Vacuum pump for milking cows. Milking machines and installations

The vacuum pump is designed to create a vacuum (vacuum) 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 a pump unit (vacuum pump) installed on the tank and an electric motor. Depending on the required power, the vacuum station is equipped with one, two or more vacuum pumps.

The milking machine is an automatic system for milking cows quickly and efficiently without damaging the teat and gland, and with minimal risk of pathogens. This is not a single whole, but an assembly of components designed to process more than a dozen cows per hour. There are many factors that can affect milk quality and udder health in dairy cattle, and milking equipment is one of them.

Vintage photo - milking a cow by hand

Early attempts at milking cows involved the use of a variety of methods. Around 380 BC, the Egyptians, along with traditional manual milking, attached a straw of wheat to the teat of cows. The milking machine was first used in 1851, although the attempt was not entirely successful.

To stimulate further inventions, the Royal Agricultural Society of England has announced a reward for the introduction of a safe milking machine. At the end of the 19th century, a machine with a vacuum pump, driven by a steam engine, was developed in Scotland. This unit, along with the introduction of the double teat cup, led to automated milking of animals. Since the beginning of the 20th century, the principle of machine milking has taken root in the dairy industry.

The principle of operation of the milking machine

Traditional milking techniques include teat cups for teat contact and product removal, milk tubes, pulsator tubes, final collection containers. Glasses consist of an inner rubber lining and an outer shell, usually made of metal. During operation, the product is sucked from the cow's udder, as a result of the created vacuum inside the glass, forcing the milk to go through the teat channel.

With machine milking, as with feeding a calf, there is an activation of nerve receptors located on the nipple. With such stimulation, the hormone oxytocin is released, which subsequently enters the udder tissues. Once in place, the hormone causes the muscle fibers to contract and the milk ducts fill with milk. The maximum milk flow comes with a calm and consistent milking of the cow, as well as with proper udder preparation. For sufficient stimulation of the nerve receptor, 12 to 15 seconds of tactile contact is required. This will ensure an adequate release of oxytocin and a good response to milk ejection.

Machine milking technology

The milking unit serves as an indispensable assistant on a dairy farm. Modern machines guarantee the milking of cows in accordance with all the rules, help to keep the milk fresh, preventing the product from colliding with air or hands. It is not difficult to manage the installation, but it requires certain skills. To obtain the desired results, it is important to follow all instructions and properly prepare the cow for the important process.

The rate of milk flow largely depends on the orifice of the lactiferous canal and on the mechanical properties of the device. After cups are attached to the teats, the flow rate reaches a limit within one minute and decreases at the end of milking. The remaining milk should be milked by hand to avoid undesirable consequences in the form of mastitis. The milk flow rate is influenced by the vacuum level and the pulsation frequency. The speed increases when a wider ripple factor is used. Most often, milking machines operate at an optimal frequency of 55-65 cycles per minute. This principle does not adversely affect the udder of the animal.

Manual milking technique

Although hand milking techniques have been refined over the centuries, they still work today. Milking methods affect the quality and quantity of milk. The most common is the fist method of milking. Cows are milked at the same time twice a day. A calving cow is milked more often (5-6 times a day).

The heifer should feel a good disposition towards her, so the animal is treated carefully and with tenderness. If the milking regime is observed and the affectionate attitude towards the heifer is observed, the cow will prepare for the ceremony in advance, and the udder will be filled with milk, which will significantly improve the process of feeding the dairy product.

The hands and udder of the heifer are thoroughly washed to avoid infection or mastitis. Wipe the bottom and side of the udder with a wet towel dipped in warm water, then wipe dry and lightly massage. First, with both hands, the entire udder is massaged, then each half separately. This event should not be delayed so as not to miss the moment of the milk tide. Any moisture on the udder can lead to cracks in the skin. The first few milk jets are squeezed into a separate bowl and covered with a napkin. Milking begins when the cow's teats are swollen and firm. Hands and udders are clean, a sterile enameled bucket is prepared - you can start milking.

The milk is completely milked, which contributes to a good milk yield and protects the cow from infections. It is the rest of the milk, stagnating, that leads to the occurrence of mastitis.

Types of milking machines

With the advent of milking machines, the work of farmers and ordinary cow owners has improved significantly. The device allows you to save time and effort, so necessary for housekeeping. There are several types of milking machines, the type of which depends on the scale of the application.

Portable milking machines

Portable milking units are ideal for small numbers of livestock (up to 20 heads). The portable machine provides an efficient and convenient way to milk animals. An oil-free, electrically driven vacuum pump creates the vacuum required for automated milking. Each unit is supplied with a vacuum regulator and pressure gauge to ensure and maintain the correct pressure level during the milking process. Pulsation in the cluster is created using a pneumatic pulsator installed in the apparatus. It satisfies all the requirements of reliability, durability and accuracy. The pulsation speed is set using the adjusting key. The coefficient is chosen by the user.

The milk is collected in a durable stainless steel bucket for further transport. Both single and double bucket options are available. A complete set of milking clusters includes the necessary fasteners for easy installation and tubing. All parts are securely mounted on a lightweight yet stable trolley that is easy to transport and requires minimal maintenance.

Portable milking machine mounted on a cart with two milk containers

milking system

The milking system is installed on farms where the animals are in their booths, and is designed for 20-100 heads. Milking is carried out using a portable device that provides pulsation and vacuum. The block is connected to the milking station. Usually, one station is installed for every two heads. The product enters the receiving vessel with liquid level control and is then pumped to the cooling tank. The system is easily scalable.

Automatic milking systems are installed on large farms and are designed for more than 100 heads.

How to choose the right milking machine

Milking machines are characterized by their technical data, mobility and type. Lightweight and small in size, the units can serve one or two cows - great for a small household. For large farms, larger devices are used. The most popular is a lightweight device, due to its mobility of movement.

The devices differ in the class of vacuum pumps.

When choosing a device, you should pay attention to the method of vacuum formation. In one case, the vacuum in the device is formed due to the operation of the pulsator and the centrifugal pump. In the other, the work of the pulsator is performed by a piston pump that affects the pressure. When choosing a device, carefully study all the advantages and disadvantages of each of the devices. For example, machines with a pulsator are more complex and expensive, but guarantee high milk yields. Piston pump units are easy to operate at a budget cost, but milking quality is lower than pulsator machines.

Pay attention to the mobility of technology. The device can be mobile or used permanently. The mobile machine is suitable for large farms. The trolley is equipped with wheels and supports, in addition to all the necessary components. The machine easily moves around the service area, processing a large number of heads. The stationary unit is designed to milk a maximum of three cows at close range.

When purchasing a milking device, you should pay attention to the quality of the teat rubber. The health of the cow's udder depends on this part of the unit. The use of rubber in the composition of rubber is considered to be of higher quality. Liners made from low-quality raw materials crack over time, accumulating bacteria, and thus causing harm to the health of the cow. You will have to replace the liner at least once a year. Please note that the price matches the quality of the purchased unit, the assembly of parts, functionality and ease of use.

Advantages and disadvantages of milking machines

studying advantages of milking machines, some advantages of the technique should be highlighted.

1. The owner of a large farm can save a lot on the wages of workers by reducing the staff. It is enough to leave a certain number of people who will control milking and keep the room clean.
2. Milking equipment minimizes the tedious and painstaking work of milkmaids and housewives of small private farms.
3. With the advent of the device, the quality of milking increases significantly. Milking with the help of the machine is ideal for any cow, and the speed is much higher compared to manual milking.
4. It takes very little time to master the skills of working with technology. The rules of operation are not complicated. You just need to follow the instructions.

Cow milking machine

The disadvantages of milking devices include the following points:




Types and main models of milking machines

Today, the choice of equipment for milking is quite wide and diverse. First of all, it is worth indicating for how many heads the device is purchased and the preferred type of pump installed in the unit. Here are just a few of the most common models of devices:




Prices for milking machines for cows

Cow milking machine

Maintenance of equipment

Milking machines are used for several hours a day and require regular service checks. The equipment is cleaned, the condition of components and fasteners is checked, any malfunctions are eliminated, and lubrication is carried out in accordance with the instructions. Be sure to check the condition of the teat rubber for integrity, as well as tubes and hoses. Meters and collectors are disassembled and washed once a day. Vacuum pumps and belt tension are also checked daily. Timely technical inspection will ensure uninterrupted operation of the units.

At present, a modern farm cannot be imagined without mechanized equipment. Automation of agriculture keeps pace with the times, almost every household has a milking machine in its arsenal.

Video - Milking machine My Milka

Igor Nikolaev

Reading time: 3 minutes

A A

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 a device, the number of livestock, milking speed, and technical characteristics are always taken into account. 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 its movement, a support frame on wheels is provided. 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; there is a check valve on the cover, 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. These are 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.

No system will work without a vacuum pump for the milking machine. It can be safely called the heart of the whole unit. Novice farmers often face the problem of choosing this equipment. There are a lot of offers and each seller praises his own. Therefore, we decided to explain in an accessible form what determines the choice of a particular model, and what can break in such equipment. Also, this information will be useful to those who decide to assemble the device with their own hands.

Components and types of devices that create pressure

The vacuum system used in the milking machine, regardless of the manufacturer, consists of the same components. This includes a cylinder, on the basis of which a vacuum is created, in fact, the vacuum pump itself, control equipment (vacuum gauge), a pulsator and a vacuum regulator for the milking machine. By the way, the last node is one of the most important.

For normal milk flow in the teat cups, the optimum pressure must be created, and it is 0.48 bar.

The vacuum pump must create a variable vacuum with exactly this indicator. If there is more, it means that the nipples will be injured in cows, and when the indicator falls below the permissible norm, glasses fall off. The frequency creates a pulsator, it ranges from 45-65 cycles per minute. The pulsator is a small valve that is fairly easy to adjust and rarely breaks.

And here we come to the most important point that determines the normal operation, namely the types of pumps:

• vacuum milking unit with a dry rotor;
• oil devices for creating a vacuum;
• water ring vacuum devices.

We’ll immediately warn the homemade ones - with your own hands you can only assemble ready-made nodes, you won’t be able to make the nodes themselves from scratch.

dry rotor

Here we encounter the first trick of the sellers. In addition to creating optimal pressure, there is such an indicator as performance. For an individual milking machine, that is, we milk one cow with one machine, it is 110 l / min. If you are going to milk two cows at the same time with one machine, then the productivity should be 220 l / min. And so on the rise.

The blades in such aggregates are graphite. This grease does indeed have a very high slip coefficient, which is the reason for the quiet operation. But with prolonged use, the blades overheat and can be deformed. Simply put, the pump wedges pretty quickly. And when contacting a service center, you may be accused of violating the operating conditions and denied warranty service.

We conclude that vacuum devices with a graphite dry rotor are a good thing, but on condition that you have no more than 2-3 cows on the farm.

Myths and truth about oil systems

If we compare the principle of operation of oil and dry units, then structurally they differ little. It's just that in these pumps, instead of graphite, a textolite blade boiled in oil is installed.

Plus, there is a constant circulation of oil. As a result of this innovation, it acts not only for its intended purpose, that is, lubrication, but also provides heat dissipation and prevents overheating.

The most common myths regarding such oil systems are rumors about the supposedly difficult setup and high consumption of lubricant. We can assure you that the adjustment in such systems is no more difficult than in dry systems. And fables about wasteful use are most likely invented by competitors.

Therefore, for small farms, where individual milking of cows is provided with one machine, it is better to take the oil system. As practice shows, such a vacuum pump can work without interruption for cooling up to 3-4 hours.

running water

Water ring pumps are installed on milking parlors with simultaneous maintenance of more than 6-8 cows. As you can understand from the name, water acts as a working medium in them, and maintaining its set temperature requires the installation of additional equipment and tracking sensors.

In liquid ring pumps, vacuum regulators for milking machines are complex multi-component devices, and adjustment here requires some training. We do not recommend taking such equipment for farms with less than 50 head of livestock. And on individual devices, such pumps are not installed at all.

The choice of vacuum equipment for cattle milking systems is a delicate matter, but with a strong desire, this issue can be sorted out. The main thing for you to decide on the number of heads, the time of operation of the pumps and the sequence of milking.

Tell us in the comments if you have ever used such systems.

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 region of low pressure and be carried away by the liquid jet. 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 - building

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 can be 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
	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

Some processes require very high pumping speeds, 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

The 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 improves efficiency by reducing power consumption, which allows for a less complex cooling system. An auxiliary pump, passing the same mass of gas, but at higher pressures, can be relatively small.