Pumps are aggregates that find the widest application in various industries, as well as in solving some tasks in everyday life. There are many varieties of this type of instrument. Among the most popular and practical in use - membrane pumps. Their popularity in Russia is growing. What are the features of their design? What are the advantages of such pumps? What should be taken into account in the process of their operation?
How the pump works
How does the membrane pump work? The scheme is as follows. This device consists of two cavities placed one opposite the other. They are separated by a membrane - very flexible, but at the same time, a solid plate. One cavity is filled with air, the other - with liquid. Between them, in turn, is a distributor, which acts on the membrane so that it moves back and forth with a small amplitude.
As a result, a certain volume of liquid is expelled from one cavity, and in the other - it is sucked. When the membrane occupies the opposite position - the substance moves in a horizontal plane - due to the presence of special valves in the unit design. The membrane pump, therefore, functions on the principle of displacement of the substance - as, indeed, the piston-type devices. But in the latter, as a rule, there are no flexible parts like a membrane. The manufacturing scheme of the unit guarantees high stability of the device.
Due to the design features, the chamber of the membrane pump is practically not contaminated. In this regard, this kind of devices in the course of practical operation behave more reliably than traditional piston. Membrane pumps are best suited for pumping water, liquids with increased density and viscosity, as well as suspensions.
Materials of construction
The pump diaphragm, as a rule, is made of rubber or flexible and extra strong grades of steel. In turn, the body of the device is usually made of materials that are resistant to corrosion and chemical agents (assuming the appropriate specificity of their use). The feed fluids or suspensions are sent to a pressure line, which is also often made of rubber or PVC.
Advantages of diaphragm pumps
The membrane pump has several advantages. Firstly, this is an exceptional simplicity of execution (in most technological implementations). As a rule, in units of this type there are no rotating parts and engines. The mechanisms that drive the pumps are not technologically sophisticated devices. As a rule, modern diaphragm pumps - with an electric drive rather simple design, with a pneumatic system, or even a manual stroke. Secondly, these aggregates work with a minimum probability of failure - in fact, this property is due to the very simple design. The membrane pump is a device that will last a long time. Thirdly, these devices are very easy to install and install, not demanding on storage and transportation conditions. Temperature, humidity and other environmental factors practically do not affect the functionality of pumps.
The aggregates in question are different. Among the most common - the pump is pneumatic. A membrane unit of this type operates without the participation of an electric drive, other kind of complex transmitting devices and rigging elements. Such a device is particularly convenient in terms of transportation. Other noteworthy features are the lack of noticeable heating, and also the tightness, which in some cases makes it possible to use the device under water. As we already noted above, there are diaphragm pumps with electric drive. They are also quite common due to their versatility (they are adapted to most electronic systems used in Russia), high productivity, reasonable prices. There are also pumps driven by a hydraulic drive.
Thus, the main criterion for classifying instruments is the type of motor. In general, the operating principle of each device is the same: the membrane (or, as it is also called, the diaphragm) bends under the influence of a mechanical engine, air (if it is a pneumatic drive) or water (using a hydraulic system) Substance. In some pump designs, two membranes are provided. One is affected by pressurized air, which causes it to flex, pushing the feed to the outlet valve. Simultaneously, in the area where the second membrane is located, a vacuum is formed, into which, due to natural physical laws, the substance is absorbed. And so with each drive movement. Two membranes in this case connects the mechanical shaft. Also in the pumping of substances involved air valves that act automatically. Thus, there are two processes in the pump - suction (when the first membrane dilates the air when moving away from the walls) and injection (when the second diaphragm transfers the pressure of the air stream to the liquid that has managed to enter the housing, thereby allowing the substance to move to the outlet). The pressure indices in the region of the back wall of the membrane that discharges the liquid and that of the one located at the entry site are thus equal. Often the unit in question is called "vacuum pump". The membrane mechanism is present in all technological implementations of the device. The reason for this is its simplicity and, at the same time, high efficiency. As for two-membrane pumps - they are usually pneumatic.
Criteria for the effectiveness of pumps
Based on which criteria are the membrane-type pumps evaluated in terms of efficiency and quality of work? Experts identify the following set of parameters.
First, the pneumatic diaphragm pump (or the one that is equipped with an electric drive) must function smoothly without the need for repair, additional adjustment, lubrication and other procedures that require the cost of production resources.
Secondly, the units of this type should be environmentally friendly. In principle, this criterion is met for most modern models of membrane pumps. Not so many devices function, for example, on gasoline or gas.
Thirdly, it is desirable that there is a workable and easy-to-use system for controlling the speed and volumes of the substances to be delivered. That is, the pump should not work only in the "on" and "off". It is necessary to be able to adjust the intensity of absorption to the type of substance and the problem to be solved in production.
Fourth, the design of the pumps should be such that in the event that solid objects enter the cavities, this does not lead to mechanical damage to the device and its failure.
Also, some technical experts consider it important that the pumps have a system to protect against voltage surges (when it comes to units on the electric drive), as well as efficiency - regarding the same type of devices.
Scope of application
There are several classes of instruments in question. There is a dosing membrane pump, manual, vacuum - and they are all successfully used in a wide variety of industries. As a rule, this industry - oil and gas, food, paint and varnish. Chemical, and also construction. Gradually, the devices are mastered and private individuals - in farms, for example. Miniature devices are becoming quite popular. In particular, some of them can consume very little electricity (despite this, the user will have a full-fledged diaphragm pump) - 12 volts. Such instruments are often used by summer residents for the design of irrigation systems or a small water supply. Reviews of many owners of personal plots are characterized by small household membrane pumps exclusively from the positive side.
Pumping these mechanisms, especially those adapted for use in industry, can be a variety of substances - water, liquids with higher density and viscosity, as well as those that allow solid inclusions (depending on the modification of the device, their permissible size varies from millimeters Up to several centimeters). Some models are adapted for pumping chemically aggressive substances.
There is a subtype of the aggregates we are considering - metering pumps. Membrane mechanisms in them, in principle, are the same as in conventional devices of a given type, but the range of their purpose is, as a rule, more narrow. Many models of devices are adapted to work just the same with reactive substances - when there is a need for their periodic dosage.
What are the features of their design? Membrane dosing pumps, as a rule, are precision, with an exceptionally tight housing. Their productivity (the intensity of pumping substances) is very flexible. At the same time, in modern models, options are provided with specifying the necessary parameters - both in the current operation mode of the unit and during the preliminary setting. Depending on the design and process type of the instrument, this can be done manually or with the help of drive elements.
Among the notable features of dosing pumps is the special ease of maintenance. In particular, they are designed, as a rule, in the form of blocks - this determines the simplicity and minimum need for labor in the assembly or installation of devices. Such pumps are usually equipped with valves adapted to the influence of harmful environments. This is especially important, since these elements are quite sensitive.
Dosing type devices have a fairly large number of moves (movements) - about 100-150 per minute. At the same time, you can adjust the amplitude - in modern models, this can be done using an interval of 0-100%.
In some cases, the specificity of production involves the use of a "hybrid" model of devices. Namely: a membrane-piston pump may be required . It combines the advantages of a diaphragm as well as a "classic" one. Let us consider the specifics of aggregates of this type.
Features of diaphragm-piston pumps
As such, the vacuum pump (membrane), by virtue of the design feature, is not always designed for processing substances with high density. In addition, according to some technical experts, its efficiency is not always optimal. Therefore, it is advisable to use a pump that has both membrane and piston features. This type of device in many cases operate with a higher efficiency and lower power consumption.
In addition, the field of application of membrane-piston pumps, as a rule, is wider than that of diaphragm pumps. In particular, they can be used not only for pumping liquids, but also for moving slurries, in filter presses, as part of the design of spray dryers. Some hydraulic-type membrane-piston pumps can also be used in the mining industry, in the thermal power station, in the ceramics industry, and in metallurgy. Thus, devices of this type, possessing the advantages inherent in both membrane and piston variants, are more universal in many modifications. That is, if the diaphragm devices are more adapted to pumping liquids (with some percentage of solid inclusions), then the "hybrid" devices can quite cope with the displacement of substances, in which, in turn, the concentration of insoluble elements can be higher.
However, this type of aggregates, as a rule, is much more expensive than piston or diaphragm separate. However, with proper optimization of the production process, costs can pay back. In addition, energy costs, due to more efficient efficiency of "hybrid" pumps, are less - at least in this part the costs of business will be reduced. Also, due to the design features of diaphragm-piston pumps, wear parts on them are often lower than when using diaphragm devices.
How to choose a pump?
Based on which criteria should you choose a diaphragm pump (if it's a non-hybrid device)? Key parameters that can talk about the performance of devices of this type are as follows:
- pressure on the outlet valve (in most cases, the minimum value should be 60 bar - but it all depends on the intended use of the pump);
- Suction height (preferably at least 4-5 meters);
- the intensity of the substance (measured in cubic meters per hour - the range of recommended parameters is very different - from 0.5 to tens of units, it all depends on the intended purpose of the device);
- the transmission distance (the length of the pipe through which the substance is fed - at least 50 meters);
- pressure of compressed air (as a rule, in the range 0.2-0.6 MPa, but there may be other values);
- permissible temperature range of pumped substances (as a rule, 0-80 degrees);
- the diameter of the openings at the inlet and outlet, as well as where the air is fed (indicated in centimeters or inches - usually for imported models);
- the limiting diameter of solid inclusions (can vary from a few millimeters to centimeters).
At the same time, the classification of pumps and the range of their purpose are so vast that the selection of optimal parameters for the choice of this type of device will always depend on the specific area of their application.
The advantages of the device in question are abound. This versatility - can use a membrane pump for water and a large number of other liquids with different physical properties. It is environmentally friendly - as a rule, drives are used in the design of devices without exhausts and gases. This is the breadth of technical performance - there is an electric, hydraulic, pneumatic, manual diaphragm pump. But we should also say about the drawbacks that are peculiar to aggregates of this type.
First, the diaphragm or diaphragm of the pump is constantly in motion. This eventually leads to their wear and tear - they become less sealed, and even completely out of order. But, as a rule, modern equipment manufacturers attach several spare membranes to the supplied set, and if they also end, one can always order new ones. For example, the company HBM, supplying its flagship product - the vacuum membrane pump (HBM specializes in such devices), complements the kits with spare parts.
Secondly, due to the intensity of operation, the instrument valves also wear out. Also in some cases, they can be clogged with solids, which are present in the liquids being fed. However, they can be replaced.
Some difficulties in the operation of pumps can be caused by the periodic appearance of steam jams at the time of liquid suction (if processing of substances characterized by high vapor pressures - for example, methyl chloride) takes place.
At the same time, the noted three shortcomings are compensated by the high maintainability of the pump, as well as the ease of replacement of worn parts. In addition, to minimize the likelihood of damage to membranes and valves, simultaneously with the units (and in some cases - as part of their design), various kinds of damping devices can be used to smooth the impulses resulting from the movement of the diaphragms. One way or another, membrane pumps are preferable to use than their traditional counterparts. The economic profitability of many industries is often predetermined by the possibility of using precisely such aggregates.