The operating principle of the homogenizer. Operating principle of high pressure homogenizer

And cooking will become easier

If you like to create ketchup, juice with pulp, mayonnaise, cream, vegetable puree, sauces, cocktails at home, then this is an excellent “magic wand” that makes your work easier and optimizes technological process cooking, can become a homogenizer.

It will perfectly grind the products, ensuring high-quality mixing and homogeneity of the structure.

Of course, this work can be done using a mixer (or even a whisk). But in this case, it is difficult to fully control the particle size and uniformity of the resulting product.

Therefore, homemade ketchups, mayonnaise, juices, despite their naturalness, are often inferior in taste and aesthetic qualities to those products that are produced industrially.

Home homogenizers are not as common in everyday life as in industry and in catering establishments, but still, those who want to achieve perfection from their dishes see homogenizers as a huge help.

But how to choose the optimal homogenizer model for your home?

Planetary and submersible homogenizers

Kitchens of public catering establishments can afford to have two types of homogenizers: planetary and submersible. For a home kitchen, two appliances is too much. You have to choose one thing.

As practice shows, submersible homogenizers can be called the most universal.

Operating mode

The simplest models operate only in pulse mode. In principle, if you cook for a small number of people, and also rarely, and ideal and thorough mixing of components is not fundamentally important for you (for example, because you work exclusively with homogeneous fractions), then this mode is quite sufficient.

But still, it is not these models that are distinguished by their more conscientious and hardworking “character”, but homogenizers that have two modes: pulse and “turbo”.

No splashing!

If you do not want your kitchen to be “endowed” with splashes, then it is best to purchase a model that has a special anti-splash nozzle shape.

In addition, the speed controller will be very helpful. For “deep” work, the speed can be increased (so that the work progresses), and for “external” work, it can be reduced.

At the same time, it is also warmly welcomed that the homogenizer has a special variator, which ensures smooth adjustment of the speed of rotation of the working nozzle.

“Friendly” to different products

However, the speed regulator is, of course, important not only to guarantee the accuracy of the work, but also as a means of correct “cooperation” of the homogenizer with different products. After all, some of them are softer, others are hard.

For home use, a homogenizer oriented at a speed range of 1,500 - 2,500 rpm is quite sufficient. Higher-speed homogenizers are representatives of professional lines.

Tandem of device shape and handle material

One of the serious points that may discourage you from buying a submersible homogenizer is that it is not always convenient to hold in your hands.

However, if a manufacturer really thinks seriously about ergonomics, then, firstly, he “sculpts” the shape that anatomically “feels” the hand, and, secondly, he pays fundamental attention to the “outfit” of the handle. If the handle is rubberized, then this is a huge bonus to the “piggy bank” of success!

Ventilation holes

When purchasing a homogenizer, you should not ignore how the ventilation holes are located on the structure. It is best if they are located at the top of the equipment. In this case, the risk that excess air flows will get into the whipped mixture is minimized.

It is also important that the ventilation openings are protected from getting the whipped mixture into them. This aspect should never be ignored when purchasing kitchen appliances.

Material

Stainless steel is the preferred material for homogenizer nozzles. And again, it is better to choose either a steel body or one made of composite materials. But standard plastic breaks down quite quickly. After all, the device, by the nature of its activity, leads an intense dynamic “life”. And don’t forget that this is, for example, not a “quiet” teapot!

Purchase

Homogenizers are a relatively new type in our country. household appliances. Also, do not forget that now many home homogenizers are a “flower” attachment for an immersion blender: it does not always work perfectly, but with it you have a choice - to buy a homogenizer separately or “as part of” the blender.

Reliable and high-quality homogenizers for your kitchen, and delicious and interesting dishes for your table!

Homogenizer

Designed for crushing and uniform distribution of fat globules in milk and liquid dairy products. Homogenizers are multi-plunger pumps high pressure with homogenizing head. Homogenizers consist of the following main components: a crank mechanism with a lubrication and cooling system, a plunger block with homogenizing (one or two stages) and pressure heads and a safety valve, a frame with a drive. The drive is carried out from an electric motor using a V-belt drive. Homogenization is carried out by passing the product under high pressure, at high speed, through a homogenizing head, which is two (one) stage slots between the ground valve and the seat, connected by a channel. The pressure in the homogenizer is regulated by rotating the screws (from 0 to 200 atm), which change the size of the gap between the valve and the seat.

Homogenizers use a forced lubrication system for the most heavily loaded, rubbing pairs in combination with oil spraying inside the housing. All parts in contact with the product are made of food grade stainless steel.

Figure 8 - Homogenizer A1-OGM

Homogenizer for two-stage homogenization: 1 - coil cooler; 2 - pipeline for chalk supply; 3 - crank mechanism; 4 - homogenizing valve; 5 - cylinder block; 6 - coupling; 7 - bed; 8 - device for extending the electric motor

Milk packaging

Figure 9 – Scheme for packaging milk in plastic bags

Automatic machine for packing milk into bags (bags): 1-roll; 2-mechanism for applying the date; 3-bactericidal lamp; -forming pipe; 5-dispenser; 6 - longitudinal welding mechanism; 7-mechanism for transverse welding and cutting of packages; 8 - brewed and cut package; 9-packet transporter; 10- bunker; 11-photocell of the counting device. The packaging paper tape is first fed from roll 1 into the chemical treatment tank, which is filled with hydrogen peroxide, and then goes around the guide roller and passes into the zone of the germicidal lamp 3. In the forming wheel, the tape is rolled into a tube 4. The paper tube passes through an electric heater, in which it is quickly heated up to 300-400°C, as a result of which hydrogen peroxide instantly decomposes, and thereby achieves reliable sterilization of bags. After the bags are sterilized, sterilized and cooled milk flows into the paper tube in a continuous stream. In this case, pricing is completely excluded. At the bottom of the conveyor there is a mechanism 7 for piecewise cutting of bags filled with milk. The cut bags are fed into the buckets of the stacker's lifting mechanism, which is fixed at the base of the machine. The packages are automatically placed in special hexagonal baskets.

2. Review of literature sources

Currently, there is a wide variety of machines for homogenizing dairy products of Russian and foreign production. These include homogenizers with a one- and two-stage homogenizing head, as well as valve and plunger ones, with high and low homogenization pressure. Let's look at some equipment options for homogenization.

Homogenizers are designed for crushing and uniform distribution of fat globules in milk and liquid dairy products. Homogenizers are high-pressure multi-plunger pumps with a homogenizing head. They are driven by electric motors using V-belt transmission.

Homogenization is carried out by passing the product under high pressure at high speed through a homogenizing head, which consists of two stages - slots between the ground valve and seat, connected by a channel. The pressure in the homogenizer is regulated by rotating screws that change the size of the gap between the valve and the seat. In this case, at the first stage, the homogenization pressure required for a particular product is set, and at the second stage, the working pressure is set.

Homogenizers consist of the following main components: a crank mechanism with a lubrication and cooling system, a plunger block with homogenizing and pressure heads and a safety valve, a frame with a drive. The homogenizer is driven by an electric motor using a V-belt drive. The crank mechanism of the homogenizer is designed to convert the rotational motion transmitted by the V-belt transmission from the electric motor into the reciprocating movement of the plungers, which, through lip seals, enter the working chambers of the plunger block and, making suction and discharge strokes, create the necessary pressure of the homogenizing liquid in it.

The crank mechanism consists of a housing; crankshaft mounted on two tapered roller bearings; bearing caps; connecting rods with covers and liners; sliders hingedly connected to the connecting rods using fingers; glasses; seals; the housing cover and the driven pulley, cantilevered to the end of the crankshaft. Internal cavity The housing of the crank mechanism is an oil bath. A oil level indicator and a drain plug are mounted in the rear wall of the housing.

2.1 Homogenizer OGB-M

Figure 10 – Homogenizer OGB – M

a – general view: 1 – bed; 2 – electric motor; 3 – V-belts; 4 – tension screw; 5 – pulley; 6 – crankshaft; 7 – homogenizing head; 12 – flushing device; b – section of the cylinder block and homogenizing head: 1 – suction channel; 2 – suction valve; 4 – discharge channel; 5 – pressure gauge; 6 – screw; 7 – spring; 8 – rod; 9 – valve; 10 – saddle.

2.2 Homogenizer A1-OGM-2.5

Figure 11 - Homogenizer A1-OGM-2.5

1 - bed; 2 - safety valve; 3 - pressure gauge head; 4 - plunger block; 5 - lubrication system pressure gauge; B - ammeter; 7 - homogenizing head.

Technical characteristics of homogenizer A1-OGM-2.5

Capacity, l/h 1250

Maximum homogenization pressure, MPa 18

Number of homogenization stages, pcs. 2

Number of plungers, pcs. 3

Installed engine power, kW 12

Overall dimensions, mm 970×860×1400

Homogenizers of the A1-OGM-2.5 brand have a forced lubrication system for the most loaded rubbing pairs, which is used in combination with oil spraying inside the housing, which increases heat transfer. The oil in these homogenizers is cooled by tap water through a coil, a cooling device placed at the bottom of the housing, and the plungers are cooled by tap water falling on them through holes in the pipe. The cooling system is equipped with a flow switch designed to control water flow. The forced lubrication system includes a strainer, an individually driven oil pump, a distribution box, a safety valve and a pressure gauge for monitoring the pressure in the oil system. A plunger block is attached to the body of the crank mechanism using two pins, which is designed to suck the product from the supply line and pump it under high pressure into the homogenizing head. The plunger block includes a block, plungers, lip seals, lower, upper and front covers, nuts, suction and discharge valves, valve seats, gaskets, bushings, springs, a flange, a fitting and a filter, which is installed in the suction canopy of the block, To the end A homogenizing head is attached to the plane of the plunger block, designed to perform two-stage homogenization of the product by passing it under high pressure through the gap between the valve and the valve seat in each stage. The homogenizing head consists of two single-stage heads of similar design, joined together and connected by a channel allowing the product to pass sequentially from the first stage to the second. Each stage of a two-stage homogenizing head consists of a body, a valve, a valve seat and a pressure device, including a glass, a rod, a spring and a pressure screw with a handle.

The homogenization pressure is adjusted by turning the screws. When establishing the product homogenization mode, 3/4 of the required homogenization pressure is set at the first stage, and then at the second stage, by rotating the pressure screw, the pressure is increased to the working pressure. A pressure gauge head is attached to the upper plane of the plunger block, which is designed to control the homogenization pressure, i.e. pressure on the discharge manifold of the plunger block. The pressure gauge head has a throttling device, which makes it possible to effectively reduce the amplitude of oscillation of the pressure gauge needle. The pressure gauge head consists of a body, a needle, a seal, a nut that presses the seal, a washer and a pressure gauge with a diaphragm seal. A safety valve is attached to the end plane of the plunger block on the side opposite to the mounting of the homogenizing head, which prevents the homogenization pressure from increasing above the nominal one. The safety valve consists of a screw, lock nut, foot, spring, valve and valve seat. The safety valve is adjusted to the maximum homogenization pressure by rotating the pressure screw, which transmits the pressing force to the valve via a spring. The frame is a welded structure made of channels covered with sheet steel. It is installed on the upper plane of the frame crank mechanism. Inside the frame, a plate on which the electric motor is mounted is hingedly mounted on two brackets. On the other side, the plate is supported by screws that regulate the tension V-belts. The frame of homogenizers brand A1-OGM-2.5 is installed on four height-adjustable supports. The side windows of the frame are closed with removable covers. The upper part of the frame is covered with a casing designed to protect the mechanisms from damage and give the homogenizer the necessary aesthetic shape. Milk or milk product is supplied by a pump into the suction channel of the plunger block. From the working cavity of the block, the product is fed under pressure through the discharge channel into the homogenizing head and passes at high speed through the annular gap formed between the ground surfaces of the homogenizing valve and its seat. In this case, the fat phase of the product is dispersed.

Subsequently, the product from the homogenizing head is sent through a pipeline for further processing or storage.

2.3 Homogenizer GM-0.5/20

Figure 12 - Homogenizer GM-0.5/20

Technical specifications

Productivity, l/hour 500

Power, kW 4

Number of homogenization stages, pcs. 2

Homogenization pressure, MPa 20

2.4 Vacuum mixer-homogenizer

Figure 13 - Vacuum mixer-homogenizer

The installation is a vacuum reactor with a mixing device, to which a homogenizer is connected for recirculation. After loading the main components into the reactor tank, the air is pumped out of the system, and the installation is switched on to the recirculation mode, during which the loaded components are crushed and mixed. The funnel built into the system allows you to reload the necessary components during the homogenization process.

The main advantage of this design is that it allows you to mix together components that, when mixed in the open air, harden during the mixing process.

2.5 Homogenizer SVA - 3

Figure 14-Homogenizer SVA - 3

Homogenizer model SBA - 3 is used to obtain a finely dispersed, uniformly mixed, stable structure of viscous products obtained from several ingredients. The product entering the homogenizer passes through narrow, constantly changing gaps between the rotor and stator. As a result, the product is crushed to a finely dispersed state and simultaneously pumped. The homogenizer is used in the food, cosmetic, chemical, pharmaceutical industries.

Technical characteristics of homogenizer SVA - 3

2.6 Homogenizers manufactured by Bertoli Srl H5150

Figure 15 - Homogenizers manufactured by Bertoli Srl

H5150 Specifications.

Capacity l/hour 22000

Number of plungers, pcs. 5

Energy consumption, kW 160

Overall dimensions, mm 1440х1680х2660

Technical advantages

1. High efficiency of milk homogenization. At a pressure of 200 bar and a temperature of 65...70C, the homogenization efficiency is 90...95%, which is 10...15% better than domestic analogues. The average size of fat globules after homogenization is 0.85 µm.

2. No vibration or noise. The homogenizer supports are attached to the frame through vibration-absorbing connections, which in practice eliminates vibration during operation. Test vibration level within 0.45...3.0 mm/sec (for different measurement points), meets EU requirements.

3. Wear resistance of the valve group. The homogenizing head is made of nickel-chromium-molybdenum alloy specifically for high pressure applications. Self-centering stainless pistons. Valves and seats are made of high-quality wear-resistant stainless alloy.

4. Fixed and adjustable performance. The homogenizer can be equipped with a control cabinet for fixed output or a control cabinet for adjustable output.

3. Design development

Currently, there is a wide variety of machines for homogenizing dairy products of Russian and foreign production. These include homogenizers with a one- and two-stage homogenizing head, as well as valve and plunger ones, with high and low homogenization pressure.

Homogenization is carried out by passing the product under high pressure at high speed through a homogenizing head, which consists of two stages - slots between the ground valve and seat, connected by a channel. The pressure in the homogenizer is regulated by rotating screws that change the size of the gap between the valve and the seat. In this case, at the first stage, the homogenization pressure required for a particular product is set, and at the second stage, the working pressure is set. This course project examines the modernization of a homogenizing head, to increase the performance of which a vortex effect is used. Let's take a closer look at the design of the modernized homogenizing head.

3.1 Homogenizing head

containing a seat and a valve with a slot located between them, formed by concentric annular grooves of the seat and valve, with a discharge chamber located in the slot, grooves for supplying the product to the slot located in the upper part of the head, a damping cavity built into the seat or valve, characterized in that that the seat and valve are designed to rotate in opposite directions under the action of a moving flow of milk and are installed in bearings located in a stationary housing containing a fitting for outputting a homogenized product, while the grooves for supplying the product to the labyrinthine slit are made in the form of a confuser obtained by boring the valve seat with the formation of conical surfaces, with the tops of their cones directed in opposite directions, and along the entire length of the conical surfaces of the seat and valve, at an angle to the generatrices, round grooves are made, directed in different sides at the seat and valve.

The homogenizing head works as follows:

The flow of a product, for example milk, is fed under pressure into the grooves and, moving towards the labyrinthine slit 3, causes the seat and valve to rotate in different directions due to the round grooves located on their conical surfaces. This helps to avoid obliteration of the gap and makes it possible to easily adjust the size of the gap during the homogenization process. When flowing at high speed through the gap, the product flow is homogenized, i.e. coarse suspensions and large particles of the product, such as fat globules, are crushed. The efficiency of product homogenization is facilitated not only by the presence of a gap around obstacles and turns, but also by the rotation of the seat and valve in opposite directions. The homogenized product is discharged through the pipe.

The proposed homogenizing head makes it possible to improve the quality of homogenization due to additional turbulization of the flow caused by the rotation of the seat and valve in opposite directions. As a result, the obliteration of the gap is significantly reduced, which has a positive effect on the quality of homogenization and, as a consequence, the productivity of the homogenization process increases.

3.2 Engineering calculations

The productivity of the homogenizer is equal to the flow rate of its pump. For plunger pumps, the flow rate depends on the diameter of the plungers and the stroke, the number of plungers and the crankshaft speed. For given machine parameters, productivity V sec can be calculated using the formula

V sec = m 3 / sec, (2.6)

where d is the diameter of the plunger, m;

S – plunger stroke, m;

P - angular velocity crankshaft rotation, rpm;

φ – volumetric efficiency of the pump (for milk = 0.85; for a viscous product much less);

z – number of plungers.

The power N required for the operation of the homogenizer is determined using the formula for calculating pump power

where p 0 is the pressure developed by the homogenizer plungers (pressure in front of the valve), N/m 2 ;

η – mechanical efficiency of the homogenizer (= 0.75).

As a result of the expenditure of a large amount of mechanical energy, which is converted into heat, the product noticeably heats up during valve homogenization.

The increase in product temperature in the homogenizer can be calculated using the formula:

∆t = deg, (2.8)

where N is the required power, W;

V sec – volumetric productivity of the homogenizer, m 3 /sec;

ρ – product density, kg/m3;

C—mass heat capacity of the product, J/(kg∙ deg).

Calculation and selection of design parameters of the homogenizing head.

The efficiency of homogenization depends on the hydraulic conditions in the valve gap area. These conditions are mainly determined by the homogenization pressure, which determines the speed of fluid movement in the gap and the height of the valve gap. In a radially diverging valve gap, the flow velocity V 1 has highest value at the beginning of the slot at radius r. As the flow expands towards the outlet, the speed decreases to a value of V 2. The highest theoretical speed V 1 depends on the homogenization pressure and can be calculated using the Torricelli formula:

Where – homogenization pressure, Pa;

Homogenizer A1-OGM is designed for crushing and uniform distribution of fat globules in milk and liquid dairy products, as well as ice cream mixtures. They are used at dairy industry enterprises in various technological lines for processing milk and producing dairy products (sour cream, cream, kefir, drinking milk, etc.). The dimensional drawing is shown in Figure 5.

Figure 5 - Dimensional drawing of homogenizer A1-OGM

1-bed; 2-safety valve; 3-gauge head; 4-plunger block; 5-pressure gauge of the lubrication system; 6 - ammeter; 7-homogenizing head

Technical specifications homogenizer is shown in Table 2.

Table 2 - Technical characteristics of homogenizer A1-OGM

The homogenizer consists of the following main components: a crank mechanism with a lubrication and cooling system, a plunger block with homogenizing and pressure heads and a safety valve, a frame with a drive. The homogenizer is driven by an electric motor using a V-belt drive (Fig. 6).

Figure 6 - General form homogenizer A1-OGM:

1-bed; 2-drain plug; 3—oil indicator; 4-crank mechanism; 5—connecting rod; 6—liner; 7-finger; 8—slider; 9—plunger; 10-homogenizing head; 11-plunger block; 12—coil; 13—electric motor; 14—slab; 15—device for tensioning belts; 16—support; 17—drive pulley; 18—driven pulley; 19-crankshaft; 20 V-belt; 21 - oil pump

The crank mechanism of the homogenizer is designed to convert the rotational motion transmitted by the V-belt transmission from the electric motor into the reciprocating movement of the plungers, which, through lip seals, enter the working chambers of the plunger block and, making suction and discharge strokes, create the necessary pressure of the homogenizing liquid in it.

The homogenizer has coercive system lubrication of the most heavily loaded rubbing pairs, which is used in combination with spraying oil inside the housing, which increases heat transfer. The oil in these homogenizers is cooled by tap water through a coil, a cooling device placed at the bottom of the housing, and the plungers are cooled by tap water falling on them through holes in the pipe.

A plunger block is attached to the body of the crank mechanism using two pins, which is designed to suck the product from the supply line and pump it under high pressure into the homogenizing head. A homogenizing head is attached to the end plane of the plunger block, designed to perform two-stage homogenization of the product by passing it under high pressure through the gap between the valve and the valve seat in each stage.

The homogenizing head consists of two single-stage heads of similar design, joined together and connected by a channel allowing the product to pass sequentially from the first stage to the second. Each stage of a two-stage homogenizing head consists of a body, a valve, a valve seat and a pressure device, including a glass, a rod, a spring and a pressure screw with a handle.

The homogenization pressure is adjusted by turning the screws. When establishing the product homogenization mode, 3/4 of the required homogenization pressure is set at the first stage, and then at the second stage, by rotating the pressure screw, the pressure is increased to the working pressure.

The frame is a welded structure made of channels covered with sheet steel. A crank mechanism is installed on the upper plane of the frame. Inside the frame, a plate on which the electric motor is mounted is hingedly mounted on two brackets. On the other side, the plate is supported by screws that regulate the tension of the V-belts. The upper part of the frame is covered with a casing designed to protect the mechanisms from damage and give the homogenizer the necessary aesthetic shape.

Milk or a dairy product is supplied by a pump into the suction channel of the plunger block. From the working cavity of the block, the product is fed under pressure through the discharge channel into the homogenizing head and passes at high speed through the annular gap formed between the ground surfaces of the homogenizing valve and its seat. In this case, the fat phase of the product is dispersed.

Subsequently, the product from the homogenizing head is sent through a pipeline for further processing or storage; ; ; .

Ultrasound is very widely used for preparing homogeneous mixtures (homogenization). It all started with the experiments of scientists Loomis and Wood on liquid media and ultrasound, they discovered that two immiscible liquids poured into one container form an emulsion if they are subjected to ultrasonic irradiation in this container. Preparation of colloidal solutions, that is, a fine suspension of oil in water, plays a big role in modern industry, this is how they make consumer goods (paints, cosmetics, mayonnaise). It is an emulsion in structure. Almost everywhere Ultrasonic method is used in industry preparing mixtures. At the time Loomis and Wood conducted their first experiments, the use of ultrasonic mixing of immiscible mixtures in industry seemed an unattainable future. The main problem then was the creation of suitable converters (sound sources). Only in 1951, thanks to the English scientists Cottel and Goodman, who developed the design of a liquid whistle, did the “re-equipment” of all industries in the world begin with a new, economical ultrasonic homogenizer.

Before the advent of ultrasonic homogenizers, physicists and industrialists prepared emulsions in very labor-intensive ways - stirring and shaking mixtures, most often using high pressures, which required a lot of energy. So, homogenizer operating at high pressures and producing 1000 liters of emulsion per hour consumed about 12 l. With. power. Ultrasonic homogenizer, consisting of a mixing chamber, liquid ultrasonic whistle, motor and pump, produces the same amount of production at a cost power 2 l. With. And at the same time, in terms of the quality of emulsification, the mixture prepared using the second method was no different from the mixture prepared using the second method. From the photo attached to the side, you can see the advantage of ultrasonic homogenizers (view on the right) compared to rapidly rotating screws for preparing emulsions under high pressure (view on the left).

Traditional products that are made using homogenizers: baby food, cosmetics, ointments, seasonings, varnishes, sauces, processed cheeses, margarine, mayonnaise, nut butter, toothpaste, tomatoes, cocktails and, of course, emulsion paints.

If we consider a device for the ultrasonic homogenization process, then ultrasonic liquid whistles, of course, have shown themselves to be the most effective, although compared to electric sources of ultrasound, liquid ultrasonic whistles are low-power. And yet, for homogenization, they have a significant advantage: ultrasonic waves arise directly in the liquid medium, and there is no loss of energy from ultrasonic waves when they pass from one medium to another.

The most widespread type of whistle was made by Cottel and Goodman in the early 50s of the 20th century, and the design has not changed since then. The essence of the operation of such a whistle is simple, in it a flow of liquid under high pressure comes out of an elliptical nozzle and is directed to a steel plate, which is an ultrasonic wave generator. Due to the simplicity and stability of their design (only the oscillating plate is destroyed), such systems are durable and inexpensive.

Performance Dependency

Homogenizer characteristics such as:

• Bandwidth— productivity liters per hour. Depends on the pump and bandwidth the whistle itself. It is worth noting that the flow rate depends on the flow rate and, accordingly, the vibration frequency of the plate against which the liquid hits.
• Operating frequency— for different environments, certain frequencies are the most optimal, therefore, for the most efficient operation of the whistle, its own liquid (density, viscosity) and a certain liquid flow rate are selected. Ultrasonic milk homogenizers operate at frequencies of 25 kHz and, accordingly, the vibration plate is adjusted for these frequencies (angles of the plate directed to the flow, thickness and length of the plate).
• Power- pump indicator, the characteristic depends on the throughput of the whistle.