Venturi nozzle: operating principle, description, application

Pipelines of different purposes must inevitably have technological nodes in which measurements of the serviced medium are made. This applies to traditional water pipes, and to the gas infrastructure, as well as to specialized industrial complexes working with special chemical liquids. In all cases, technologists provide for the equipping of circuits with special flowmeters. One of the most attractive from the point of view of performance features of such equipment is the Venturi nozzle, built in at a certain point of measurement. This component has many advantages, but when choosing a particular model, you should also consider the nuances of use.

General information about the nozzle

The main function of this nozzle is to measure the environment that the target water supply serves. At the same time, the peculiarity of the device is not so much the possibility of contacting liquids with different properties, but rather constructive merits. The point is that the nozzle, or Venturi tube, is able to maintain the optimum pressure index at the time of passage of the medium. That is, the narrowing of the channel, of course, affects this parameter, but not as much as in the case of other types of flowmeters.

There is another important feature. The fact is that the quality of measuring the volume of the passing fluid is often influenced by the diameter of the channel, which, with respect to the measuring device, is the source of the medium. During operation, the Venturi nozzle practically does not change the accuracy of the measurement, depending on the parameters of this channel.

Device

This is a small device in the form of a pipe, the device of which provides the presence of technological sections, designed to perform measurement operations. As a rule, the middle, that is, the central part of the nozzle, is pulled by a clamp, from which a special chamber for measuring, and also a hole for drawing pressure, flow into one of the sides. On the other hand, the shape of the tube turns into a cone and forms a throat. There are several pressure-collecting holes, as well as a diffuser. Usually the jet pump is connected from this side either directly or by means of special sanitary fittings.

Among the design advantages of this product, experts note the efficiency of work in the constrained conditions of the pipeline. However, there is a significant plus for inexperienced masters. It consists in a simplified model of nozzle installation.

How does the Venturi nozzle work?

The device was named after the Italian scientist precisely for the reason that he discovered the effect of reducing pressure, when the working medium passes through the narrowed section. It is according to this principle, supplemented by Bernoulli's law, that such tubes function. In practice, this means that the liquid passes through the narrowed section, during which the pressure in the special annular chambers that the venturi nozzle is supplied is withdrawn. The principle of operation also presupposes the interaction of the tapping channels with direct measurement instruments. For accurate measurement, in particular, a manometer is used, which can be represented both as an analog device and a digital apparatus.

Characteristics

The main criterion for choosing such pipes is the characteristic of the diameter. The most common formats are in the range from 6 to 12 mm. There are also large sizes, which should be selected for specific pipelines. It is also possible to use adapters of the appropriate size, so a strict fit for a particular branch pipe is not so important. In addition to the diameter, the material from which the Venturi tube or the measuring armature as a whole is made is of great importance. Usually stainless steel or carbon steel is used as a base. However, the operational and protective properties are largely determined by the type of coating. Specialists for ensuring durability recommend accessing models treated with enamel or primer, protecting, among other things, and chemical effects. If we are talking about installation in industrial channels, then the best solution in terms of reliability will be galvanized galvanized coatings.

Varieties

The main differences are of a structural nature in the sense that the individual technological parts have a special design. For example, a common type is a nozzle in which a cast conical part is provided without machining. Such models are produced by injection molding using special sand matrices, with the workpiece being rounded only and the neck. A more complicated modification is the model, which also provides for the preliminary processing of the input sections with which the jet pump interacts in different versions. In this case, the central substrate can be made without special treatment.

Principal differences from the above-mentioned species have a device made not by injection but by a welded method. In this case, the conical part can be realized both in a straight line and in a rounded form.

Applications

The design features are due precisely to non-standard ways of using the nozzle. In particular, the armature of this type has found application in injector units that work in conjunction with the mentioned jet pumps. Such mechanisms serve to compress gas mixtures, liquid vapors, and also for their subsequent dispatch to places with increased pressure. It does not dispense with such a nozzle and gas cleaning system in some variations. For example, a nozzle is equipped with a high-speed gas scrubber that filters the served mixtures from submicron and micron particles. Devices of this type are also used in some thermal and steam boilers, but mainly from the industrial sector.

Advantages and disadvantages of the Venturi nozzle

To the undoubted advantages of valves operating on the Venturi effect, one can attribute the possibilities of installation in nodes with varying parameters of feeding channels. However, for the full-fledged use of this advantage, it is necessary to prepare the corresponding adapters from the very beginning. For example, if a Venturi nozzle is being pumped to a pumping station operating at different times of the year, depending on the hydraulic requirements, the volumes of liquid supply may change - accordingly, the settings of the feeding source are also adjusted.

As for the shortcomings, they are reduced to the short-lived use of pipes that do not have a high-quality protective coating. On the other hand, models with the presence of modern surface treatments are much more expensive.

Conclusion

Modern pipelines along with pumping stations are actively transferred to automated control and management facilities with the introduction of electronic consoles. In some functional parameters, the operators of such installations monitor and measure the measuring equipment.

Perhaps the Venturi nozzle is one of the few devices in its class, in which operational efficiency is based precisely on the physical principle of control. The technique of integrating such products into the piping structure determines both the accuracy of the measurements and the minimal negative impact on the functioning of the main channel. It is another matter that regular maintenance of the measuring units is required to maintain optimum performance.