Pumping equipment occupies an important place in the organization of water supply and heating systems. At a basic level, this technique ensures the pumping of liquid from the source to the point of consumption. However, with the optimization and rationalization of the processes of transportation of liquid media, the task of maintaining a sufficient speed of movement in the delivery circuit was singled out. The device of the circulation pump, based on an electric motor with a rotor, is guided by its execution.
Unit design
The body is predominantly made on a monoblock basis, which increases the degree of tightness, but also reduces the possibility of repair activities. The operation of the hydraulic infrastructure is provided by an electric motor with an output for connection to the network (some designs allow double-sided cable entry). By the way, in a modern deviceThe water circulating pump is equipped with a wide range of electrical protections, including variable speed load adapters, a safety block and an auto-shutdown system.
The pump base also includes a stator, impeller, shaft, flange components, terminal box, pipes for connecting underwater communications, etc. This is the working group on which most pumps designed for heating systems are based. Special attention should be paid to the auxiliary devices of the circulation pump. Repair operations, as a rule, are associated with their replacement. This applies in particular to seals, thrust bearings, plugs and insulation materials. These elements have a different operational resource, but at certain time intervals they are deformed or worn out, requiring renewal.
Much in the reliability of the circulation pump and its components depends on the quality of the materials of manufacture. The body is often made of cast iron or steel alloy, although some models use high-strength plastic to reduce weight. Fittings are made of composites, rubber (synthetic rubber), thermoplastics and extruded aluminum. In the latest versions of pumps, there is a rejection of metal rubbing elements in favor of ceramic ones. This decision affects the price tag upward, but increases the resource of the same bearing.
General principle of equipment operation
The function of circulation pumps is different in that they are not directly involved in the operations of water intake and return. At the very least, the traditional design of a circulation pump for heating is designed to maintain a sufficient speed of movement of water in the circuit due to the action of the impeller. At the installation point of the unit, the liquid exits at a higher pressure, which affects the flow rate. In other words, the speed regime on the way to the pump impeller is transformed by increasing the pressure, which, at a minimum, ensures the constant movement of the coolant.
It has already been noted that heating systems are targets for the use of a circulation pump. But can they be used in a water supply system? As in the heating circuit, such equipment may well serve as a pressure and flow rate stabilizer. However, it is important to take into account that the pressure control functions in heating and water supply systems differ according to loads. If in the first case it is only required to maintain the movement of the flow, then a full-fledged supply of water, for example, to the second floor requires much more resources, for which the principle of operation of the circulation pump is not calculated. The device of some models allows the connection of an expansion tank (hydraulic tank), the presence of which can increase the pressure capacity, but centrifugal self-priming pumps do better with the tasks of water supply.
And vice versa, not every surface pump from the centrifugal groupcan be integrated into the heating system. The fact is that the coolant medium is distinguished not only by a high temperature of up to 110 ° C, but also by the presence of antifreeze mixtures. To serve such media, special heat-resistant pipes in the heating system and pumps with acceptable characteristics of the internal surfaces that distinguish circulation installations should be initially used.
Operation of wet rotor models
In this case, the place of the rotor is in the zone of the internal flow of the coolant, that is, the element is in direct contact with the serviced medium. The key operational effect of this configuration is the indirect lubrication by the fluid carried by the unit. This results in an optimized design of the wet rotor circulation pump, in which there is no special infrastructure for lubricating the rubbing parts of the engine. Among the external factors of the application of such equipment, low noise level and ease of maintenance can be noted.
However, the simplification of the pump design has its downsides. For example, manufacturers set stringent requirements for pump placement. Its body must be placed so that the rotor occupies a strictly horizontal position, otherwise the equipment will fail. Also, due to the sensitivity of the filling to contaminants, the device of a “wet” circulation pump in some versions involves the introduction of a cleaning filter on the inlet pipe. This is due precisely to the fact that the lubricantthe coolant may contain small solid inclusions, which adversely affect the state of the same rotor during long-term operation. Another negative factor follows from this - a decrease in productivity up to 40%. For this reason, wet rotor models are only used in networks with few short branches.
Operation of dry rotor models
In this pump configuration, the rotor is isolated from the coolant flow by means of seals and gland elements. The task of lubricating moving parts is solved separately with the help of technical oils. But there are also different variations of the device and the principle of operation of the circulation pump with a "dry" rotor:
- Console models. It is supposed to separate the electric motor and its working infrastructure due to a special coupling. Both parts are in different blocks, but on the same level, which excludes the possibility of their non-parallel interaction.
- Monoblock constructions. Also, the motor is separated from the working part, but everything is placed in one block, which makes it easy to install and maintain the pump.
- Inline configuration. In fact, a modification of the console system, but with an improved implementation of the connecting equipment. For this, not only a coupling is used, but also a set of sealing rings made of ceramic or steel. Through these rings, a high degree of tightness of the water-bearing part is ensured, which increases the reliability of the unit. In addition, the circulation pump arrangement in the Inline configuration assumes a linearplacement of outgoing and inflowing pipes. In comparison, other versions of dry rotor models are characterized by radial or circular placement of nozzles for communication support.
In general, the isolation of the rotor from the coolant gives a positive effect in terms of performance (efficiency over 70%), so this technique is often used in the maintenance of long heating networks with high throughput. This is the best solution for industrial facilities, but in the domestic sphere it is rather troublesome and uncomfortable in terms of maintenance.
Performance
First of all, when evaluating the characteristics of the circulation pump, you should make sure that it is in principle suitable for working with the target liquid medium in a specific temperature regime. As already mentioned, such equipment can withstand from 90 to 110 ° C. Then you can go to the design parameters, the main of which, in addition to the dimensions and configuration of the engine placement, will be the diameter of the threaded connection. For example, the Grundfos UPS-25/40 circulation pump device allows connection to pipes with an external thread diameter of 25 mm. The second digit in the marking of the Danish unit indicates the force of pressure. In numerical terms, this is 40 dm or 4 m of water column, which can be maintained at maximum capacity utilization. Again, this value should not be considered as the main operating parameter that will deliver water to a given height. It's no morethan the level of rise within the heating circulation network. In comparison, booster pressure models for water supply systems are capable of lifting liquid by 12-15 m in normal operating mode. As part of servicing heating circuits, pumps with an inlet pipe diameter of 32 mm and a head pressure of about 60 dm can also be used.
For ease of calculation of the required power, pump manufacturers specifically indicate the speed of the coolant. This value directly depends on the power potential of the engine and the size of the nozzle. Usually, 1 kW equals 0.06 m3/h. An alternative calculation system suggests starting from the fact that if the diameter of the outlet in the device of the circulation pump for heating is the same 25 mm, then the flow rate will reach 30 l / min. But this is a small value, since most modern models of even the household segment reach 170-180 l / min in terms of performance. The balance between design capacity and motor power is ensured by the shaft rotation adjustment function. Models with this capability allow for step shifting from 2 to 4 speeds.
Pump Electrical Engineering
Usually, asynchronous electric motors connected to a 220 V network are used as a power unit. The average current strength is 0, 12-0, 18 A. The connection base is a complex of a terminal box, a frequency switch and cable connections. In the device of Wilo circulation pumps from the Star-RS line, there is alsoprovides for condensate drainage and double-sided cable connection with blocking current protection system.
But it is far from always possible to implement a full range of devices for electrical protection on the basis of the pump itself. Therefore, external devices will also play a significant role in organizing the power supply system. At a minimum, a voltage stabilizer and a short circuit protection system should be provided - of course, grounding requirements cannot be ignored. More importantly, in networks with periodic power outages, it will not be out of place to consider the issue of providing backup power to the circulation pump. Devices for solving such problems are presented in a wide range - from external batteries (batteries) to autonomous generators. The choice of specific equipment depends on the conditions and modes of operation of the pump. If we are talking about a private house, where the power supply is interrupted in exceptional cases, then you can choose a battery of the appropriate size with regular support for the energy resource. But in conditions of an acute shortage of electricity at remote sites, it is better to use a generator unit running on gasoline or diesel fuel with an auto-start system. By the way, the operation of low-power pumps up to 30 W for a couple of days can be supported by car batteries, but this option should be used only in extreme cases.
Pump installation
By the time of installation, both the place of operation and the unit itself must be prepared. As regards the first condition, we must be prepared toconnecting a pipe with stopcocks in front of the connection points to shut off the water. The pump, in turn, must be thoroughly flushed and checked for structural integrity. Insertion is carried out using a coupling and a locknut with sealing materials. To increase the reliability of the regulation circuit, a bypass is sometimes provided in the mounting device of the circulation pump. This is a crawler on the equipment placement circuit, which is a pipeline section running parallel to the critical process zone and performing the function of a backup route for the coolant delivery. On the same segment, you can install additional functional equipment such as filters, air vents and just shutoff valves.
Maintenance
In intensive operation mode, it is recommended to check the condition of the working part and connect the pump monthly. Comprehensive maintenance work is carried out before and after the heating season, together with pressure testing of the plumbing system. Among the main maintenance activities of the pump, the following should be highlighted:
- Checking the technical and structural condition of the equipment.
- Replacement of wearing parts if necessary. As already noted, the circulation pump device contains parts with a limited resource set by the manufacturer. For example, seals and couplings last an average of 1-1.5 years before they need to be replaced.
- Cleaning the housing surfaces and functionalparts from contamination.
- Checking the operation of the engine - it is necessary to check its ability to maintain the power load, the level of noise and vibration.
- Particular attention should be paid to the tightness of the structure and the connecting nodes.
- Checking the electrical infrastructure and the quality of connections with devices connected to the pump.
Possible breakdowns and repairs
During the operation of the equipment, you may encounter the following technical problems:
- The unit does not start. Possible causes include a broken electrical connection or a failed capacitor. If a “wet” rotor is provided in the circulation pump device, then as a result of its contamination with coolant impurities, the engine may well block. Accordingly, a general revision of the electrical system with communications, checking the capacitor and cleaning the rotor will be required.
- The pump is noisy and vibrates a lot. As a rule, such problems are associated with high water consumption, which does not correspond to the capacity of the equipment. Airing the heating circuit is also not ruled out. Air from the system must be removed regularly, for which an automatic air duct is used.
- The unit turns on and immediately turns off. A common problem, more common on models with a console device. Repair of the circulation pump for heating in this case comes down to restoring the tightness of the structure at the interface of the working units. In the area between the stator jacket and the rotor, one should alsoclean limescale if present.
Conclusion
The circulation of the coolant can be organized without the support of pumping equipment in the natural mode of motion. Such schemes are used in private homes, but they do not differ in high performance, in terms of heat transfer. At the same time, for example, the device of the Grundfos circulation pump provides for the possibility of connecting boiler equipment, which takes the function of the unit far beyond the regulation of the flow of the heating system alone. There are new opportunities for providing the DHW system, but within the technical and operational potential of the equipment used. It is also possible to combine the heating circuit with the air conditioning system, in which the circulation pump will be used, however, such configurations require careful calculation at the design stage.
