the suction cavity of the pump makes it possible to cool the pump more efficiently, reduce the liquid flow rate, increase the pump performance and the magnitude of the created vacuum. In addition, the supply of coolant improves the coefficient of friction of the rubbing pair of the working part of the pump rotors.

Claim

Vacuum unit for machine milking, containing a vacuum pump with suction and discharge pipes and electric motors, characterized in that it is equipped with a system for supplying coolant mixed with a gas flow to the suction cavity of the pump, consisting of a liquid tank, a suction pipeline with a jet in the intake parts having a calibrated section for metered suction of liquid from the tank, and a manifold at the inlet to the suction pipe of the pump, which ensures uniform distribution of liquid throughout the entire volume of the suction pipe.

The vacuum pump is designed to create a vacuum (discharge) in the system by pumping air out of it. The vacuum pump is the driving force behind any milking equipment.

Pump classification

Vacuum pumps are classified as follows:

1. By design:

2. By the magnitude of the vacuum created:

low vacuum pumps;
medium vacuum pumps;
high vacuum pumps.

3. By appointment:

"dry" (for suction of gases);
"wet" (for suction of gas together with liquid).

Rotary vane (oil) pumps operate using oil, while liquid ring pumps use water.

The main advantages of liquid ring pumps are:

the absence of rubbing working bodies, since the seal between the rotor and the stator is a layer of water.
environmental friendliness
compactness
low noise level.

However, liquid ring pumps have lower productivity, are difficult to operate and operate only at positive temperatures.

Scheme of a liquid ring vacuum pump

Rotary vane pumps are characterized by high operational reliability and
high performance. Oil pumps can operate at sub-zero temperatures.
The disadvantages of rotary vane pumps include:

high noise level
complex service
higher price compared to liquid ring pumps.

Diagram of a rotary vane pump

1 - rotor; 2 - body; 3 - rectangular plates; 4 and 7 - branch pipes; 5 and 6 - the working cavity of the pump. The arrows indicate the movement of air (the areas of air suction and vacuum injection).

Vacuum stations

Vacuum stations are installed in milking systems to create vacuum pressure. They are also used in other sectors of the economy where a stable vacuum is required.
Vacuum stations consist of a water tank and pump unit(vacuum pump) installed on the tank and electric motor. Depending on the required power, the vacuum station is equipped with one, two or more vacuum pumps.

To create a vacuum during the operation of the milking machine, air installations are used, consisting of a vacuum pump, a vacuum cylinder-receiver, a vacuum regulator, a vacuum gauge, a piping system with fittings and an engine, which are divided into rotary, piston and ejector. In turn, rotary vacuum pumps are divided into vane, water ring, Roots type and others. The most widespread on farms are rotary bladed vacuum units of the brand UVU-60/45 and water ring air pumps VVN-3, VVN-6, VVN-12.

The principle of operation of ejector (jet) pumps is as follows. When a liquid (or gas) flows through a pipe that has a constriction, the pressure in the constriction is lower than in the rest of the pipe (if the flow velocity in the constriction does not reach the speed of sound). This was first established by the Italian physicist G. Venturi (1746-1822), after whom the tube based on this phenomenon was named. If the evacuated volume is connected to the pipe at the point of its narrowing, then the gas from it will pass into the area reduced pressure and carried away by the liquid. Ejector (jet) installations are mounted on the exhaust pipe of the tractor and the vacuum is created due to the high-speed flow of exhaust gases.

A rotary bladed vacuum unit of the UVU type includes (Fig. 2.2) an electric motor 1, a vacuum cylinder 3, a vacuum regulator 4, a vacuum gauge 6, a vacuum line 5, a vacuum pump 2. In case of frequent power outages, it can be equipped with a backup internal combustion engine 7. The UVU-60/45 unified pump operates at a vacuum of 53 kPa with an air capacity of 60 and 40 m 3 /h. To obtain the required flow rate, the rotor speed is changed by placing pulleys of different diameters on the motor shaft.

Rice. 2.2 General view of the vacuum unit UVU 60/45

The rotary vane vacuum pump is designed for operation in areas with a moderate climate in the open air in the range from minus 10 to plus 40 0С and at an altitude of not more than 1000 m, is available in four versions.

Inside the cast-iron cylindrical body 22 (Fig. 2.3) with a ribbed surface for better thermal insulation, the rotor 17 rotates. The rotor has four grooves in which textolite blades 16 move freely. The rotor rotates in ball bearings 14 installed in the mounting holes of the covers 12 and 19, located eccentrically relative to the body axis. The bearings from the side of the internal cavity of the pump are closed with washers 15. To orient the covers relative to the housing, pins 5 are installed when assembling the pump. The direction of rotation of the rotor is indicated by an arrow on the pump housing. Depending on the version, the pump has one or two output ends of the rotor.

In the middle part of the cylindrical body there are exhaust windows that connect to the exhaust pipe of the frame. A muffler is mounted at the end of the exhaust pipe, the body of which is filled with glass wool to retain the used lubricant.

The technological process of the vacuum installation is as follows. When the rotor 17 rotates (Fig. 2.3), the blades 16, under the action of centrifugal forces, are pressed against the body 22, and form closed spaces bounded by the rotor 17, the body 22 and the end walls 12 and 21, the volume of which first increases in one revolution, creating a vacuum between blades on the suction side and then decreases. In this case, the air is compressed and forced into the atmosphere through the exhaust port.

To lubricate bearings and friction surfaces, the pump is equipped with a wick-type oiler, which ensures a uniform and continuous supply of oil to the pump.

The oiler consists of two main components: glass 5 (Fig. 2.4) with a capacity of 0.6 l and cup 2. Oil is poured into a glass, which is closed with a lid 7 and fixed on the cup with an arc 6. Oil flows out of the glass into the cup until until its level reaches the top of the wedge-shaped cutout of the cover tube. The oil level in the cup of the oiler, version UVD.10.020, is not adjustable. The oil level in the cup of the UVA 12.000 oiler depends on the length of the protruding end of the tube and must be within 13.18 mm. When the oil level drops, air enters the glass through a cut in the tube and the oil flows out until it reaches the set level.

The lubrication process is as follows. From the cup, the oil flows through the wicks 3 into the oil-conducting channels and, under the influence of the pressure difference in the oiler and the pump, through the hoses 9, holes in the covers 12, 21 (Fig. 2.3) of the pump enters the ball bearings 14, through the channels of the washers 15 into the grooves of the rotor 17, lubricating surfaces of the blades 16, pump housing and covers. The oil is then blown out by air through the pump outlet.

The oiler provides oil supply to the pump with a flow rate of 0.25.0.4 g / m 3 of air, which corresponds to the outflow of oil from the glass during the operation of the installation by one division on average for 1.5 hours of operation of a vacuum installation with a capacity of 0.75 m 3 / min , and an average of 1.1 hours for a vacuum plant with a capacity of 1 m 3 /min.

Control over the flow of oil into the bearings is carried out visually through plastic hoses, and the total flow - according to the divisions on the glass.

Rice. 2.3 Vacuum pump:
1.20 - bolts; 2, 15 - washers; 3 - retaining ring; 4 - pulley; 5 - pin; 6 - key; 7 - screw; 8, 22 - covers; 9 - cork; 10.11 - gaskets; 12 - right cover; 13 - cuff; 14 - ball bearing; 16 - scapula; 17 - rotor; 18 - body; 19 - left cover; 21 - bushing; 22 - body

Ensuring the required oil consumption during operation is carried out by periodically cleaning the oil-conducting channels in cup 2 (Fig. 2.4) and plugs 4, washing the wicks in diesel fuel or changing the number of threads in the wick, and for the UVA 12.000 oiler also by changing the length of the protruding part of the tube.

To exclude possible reverse rotation of the rotor and breakage of the blades when the electric motor is turned off, the pump inlet is connected to the vacuum line through a safety valve.

Rice. 2.4 Lubricator UVD.10.020:
1 - bracket; 2 - cup; 3 - wick; 4 - cork; 5 - glass; 6 - arc; 7 - cover; 8 - gasket; 9 - hose

Rice. 2.5 Vacuum regulator

Vacuum bottle 3 (Fig. 2.2) smooths out the vacuum pulsation that inevitably occurs during pump operation, collects moisture and milk that have entered the vacuum line, and is also used as a drain tank when flushing pipelines. When the pump is running, the lid of the vacuum bottle must be tightly closed.

Vacuum regulator 4 (Fig. 2.2) maintains a stable vacuum in the vacuum line. It consists of a valve 1 (Fig. 2.5), a spring 3, a set of weights 4, damping plates 5 and an indicator 2.

The vacuum regulator works as follows. The force acting on valve 1 from below, due to the difference between atmospheric and vacuum pressure in the vacuum line, lifts the valve up, overcoming the weight of load 4. As a result, atmospheric air begins to flow through indicator 2 into the vacuum line. The vacuum value at which valve 1 rises is set by the weight of the load 4. The amount of air flow through the vacuum regulator is controlled by the readings of indicator 2. At normal flow, the arrow of indicator 2 should be in the middle position. To mitigate the vibration of the load 4, they are suspended on the spring 3, and the bottom damping plates 5 are in the oil layer.

VVN type water ring machines are designed to create a vacuum in closed devices and systems. They are manufactured in two versions: VVN1 - with a nominal suction pressure of 0.04 MPa; ВВН2 - with a nominal suction pressure of 0.02 MPa.

VVN type machines are liquid ring machines with direct drive from an electric motor through an elastic coupling.

The VVN-12 water ring installation consists of a water ring machine 4 (Fig. 2.6), driven by an electric motor 1 through a coupling 2. All this is placed on the foundation plate 3.

The water ring machine consists of a cylinder body 2 (Fig. 2.7), closed at the ends with end caps. The impeller 1 is eccentrically located in the cylinder and is fixed on the shaft. The shaft exit from the fronts is sealed with soft packing glands. The water supplied to the machine feeds the water ring 7 and creates a hydraulic seal in the glands. The shaft rotates in bearings located in housings attached to the fronts.

Before putting into operation through the suction pipe 5, the machine is filled approximately up to the axis of the shaft with water. When starting, the liquid is thrown by centrifugal force from the rotor hub to the housing. This forms a liquid ring and crescent-shaped space, which is the working cavity. The working cavity is divided into separate cells, limited by the blades, wheel hub, fronts and the inner surface of the liquid ring. When the wheel rotates, the volume of the cells increases (clockwise rotation in Fig. 2.7) and gas is sucked through the suction window 6. Then the volume of the cells decreases, the gas is compressed and pushed out through the discharge window 3. Water is ejected along with the gas through the discharge pipe 4. To separate water from gases and collect it directly on the discharge pipe in vacuum pumps, a water separator with an open overflow pipe is installed. To separate water from gas in VVN-12 vacuum pumps, a direct-flow separator 5 is used (Fig. 2.6). The straight-through separator is a non-separable vessel with a volume of about 24 liters with a multi-bladed grate built inside, through which the gas-liquid mixture ejected from the pump is separated. It provides almost complete separation of water from gas in all possible operating modes.

When using the machine as a compressor, a water trap is attached to the separator drain pipe, ensuring that water is drained without gas leakage.

The advantage of water ring vacuum machines over vane vacuum pumps is that during rotation the rotor does not touch the stator walls. However, when the rotor rotates, the temperature of the water in the pump stator rises, which reduces its supply. To increase the stability of the VVN pump, a special water cooler is installed.

Rice. 2.6 General view of the vacuum pump VVN-12

Rice. 2.7 Diagram of a water ring machine

The main applicability parameters of water ring machines are presented in Table 2.1.

2.1. Indicators of water ring vacuum machines
Indicator	Size
Indicator	VVN-3	VVN-6	VVN-12	VVN-25
Performance at nominal suction pressure, m 3 / min	3 (2,7)	6(5,4)	12 (10,8)	25 (22,5)
Nominal vacuum pressure from barometric pressure, %	60 (80)
Maximum vacuum from barometric pressure, %	90		96
Specific water consumption at nominal mode, dm 3 / s	0,13 (0,2)	0,3 (0,47)	0,5 (0,75)	1,0 (1,5)
power, kWt	13	22	30	75
Weight, kg	125	215	455	980
Note: in parentheses are the values for vacuum pumps version 2

Rice. 2.8 General view of the water ring vacuum unit UVV-F-60D:
1 - vacuum line; 2 - fuse; 3 - pump; 4 - water tank; 5 - electric motor; 6 - exhaust pipe; 7 - discharge pipe

The vacuum water ring unit UVV-F-60D is designed to create a vacuum and is used to complete all types of milking machines. The unit is not intended for pumping out aggressive gases and vapours.

It consists of a water ring vacuum pump 3 (Fig. 2.8) driven by an electric motor 5 (power 6 kW) installed above the water tank 4. The vacuum pump is connected to the vacuum line 1 through a fuse 2. Residual air along with water is expelled from the room through pipeline 6 .

The main technical characteristics of the water ring vacuum unit UVV-F-60D are presented in Table. 2.2.

2.2 Main technical characteristics of the UVV-F-60D unit
Parameter name and unit of measurement	Parameter value
Productivity at h=50kPa, m 3 / h	60±6
Power consumed at nominal mode, kW	4±0.4
Ultimate residual pressure, kPa	15±5
Overall dimensions, m	0.65x0.36x0.75
Weight without water, kg	110
The volume of liquid poured into the water separator, dm 3	50
Nominal passage with a branch pipe, mm	40

For some processes, very high pumping speed is required, even if not at very low pressures. These requirements are met by two-rotor volumetric pumps of the Roots blower type. The scheme of such a pump is shown in fig. 2.9.

Rice. 2.9 Scheme of a Roots-type twin-rotor pump

Two long rotors with a figure-of-eight cross-section rotate in opposite directions without touching each other or against the casing walls, so that the pump can run without lubrication. There is also no need for an oil seal, since the gaps between the fitted structural parts are very small.

The rotor rotates at a frequency of up to 50 s -1 , and high pumping speed is maintained up to pressures of the order of one millionth of an atmospheric pressure. Each rotor can have two or three lobes.

Although these pumps are capable of direct exhaust to the atmosphere, they usually have an auxiliary rotary oil pump installed at their outlet, which not only lowers their ultimate pressure, but also increases efficiency, reducing power consumption, which saves money. complex system cooling. An auxiliary pump that passes the same mass of gas, but at more high pressures, may be relatively small.

The vacuum system of milking machines is a set of interconnected pipelines and devices for creating vacuum measurement and regulation. The elements of the vacuum system are: pipelines; tank vacuum bottle; Vacuum pump; instruments for measuring vacuum gauge and vacuum regulation vacuum regulator. One of the conditions for increasing the efficiency of milking machines is to ensure vacuum stability in the process of milking. Requirements for the design of the vacuum system: To reduce losses, thereby...

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LECTURE #19

topic: milking machine vacuum systems

PLAN:

Vacuum systems of milking machines and elements of their calculation.

Appointment and classification of vacuum pumps.

Fundamentals of calculation of a rotary vacuum pump.

Maintenance of milking equipment.

LITERATURE.

Belyanchikov N.N. Mechanization technological processes. - M.: Agropromizdat, 1989, Section 2, ch. 7. §5.

1. Vacuum systems of milking machines and elements of their calculation.

The vacuum system of milking machines is a set of interconnected pipelines and devices for creating, measuring and regulating vacuum.

The elements of the vacuum system are: pipelines; tank (vacuum bottle); Vacuum pump; devices for measurement (vacuum gauge) and regulation of vacuum (vacuum regulator).

One of the conditions for increasing the efficiency of milking machines is to ensurevacuum stability milking process.

Requirements to the design of the vacuum system:

To reduce losses (thereby reduce vacuum fluctuations), the network must:

have the smallest length;

have minimal air pressure losses in the system due to the most rational scheme and optimal diameter pipelines in all sections of the network;

differ in simplicity, reliability of pipe connection structures;

have the least number of turns and the minimum allowable number of fittings (faucets, valves, etc.).

Research has established thatthe higher the vacuum and the volume of space, and the shorter the length of the vacuum system, the more perfect the design scheme of the vacuum system (from the point of view of the stability of the vacuum in it).

The resistance in the air duct is divided into distributed (air friction against the walls) and local.

Pressure loss to overcome resistance from air friction against pipe walls:

The resistance coefficient depends on the nature of the air movement in the pipe:

a) in laminar motion

b) with turbulent motion

local losses pressure:

Air consumption by the pneumatic system of the milking machine is determined by the approximate formula:

where 1.35 is the coefficient of imperfection of the pulsator and collector, allowing air leakage; – pulsation frequency, pool/s; - the initial volume of air at atmospheric pressure, enclosed in the chambers and pipes of one milking machine, m 3 ; - coefficient taking into account air leakage from the vacuum system of the milking machine due to insufficient tightness; n yes - the number of milking machines.

The coefficient is determined by the formula:

where;

– leaks in pipe connections; – air leaks between the teat rubber and the teat; – air leaks through the milking cups when dressing them; – suctions in case of accidental dropping of hoses and glasses; - loss of vacuum supply during the hot time of the day due to dilution of the lubricant in the pump; – loss of vacuum supply due to an increase in the temperature of the pump during long continuous operation.

Thus, the total losses are approximately equal in size to the air consumption of the device. In this regard, the coefficient of increase in the supply margin of the vacuum pump is taken equal to 2 - 3, that is

The degree of uneven air flow is determined by the formula:

where is the number of blades.

Pumps of type RVN - (4 blades) have a non-uniformity of 31%. To reduce the influence of which, it is necessary to include a vacuum cylinder with a capacity of 20 - 25 liters in the system.

The diameter of the vacuum line is determined by the formula:

where is the total length of the vacuum line, m; - volume of air flowing through the pipeline, m 3 min.

The required number of vacuum pumps to maintain a stable mode in the system:

where is the performance of the vacuum pump at a given vacuum value.

Noteworthy is such a vacuum distribution system in milking machines, in which each vacuum pump has its own purpose and is included in the vacuum line independently. One pump is used to transport milk, the other is for the operation of the milking machine, the third is for automation of the milking machine. This distribution of vacuum pumps allows a constant level of vacuum in the system and guarantees trouble-free operation of equipment powered by vacuum.

2. Appointment and classification of vacuum pumps.

The vacuum pump is designed to create a vacuum (discharge) in the system by pumping air out of it.

Vacuum pumps are classified as follows:

1. By design

piston;

Injection;

Rotary.

In turn, rotary pumps are divided into 4 types:

lamellar;

Water ring;

With rolling piston;

Two-rotor.

2. By the magnitude of the vacuum created

Low vacuum pumps;

Medium vacuum pumps;

High vacuum pumps.

3. By appointment

- "dry" (for suction of gases);

- “wet” (for suction of gas together with liquid).

4. By nature of use

Stationary;

Mobile.

Until 1952, milking machines in our country were equipped with piston-type vacuum pumps. They were different large sizes and metal consumption; had wear mechanisms - a crank mechanism and an air distributor mechanism.

Currently, rotary vane pumps of the RVN brands - 40/350 are most widely used on milking machines; UVU - 60/45; VC - 40/130 and others.

circuit diagram rotary vacuum pump.

With such vacuum pumps it is possible to obtain a vacuum of the order of 97 - 99%, mechanical efficiency. 0.8 - 0.9.

The performance of RVN - 40/350 at a vacuum of 50 kPa is 11.1 dm 3 / s (40 m 3 / h).

The UVU-60/45 unified vacuum unit can operate in 2 modes: at a vacuum of 53 kPa, provide a capacity of 60 or 45 m 3 /h (achieved by changing the rotor speed by replacing the V-belt pulley on the electric motor shaft).

Water ring pump (VVN) with a liquid piston.

1 - exhaust pipe;

2 - vacuum wire;

3 - rotor;

4 - stator;

5 - water ring;

6 - water cooler.

No lubrication is required here. The seal between the rotor and the stator is achieved by a layer of water.

Flaw : low efficiency (0.48 - 0.52); can only work at positive temperatures.

The main characteristics of vacuum pumps are performance, metal consumption and energy consumption.

3. Fundamentals of calculation of a rotary vacuum pump.

The useful volume of the suction chamber is determined by the formula:

where is the stator diameter;

- eccentricity;

is the length of the rotor.

With the number of blades and angular velocity, the performance of a vane pump is:

M 3 /s.

or, m 3 / s.

The most widespread are 4 cavity (=4) vacuum pumps, at = 90 0 (that is, the blades are perpendicular to each other).

Then:

M 3 /s.

Analysis : theoretical capacity of the vacuum pumpdirectly proportional to its geometrical dimensions and rotor speed.

Performance adjusted to vacuum conditions in the system will be less. This reduction is taken into account by the manometric coefficient:

where is a barometer ( Atmosphere pressure, kPa); – vacuum in the system, kPa.

The higher the< , а следовательно и меньше производительность.

In addition, the actual performance of the vacuum pump depends on the degree of filling of the suction chamber, which is taken into account by the filling factor. The value depends on the design of the pump and is determined experimentally.

Then, the actual performance of the vacuum pump (4-blade, at = 90 0 ) is equal to:

M 3 /s.

since the milking machines use a vacuum of 350 mm Hg. up to 500 mm Hg, then; .

Power required to drive the vacuum pump:

kW or,

where is the torque due to the suction resistance, Nm; is the angular velocity of the rotor, rad/s; – efficiency vacuum pump and electric motor with transmission (= 0.75 - 0.85); – performance, m 3 /with; – vacuum value, Pa.

The torque is determined by the formula:

where is the calculated vacuum value, N/m 2 .

Dependences of pump performance and power consumption on the angular velocity of the rotor

The mechanical characteristic of the vacuum pump resembles that of a fan, and the load diagram is parallel to the straight line of the abscissa after start-up

Load diagram.

The power required to drive the pump depends on the amount of vacuum

4. Maintenance of milking equipment.

In order to maintain the milking system in good order, it is necessary to follow certain rules of care and use detergents.

Detergents.

Requirements for them:

Possess high detergent properties;

be harmless to human health;

Do not change the properties of milk;

Do not destroy the material of the equipment;

Be cheap and easy to use.

Detergents.

Highly alkaline detergents are used (the main part is caustic sodium NaOH ); moderately alkaline detergents; neutral detergents and acidic agents (solution of nitric, hydrochloric and acetic acids) to remove milkstone.

Disinfectants.

Bleaching powder;
Sodium hypochlorite;
calcium hypochlorite;
Chloramine b.

The care process includes the following steps:

Rinse equipment with clean water;
Washing with detergent solutions;
rinsing;
Disinfection;
Rinsing.

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