- Stages of construction of a channelless heating main using PI pipes
- Determination of the trace of the track on the ground
- Site preparation
- Digging a trench
- Delivery of pipes and other materials, storage at the facility
- Preparation of the base for pipelines
- Installation of pipelines
- Hydraulic and other tests
- Backfilling of pipelines
- Restoration of improvement
The construction of a heating network is a process that has many important points. Having studied the proposed material, you will be able to control the installation sequence, assess the correctness of the work and learn about the main points of the construction contract.
Before describing in detail the process of performing construction work, you should take some time to conclude a construction contract and select an appropriate construction company.
Minimum requirements for a construction company:
- Availability of serviceable equipment (excavator, crane, trucks).
- Availability of specialists (welder, electrician).
- Sufficient workforce.
- Long stay in the construction services market.
If the company does not correspond even to one of the points, it is almost impossible to carry out work on the installation of a heating network. References to the conclusion of a subcontracting agreement are not an excuse – it will be cheaper and easier to work directly, without intermediaries.
Requirements for a building contract:
- Subject of the contract.
This item should be written something like this: “The contractor undertakes to perform construction and installation work on the project” PROJECT NAME “. Such a wording excludes amateur activities on the site and any deviation from the original version is easy to prove in court.
- Period of execution.
The summer period, the end of spring, the beginning of autumn are suitable for the construction of a heating network. The reason for this is a significant increase in the complexity of work in winter, the rise in cost and the impossibility of implementing some measures, for example, a tie-in of a pipeline under construction into an existing one. If in the summer the supply of hot water to consumers can be stopped for a while, then the lack of heat carrier at the subscribers after the start of the heating season is equivalent to an accident. Breaking the deadline into stages and fixing the work schedule in the contract is the best option.
In this paragraph, in addition to the maximum amount, it should be noted the possibility of an advance payment. If there is a need, they also provide for a phased payment for the work, however, the full transfer of funds should be only after all tests and commissioning of the facility.
- Liability, guarantees, penalties.
When designing these sections, you should not be limited to references to legislation. The warranty period prescribed in the contract for 5 years or the payment of a fine for late obligations will become additional guarantees of the decency of both parties. Do not forget about the phrase “Payment of a penalty or fine does not relieve the parties from their obligations”.
At the signing of a contract with a suitable company, the customer’s work should not end. Each stage can be, and in some cases it is necessary, to control. Considering all the methods of laying pipelines is a long and not very necessary matter. For example, let’s take the most popular way – channelless laying. It is with this pipe-laying that most errors arise, which subsequently affect both the final cost of the construction and the ease of operation. The most suitable burial material for construction without canals and tunnels today is pre-insulated pipes (PI pipes). The presence of an on-line remote monitoring system adds cost and complexity to the installation, however, if properly assembled, greatly simplifies maintenance..
PI-pipe is of the following design: steel pipe – a layer of polyurethane foam insulation with wires of the operational remote control system located in it (at least 3) – polyethylene pipe-sheath. For external laying, this type of pipes is also produced, however, they have certain differences. Firstly, there is no UEC system, and secondly, the insulation is covered not with plastic exposed to sunlight, but with a layer of galvanized.
Stages of construction of a channelless heating main using PI pipes
Determination of the trace of the track on the ground
This stage of construction can be done with the help of specialists, but in some cases, you can do it yourself. If the length is small and on the drawing, as well as on the terrain, there are a sufficient number of landmarks to which you can make a binding, then several people with tape measures will be enough to set the axis of the track in nature. Determination of the distance from the object to the point of interest on the route, if it is not indicated in the project, is easily calculated manually. The length in the drawing is measured with a ruler and multiplied by the scale. The minimum number of such defining segments is 2. In order to test yourself, it is better to take 3 or more.
You should not engage in self-breakdown in the event that the terrain is relatively open. Trees and shrubs, even if at first glance they are quite accurately indicated in the project, cannot be taken as landmarks. Basically, distances are measured from the corners of buildings..
This stage involves the removal of vegetation, removal of the fertile soil layer, dismantling of temporary structures and small architectural forms (urns, benches, etc.). When carrying out work, remember that permission must be obtained to remove trees and other green spaces. Otherwise, your actions will be regarded as a direct violation of the law..
Digging a trench
Before you start digging the ground with an excavator, you need to make sure that no other communications pass along the track of the track. In an urban setting, this is a utopia. To determine the location of one or another underground facility, it is necessary to call the responsible employees of organizations that own communications at the excavation site. If the representative claims that there are no structures belonging to his company in this place, then this statement must be recorded in writing. Those who declared the presence of their objects must be left until the immediate removal of soil. If communication is damaged in the presence of a representative of the organization, all responsibility for this will be on him and not on you. It should come as no surprise that many of the company employees who visit the construction site will not know exactly where the pipeline or cable runs. Communications have been in the ground for decades – not every specialist has been working for such a long time in one organization.
In places where it is most likely to intersect with communications, the soil should be removed manually. Damage to a high-voltage cable or gas line is quite dangerous and not worth the hours gained by using an excavator instead of workers with shovels..
We should not forget about the removal of land to the dump. When laying a heating network channellessly, not all of the excavated soil is used for backfilling. Before starting work, you need to decide where to take the surplus for permanent residence.
Delivery of pipes and other materials, storage at the facility
The PI-pipe is quite heavy and its loading / unloading without the use of special equipment is possible only at the minimum diameters. The same applies to fittings. Dumping from the body to the ground is prohibited due to the high probability of damage to the plastic sheathing pipe.
If PI products are delivered to the site directly from the factory, then the incoming control must be carried out here..
For pipes, attention should be paid to the following circumstances:
- matching the wall thickness of the steel pipe;
- conformity of the wall thickness of the plastic pipe-shell;
- dryness of the insulation (checked by the resistance of the SODK wires);
- the correct laying of the SODK wires (when ringing, there should be no short-circuit or break, twisting).
The same points apply to fittings as well. All valves are additionally checked for closing / opening. Couplings are rated for ovality and bore. Too much deformation will not allow it to be put on the pipe.
When organizing storage, it should be borne in mind that insulating foam tends to absorb moisture and, therefore, open areas of insulation must be protected from moisture ingress. The easiest way is to paint these areas. Some factories do this initially, some do not. Consideration should also be given to storing couplings. Manufacturers supply them in white plastic wrappers. It is possible to remove these protective coatings only just before the installation (shrinkage), even if the coupling is put on the pipe, under the influence of sunlight it can significantly reduce the diameter and it will be impossible to move it to the side.
Preparation of the base for pipelines
Due to the fact that the pipe coating is plastic and due to the thermal expansion of the metal components will move in the ground, it is not customary to lay the pipeline directly to the bottom of the excavated pit. To exclude damage to the shell pipe, a sand cushion of about 10 cm is provided.Pipes are also backfilled with sand, and only the top layer with the excavated soil.
It should be borne in mind that most builders try to cheat at this stage. For the species, they make a powder of sand, and the full amount of sand is provided for payment, including transportation costs. It is easy to check the size of the base made – the layer should be about half of the shovel. It is enough to dig in several places and the honesty of employees will be visible even to a non-specialist.
However, if the soil is already sandy, then these works can be abandoned. These are mainly areas located near rivers and other water bodies. The main thing is to soberly assess the basis on which the pipes will subsequently lie.
Apart from sand, there should be nothing in the trench. Rubbish and other remnants of human presence must be removed.
Installation of pipelines
This stage can be divided into several more sequential actions:
- laying pipes in a trench
- pipeline flushing
- installation of the UEC system
- installation of couplings
- zaphenka joints
- sealing couplings
The sequence should be just that. Welding of the pipeline outside the trench is not allowed. If this requirement is not met, then when trying to lower the finished structure into place (the bottom of the pit), the welded joints, as well as all other parts, are exposed to dangerous stress and there is a high probability of the appearance of hidden subsurface defects.
One item (flushing) can often be abandoned. If there is confidence that a lot of sand has not accumulated in the pipes, a yard cat has not got lost in them or some enterprising builder has not hidden a brick there. This is usually achieved quite simply. During installation, the non-welded ends of the pipeline are closed with plugs.
Hydraulic and other tests
After the network is installed, a series of tests should be performed. First of all, hydraulics are carried out. The purpose of this test is to assess the strength of welded joints and the effect of pressure on the route as a whole. You should also check the UEC system. Its inoperability suggests that a considerable percentage of the funds have been wasted. Remote monitoring test results should be documented and retained for future use. For a subsequent assessment of the wetting of the insulation, it is necessary to know what its dryness was initially.
Backfilling of pipelines
The pipelines of the channelless laying are filled up in layers. The 1st layer is sand. A small layer of soil is poured next. A signal tape is laid on it – a thin polyethylene strip of bright color with an inscription like “caution heating network”. Everything is filled up with soil, the fertile layer returns on top and grass is sown.
Restoration of improvement
The final stage of any construction is the restoration of the improvement. In order for this process to be precisely the restoration of the original, and not the construction of a new image of the area, even before the start of construction, what is should be recorded with the help of a camera. Often, the absence of this small fact leads to the fact that after dismantling the asphalt, in the opinion of the regulatory authorities, was paving slabs, the lawn was of the quality for a football field, and not self-seeding of incomprehensible vegetation, and all the shops with trash cans were designer. There is no need to rely on evidence from the builders. If you are forced to do extra work, they will have additional funds.
To simplify your own life after construction, it is advisable to donate the heating network or transfer it to the balance of the operating organization in scientific language. This must be achieved for the following reasons:
- you will not need to contain it;
- if an accident occurs, then you will not have to eliminate it;
- upon expiration of its service life, the replacement will be made by the owner, that is, not you either.
However, it is not always possible to voluntarily get rid of the networks on your balance sheet. If you also could not get rid of them, then it is imperative to give the existing power engineer additional responsibilities for opening / closing valves and preparing the necessary documents for the beginning of the heating season. With a long route, you can additionally hire a person responsible for the heat economy.
Another mandatory point is the conclusion of a service contract with an organization engaged in the operation of heating networks. During the winter period, it must invariably be valid. So in case of an impulse, only they can come to your aid. Due to the fact that at negative outside air temperatures, the elimination of the accident must be carried out instantly, ordinary construction companies will not be suitable for this business. They do not have round-the-clock repair teams, and the equipment can be far away.
If you follow the advice from the proposed articles, then the process of designing and building a heating network will not be too complicated and unclear. In the case of a cool attitude, there is a risk of being deceived and ultimately receiving unfinished or incorrectly assembled communication. By adhering to simple rules, you can avoid cost overruns and protect yourself from headaches when servicing networks after their construction.