Pre-insulated pipe: description, characteristics, application, photo

2024 Author: Howard Calhoun | [email protected]. Last modified: 2024-01-07 20:55

When assembling transportation networks for various purposes, for example, heating communications or pipelines intended for the distillation of oil and gas, until recently, ordinary pipes made of steel were mainly used. For the most part, products of this type still cope well with their work. However, such pipes still have one rather serious drawback. Whatever the thickness of their walls, they cannot protect the distilled liquid from the cold in winter.

The result of the freezing of water or coolant in the lines is usually the failure of the latter. At the same time, in utility steel networks during the cold season, among other things, there are also significant heat losses, which makes their operation much more expensive.

What are PPU pipes

To prevent freezing of liquids transported along highways, the latter, when assembling the network on the street, either lay very deep underground, or are additionally insulated usingspecial materials. Both methods are labor-intensive and technologically complex. Therefore, pipes of a special design - pre-insulated pipes - have become increasingly popular lately.

Products of this type are insulated at the production stage using a modern insulator with a very low degree of thermal conductivity - polyurethane foam. These pipes are more expensive than conventional ones. However, the lines assembled from them can serve in the future without the need for repairs for decades.

PPU pipe design

Outwardly, such products are very similar to the well-known sandwich chimneys. That is, they consist of three main layers:

• actual steel pipe, through which the liquid will be pumped in the future;
• polyurethane foam layer;
• outer containment.

Special signal cables pass through the polyurethane foam layer in such pipes. Thanks to their presence, it is always possible to determine the location of the accident on the highway with high accuracy and quickly carry out repair work.

What specifications may have

Today, pre-insulated pipes are supplied to the market in a wide range. Such products may differ by:

• diameter;
• wall thickness;
• insulating layer thickness;
• number of signal cables installed, etc.

The cost of products of thisvarieties directly depends on their diameter and the thickness of the insulating layer. According to the latter indicator, PPU pipes are selected taking into account the climate of the region in which the network is supposed to be assembled, as well as the depth of the latter. In warm regions, pipelines with an insulating layer thickness of 5 cm are usually assembled. In the northern regions, pipes with an insulating layer of 10 cm or more are used.

Signal cables in the insulating layer of such products, depending on the diameter, can be laid two or three.

GOST standards

Pre-insulated pipes are produced in our country with strict observance of GOST requirements. The insulation used in the manufacture of such products, in any case, must meet the following requirements:

• water absorption by volume - 10%;
• compressive elasticity - not less than 0.3 MPa (deformation in all directions - up to 10%);
• density - up to 60 kg/m3.

When heated to 110 °C, the length of the PPU insulator used in the assembly of pipes should not exceed 3%.

Polyurethane foam for pipe insulation can be made using different technologies. But most often such material is made on the basis of carbon dioxide and freon. In most cases, in the manufacture of PPU pipes, polyurethane foam of such well-established brands as Dow, Izolan, Huntsman, Elostokam is used.

Types by design

Currently, there are two main types of pre-insulated pipes on the market:

• hard;
• flexible.

Products of the first variety are made of ordinary or galvanized steel with polyurethane foam insulation. Outside, such pipes are sheathed with sheets of hard steel or stainless steel.

Flexible products of this type are made using a similar technology. However, such pipes are not covered with a sheath of steel, but of corrugated plastic. Of course, such products do not differ in too much flexibility. After all, polyurethane foam - the material itself is quite rigid and not too elastic. However, it is still possible to bend pipes of this variety a little when laying.

Of course, in the manufacture of plastic shells of pre-insulated pipes, GOST standards are also observed without fail. Used for their assembly is usually the highest quality light-stabilized material.

Sometimes protective sheaths with an insulating layer can be supplied separately from the pipes themselves. In this case, before their installation, when assembling the pipeline, the pipes are preliminarily checked for tightness, and then coated with an anti-corrosion compound.

How an insulating layer is applied to the PPU-pipe

Many domestic factories produce such products. Pre-insulated pipes are also supplied to the Russian market, of course, by foreign companies.

Judging by the reviews, domestic products of this type in terms of quality today at a lower cost are practically in no way inferior to imported ones. For example, simply excellent reviews from consumers deserved such products, released"Novosibirsk Plant of Preinsulated Pipes", "Orlovsky Pipe Insulation Plant", Stroyizolyatsiya Plant (Seversk), etc.

In any case, in the manufacture of such products, specialists without fail, among other things, make sure that the adhesion between the polyurethane foam and the steel pipe is as strong as possible. To prevent the insulation from slipping on the steel and holding it as securely as possible, before applying it, the base is carefully cleaned to form a rough surface while removing rust.

When foaming the polyurethane foam itself, the specified thermal regime must be maintained exactly. The adhesion between the foam-filled inner shell can also be improved by treating with a final discharge.

So that the insulator that has not yet hardened does not flow out, a special metal plug is attached to the end of the pipe. After the material has hardened, this element is removed from the pre-insulated PPU pipe. Such products go on sale with an open end of the polyurethane foam layer.

Use area

The most widespread PPU pipes at the moment are, of course, primarily in industry. The following products are used during assembly mainly:

• oil pipelines;
• gas pipelines;
• steam lines.

Pre-insulated pipes are often used for heating networks designed for pumping heated liquids. Such communications are usually mounted in hotworkshops of enterprises of various specializations.

Recently, pre-insulated pipes have begun to gain immense popularity among public utilities. Organizations of such specialization use these products when laying centralized heating systems and water pipes in cities and towns. The use of such pipes in this case can significantly improve the quality of public service.

Key Benefits

Pre-insulated pipes for heating mains, water pipelines, oil pipelines, etc., or rather, for assembly, are used in our country, thus, quite often. But what explains the popularity of modern products of this type?

The unconditional advantages of PPU pipes, in comparison with conventional ones, include:

• the ability to install any communications as soon as possible and with minimal labor;
• reduce heat loss (usually from 40% to 2%);
• significant increase in pipeline efficiency;
• increasing the service life of networks by 2-5 times;
• reducing pipeline repair costs.

Due to the presence of a protective shell, such lines are practically not afraid of exposure to aggressive environments. It is allowed to lay PPU pipelines without grounding and preliminary drainage arrangement. Polyurethane foam differs, among other things, in that it does not allow moisture to pass through. Consequently, steel pipes insulated using this material are much lessprone to rust.

Flaws

There are practically no cons for PPU pipes. Perhaps the only drawback of such products is their rather high cost. However, this minus is more than compensated by the long service life of the PPU lines and the lack of the need for their frequent repairs.

Mounting Features

PPU pipes are made, thus, from high-quality steel. Consequently, their installation is carried out using welding. Of course, the laying of pre-insulated pipes during the assembly of various kinds of industrial and utility networks is carried out using a special technology. Polyurethane foam - a material, unfortunately, does not tolerate too high temperatures. Therefore, when welding such pipes, special protective screens are mandatory.

After connecting the segments, the craftsmen who assemble the PPU line must check the quality of the seams. After the metal has completely cooled at the joints, special couplings are applied to the pipes, among other things. A feature of such structural elements of PPU-lines is that they are made of heat-shrinkable material. After cooling, such a coupling decreases in size and tightly fits the weld, thereby ensuring complete tightness. When using docking elements of this type, a small cavity remains at the joints of the pipes, into which mounting foam or polyurethane foam is subsequently poured.

Described abovethe technology is used both in the assembly of large industrial highways and small household engineering communication networks.