Insulation for sewer pipes: types and scope of application

The work of sewer pipelines is influenced by many factors, including cold. In order for the system to function normally even at very low temperatures, it is necessary to choose the right insulation for sewer pipes and install it.

Thermal insulation materials are presented on the market by a wide range, and sometimes it is difficult to decide on a purchase, do you agree? We will help you in resolving this issue. The article presents an overview of various types of insulation, describes their characteristics, features of installation and use.

Rules for choosing insulation

There is a huge selection of insulation materials on the construction market, but not everything can be used as insulation for sewage pipes.

The main task of the insulation is not heating the outlet, but a reduction in heat exchange between the external environment and the fluid circulating through the pipes.

In order for pipe insulation to effectively perform its main function - heat preservation, it must meet 7 basic requirements:

• have a thermal conductivity coefficient as low as possible;
• maintain their properties for a long time;
• to withstand large temperature differences;
• have good waterproofing properties;
• resistant to aggressive environmental influences;
• do not sustain combustion or emit toxic smoke;
• be easy to install.

Insulation subject to outdoor sewer pipes and highway, laid in unheated premises. An exception is only those regions where even in winter there is no lower than 0 ° С.

For the rest, the only question is the choice of method and material. Insulation is chosen based on the reputation of the manufacturer or brand, but the surest way is to focus on the material of manufacture.

Most often sewer pipes are insulated with mineral wool, expanded clay, polystyrene foam and polyurethane foam insulation. Liquid insulants are also used. All of them are used for passive insulation.

In addition to these, there are 2 more options for protecting pipes from frost - laying below the freezing level of soil layers and the use of active insulants. The latter includes cable insulation.

Mineral wool insulation

From the definition, enshrined in GOST 31913-2011, it can be concluded that mineral wool should be attributed to the class of fibrous materials, in the production of which melts of rocks and metal slags.

The concept itself combines 3 types of material:

• fiberglass;
• slag wool;
• stone wool.

They have different thickness and fiber length, different thermal conductivity, moisture resistance, they react differently to mechanical loads, but the composition is identical in all. Characteristics of the mineral wool released by different manufacturers differ among themselves.

The basis of mineral wool is rocks, there are about 90% of them in it. The rest falls on additives - bentonite clay and resins with phenol in the base.

Mineral wool has a number of qualities that make you think before making a choice in its favor.

The disadvantages of insulation include:

• the presence in its composition of formaldehyde resins that adversely affect health;
• the ability to shrink under the influence of mechanical loads and, as a consequence, the appearance of "cold bridges";
• high water absorption because of what the heater needs good waterproofing.

Wadded heaters are used for arranging open sections of sewage pipelines. They are not placed around pipes located in the ground.

When wet, this type of insulation almost completely loses its qualities and often causes rust on metal underground communications.

Installation of insulation from mineral wool is carried out in 3 stages:

1. On the pipes in the form of a spiral stick foil tape.
2. Pipe tightly wrapped with insulation. In this case, the seams at the joints should be the same.
3. Thermal insulation is fixed on the pipes by wrapping it with sanitary tape.

Taking into account the fact that the density of the material is low and it absorbs moisture well, waterproofing will be required. To do this, use the foil or roofing material. Facilitates the presence of foil on the insulation layer, but the ends still have to be isolated.

Warming of glass wool pipes

Glass wool, as one of the variants of mineral wool, has all its positive and negative characteristics. It is a natural material derived from such raw materials as quartzite or sand.

The thermal conductivity coefficient of this heat insulator is in the range of 0.028-0.034. The greater the thickness, the smaller it is. The average density is 150–200 kg / mᶾ.

To reduce the hygroscopicity, some manufacturers produce glass wool with a ready-made layer of insulation. It can be both a foil, and fiberglass. These include such popular heaters as Ursa, Knauf, Isover. Glass fiber heat insulator comes to the construction market in the form of mats, rolls, cylinders.

Is it possible to warm the sewer pipe slag?

The material is a by-product of iron smelting technology. Slag has a loose structure and one very unpleasant feature inherent in the products of blast-furnace production - residual acidity.

Under moisture conditions, acids are formed on the surface insulated by this material, which have a negative effect on both the metal and the plastic. Slag melts at a temperature of 300 ° C, has a coefficient of thermal conductivity of 0.46-0.48, the thickness of the fiber in the range from 4 to 12 microns. It has low environmental friendliness

The water absorption coefficient of this insulation for sewer pipes is higher than that of glass wool. The material is not resistant to temperature changes, hence its service life is short.

For this reason, for insulation of sewer pipes, it, like other cotton-wool options, is rarely used; it is used only for insulation of above-ground communications sections.

The starting material for its production mineral wool is rocks. Basalt wool - a durable material with a density of 25-200 gk / mᶾ and a small coefficient of thermal conductivity - 0.03 - 0.04.

It is very resistant to temperature extremes - it does not lose its original properties in the range of -60 + 200 ° С, and it starts to melt when the temperature rises above 1000 ° С.

Stone wool fibers have the same parameters as slag, but they are much more elastic. Therefore, they do not break, do not get into the respiratory system, do not irritate the skin. But there are drawbacks to this type of mineral wool - high cost, insufficient strength and all the same phenolic substance in some grades of material.

Polystyrene foam insulator for pipes

Polystyrene shells are a popular insulator for sewer pipe insulation. Two percent of its composition is small, from 1 to 5 mm, polystyrene granules, the remaining 98% are air. After the material is processed by the gasifier, the granules acquire lightness, elasticity, attract each other and stick together.

By pressing followed by high-temperature steam treatment, the material is given the desired shape.

In fact, this is a simple foam, but in the form of a shell, designed for repeated use. The difference between the thermal conductivity coefficient of polystyrene foam insulation (0.03-0.05) and mineral wool is small. The shell, having the form of hemispheres, copes with the task of heat conservation quite effectively.

Since the foam is not very resistant to mechanical stress, manufacturers supply the shells with an external coating of aluminum foil, fiberglass and other materials.

High heat-insulating properties provide thin-walled microcells that do not allow heat. The service life of the thermal insulation shell is quite large - about 50 years.

There are 2 types of this material - ordinary and extruded polystyrene foam. The characteristics of the latter are higher, but the cost differs in a big way.

Despite a lot of positive qualities, foam polystyrene has its drawbacks. It does not tolerate ultraviolet radiation, so when laying pipes in open areas, additional sun protection is required. This material is dense, but fragile, and during combustion may cause poisoning, because the smoke it emits is poisonous.

Installation works are so simple that they do not require special qualifications. Wearing insulation segments on the sewer pipe, perform an overlap, shifting them along the length relative to each other by 200-300 mm. In order to avoid the appearance of cold bridges, the elements of thermal insulation are joined to each other with the help of a quarter or tongue and groove system.

After completing the connection, both parts are strongly compressed. Places of contact are taped. Sometimes the joints are coated with glue, but then the insulation loses the advantage of being reusable, because when dismantling it will have to cut.

A protective coating is put on the casing, which comes with it or is simply wrapped with plastic wrap if it is not present.

Shells are used both on elevated roads and for underground pipe laying. This insulation can be put on a pipe with a minimum diameter of 1.7 cm and a maximum diameter of 122 cm. Already with a diameter of 200 mm, the cylinder consists of 4 elements, and large products may have 8.

Trenches with sewer pipes fall asleep first with sand to a height of about 0.2 m, then with earth. In regions with very cold winters, insulation in the form of expanded polystyrene shells is supplemented with insulating cable, placing it under the shell.

Polyurethane Shells

Polyurethane foam cylinders are a good alternative to foam plastic counterparts. They differ in comparison with them in greater density, and the coefficient of thermal conductivity is almost the same.

Higher in polyurethane foam and resistance to mechanical stress. He has a wider temperature range in which it can be operated without loss of strength characteristics.

Thermal insulation has the form of semi-cylinders, equipped with transverse or longitudinal latches. To increase the reliability of protection, the shells are sometimes enclosed in special galvanized casings equipped with locks, but more often they simply apply a special coating.

Application of polyethylene foam

Foamed polyethylene is often used as a sewer pipe heater. This is not a very dense material - up to 40 kg / mᶾ. The coefficient of thermal conductivity is within 0.05.

Does not change its properties during operation in the temperature range -50 ° C - + 90 ° C. The small thickness of the material saves space, so its use is justified where there is a very small gap between the pipes and the wall.

The advantage of insulation is lightness, durability, affordable price. Manufacturers make this heater such as Magniflex and Penofol, Energoflex, Thermoflex. Release it in the form of cylinders of different diameters and in rolls. There are foil one and 2-sided options.

This variant of thermal insulation in the arrangement of sewage pipes is rarely used, it is used for insulating communication lines located in basements and above the ground.

The use of folgoisol for pipe insulation

Most often, the material is used for external communications made from metal pipes. There are 2 types of folgoisol - SRF and FG. In its production, foil is used - corrugated or aluminum and bitumen-polymer layer for the bond.

In the sale comes in the form of rolls. The material is durable, environmentally friendly, has a long lifespan. It has proven itself in regions with different climates.

Foamed rubber as a heater

This insulation material is made on the basis of natural or combined rubber. It differs in high fire safety, elasticity. Pipe insulation using this material is done by gluing. As a result of the interpenetration of surfaces, a strong seam is obtained.

Manufacturers such as the Italian company are producing insulation. K-FLEXGerman companies ARMAFLEX and KAYFLEKS. Due to the high cost, foam rubber is used extremely rarely for insulation of sewage pipes.

Warming sewers expanded clay

The material is used for thermal insulation of sewage pipes laid underground. Its normal functioning is possible only in a dry environment, so the work on warming is performed in warm, dry weather.

The technology is simple:

1. Under the pipe place 2 layers of the membrane with the overlay of the canvas on the walls of the trench.
2. Expanded clay.
3. Overlap the edges of the panels on top of the expanded clay.

In contact with moisture, this bulk material loses its properties. It is advisable to use it in areas with a temperate climate, since It is not very effective in the role of insulation.

The density of the material depends on its brand. There are several types of expanded clay with different density, shapes and sizes of granules. High-quality expanded clay has a regular rounded shape and a uniform internal structure.

Insulating paint as a heater

Visually insulating paint resembles the usual. Its advantage is that it can be applied to the surface of any shape. The paint layer forms an airtight elastic coating that works on the principle of a thermos.

For the production of microspheres using ceramics, perlite, foam glass and other substances with thermal insulation properties. The paint is very easy to use and creates a coating that is durable.

The effect of coating with such paint is the same as from insulation with mineral wool or polystyrene foam. It is applied both manually using a roller or brush, and spray.

When you need a warming cable

If sewer pipes due to the impossibility of their penetration, are laid on the surface of the earth, then the most effective method of insulation for them will be a combination of several materials plus electrical cable.

The same method of warming is also advisable in the case when the pipes are at a depth of less than the level of soil freezing.

There are products of 2 types: resistive and self-regulating. In addition to the first, thermostats are definitely needed. It can be both one and 2-core. The most practical option is self-regulating cablehaving effective protection against overheating and good thermal conductivity.

Its resistance decreases with decreasing temperature and increases with its growth. The third type of cable - zone is used when you need to bring heat only to individual sections.

Conclusions and useful video on the topic

The author answers the question about the expediency of insulating pipes located below the freezing level:

The advantages of using heat-insulating cylinders of extruded polystyrene foam:

Trouble-free service sewer system is largely dependent on the quality of thermal insulation of pipes. Of all the existing methods of heat insulation of sewage pipes, one should choose the one that corresponds to the climatic conditions, the depth of laying the pipes, and the peculiarities of the pipeline.

Do you have practical skills to heat sewer pipes? Share your knowledge, ask questions about the topic of the article and participate in discussions. The communication unit is located below.