All about asbestos cords

Chimney thread or asbestos cord is used in construction as a sealing element, which is a component of thermal insulation. Finding out what temperature a thread 10 mm in diameter and of a different size can withstand, as well as finding out why such a rope is needed, will be useful to all owners of private housing. An asbestos cord will certainly come in handy when arranging stoves and fireplaces, laying autonomous heating systems, it will be much cheaper than other materials with similar properties.

Asbestos cord is a rope in skeins with a multilayer structure. The thread used here is made according to the standards of GOST 1779-83. Initially, the product was produced for operation as part of heating systems, elements of machines and units, but has found its application in other areas of activity, including in the construction of stoves and fireplaces. With the help of an asbestos cord, it is possible to achieve high tightness of the joints, prevent cases of ignition and the spread of fire by negligence.

By its structure, such a product consists of fibers and threads of various origins. A significant share of them is occupied by asbestos chrysotile elements obtained from magnesium hydrosilicate. The rest comes from cotton and synthetic fibers mixed into the base.

Asbestos cord finds its application in mechanical engineering, in heating systems of various types, acts as a thermal insulating element or sealant. Due to its resistance to direct contact with fire, the material can be used as a natural barrier to the spread of combustion. Special varieties of such products are used in the construction of stoves and chimneys, fireplaces and hearths.

Most of the cords can only be used in industrial production or heating networks. Here they are installed on pipelines for various purposes, through which water vapor or gaseous substances are transported. For home use in suburban construction, a special series is suitable - SHAU. It was originally manufactured for use as a seal.

For asbestos cords, a set of certain properties is characteristic, due to which the material acquired its fame. Among the most important of them are the following.

• Product weight. The standard weight with a diameter of 3 mm is 6 g / m. A product with a section of 10 mm will already weigh 68 g per 1 lm. With a diameter of 20 mm, the mass will be 0.225 kg / lm.
• Biological resistance. According to this indicator, asbestos cord surpasses many analogues. It is resistant to rot and mold, does not attract rodents, insects.
• Heat resistance. Asbestos does not burn at temperatures up to +400 degrees, it can withstand significant heating for a long time. With a decrease in atmospheric parameters, it does not change its properties. Also, the cord is resistant to contact with a coolant that changes its temperature indicators. When heated, it does not lose its fire retardant properties.The fibers of the mineral become brittle at temperatures above +700 degrees, melting occurs when it rises to + 1500 ° C.
• Strength. The sealing material is capable of withstanding significant breaking loads and is distinguished by its mechanical strength due to its complex poly-fiber structure. In especially critical joints, steel reinforcement is wound over the base, which provides additional protection for the material.
• Resistant to wet environments. The chrysotile base does not absorb moisture. She has the ability to push her away. When wet, the seal does not swell, retains its original dimensions and characteristics. Products made from a mixture with synthetic fibers are also resistant to moisture, but with a significant proportion of cotton, these indicators are slightly reduced.

The asbestos cord produced today is a chrysotile-based product belonging to the silicate group. It is completely safe for human health, does not emit potentially hazardous substances during operation. This strikingly distinguishes it from products based on amphibole asbestos, which are banned for use in most countries of the world.

The classification of asbestos cord divides it into general purpose products, down and sealing options. Depending on belonging to a specific type, the performance properties and composition of the material change. The classification also provides for the determination of the fiber winding density. According to this indicator, the products are divided into lumpy and whole.

There are 4 main varieties in total. Their marking is determined by GOST, some varieties additionally provide for the production of products according to TU. Basically, this category includes products whose dimensional parameters go beyond the established framework.

For downy asbestos cords, the standards do not establish standard diameters. Their main purpose is to seal units and parts of units operating at extremely high temperatures. Inside the down lay there is a core made of asbestos, synthetic and cotton fibers, braided with fabric. This thermal insulating material can be used in systems with pressures not exceeding 0.1 MPa.

Sealing or stove type of asbestos cord. It is made of a multiple folded SHAP product, and then it is additionally braided from the outside with asbestos fiber. This multi-layer structure affects the size range of the material. Here it is much higher than that of the standard options.

The scope of SHAU is not limited to the laying of stoves and fireplaces. It is used as a thermal insulator in door and window openings, and is laid during the construction of buildings and structures. The sealing type cord is well suited for use in mechanical engineering, including for insulating heating parts and mechanisms. It is not afraid of intense bursting loads, prolonged increase in operating temperatures, and has a long service life.

A specialized type of asbestos cord STEP is used in gas generating plants as a sealing material. Produced in the size range from 15 to 40 mm, it is characterized by increased strength. Such products can be operated at operating temperatures up to +400 degrees under pressure up to 0.15 MPa.

The structure of the STEP is multi-layered. The outer braid is made of stainless steel wire. Inside there is a core of several SHAON products, twisted together. This provides resistance to intense mechanical and bursting loads. The material is most often used to seal hatches and gaps in gas generator plants.

General purpose cords are made of chrysotile asbestos mixed with polymer and cotton fibers. Products of this type have the following distinctive features:

• resistance to vibration loads;
• wide range of applications;
• wide size range;
• the ability to operate in contact with gas, water, steam;
• working pressure up to 0.1 MPa.

SHAON is produced both with and without a core (up to 8 mm in diameter). The asbestos cloth is single-strand here, twisted from several folds. In versions with a core, the diameter of the products varies from 10 to 25 mm. There is a central strand inside the cord. The content of chrysotile asbestos here should be from 78%.

This category includes cords that have an asbestos (chrysotile) fiber central thread. Other layers are wound on top of it. They are formed from yarn and cotton fibers.

In the absence of a core, an asbestos cord looks like a multi-layer rope twisted from yarn. Direction twisting is not the same, and the composition, in addition to asbestos fiber, may include a downy tray, cotton and woolen fibers.

Depending on the marking, asbestos cords are produced in a different size range. The following indicators are considered standard:

• STEP: 10mm, 15mm;
• ShAP: has no approved values;
• SHAON: from 0.7 to 25 mm, sizes 3, 4, 5, 6, 8, 10, 12, 15 mm are considered popular.

It is very important to choose the right asbestos cord as it should fit snugly where it is attached. A thread that is too thin will create unnecessary gaps. The thick one will require replacement of the hinges on the doors. The diameter of the cord is considered to be from 15 to 40 mm. It is in this range that it is used in ovens.

The type of construction of the heating source that needs to be sealed is also of great importance. When insulating around a cast-iron stove or for a smokehouse, it is worth choosing cords with the SHAU marking. For the chimney, SHAON or STEP are suitable, if we are talking about a gas boiler. Downy cords are rarely used in everyday life.

In addition, when choosing a product, you need to pay attention to quality indicators, functionality and reliability. The defining parameters in this case will be the following points.

• The presence of a core. It provides increased strength and resilience. In products with a core, it is necessary to check if the center thread is visible. If it is noticeable, the quality of the product should be questioned.
• No damage to the surface. Signs of delamination, rupture are not allowed. The cove should look solid and smooth. Protruding ends of threads up to 25 mm long are allowed. They remain when connecting the lengths of the cord.
• Humidity level. The asbestos cord must meet the requirements of GOST for this indicator, established at the level of 3%. You can measure this parameter when buying material with a special device. For viscose cords, an increase of up to 4.5% is allowed.
• The amount of asbestos in the composition. First, this mineral must be presented in the form of chrysotile fibers, safe for human health. Secondly, its content cannot be less than 78%. Products for tropical climates are made from a mixture of asbestos and lavsan.

These are the main parameters that are recommended to pay attention to when choosing an asbestos cord for use. It is strictly forbidden to violate the manufacturer's recommendations for using the product. The wrong choice of sealing material can lead to the fact that it will not perform its function.

Correct use of asbestos cord avoids serious problems during its operation.In modern country houses, this element is most often required to be installed in heating units, stoves or fireplaces. The cord can be used to replace the old seal layer or insulate only the built oven. Before fixing it on the boiler door, chimney, it is necessary to carry out some preparation.

The procedure for using an asbestos cord will be as follows.

• Cleaning the installation site from dirt, dust, traces of the old seal. Metal elements can be sanded with sandpaper.
• Glue application. If the design of the heater assumes the presence of a special groove for the sealing cord, it is worth applying the agent to it. In other cases, the adhesive is applied at the place of the intended attachment of the asbestos thread. You can apply markings.
• Distribution of the sealant. It is not necessary to wet it with glue: the composition that has already been applied to the surface is enough. The cord is applied to the junction or placed in a groove, pressed tightly. At the junction, you need to apply the thread so that it does not form a gap, then fix it with glue.
• Bonding. This process is easiest in the case of boiler and stove doors. Simply press down on the insulation area by closing the sash. Then heat the unit for 3 hours or more, and then check the quality of the connection of the asbestos cord with the surface.

If thread is used to insulate the oven hob, you will have to remove this part. At the place of its attachment, traces of old glue and cord are removed, a primer is applied to increase adhesion. Only then can you start installing new insulation. After gluing, the cord is kept for 7-10 minutes, then the hob is placed on top of it. The remaining gaps are sealed with clay or other suitable mortar.

If everything is done correctly, then during the operation of heating units and stoves, smoke will not enter the room. This will ensure the safety of life and health of people living in the house.