Underground laying of heating mains for industrial use - not a rarity, as it is located a large diameter pipe above the ground, especially in urban areas, it is often impossible. Laying of pipelines of heating private houses, if the boiler is located in a separate building, it is better to perform on the ground, but sometimes circumstances also forced to do it in a trench.
Laying of heating pipes in the ground deprives the consumer the possibility of visual inspection of the pipeline state, so the quality of work in this case the increased requirements. In addition, the heating pipe in the ground zaglublonnuyu affects a number of additional, specific factors that must be considered. Consider these factors and the existing rules of performing the work required to wisely lay pipes for heating the ground.
Factors acting on the heating pipes in the ground
heating pipe zaglublonnaya into the ground, exposed to the same influences as external execution pipeline plus factors caused recessed:
- the internal pressure of the coolant, causing ring and longitudinal tensile stress in the cross section of the pipe;
- coolant temperature - a factor other than thermal effect also causes the voltage of the pipeline;
- Soil temperature - in the winter account of this factor is particularly important;
- soil deformation - on any tube affects its displacement (precipitate shift, etc.);
- voltage preliminary bending of the pipeline - the profile of the trench often repeats terrain;
- vertical load - the weight of the impact layer filling the trench;
- bioactivity effect of soil on the wall and bottom of the pipe - a vertical load resistance;
- vibration loads - from passing transport and earthworks in the neighborhood, etc .;
- Moisture - rain and ground water;
- exposure to chemicals - compounds in the composition of the soil and the coolant;
- biological factor - bacteria decomposition.
Thus, the pipeline laying into the ground should be made taking into account all the above factors and the solution of the problem how to insulate the heating pipes in the ground.
Terms laying a pipeline in trench heating
Laid in the ground the heating conduit is contacted with the two media - coolant and ground. coolant parameters (temperature, pressure) and chemical composition (water, antifreeze) consumers are known in advance - of the characteristics of the heating boiler or by the operator of the heat pipe, which is planned bump into.
It remains properly arrange the trench when the trench method selected pipeline installation. Modern technologies allow to perform the laying of pipes in the ground and trenchless method that has several varieties.
Digging trenches for heating conduit
Important! Before it is necessary to issue in the administration of the settlement permit for the start of production of the trench device excavation, to which will be attached plan the location of all roads to avoid damage and accidents cases.
Excavation work on the device trenches begin with the planning area through which it will pass. If on the hilly terrain does not perform layout, the reliefs of the trench and the area match, the pipeline will be laid in waves and before backfilling will be under the influence of preliminary stress.
After closure begin to lay axial markings trench that runs on a cord spanned by pegs driven into the ground.
The width of the trench at the bottom for laying pipes up to 700 mm, according to the SNP 2.05.06-85 "underground laying of pipelines," determined by the formula D (diameter of pipe) + 300 mm. If work is carried out manually, the deviation from this value is not critical - priority is given to ease of execution.
The second, more important parameter - the value of penetration. heating pipeline is laid in the ground below freezing, which depends on the region and is determined by tabular method. Detail table from the reduced snip for clarity.
To calculate the depth of the tube to the desired depth added value freezing tube diameter plus a 50 cm. Calculation of the depth of the trench is performed also taking into account the properties of the soil the lower part thereof - if the base clay, its leveled and compacted, after which the pipeline is laid. If the bottom of the trench - sandy or with the inclusion of large fragments of stone, under the pipeline must perform 5-7 cm thick pad of crushed stone fractions 20-40 mm, which is poured over the clay layer of the same thickness and compacted. This is done to ensure that water does not eroded under the base pipe, which would lead to subsidence of the pipeline deformation.
Parallel to this work assesses the excavated trench digging at the ground - it is removed from the large rock inclusions, capable after filling pipe wall damage. Furthermore, it is necessary to stock the necessary quantity of loose material for laying it on the first conduit damping layer.
Important! If the trench device produced in the winter period, before laying pipeline it is removed from the snow and ice.
Mounting of the heating pipe
For heating conduit devices utilize tubes of steel or polymers, whose diameter depends on the heated area, the characteristics and parameters of the heating equipment coolant.
A compound of the heating elements produce pipeline depending on the material chosen - by welding or by fitting. Installation start in the direction of the building and perform one of two ways:
- operate the assembly piping on the surface and then dipped it in the trench;
- lead assembly in a trench, raising the extreme end of the pipe to the surface level to connect to the next moiety to the joint laying on the basis of availability.
Important! Elevation adjustment start heating supply pipe must be lower than the end point of the outlet (drain) pipe heating system.
pipeline Thermal Insulation
insulation piping equipment is performed regardless of the tube material. Thermal insulation reduces the heat loss and the formation of condensate inside the pipe, as well as slow down the process of freezing of the system in case of unforeseen frost in the presence of a water circuit.
Important! Warming heat pipe does not increase the temperature of the coolant, and only delays a certain period of the freezing system. In addition, a material for insulation with a zero coefficient of thermal conductivity, providing absolute thermal insulation, does not exist - a water circuit without heat input still freeze.
Requirements to a heater pipe the installation of the system in the ground:
- low thermal conductivity;
- sufficient thermal stability - the ability to maintain its characteristics in contact with the hot surface of the tube;
- hydrophobicity - water resistance and waterproofing property;
- water vapor transmission rate - the ability to rapidly degraded when getting wet drying;
- biological inertness - resistance to bacteria;
- chemical resistance - inertness to land contained in chemical compounds.
Insulation, there are many kinds, and the extent to which they have different requirements, so the solution to the problem than to warm the thermal conductivity must be determined with reference to the specific conditions operation.
Thermal insulation of mineral wool
Of the three types of insulation of mineral wool for thermal insulation of pipes in the ground are suitable two:
- glass wool;
- rock (basalt) wool.
Thus basalt wool preferable effect less hygroscopicity (ability to accumulate moisture from the environment) and a low shrinkage.
Better use of foil material, reinforced stitching on all area (quilted), which is stronger and easier to work. Insulation is placed foil layer outside.
If the heating pipes, steel, it is made of anti-corrosion treatment before warming - applying protective lacquer coating quality and budget one of which is a solution of lead or red iron oxide based on natural drying oil.
For warming heat pipe diameters up to 150 mm is convenient to use a linear method for stacking the mineral wool, when cut to size pieces are superimposed on top of the pipe and the spiral binding wire strapped without allowing substantial seal material. The longitudinal connection edges bottom heater arranged with an overlap on each other at 10 cm, the cross - also overlap.
To protect the insulation from moisture on top of it is arranged waterproofing of roofing material in one layer, are constructed on the same technology.
Insulation to fulfill its function, it is necessary to protect it from damage, compaction under the weight of the soil and further isolate from moisture. To do this, on top of the roofing material attached guards made of galvanized iron or fiberglass. Longitudinal joint casing is performed overlaps 2-3 cm and self-tapping metal fastener. Transverse joints between casings is also arranged with an overlap and wrapped with clamps.
Processing of the contact surfaces of the longitudinal and transverse seams bituminous mastic before coupling creates an additional barrier to moisture precipitation and groundwater.
Schematically, the final result of the heat insulation pipe is as follows:
Thermal insulation shell made of mineral wool or foam
The modern market offers a more functional insulation materials, installation of which is simple, and the specifications above. This ready shell under certain diameter pipe called shell.
The shell of the mineral wool is a sleeve with a longitudinal slit or two longitudinal half of the coupling for mounting on a pipeline and then fixing the crimping collars. For valves and piping shaped elements (elbows, tees, reducers) are also provided respective insulating shell configuration.
Casings made of polyurethane foam (PUF), depending on the diameter, are composed of two or three parts imposed on the pipe circumference and connected to a locking system performance joints.
Both insulation also produced in the form of ready-made multi-layer shells, protected from the outside or steel GRP casing with transverse grooves at the edges to set the crimp collars at connection.
Important! The outer protective jacket must be not only sealed, but sufficiently rigid to protect the insulating layer from the seal which reduces its effectiveness significantly.
Installation of pipe runs under the roadway
If a private home heating pipe should be laid under the track, which goes passenger vehicles, she need more protection against vertical load.
In this situation, a trench dug across the track and a desired depth into it the prepared substrate (Draft device cushion seal) fit sleeve - a steel pipe with a wall thickness of 5 mm. heating pipe at the site is installed in the ground through the sleeve, and with a device inside the only thermal insulation - in housings of galvanizing is not necessary. At the entrance to the sleeve and at the exit from it operate plug of foam to prevent moisture penetration into the sleeve.
The pipe in the sleeve should not have joints as in case of depressurization access to them for the production of the repair will be difficult and time consuming.
Important! If the protective sleeve is not used, and the piping material - a polymer, the pipe penetration value should equal the sum of the depth of freezing the soil pipe of the same diameter and 1 m.
backfilling
By filling the trench start after checking the heating system in operation - if the pressurization circuit detects defects in its integrity, it will be necessary to remove them.
Backfill the trench - important stage of work on the correct implementation of which depends on the uniformity of load distribution and durability of the pipeline section in the ground.
Filling the trench with start laying ductile soft soil at the sides of the pipe (in the sinuses). This is done uniformly over the entire length of the pipeline, preventing its movement to the sides. Laid on the sides of the ground carefully sealed, and then from the same material is performed filling pipe a protective layer of at least 15 cm over the entire width and length of the trench in accordance the requirements of SNIP. The seal of this layer is performed to a lesser extent - it is a necessary condition for the formation of durable protective tube set from the ground, relying more on the sinus on either side of the tube.
After the closure seal of the protective layer the trench is filled completely soil excavated during excavation, removing from large rocks. Filling must be performed uniformly over the entire length of the trench, avoiding the formation of pipe sections with large difference in vertical load on the ground.
Uniformly increasing load on the backfill will be adopted more protective dirt dome over the pipe, and the residual amount of force to compress the pipe is not terrible - it is designed for it.
If the trench fill individual sections, the difference in the vertical load on the sleep and outdoor pipeline segments results in a effort to break, which pipe resists worse.
Trenchless pipe laying methods
There gaskets technology pipeline in the ground without trenching device.
Such methods are designed to:
- reduce the amount of earthworks - saving in time and cost;
- to minimize damage to infrastructure - less than the cost of restoration and decorative pavements, unforeseen damage highways;
- to lay the pipe in a straight line without bending around obstacles small degree of complexity;
- minimize the damage caused by the production of earthmoving environment.
To date, the following methods are used in the trenchless industry:
- sanitation;
- piercing.
readjustment - a replacement of old pipes with new, which, in turn, is produced in two ways: by relining and renovating.
relining It based on the broach inside the pipework of the new smaller diameter of the polymer tube with preservation old as the containment.
renovation - installation of a new pipe to replace worn-out with the destruction of the old, the wreckage of which will also protect the new line from external damage.
Puncturing (punching) - a combination of two dug to the required depth of pits puncture, made at a certain height of the wall.
Of the following methods in the home will be only the method of relining. At one end of the old pipe is inserted Tross and pushing it to exit the other end. Then to the wire ropes securing the new whip and pulled him back. The possibility of this method depends on several factors:
- status old pipeline lumen;
- the diameter of the new pipe;
- flexibility of the new whip;
- length of the repair area;
- the ratio of old and new pipe diameters.
In a favorable combination of these factors technical performance of the new tube assembly is easy. However, all of this applies to broach a new line without insulation, and insulation state of the old pipe is unlikely to be satisfactory. Since insulate heating pipes is not possible within the old line, then it applied to heating method loses its appeal.
Therefore, when the heating apparatus piping recessed into the ground in a private dwelling without digging trenches or at least alternative pipe laying on the ground with the backfill, are indispensable.