Steam and hot water pipelines are used to heat buildings, production and storage facilities. The most common material for such communications is steel, however, there are other options, from which such systems are produced. Such designs are divided into categories and types, which have unique technical characteristics.
Heating pipes can transport not only hot water, ay steam
Features of pipelines for heating networks
The environment is transported on such pipelines, usually, has a higher temperature 115 ° C. The rate of excess pressure in the system can reach 1,6 MPa. Pipes for such networks are made of different materials, but the leading position is occupied by the use of steel. Steel pipes have high strength and reliability in use. For, to improve their technical characteristics, in most cases, steel products undergo heat treatment. This procedure reduces the effects of water hammer in the system. There must be an item in the documentation, that tells the story, what mode of heat treatment was used in the creation of pipes.
In some cases, heat treatment is not performed. This happens for the following reasons:
- in case, if the required technical characteristics have already been achieved in the pipe manufacturing process;
- if the pipe has already undergone heat treatment during manufacture by hot forming.
It is very important to achieve the desired technical characteristics, to eliminate the possibility of water hammer. This emergency situation leads to depressurization of the system, resulting in a leakage of the medium, transported (water, pair).
In addition to steel alloys, the following materials are used for the production of water and steam pipelines:
- cast iron;
- non-ferrous metals.
In networks, operating at high temperatures, steel pipes are most often used
The rules of the State Technical Supervision do not apply to communications, which belong to the I category with an index of outer diameter smaller, than 51 mm and construction II, III, IV category with indicators of outer diameter less 76 mm. exept this, pipelines do not fall under these rules, located to the latch of the steam boiler and temporary mains, laid for a short time (to 1 year).
categories of pipelines
Steam and hot water pipelines are divided into 4 main categories of operating parameters of water and steam. Basic operating parameters, according to which the category of this or that communication is calculated, such:
- for constructions, carrying steam from boilers operating parameters, the pressure and temperature of the medium at the outlet are considered;
- for steam communications, which carry out work from turbines - the highest indicator of back pressure and temperature (idling);
- for steam structures of different steam selections (unregulated, adjustable) - the highest value of pressure and temperature of the medium in the selection.
- for constructions, transporting steam from reduction and reduction-cooling installations - the highest indicator of pressure and temperature of environment.
- for communications, carrying nutrient water after diaerators of the increased pressure - nominal pressure of the environment taking into account characteristics of system.
- for hot water pipes (feed and return) - the highest pressure and temperature, given the pumping structures and terrain.
Each pipeline has its own category, which is determined based on the pressure and temperature of the working environment
The dependence of categories on temperature is presented ??in table №1.
Table 1
| Category | Temperature, ° C |
| IV | 115-250 |
| III | 250-350 (1 group) or to 250 (2 group) |
| II | 350-450 (1 group) or to 350 (2 group) |
| I | above 560 (1 group), 520-560 (2 group), 450-520 (3 group), to 450 (4 group) |
Importantly! Usually, heat network category, which is calculated by the operating parameters of water or gas at its inlet, specified in the technical documentation and applies to all communications, regardless of its length.
In some cases, non-compliance with these rules is allowed, however, this requires a clear explanation of deviations from the law, which must be submitted to the appropriate authorities for consideration.
The dependence of categories on pressure is shown in table №2.
Table 2
| Category | Pressure, MPa |
| IV | 0,07-1,6 |
| III | To 4,0 (1 group) or 1,6-4,0 (2 group) |
| II | To 8,0 (1 group) or more 4,0 (2 group) |
| I | — |
| — | |
| — | |
| more 8,0 |
see heating networks
Depending on various factors, all heating networks, which include hot water and steam pipelines, subdivided into species. Consider the main factors, by which the division of these structures:
- by heat supply;
- on the transported environment;
- by type of gasket;
- according to the project scheme.
Depending on the heat source:
- centralized (from a thermal or nuclear power plant);
- decentralized (from autonomous boilers).
DHW and heating networks must have an even number of pipes
The following types of pipelines are distinguished in the transported medium:
- water;
- steam.
Constructions, which tolerate hot water, have one distinctive feature - an even number of pipes in the system. It has to do with that, that in addition to transporting hot water, such a system must have a diversion. exept this, pipelines, transporting hot water, differ in the number of pipes (two, four, etc.. D.).
The steam pipeline is a more complex system (from an engineering point of view). It has to do with that, that par, moving on it, heated to temperature, which exceeds the water temperature. In case of incorrect production or installation of the steam pipeline, pipes can be deformed under the influence of strong heat. exept this, it is necessary to take into account another factor - the occurrence of condensation on the walls of the pipes. Determination of steam flow by pipe diameter and pressure is based on speed. If necessary, this figure can be determined from a table on the Internet or calculated yourself.
According to the type of gasket, all heating networks are differentiated into:
- overhead (open);
- underground (hidden);
Underground, in turn, are divided into:
- channel;
- channelless.
Highways are laid on the ground or underground
Overhead structures, usually, paved in those cases, when it is necessary to secure the pipeline from seismically active (mobile) underground soils, as well as in cases, when the hidden gasket is difficult due to the densely built-up area, which already has a wide network of underground communications. Installation of the pipeline must take place in accordance with building codes and regulations (SNiP) on reliable metal support, which are able to record communication above the ground along its entire length.
Underground (hidden) highways are performed taking into account SNiP channel or channelless method. The channel method involves laying a pipe in a concrete channel. This measure protects the communication from temperature and corrosion, as well as from the movement of soils. All channels are divided by design features:
- trays;
- monolithic.
Ductless laying is the most popular due to its economic feasibility. In this case, the pipes are laid directly in the pre-prepared trench. Usually, this option involves the use of structures made of materials, possessing excellent anticorrosive indicators: polyvinyl chloride (Pvc), polyethylene (PE) etc.. D.
Types of pipelines according to the design scheme
According to the design schemes, all heating networks, which include water and steam pipelines, can be differentiated into:
- trunk;
- distributive;
- offshoot.
Useful Information! exept this, there is a special subspecies of heating networks, which is called quarterly. The quarterly network is a transitional element between the distribution system and consumers.
Trunk pipelines have no branches, they are transit
Trunk pipelines are transit and do not have branches. The transfer of the environment for such communications is carried out from the source to the distribution systems. The temperature in such structures varies from 90 to 150 ° C, and the cross section of the pipes is from 525 to 1020 mm.
Distribution systems transport heat from the main communications to the end user (in the house and apartment). The diameter of such pipelines reaches 525 mm, and the temperature ranges from 85 to 110 ° C.
A branch is a segment of the heating network, which is connected to the heating point with the main pipeline or a residential building with a distribution system.
Design of pipelines: substantive provisions
Projects for pipelines, which transport hot water or gas, performed only by the competent authorities. There are certain rules, prescribed in the technical documentation, according to which the design of these structures should take place. The following parameters must be taken into account when calculating:
- temperature indicators;
- thermal expansion of the material, from which communication is performed;
- working and maximum pressure;
- construction weight.
Taking into account the received data experts define service life of the pipeline and register it in passports of designs.. exept this, the documentation must indicate the number of starts set during the design process. The structure should be designed as conveniently as possible for preventive inspections and control.
The design of the network should allow to inspect and service pipes without problems and difficulties
Joining of details and connecting elements of a design is made by a welding method. Flange and threaded connections are only permitted in those cases, When: structural elements of communication have flanges, cast iron pipes with a diameter of not more are installed 100 mm, belonging to the IV category. Coupling by means of tees is allowed only in that case, if the design belongs to category III or IV.
All elements of the pipeline construction must be protected from the harmful effects of corrosion. As well as all parts of communication, which have a higher temperature 55 ° C and are publicly available to service personnel, must have the necessary thermal insulation.
Underground (hidden) installation of pipelines
Project, on which installation of pipeline communication will be carried out, transports hot water or steam, must be performed in accordance with building codes and regulations (SNiP) competent organizations.
According to SNiP, joint installation of pipelines in the ground is prohibited, if at least one of them belongs to category I.. Also, mounting the system in a semi-permeable trench, need to be considered, that its height must be at least 1,5 meters, and the distance between the insulated pipes is a minimum 60 cm.
Segments, on which various shut-off valves are mounted, should be located in the thickenings of the tunnel, for, to carry out preventive inspection or repair of the equipment without problems.
The dimensions of the tunnel for the underground highway must meet the requirements of accepted standards
exept this, it is worth paying attention to that, that when installing pipes in through trenches, the height of the tunnel must be at least 2 m, and the width between the insulated pipes is a minimum 70 cm.
Overhead (open) installation of pipelines
If, if it is necessary to carry out an open laying of communication, transports hot water or steam, it is necessary to consider some building codes and regulations. Unlike concealed mounting, open installation of communication allows the joint location of pipelines of any category.
This version of the gasket, usually, is limited to the city development plan and is performed much less frequently. Open wiring of pipelines is often used in industrial enterprises of various orientations.
This method has its advantages, example, it can be used in those cases, when the underground option is excluded due to various factors. Terms, when open piping is required, such:
- high rate of stagnation of groundwater;
- seismically active areas;
- permafrost area.
A very important point, it is considered to equip the open type of pipeline communication with the necessary thermal insulation. Insulation, which is located on an open highway does not feel soil pressure, and is not exposed to moisture and active chemical compounds, which affects its service life and performance.
exept this, the cost of overhead gasket is significantly lower, than the underground. In some cases, savings can be made 40%.
Terrestrial highways require insulation, different materials and insulation are used for this purpose
Fittings and other devices for hot water and steam pipelines
All pipelines comply with building codes and regulations, which are a part of heating networks, must be equipped with the necessary measuring instruments, shut-off and control valves. It is worth considering, the tuning devices must meet the required parameters, example, the pressure in the protective element should not be higher than the estimated more than 10%. If the system operates under reduced pressure, then the safety devices must be individually adjusted, which is suitable for the conditions in the system.
pay attention! Safety valves must be equipped with exhaust systems, to redirect the environment if necessary and to protect service personnel from possible burns at valve operation. Exhaust pipes must be protected against freezing and equipped with a condensate drain system.
exept this, any fittings must have special markings on the housing. The label describes the following parameters:
- product marking manufacturer;
- diameter of the conditional passage (Two);
- conditional pressure and water temperature, transported or steam;
- direction, which indicates the movement of the medium;
- Steel brand.
manometer selection
Selection of a manometer for a pipeline system is a very responsible measure, as this device monitors the pressure of water or steam in the pipeline and can provide information about the emergency.
The accuracy of the manometer must correspond to this class:
- 2,5 - at indicators of pressure of the environment, not exceeding 2,5 MPa;
- 1,5 - at indicators of pressure of environment more than 2,5 MPa;
- 1,0 - at indicators of pressure of environment more than 14 MPa.
The scale of the device must contain a red line, by which you can determine the allowable pressure in the system. Installation of the device is performed on a section of pipeline, which is located in an accessible place. The manometer is mounted either strictly vertically or with a permissible forward slope 30 °.
Pipelines, transporting steam and hot water - a special type of construction, which must be designed and operated in strict accordance with the rules of SNiP. Such mains differ in pressure and temperature and pipes are used for each type, which have the appropriate technical characteristics.
