Pumps nd 2 5. Dosing pumps
Dosing pumps are special devices necessary for volumetric dosing under the pressure of any liquids. Such a device, whether it is a manufacturer of Prominent, Evo, Tekna, Dlx, Seko, Etatron, Emec or any other, is an integral element in various industries.
You will learn more about such units from this article.
After adjusting the size of the pump, it is necessary to discuss its design. The dosing pumps available in the market are made of various materials. Some of the most important factors to consider when choosing a pump for dosing chemicals at a sewage treatment plant are corrosion resistance, wear and solvent exposure.
This is necessary because solvent-based chemicals, for example, can destroy plastic pump heads, and acids and bases are only compatible with stainless steel and some well-known steel alloys. Abrasive slurries can also cause wear on some building materials. When choosing a metering pump, leakage protection must also be considered.
1 Device and principle of operation
A device having a dispenser consists of the following elements:
- electric motor itself;
- gearbox;
- system adjustment device;
- hydraulic cylinder;
- buttons for control.
A system adjustment device is needed to convert the rotational moment of the drive shaft to the reciprocating movement of the piston mechanism. Also adjustment device for Prominent, Evo, Tekna, Dlx, Seko, Etatron, Emec allows you to control and adjust the piston stroke length. The hydraulic cylinder ND is necessary so that the device can carry out the work process itself.
Two diaphragm heads are available with leak detection and alarm capabilities. These devices are invaluable in cases where leaks need to be recorded immediately. Their use, for example, in systems in which contact between the process fluid and the pump hydraulic fluid is unacceptable or when leaks cannot be tolerated due to the toxic or dangerous properties of the pumped liquid.
Another important aspect of choosing the right pump is the type of drive. It must correspond to the available resources of electric energy, air, gas or other means of pump movement. If the metering pump is installed outdoors, the motor must be protected from direct sunlight.
As for the principle of operation, the operation of the Prominent, Evo, Tekna, Dlx, Seko, Etatron or Emec ND system consists in suctioning the required volume of acid or other liquid during the return stroke to the device with its further pushing into the dosing line.
Most pumps operate at freezing temperatures, provided that the pumped liquid does not freeze and the appropriate lubricants are not used. In most cases, it may be necessary to control the temperature and take measures against frost. When working in aggressive environments, a special protective coating may be required.
Control systems There are several options for controlling metering pumps in a sewage treatment plant. They can be adjusted manually by changing the stroke length of the pump, so that the pump can operate from 10 to 100% of its power. Using the manual speed controller, you can set the speed. The combination of the two methods will provide additional adjustment within the range of the drive depending on the speed.
Due to the change in the frequency and stroke length of the electromagnetic devices of the system, there is the possibility of adjusting and the performance of ND, which allows to achieve an accurate dosage of acid and other liquids. As for the productivity itself, depending on the needs (for small tests in the laboratory and for industrial purposes), it can vary from 5-20 ml / h to 40,000 l / h, this is the main characteristic of the systems.
The flow rate of the metering pump can also be controlled automatically in response to a process signal using electric or pneumatic positioning mechanisms that change the pump stroke or speed controllers that change the stroke speed. Using a positioning mechanism provides the greatest ratio between the maximum and minimum capacity of the pump 10.
Using a speed controller will provide a ratio equal to the speed of the pump relative to its minimum operating speed. It is not practical to use a speed controller for metering pumps with motors that operate at speeds of less than 100-150 strokes per minute, since the adjustment range will not be very wide.
1.1 Varieties
Dosing pumps can be used in various fields of human activity. A huge range of uses has led to the production of many types of ND systems, which differ in type, modification and performance. In the presence of such a diversity of species, it was decided to divide the ND according to several characteristics. By their design, they distinguish:
The engine delay leads to a longer stroke, and, from a practical point of view, motor-driven pumps should not operate at a speed of less than 15 strokes per minute. Solenoidal diaphragm pumps receiving electromagnetic pulses can operate with less than one cycle per minute, since the characteristics and time of each stroke from the beginning to the end are the same at any speed.
The moving parts of modern diaphragm pumps provide long-lasting and reliable operation at all operating speeds. When pumping out viscous or abrasive chemicals, high speeds should be avoided. When the metering pump is controlled by automatic, electrical or pneumatic positioning mechanisms, the number of doses remains constant until the volume of each dose is reduced, maintaining doses uniformly distributed in a continuous flow line. Using the speed controller changes the speed.
- lP plunger systems;
- diaphragm or diaphragm dosing pumps.
Also, Prominent, Evo, Tekna, Dlx, Seko, Etatron or Emec LP systems can differ in type of drive, they can be equipped with mechanical or hydraulic drives. It should also be noted that recently a peristaltic apparatus with a dispenser is most used and distributed.
The volume remains the same, but the doses are given at a lower frequency. However, this can lead to an unfavorable result due to the fact that discrete chemical volumes are distributed over much wider limits. Therefore, the choice of a dosing pump control system depending on the specific application is key.
Acquaintance of operators of plants for cleaning from size factors and the choice of metering pumps will help to discuss the right issues with the supplier. Once the pump is selected, the pump can be installed, and this process must again be adapted to the specific working environment.
The peristaltic apparatus in the ND system allows the dosage of viscous, corrosive, and also crystallizing elements. Unlike plunger devices that cannot work with such fluids, a peristaltic unit with a dispenser does an excellent job of this task. We dwell on two types of ND.
It is recommended that the entire installation process of the metering pump be planned from the outlet tank or other fluid source to the supply point and determine which accessories are needed. The suction line should also be sized appropriately, with minimal curves and elbows. Dosing pump accessories can include nozzle fittings, diaphragm isolation valves, check and bypass valves, pulsating dampers, and more.
Thus, reliable and energy-efficient metering pumps for handling a wide range of liquids and suspensions should be used for water treatment. Choosing the most suitable chemical metering pump will help you achieve faster and safer process optimization goals and better wastewater treatment efficiency.
1.2 Plunger
Plunger systems with a dispenser: Prominent, Evo, Tekna, Dlx, Seko, Etatron or Emec are designed to dispense large volumes or create a strong pressure head of an aggressive fluid. In particular, we are talking about toxic or aggressive environments, the density of which can be 2000 kg / m³. Plunger pumps operate on the principle of moving the piston of the structure, within which a vacuum or high pressure is generated.
The range of application is extremely versatile: it covers a wide range of flow rates and offers various sizes of dosing heads, materials and accessories. Seamless dosing with low heart rate. This means less stress in all parts of the assembly, such as hoses and valves, and contributes to longer service intervals throughout the system.
Engines that meet all operational requirements. An ideal choice of materials - casing and waterproof parts. Over the years, capital and spare parts costs are low: a wide selection of metering heads, valves and accessories allows you to choose the exact degree of chemical resistance required. All parts in contact with liquids must be resistant to the chemicals used.
When a vacuum is formed in the plunger device having a dispenser, the system absorbs the liquid, and when pumping it pushes it out. The operation of the Prominent, Evo, Tekna, Dlx, Seko, Etatron or Emec systems is due to the operation of the valves. Before buying a plunger device material compatibility should be considered, of which the system is made, with the liquid that you will work with. The drives of such ND are usually mechanical.
Safe and trouble free operation. A standard built-in safety valve and active diaphragm protection system protect the pump and the entire system from overpressure if the exhaust pipe is blocked. In addition, the degassing valve of the pump provides high pump reliability, installation and process reliability.
Approval Protocols and Certificates. Flexibility - in the configuration of the pump and its use. We offer metering pumps in various configurations to meet your requirements: Flexible flow control: manual or automatic stroke adjustment with an electric servomotor. The pumps are equipped with a double diaphragm with a fault indicator or special metering heads for electric heating. Impregnated parts are available in a combination of materials that are suitable for almost all dosing tasks.
1.3 Membrane or diaphragm
As for the diaphragm systems Prominent, Evo, Tekna, Dlx, Seko, Etatron, Emec or from other manufacturers, in this design the suction procedure is carried out as a result of the functioning of the membrane, in particular, its oscillation. The same membrane also acts as a working chamber. In general, by design, such units having a dispenser resemble a piston device.
Choose the best combination for your special dosing tasks. Suitable for demanding applications. Dosing of various chemicals at all stages of the power plant.
- For boiler water supply, water cooling and process water treatment.
- Dosing of high pressure ammonia, hydrazine and phosphate.
Dosing of chemicals in oil and gas production processes. Distribution of additives and odorizing gas catalysts for safety aspects in the event of a leak.
- Dosing of chemicals for cleaning and technological treatment of water.
- Isolation of paraffin as lubricants in oil pipelines.
- Drying inhibitors and anti-corrosion chemicals to protect pipelines.
To ensure that the fluid flow is almost continuous, the system is equipped with two chambers interconnected, each of which has a valve mounted on the suction or pressure line. When compressed air is supplied to the air chamber, water or other liquid begins to be displaced into the pressure pipe.
Dosing of alcohol or methanol in wastewater treatment. Cleaning of kerosene and gasoline in the field of engineering and aviation. Dosing of ethanol and methanol. Use of alcohol for food purposes for disinfection of meat and wrapping baking. Rough environment Higher speeds and pressures. . We will be happy to tell you how to best solve your problem. Their reliability has been proven by countless trials, long-term experience and user preferences.
Our production of centrifugal pumps with a magnetic drive contains more than 10 different designs and 100 different models. From compact designs for various process plants to complex manufacturing processes. These pumps are characterized by high reliability, durability, durability and absolutely do not require maintenance. The goal of the effort is always an affordable price, performance, quality, ease of use and flexibility.
2 Advantages and disadvantages of orifice plates
The dosing pumps Aqua, Prominent, Evo, Tekna, Dlx, Seko, Etatron, Emec have both advantages and disadvantages of construction. Let's start with the pros:
- In the design of the working chamber of the device having a dispenser, there are no moving mechanisms. As a result, the ingress of impurities or dirt into the liquid during operation through the dispenser is eliminated. Typically, such membrane NDs are used for work in the pharmaceutical industry.
- Such structures can be made without problems from materials resistant to corrosion and other aggressive environments. This factor is fundamental in the operation of these NDs in the chemical industry.
- In the working chamber of the system there are no so-called stagnant zones. therefore these designs can be considered universal.
Also consider the disadvantages:
Gear pumps work effortlessly and have a wide range of applications. We also offer a wide range of compact pump types for the most complex processes and instrument types. Specialty - leaky pumps with a magnetic drive. The use of these pumps ranges from clean water to medical technology or special use for complex technological tasks.
Electromagnetic pumps are the most widely used types of pumps used for dispensing liquids. These pumps are typically designed to dispense low viscosity liquids with varying chemical aggressiveness. Depending on the type of liquid, concentration and temperature, a material is selected that is in contact with the liquid to be dispensed.
- Compared to plunger devices, the membrane designs of Prominent, Evo, Tekna, Dlx, Seko, Etatron, Emec or from another manufacturer are less accurate in terms of dosage. If over time the membrane stretches on the dispenser or traces of mechanical stress appear on it, then this also greatly affects the accuracy.
- Due to the small strength of the membrane itself, large particles can cause its destruction. In addition, the tightness of the chamber may simply be lost.
- Again, due to the physical characteristics of the chamber, the performance and working pressure of a system with a dispenser will not be particularly high.
An important structural element of the pump is a strong diaphragm, which should safely separate the pump part from the magnet, so that even at maximum working pressure, no liquid penetrates into the inside of the pump and the magnet or control electronics are not damaged.
When designing a pump, you must remember that the pump is so voluminous, and therefore the fluid supply is not completely smooth, but pulsating. Pumps of this type are self-priming, the suction height is determined by the frequency of the pump and the viscosity of the fluid.
Recommended pump accessories include a non-return valve that prevents clogging and ventilation of the pump ball valves when changing the tank, a level switch and, in particular, an injection valve without a non-return valve that provides minimal back pressure at the pump outlet to provide more accurate metering.
2.1 Application
- In chemical plants, NDs are used for mixing, dosing and dissolving chemical components and various additives, in particular flammable and toxic substances.
- At refineries, designs are used to add and dose colored additives to fuel and various consumables for vehicles.
- On oil and gas rigs, ND are necessary for the injection of various additives and additives at the wellhead.
- At desalination stations, metering pumps perform the function of processing all kinds of systems, in particular in multi-stage evaporators.
- In addition, metering pumps are used in power plants and steam generators for processing chemical systems.
- The most common industry is the use of structures in wastewater treatment plants. Here the dosage of chemicals that are used to process the liquid is carried out. We are talking about many elements, in particular - sodium hypochlorite, iron sulfate, chlorine dioxide, lime, etc.
- At the enterprises of the food industry, with the help of dosing designs, various fatty acids, mayonnaise, tomato, fruit purees, all kinds of sauces, syrups, oils and so on are added to packaging.
- In the manufacture of a variety of drinks dispensing devices help to ensure the correct supply of chemical components, dyes or preservatives, as well as other elements in the composition of the product.
- Even in the manufacture of plastic, ND are used for dosing and mixing various types of raw materials, additives and all kinds of additives that result in a product that meets the requirements and standards.
- In the manufacture of ceramic products or utensils, NDs allow the dosage of dyes to be correctly carried out, as well as the supply of the base mass to the spray device.
- In the steel industry, metering pumps are used to clean the system from scale.
As you can see, there are many areas of application for metering pumps; they are used in almost all sectors of human life. Moreover, without such pumps it is now difficult to imagine any production. In addition to production, the devices are also used for domestic purposes.
The control of the characteristics of the fluid pumping process in modern pumps is provided in manual and automatic modes. Depending on the requirements for operation, it may be necessary to take into account certain parameters. For example, the user can adjust the feed volumes and the intensity of the function. However, there are certain types of equipment that are specifically designed for the point service of certain environments. These include dosing pumps used in the food, pharmaceutical and chemical industries.
Features of dosing pump
Dosing units provide the possibility of volumetric pressure pumping of liquids, suspensions and emulsions. However, most of these pumps can serve both neutral and aggressive environments. For this reason, their use is common in the chemical industry. Depending on the characteristics of the material used in the flow part, the specific purpose of the equipment is determined. The main difference from traditional household units is that dosing pumps allow you to adjust the pressure level from the exit point to the entrance of the working medium. In this case, the absolute indicator of the inlet pressure exceeds the same indicator of the pumped liquid. Among the main technical and operational characteristics of such equipment, the ability to work with certain environments and the diameter of the passage of the nozzles is noted.
Hose metering pumps
This type of metering pump is designed to work with liquids and pasty substances. The principle of operation is based on mechanical action on the working channel, which is most often represented by a strong but flexible tube. That is, during operation, mechanical pressure is applied to the hose with the medium, as a result of which the liquid is pushed to the outlet. As a physical activator, rollers rolling around the circumference are used. By design, metering pumps of this type are a device including flexible pipes and a hose with a set of rollers. Also, the infrastructure part is provided by the track into which the tube line is laid. It is in him that the physical effect occurs.
Diaphragm units
This is a volumetric pump in which a flexible plate fixed at the edges of the structure performs the function of the working body. To a certain extent, it acts as a piston. The membrane bends during operation, which leads to fluid displacement. In this case, the force impact can be different. For example, it is practiced using mechanical drives, hydraulics, and pneumatic devices that deform the plate by changing the pressure in the working cavity. Due to the absence of gearboxes and motors, metering pumps are considered the safest and most reliable. This is especially important in the maintenance of flammable liquids, since the function of the unit has no prerequisites for the formation of a spark.
Plunger models
This is a type of reciprocating hydraulic machines based on reciprocating movements. The valve distribution system does not allow the use of such units for reverse action, which distinguishes them from other volumetric devices. The reverse movement of the piston in the pipeline leads to the closure of the valve, which prevents the leakage of medium into the channel. At the same time, the valve on the discharge side opens, and through it, the liquid escapes to the receiving point. In the process, dosing provides an uneven speed of fluid movement, which causes its main drawback. The spasmodic effect is compensated for in various ways, including by introducing several piston elements into the design.
Unit marking
If the structural design of the units are carried out in accordance with the requirements of a specific form factor, then in terms of functional content and controls mechanisms, manufacturers develop common standards. So, the ND metering pump provides for manual regulation of fluid transfer from the moment the unit stops. If the system is provided with the possibility of automatic and remote monitoring, then the equipment is assigned the designation NDE.
Also, manufacturers indicate a dosing index, which averages 1-2.5. There are also devices in which this indicator is not observed at all. As a rule, models with an initial index do not have a heating jacket, and the highest level of metering accuracy is characterized by the presence of a shut-off or flushing fluid in the inlet design. This classification also applies to all types of aggregates. For example, a metering plunger pump ND can have both a first accuracy index and a second.
