Thermal network: gasket, operating rules and repair

Distribution and transportation of the coolant between consumers takes place through a special heat network. It is one of the main elements of the entire structure of engineering communications. On how it works, reliability and quality of transmission depend directly. Pipelines of heat networks are not the only elements of this structure. In addition to these, it also includes various structures. These include, in particular, throttle and pumping stations, heat points.

Structure

The heat network, based on a centralized supply scheme, is divided into two levels: the main and quarter (microdistrict). The first consists of elements connecting heat sources with local (regional) points of its distribution among end users. In most cases, they represent a looped pipe system (diameter 500-1400 mm) and engineering structures. These elements are located throughout the city, which ensures the reliability of the transfer and the ability to meet the demand for consumption. Thanks to the separation, operation of heat networks is much easier. Thus, various control schemes are created that increase the reliability of work and increase the quality of supply. Designing and laying of main-type thermal networks are carried out taking into account possible failures in the operation of an underwater element. In this connection, backup communications are created. They are connected to heat sources. With this approach, a unified management system is created. It is able to provide uninterruptedly the declared parameters of thermal and hydraulic regimes. In this case, work is carried out even if one of its elements (supplying source, one of the branches of the main line) fails. Distribution of the coolant under such conditions occurs more qualitatively, losses are reduced as a result of transmission, fuel economy is observed.

Control

The rules of heat networks provide for the existence of special elements, through which the structure is managed. To them, in particular, include locking mechanisms - latches. With their help, the common heat network is divided into separate sections. The impact on the valves allows you to include (cut off) small sections of the main line, as well as pumping and throttling stations located on them. Most modern appliances are equipped with an electric drive. They are placed on average every 1-3 km of the main line. Overall network management includes monitoring the mode of operation and the state of structural elements, preventing possible malfunctions. To protect against hydraulic shocks , a special discharge device is installed at local points.

Quarterly heat network. Features

These structures are branched dead-end systems. They connect with the heat points. Management occurs both in manual and offline modes. Such a structure has a diameter of up to 400 mm, in connection with this, interruptions in supplying consumers with thermal energy as a result of failure of such a network are considered permissible. However, as a result of the general arrangement of supply schemes in the event of a malfunction, only a small portion of end-users suffer. Repair of heat networks in this case does not take much time. The points through which the medium enters the system are automatized. This allows you to save on the consumption of thermal energy.

Connection to the main line

The connection of distribution networks to the common system takes place by means of mixers or pumps (mixing-circular), less often through water heaters. The application of the latter makes the system more flexible and reliable. This is possible due to the separation of the hydraulic modes of the main and distribution systems. A medium that enters general networks from different sources may have different temperatures that exceed those already found in the pipeline. Supply systems equipped with pumps exclude hydraulic isolation of the mains from distribution schemes. As a result, the management of the corresponding emergency mode becomes more complicated. In this case, it becomes possible to independently maintain, by means of a pump in the distribution networks, circular and temperature conditions that will differ from the main ones.

Two-level view of the system

The scheme of the large structure of the heat network has a two-level view. At the top there is a ring road. From it branch to the heat points of the regions. In joining, the ordinary method is used. In the event of a failure of the section of the main line to which the heat point is connected, the final consumers are deprived of thermal energy. To a local point, users are connected by means of local systems - this is the lower level.

Feed reservation

In the backbone network, the coolant comes from the CHPP and the district boiler house. In this case, it is possible to implement the feed reservation process in the event of a breakdown of one of the media heating points. This is done by installing the jumper on the supply and return lines. A single ring heat network is formed by a combination of these elements. The projected diameter of the conductive elements of the systems is calculated in such a way as to provide the capacity of the necessary carrier even in emergency situations. In the conditions of stable uninterrupted operation, the coolant moves through all the heat pipes of the network. In this case, the use of jumpers loses its meaning. For more efficient use of jumpers and lower costs for heating the coolant, the "unloaded reserve" method is used. In this case there is a complete overlap of the jumpers. The jumper is switched on only when the heat network components fail.

Heat networks

On these elements, the carrier moves, in the form of water. Heat pipes are installed aboveground and underground methods. In the first case, the gasket has a number of significant advantages: extended service life, easy system status monitoring, easy access for troubleshooting. However, the installation of an overhead heat pipe in the conditions of modern cities is practically impossible due to architectural limitations. Under these conditions, most systems are underground. To install such pipelines, special channels are torn out.

Using the system

Thermal testing of heat networks is carried out before the start-up. The installed elements are filled with hot water of different temperatures. The liquid subsequently repeatedly merges during its service life. As a result of all internal influences, the walls of the pipe change, the way out of this situation is the installation of compensators in the pipelines. The two ends of the section are fixedly fixed to the supports. A compensator is installed in the middle. In addition, the pipelines are fixedly fixed near heat exchangers, pumps. This is done to relieve the load exerted by temperature deformation. The supports are placed in channels or special chambers. In the channels, the pipeline is laid on mobile supports. For the purpose of constant monitoring of the state of systems, special underground chambers are being constructed. They accommodate various valves, drain valves, air valves and expansion joints. In some cases (for example, when the diameter of the water pipe is more than 500 mm), to conduct testing of thermal networks and more comfortable maintenance above the chambers, ground pavilions are erected. Placement of points and pumping stations takes place in specially equipped buildings.

Choosing the best option for heating networks

At present, there are a huge number of schemes of heat networks and ways of their laying. Therefore, several options are considered at the design stage. Comparing all possible conditions, make technical and economic calculations, choose the least expensive option with the best characteristics. According to these calculations, the diameter of the elements used, the insulation materials and their thickness, the power of the installed pumps are determined. In addition, the cost of the construction and maintenance of the heat pipe, heat losses during transmission from the source to the consumer is recorded.

Russian heat supply systems

Most of the currently used heat networks in Russia were built in the USSR, after the collapse of which the financing for the re-laying and renewal of operating heat pipes has dramatically decreased. Planned inspections of the state of systems and their regular replacements ceased, and state control also began to weaken. The general situation with heat networks in the country began to deteriorate sharply. In conditions of significant savings, the quality requirements for the elements used in the re-laying of already existing systems began to decline. Savings led to a cheaper work, which affected their final quality. The systems built in these years had a low lifespan and required a repeated replacement within 5-7 years. All this led to a sharp increase in the number of malfunctions, which led to an increase in the capacity of emergency services. Heat losses during transfer of the carrier are estimated in the range of 20-50% of the total output in the heating season and from 30 to 70% in the summer. These figures exceed several times the norms adopted in the developed countries of Europe.