The situation with a leakage of the heating circuit is not uncommon, since the heating system consists of many nodes and elements, the tightness of which is connected to each other sooner or later is broken. In addition to joints, a depressurization zone can also be a whole span of a pipe that is physically worn out or damaged due to the influence of some factor.
Sealant for heating pipes, produced in various types and designs, helps to solve the problem of a leak or ensure long-term tightness of the connections of its elements during the installation of the system.
Requirements for sealing materials for heating systems
The first thing to do in case of violation of the tightness of the heating system is to eliminate the leakage of the coolant, thoroughly or temporarily — before the overhaul. And the main thing that needs to be ensured when installing heating is its reliable tightness.
From these factors follow the requirements for sealants used in the installation and repair of water heating systems:
- ease of use;
- heat resistance;
- high adhesion and strength;
- rather fast achievement of the sealing effect;
- safety of use.
Read also about sealant for furnaces.
Types of sealing compounds, their characteristics and methods of application
At the place of use, sealants for heating systems are divided into compositions:
- for external use — they are applied to the place of damage to the pipeline from the outside and, after curing, restore the tightness of the system;
- for internal use (liquid, volumetric action) — they are introduced into the circuit and seal the damage from the inside;
- sealing — applied to gaskets and threads to improve the tightness of joints.
The choice of type of sealant depends on the degree of damage and the availability of the repair site. In addition, the choice of sealant determines the way the heating system is prepared for the upcoming repair.
Consider sealants in relation to common types of damage and connections of elements of the heating system.
Sealing compounds for external use
These sealants are produced as one- or two-component.
Considering that the coolant in the pipes of the heating system is not only hot, but also under pressure, it is necessary to seal the damage on the pipeline very carefully. First of all, the sealant must be designed for operation at high temperatures, which is indicated on its packaging in the form of a “heat-resistant” marking and operating temperature range values.
Important! Acrylic-based sealant (acrylic) is used only for sealing cold water pipelines. Acrylic glue is not suitable for repairing pipes of heating and hot water systems, since after curing it is not plastic and therefore collapses during temperature deformations of the base.
Of the one-component compositions for the repair of water heating systems, sealing adhesives based on silicone are common.
Heat-resistant sealants based on silicone
To restore the tightness of heating systems from the outside, the most common use of sealants based on various types of silicone, including rubber.
For the repair of steel pipes, it is necessary to use neutral types of silicone (a mark with this parameter is on the package), because the “acidic” silicone adhesives that are also produced, which form acetic acid when cured, react with the metal.
If the material meets the necessary temperature requirements, to ensure success, it is necessary to increase the efficiency and reliability of its application by additional means. As a rule, the manufacturer recommends such sealants for use as a filler for cracks or holes. If another application is indicated on the material, but its characteristics and potential are high, the adhesive is quite suitable for use. For example, a composition recommended for sealing components on an engine can easily cope with the same task in a home heating system.
And yet, given the responsibility of the application, it is necessary to apply silicone sealants to the pipes of the heating system in combination with a reinforcing mesh, which is successfully used as a strip fiberglass tape “serpyanka”.
A layer of sealant is applied to the prepared surface of the pipe (drying, cleaning, degreasing), on top of which coils of serpyanka are butted, then sealant again, after which the tape is already wound in turns with an overlap of 1 cm. The number of layers of serpyanka with glue between them should be 4–5 , while it is necessary to prevent the formation of air bubbles or loose areas between them. The last 2–3 turns of the sickle are made on the section of the pipe without glue and are tightened to it with a nylon clamp, which, after the silicone has cured, will be removed along with the extra turns of the tape. The top repair layer is made of sealant and smoothed out.
Work should be carried out at a temperature not lower than +5 ° C, silicone should be at room temperature (20–25 degrees). The curing of the composition, which occurs due to the contact of silicone with moisture, occurs depending on the type of silicone and is several millimeters per day.
MakroFlex, Masterteks, Titan, MasterSil silicone sealants are products that have proven themselves well abroad and in EU.
Two-component compositions for the repair of heating and hot water systems are various types of adhesives based on epoxy resins and polyurethane.
These compositions are less common for the production of pipeline repairs, as they require certain skills in maintaining proportions when preparing the mixture, they have a short “survivability” time of the solution after mixing the components and a high cost relative to other adhesives.
There are also one-component polyurethane sealants, which cure on contact with air. The quality of these mixtures is also high, it takes a little longer to cure than two-component formulations, and they are also significantly more expensive than silicone materials. The main disadvantage of polyurethane sealants is toxicity during work — the room must be well ventilated, and work must be done in protective clothing and gloves to avoid getting glue on exposed skin.
To ensure success when using two-component compounds, it is also necessary to carefully prepare the pipe section to be repaired and, in combination with glue, use a reinforcing tape — serpyanka.
Such sealants are used in situations where, in order to detect a leak, it is necessary to perform a large amount of dismantling of the decorative and insulating shells of the heating system (for example, the “warm floor” system), or the intensity of the leak is insignificant — there is no coolant leak, but its volume decreases, and the pressure in the system with the circulator running is reduced.
Important! If there is no visual leakage and reduced pressure in the heating system, before adding liquid sealant to the circuit, it is necessary to check the performance of the expansion tank — the pressure drop of the coolant may also be due to the destruction of its membrane.
Liquid sealant, unlike external adhesives, acts on damage to the pipeline or radiator from the inside. The sealing composition is introduced into the coolant of the circuit cut off from the main heating system. When the sealant is added to the water, no reaction occurs, but in the places of leakage, where the coolant comes into contact with air, the polymerization of the adhesive begins and the sealing of the damage begins.
Many varieties of liquid sealants are produced, focused on use in certain heating systems, differing in the type of coolant, the fuel of the heating unit, the material of the pipeline, radiators, etc.
If the leakage of the system is not significant, and the sealing compound is selected and used correctly, then the probability of success in repairing damage from the inside is high.
Important! In heating systems with pipes and radiators made of steel or aluminum, if sealing is necessary, it is permissible to use a vehicle cooling system repair agent, but not a powder type deposited in the lower part of the pipeline and its elements, but liquid.
Mode of application
This means of dealing with leaks in heating systems is relatively new, and there is no universal technology for its use, although the principle of operation for all liquid formulations is common.
The sealant is purchased in accordance with the characteristics of the heating system installed in the housing. In addition, when buying a composition, you need to know how much coolant the heating circuit holds in order to purchase the sealant in the required quantity — the adhesive instructions indicate the concentration in which it must be present in the system.
The use of each type of such a sealant has its own nuances: the admissibility of the presence of filters in the circuit, the method of introducing the composition into the coolant, the duration of action, the size of the damage, the possibility of the presence of glue in the system after the effect has been achieved, etc. The algorithm for sealing with a liquid composition is described in detail in the instructions for its use, but often for independent performance of this operation it is necessary to have a special tool or equipment, such as a compact electric pump for the initial introduction of the sealant into the circuit and its complete dissolution and uniform distribution throughout the volume of the coolant. Therefore, without having practical skills in this matter, it is better to turn to specialists who will perform this procedure without possible negative consequences such as clogging the system or failure of its nodes.
Many years ago, linen tow was used to seal threaded joints, the strands of which were wound on the external thread and covered with red lead on natural drying oil (GOST), after which the joint was assembled along the thread. With the advent of modern artificial heat carriers in heating systems, tow partially lost its effectiveness due to the high degree of permeability of antifreezes and gave way to FUM tape, although it is used in combination with a special Unipack paste, which also contains flax fibers, when assembling cast iron pipelines of large diameters or simply for lack of fluoroplast.
FUM-tape is a synthetic fluoroplastic material of a matte, less often transparent color, which, due to the fluorine content, endures mechanical and thermal influences without compromising its qualities.
Depending on the conditions of use, fluoroplastic tape is produced in several varieties:
- industrial, containing 20% vaseline;
- for acid environments;
- for systems with special requirements for the cleanliness of the environment.
Important! Fum-tape is used for sealing joints in systems with cold and hot water at a maximum pressure value of 9.5 MPa.
- the tape is wound tightly, with light tension, in the direction of the thread;
- the end of the tape should not be located at the end of the joint.
FUM tape is wound on the thread with a number of layers depending on the thread diameter:
- Ø 16–25 mm — 3 layers;
- Ø 25–42 mm — 4 layers.
The number of layers is very conditional, since low-quality material will require twice as much consumption.
Disadvantages of FUM tape:
- when assembling coarse threaded connections, the tape is torn and squeezed out;
- does not have adhesion to the surface of materials;
- does not provide sealing for threads with a diameter of more than 25 mm, therefore it cannot be used when assembling heating radiators.
For sealing threaded connections, liquid and pasty compositions are also used, which can be drying or remain elastic throughout the entire service life.
An example is the same non-hardening Unipack paste with flax fibers in the composition, which is used as an independent material that provides not only the tightness of threaded connections, but also their protection against corrosion, as well as ease of disassembly
Drying pastes are solvent-based sealants, a modern material that is plastic when assembling the joint and hardens after a certain time. For more efficient use, they can be used in combination with a linen strand, which slows down the assembly process; after drying, they provide a strong connection without shrinkage during operation.
The disadvantage is the impossibility of tightening the threaded connection without compromising the tightness of the joint.
Anaerobic sealants are ready-to-use mixtures that differ in properties depending on the application conditions (pressure, temperature, vibration), thread diameter, assembly density, etc.
- ease of use;
- low labor intensity of the process due to lubricating qualities;
- seals the threaded connection even with low assembly force;
- a wide range of working pressures of the medium in the pipeline;
- easy removal of excess mixture at the end of work;
- the presence of species with varying degrees of fixation;
- the optimal ratio of the “price-quality” indicator.
Anaerobic sealants are applied to both connected threaded surfaces (internal and external), previously cleaned and degreased. The instructions for use, as a rule, indicate the air temperature acceptable for the production of work — usually it is about 15 degrees Celsius (if the composition curing accelerators are not used in the process).
An example of anaerobic adhesive is the universal heat-resistant sealant for heating pipes PERMATEX 59214, which has proven itself well in the European market.
The sealing and sealing compound of medium strength, heat and vibration resistant, allows adjustment of the threaded connection within 24 hours after assembly. The maximum working pressure is 700 atm., the limiting temperature is + 200°C.
Sealant for the repair and connection of heating pipes is a material that cannot be dispensed with when installing a heating system, so it is difficult to overestimate the importance of choosing this material when installing and repairing coolant circuits. From which it follows that when buying adhesives, preference should be given to products from well-known manufacturers, whose rating on the European market is quite high.