Pumps are units that are most widely used in various industries, as well as in solving some problems in everyday life. There are a large number of varieties of this type of device. Among the most popular and practical to use are diaphragm pumps. Their popularity in Russia is growing. What are the features of their design? What are the advantages of such pumps? What should be considered during their operation?
How the pump works
What is the principle of a diaphragm pump? The scheme is as follows. This device consists of two cavities placed one opposite the other. They are separated by a membrane - a very flexible, but at the same time durable plate. One cavity is filled with air, the other with liquid. Between them, in turn, is a distributor that acts on the membrane so that it moves back and forth with a small amplitude.
As a result, a certain volume of liquid is displaced from one cavity, and is absorbed into another. When the membrane occupies the opposite position - the substance moves in a horizontal plane - due to the presence of special valves in the design of the unit. The diaphragm pump, thus, operates on the principle of displacement of matter - as, however, and piston type devices. But in the latter, as a rule, there are no flexible parts like a membrane. The unit manufacturing scheme guarantees high stability of the device.
Due to the design features, the membrane pump chamber is practically not contaminated. In this regard, this kind of devices in the course of practical operation behave more reliably than traditional piston ones. Diaphragm pumps are best suited for pumping water, liquids with increased density and viscosity, as well as suspensions.
Construction materials
The pump diaphragm is usually made of rubber or flexible and especially durable steel grades. In turn, the case of the device is usually made of materials that are resistant to corrosion and chemicals (if the corresponding specificity of their involvement is assumed). The supplied liquids or suspensions are sent to a pressure pipe, which is most often also made of rubber or PVC.
Benefits of Diaphragm Pumps
The diaphragm pump has several advantages. Firstly, it is an exceptional ease of execution (in most technological implementations). As a rule, in units of this type are not provided for rotating parts and engines. The mechanisms that drive the pumps do not constitute technologically sophisticated devices. As a rule, modern diaphragm pumps are electrically driven with a fairly simple design, with a pneumatic system, or even a manual stroke. Secondly, these units operate with a minimum probability of failure - in fact, this property is due to the simplicity of the design. A diaphragm pump is a device that will last a long time. Thirdly, these devices are very easy to install and install, not demanding on the conditions of storage and transportation. Temperature, humidity and other environmental factors practically do not affect the functionality of the pumps.
Technological Executions
The units in question are different. Among the most common is a pneumatic pump. A membrane unit of this type works without the participation of an electric drive, or any other complex transmitting devices and accessories. Such a device is particularly convenient in terms of transportation. Among other notable properties are the absence of noticeable heating, as well as the tightness, which in some cases allows the device to be used under water. As we noted above, there are electric diaphragm pumps. They are also quite common due to their versatility (they are adapted to the majority of electronic systems used in Russia), high performance, reasonable price. There are also hydraulically driven pumps.
Thus, the main criterion for the classification of devices is the type of motor. In general, the principle of operation of each type of device is the same: the membrane (or, as it is also called, the diaphragm) bends under the influence of a mechanical motor, air (if we are talking about a pneumatic drive) or water (when using a hydraulic system), as a result of which the feed substances. Some pump designs have two diaphragms. Compressed air acts on one , as a result of which it bends, moving the feed substance to the outlet valve. At the same time, in the area where the second membrane is located, a vacuum is formed in which, due to natural physical laws, the substance is absorbed. And so with every drive movement. Two membranes in this case are connected by a mechanical shaft. Also in the pumping substance involved air valves that operate automatically. Thus, two processes occur in the pump: suction (when the first membrane cuts air when moving from the walls) and discharge (when the second diaphragm transfers the pressure of the pneumatic flow to the liquid, which managed to get into the housing, thereby ensuring the movement of the substance to the outlet). The pressure indicators in the region of the back wall of the membrane that releases the liquid, and that located at the inlet, are thus equal. Often the unit in question has a different name - "vacuum pump". At the same time, a 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 double-diaphragm pumps, they are usually pneumatic.
Pump Performance Criteria
Based on what criteria are diaphragm type pumps evaluated in terms of efficiency and quality of work? Experts identify the following set of parameters.
Firstly, a pneumatic diaphragm pump (or one that is equipped with an electric drive) must run smoothly without the need for repairs, additional adjustments, lubrication or other procedures that require production resources.
Secondly, units of this type must be environmentally friendly. In principle, this criterion is met for most modern diaphragm pump models. Not many devices operate, for example, on gasoline or gas.
Thirdly, it is desirable that there should be a workable and easy-to-use system for controlling the speed and volume of the supplied substances. That is, the pump should not work only in the "on" and "off" mode. It is necessary to be able to adjust the intensity of absorption according to the type of substance and the problem to be solved at the factory.
Fourthly, the design of the pumps should be such that, if solid objects get into the cavities, this does not lead to mechanical damage to the device and its breakdown.
Also, some technical experts consider it important that the pumps have a system for protection against power surges (if we are talking about units on an electric drive), as well as efficiency - regarding the same type of devices.
Scope of application
There are several classes of devices in question. There is a metering diaphragm pump, manual, vacuum - and all of them are successfully used in a variety of industries. As a rule, this is the industry - oil and gas, food, paint and varnish. chemical as well as construction. Gradually, devices are mastered by 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 diaphragm pump in their hands) - 12 Volts. Such devices are often used by summer residents to design irrigation systems or a small water supply. Reviews of many owners of personal plots characterize small household diaphragm pumps exclusively on the positive side.
A variety of substances can pump these mechanisms, especially those that are adapted for use in industry - water, liquids with a higher density and viscosity, as well as those that allow solid inclusions (depending on the modification of the device, their allowable size varies from millimeters up to a few centimeters). Some models are adapted for pumping chemically aggressive substances.
Dosing pumps
There is a subtype of the units under consideration - metering pumps. The membrane mechanisms in them, in principle, are the same as in conventional devices of this type, however, the spectrum of their purpose, as a rule, is narrower. Many models of devices are adapted to work just with chemically active substances - when there is a need for their periodic dosage.
What are the features of their design? Diaphragm metering pumps, as a rule, are precision, having an exceptional tightness of the housing. Their performance (pumping rate) is very flexibly regulated. At the same time, modern models provide options with setting the necessary parameters - both in the mode of the current operation of the unit, and in the process of pre-setting. Depending on the design and technological type of the device, this can be done manually or using drive elements.
Among the notable features of metering pumps is the special ease of maintenance. In particular, they are designed, as a rule, in the form of blocks - this leads to simplicity and minimal labor costs for the assembly or installation of devices. Such pumps are usually equipped with valves adapted to the effects 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. In this case, you can adjust the amplitude - in modern models this can be done using the interval 0-100%.
In some cases, the specifics of production involve the use of a "hybrid" model of devices. Namely: a diaphragm piston pump may be required . It combines the advantages of aperture, as well as the "classic". Consider the specifics of units of this type.
Features of diaphragm piston pumps
As such, a vacuum pump (diaphragm), due to the design features, is not always designed to process substances with a high density. In addition, according to some technical experts, its efficiency is not always optimal. Therefore, it is advisable to use a pump with signs of both a diaphragm and a piston. This type of device in many cases works with higher efficiency and reduced energy consumption.
In addition, the scope of diaphragm piston pumps is generally wider than that of diaphragm pumps. In particular, they can be used not only for pumping liquids, but also for moving sludge, in filter presses, as part of the design of spray dryers. Some hydraulic piston diaphragm pumps can also be used in the mining industry, in thermal power plants, in the ceramic industry, and in metallurgy. Thus, devices of this type, having the advantages inherent in both membrane and piston versions, are more universal in many modifications. That is, if diaphragm devices are more adapted for pumping liquids (with a certain percentage of solid inclusions), then “hybrid” devices can quite cope with the movement of substances, in which, in turn, the concentration of insoluble elements may be higher.
However, this type of aggregates, as a rule, is much more expensive than piston or diaphragm separately. However, with proper optimization of the production process, costs can pay back. In addition, energy consumption, due to the more efficient efficiency of “hybrid” pumps, is less - at least in this part, business costs will be reduced. Also, due to the design features of diaphragm piston pumps, the wear of parts on them is often lower than when using diaphragm devices.
How to choose a pump?
Based on what criteria should I choose a diaphragm pump (if we are talking about a device that is not a hybrid type)? The key parameters that can talk about the performance of devices of this type are as follows:
- pressure at the outlet valve (in most cases, the minimum value should be 60 bar - but it all depends on the intended area of use of the pump);
- suction height (preferably at least 4-5 meters);
- the supply rate of the substance (measured in cubic meters per hour - the spread of the recommended parameters is very different - from 0.5 to tens of units, it all depends on the purpose of the device);
- pressure transmission distance (the length of the pipe through which the substance is supplied is at least 50 meters);
- pressure of compressed air (as a rule, in the range of 0.2-0.6 MPa, but there may be other values);
- the permissible temperature range of the pumped substances (usually 0-80 degrees);
- the diameter of the holes at the inlet and outlet, as well as where the air is supplied (indicated in centimeters or inches - usually for imported models);
- the maximum diameter of solid inclusions (may vary from a few millimeters to centimeters).
At the same time, the classification of pumps and the spectrum of their use are so extensive that the selection of optimal parameters when choosing this type of device will always depend on the specific scope of their application.
disadvantages
The advantages of the device in question abound. This is versatility - a membrane pump for water and a large number of other liquids with different physical properties can be used. This is environmentally friendly - as a rule, in the design of devices drives without exhausts and gases are used. This is the breadth of technical performance - there is an electric, hydraulic, pneumatic, manual diaphragm pump. But it should also be said about the shortcomings that are inherent in units of this type.
First, the diaphragm or diaphragm of the pump is constantly in motion. This over time leads to their wear and tear - they become less leakproof, or even fail. But, as a rule, modern equipment manufacturers attach several spare membranes to the supplied kit, and if they run out, you can always order new ones. For example, HBM, supplying its flagship product - a vacuum membrane pump (HBM specializes in such devices), complements the kits with spare parts.
Secondly, due to the intensity of operation, instrument valves also wear out. It is also possible in some cases that they become clogged with solids that are present in the supplied liquids. However, they can be replaced.
Some difficulties in the operation of the pumps may be due to the periodic appearance of steam plugs at the time of liquid absorption (if substances are processed that are characterized by high vapor pressure - for example, methyl chloride).
However, the noted three drawbacks are compensated by the high maintainability of the pump, as well as the ease of replacing worn parts. In addition, in order to minimize the likelihood of damage to the membranes and valves, various types of damping devices can be used at the same time as the units (and, in some cases, as part of their design) to smooth out pulses resulting from the movement of the diaphragms. One way or another, diaphragm pumps are preferred over their traditional counterparts. The economic profitability of many industries is often determined by the ability to use just such units.