Manufacturing technology of fiberglass pipes. Production technology of fiberglass pipes Fpipes. Spin Molding Method

Fiberglass is a glass-filled composite material. It consists of a binder (which is used as a polyester resin) and a filler (fiberglass). The main purpose of the filler is to reinforce and give the material the necessary strength. Thanks to the addition of polyester resin, the solidity of the material is ensured, the protection of fiberglass from the negative effects of aggressive environments and the most efficient use of its strength.

November 26, 2014 1862

Fiberglass is a material characterized by a low specific gravity, having a fairly wide range of applications from housing and communal services to the defense industry. Characterized by low thermal conductivity (approximately like wood), high specific strength (greater than steel), moisture resistance, biological stability and weather resistance inherent in polymers, this material does not have the disadvantages that thermoplastics have. This is one of the least expensive and most affordable composite building materials.

The main costs in the manufacture of fiberglass products, as a rule, fall on equipment and labor. The second point of costs is associated with labor intensity and significant time costs. Thus, at present, products made from this material are inferior in price to metal products. This is largely due to the complexity and duration of the procedure for gluing fiberglass parts, resulting in the emergence of serious obstacles in mass production. The use of fiberglass is most beneficial in the case of small-scale production. High efficiency of large-scale production is achieved by using automatic continuous winding technology.

In the manufacture of fiberglass pipes, the role of reinforcing fibers is usually given to roving or glass thread. Epoxy, polyester resins are used as a binder. Today, there are two main methods that are used in the manufacture of fiberglass pipes: the continuous winding method and the rotational molding method.

The intermittent winding technology, which was adopted from enterprises operating in the defense industry, is not widely used. This method is usually used in the manufacture of fiberglass pipes on an epoxy binder. Most of the fiberglass pipes in the world are produced using the technology of continuous winding of fiber and a binder component on a mandrel. After winding is completed, the pipe hardens. Then it is removed from the mandrel, tested and sent to the customer.

In this case, the pipe is produced using a "walking" mandrel and a stepwise cooling procedure. The sectors of the mandrel, which move in the longitudinal direction, move the wound pipe through special furnaces, where preliminary heat treatment is carried out. Next, the pipe is removed from the mandrel. Final hardening is carried out in subsequent furnaces. After that, the resulting workpiece is cut using a "diamond" wheel into pieces of the required length.

The technological process for the production of fiberglass pipes consists in layer-by-layer application of glass materials to a mandrel made of steel, which are pre-impregnated with “cold” curing resin. When selecting the type of resin, the properties of the liquid that is planned to be transported through the pipeline are taken into account. The reinforcement scheme is determined by carrying out a calculation, which should be carried out in accordance with international ASTM / AWWA standards, based on the specified installation conditions and subsequent operation of the pipeline. After polymerization is completed, an inert, monolithic, very strong structure with a wall consisting of several layers is formed. Fiberglass liner (inner wall) provides the required resistance to aggressive and abrasive media transported through the pipeline, and tightness.

The value of the absolute roughness of the inner wall is 23 µm. The power layer is designed to provide mechanical strength under the combined effect of external and internal loads during pipeline operation. The function of the outer layer (also called gel coat) is to provide the necessary smoothness of the outer surface of the pipe, moisture resistance, resistance to chemicals, ultraviolet radiation, and various atmospheric phenomena.

The technological line for the production of fiberglass pipes by the method of continuous winding includes a roving supply section, an installation designed to prepare a binder, a bath with a binder (roving threads are moved and wetted through it), a winding section equipped with rotation shafts (the diameter of the final product depends on the size of the latter). ), as well as the authorities providing control of all equipment.

Fiberglass pipes manufactured using this technology have a number of advantages, including high specific strength, corrosion resistance, low weight, durability (operation life up to sixty years without repair), reliability, low installation and subsequent maintenance costs. , high maintainability, low hydraulic resistance, a guarantee of maintaining the purity of the transported products from the point of view of ecology.

The second method for the production of fiberglass pipes - centrifugal molding, was proposed by Hobas. The technological process of manufacturing pipes using this technology takes place in the direction from the outer surface to the inner, using a rotating mold. The raw materials for the manufacture of pipes using this method are chopped glass fiber bundles, sand and polyester resin. These materials are fed onto a rotating die. As a result, the formation of the pipe structure begins with the outer layer. During manufacture, filler, glass fiber and solid raw materials are added to the liquid resin. The polymerization of the resin is carried out under the influence of a catalyst. Additional acceleration of this process is achieved by heating. The irreversibility of the polymerization procedure is due to 3-dimensional spatial chemical bonds. Thus, the material retains full dimensional stability, even if the ambient temperature is elevated.

Fiberglass pipes made by the method of centrifugal molding are used in laying sewers, drainage, construction of pipelines through which drinking and process water is transported, industrial pipelines, hydroelectric power plants, etc.

In addition, it should be noted that such fiberglass pipes can be used using different laying methods. These include: drag-and-drop technology, microtunneling, above-ground laying and open laying.

Due to the combination of the positive characteristics of glass and polymers, fiberglass pipes have received almost unlimited prospects for application - from the arrangement of ventilation ducts to the laying of petrochemical routes.

In this article, we will consider the main characteristics of fiberglass pipes, marking, polymer composite manufacturing technologies and compositions of binder components that determine the scope of the composite.

We will also give important selection criteria, paying attention to the best manufacturers, because an important role in the quality of products is assigned to the technical capacities and reputation of the manufacturer.

Fiberglass is a plastic material that contains glass fiber components and a binder filler (thermoplastic and thermosetting polymers). Along with a relatively low density, fiberglass products are distinguished by good strength properties.

Over the past 30-40 years, fiberglass has been widely used for the manufacture of pipelines for various purposes.

The polymer composite is a worthy alternative to glass, ceramics, metal and concrete in the production of structures designed for operation in extreme conditions (petrochemistry, aviation, gas production, shipbuilding, etc.)

Highways combine the qualities of glass and polymers:

Light weight. The average weight of fiberglass is 1.1 g/cc. For comparison, the same parameter for steel and copper is much higher - 7.8 and 8.9, respectively. Due to its lightness, installation work and material transportation are facilitated.
Corrosion resistance. The components of the composite have a low reactivity, therefore they are not subject to electrochemical corrosion and bacterial decomposition. This quality is a decisive argument in favor of fiberglass for underground engineering networks.
High mechanical properties. The absolute tensile strength of the composite is inferior to that of steel, but the specific strength parameter significantly exceeds thermoplastic polymers (PVC, HDPE).
weather resistance. Boundary temperature range (-60 °С..+80 °С), treatment of pipes with a protective layer of gelcoat provides immunity to UV rays. In addition, the material is resistant to wind (limit - 300 km / h). Some manufacturers claim seismic resistance of pipe fittings.
Fire resistance. Fireproof glass is the main component of fiberglass, so the material is difficult to ignite. When burning, the poisonous gas dioxin is not released.

Fiberglass has a low thermal conductivity, which explains its thermal insulation qualities.

Disadvantages of composite pipes: susceptibility to abrasive wear, generation of carcinogenic dust due to mechanical processing and high cost compared to plastic

As the inner walls wear out, the fibers are exposed and break off - particles can get into the transported medium.

Image Gallery

What does the production of fiberglass pipes look like? What should be fiberglass pipes according to GOST? How attractive are their characteristics against the background of alternative solutions? Let's try to answer these questions.

What it is

What is fiberglass? The name, in general, gives an exhaustive idea of the composition of the material: the binder (epoxy or polyester resin) is reinforced with fiberglass. Reinforcement provides resistance to tensile and bending loads; binder guarantees impact resistance.

Please note: the resins used are typical thermoplastics.
During hardening, irreversible chemical changes occur in them; if so, unlike thermoplastics, contact welding of products is impossible.
For connection with bolts, threads, etc.

Story

The production technology originated in the fifties of the last century, when the industrial production of epoxy resins began. Like any new technology, at the initial stage this one was not very popular: the lack of experience in using fiberglass was complemented by the low price of traditional materials (steel, copper and aluminum).

Around the mid-1960s, however, the picture began to change.

What happened?

Prices for steel and non-ferrous metals rose.
Commercial development of offshore oil and gas fields has begun. Fiberglass tubing (tubing) favorably differed from metal pipes in light weight and, more importantly, corrosion resistance: contact with salt water did not cause them any damage, unlike competing products.
Finally, the fiberglass production technologies themselves also did not stand still: it became cheaper and stronger.

The result was not long in coming: by the end of the 60s, the American company Ameron entered the North American and then the Middle East market with its high-pressure fiberglass pipes. By the 80s, European and, a little later, Soviet (later Russian) manufacturers pulled themselves up.

Advantages

Why fiberglass gained popularity?

The list of its advantages is not too long, but it looks very convincing.

Very reasonable cost against the background of high-alloy and stainless steels.
Resistance to corrosion and aggressive environments.

Useful: if it is necessary to transport especially aggressive liquids, pipeline elements are lined with high-pressure polyethylene.

light weight. The specific strength of fiberglass (strength related to density) is 3.5 times higher than that of steel; Thus, equal-strength structures made of these materials will differ in weight by several times.

The possibility of obtaining a material with desired mechanical properties due to a specific reinforcement scheme. For example, the spiral-ring winding of fiberglass provides the highest resistance to internal pressure.

Production

What does the production of fiberglass pipes look like?

To date, four main technologies for their manufacture can be distinguished.

Name	Description
Extrusion	The resin is mixed with a hardener and chopped fiberglass, after which it is forced by an extruder through an annular hole. The production is cheap, technologically advanced, but the absence of a regular reinforcing frame affects the final strength of the products.
pultrusion	The pipe is formed between the inner and outer mandrels. Both surfaces are perfect; however, a number of technological limitations do not allow the production of pipes of large diameters and with high working pressure in this way.
Centrifugal molding	Reinforcement is a finished sleeve made of fiberglass, which is pressed against the surface of a rotating mold by centrifugal forces. They also contribute to the uniform distribution of the resin along the future walls. The main advantage of the technology is the ability to obtain a smooth outer surface; The main disadvantage is energy consumption and, accordingly, high cost.
winding	Fiberglass impregnated with a binder (filament, tape or fabric) is wound on a cylindrical mandrel. Equipment for the production of fiberglass pipes by winding is the most common due to its relative simplicity and high productivity.

The last method of production has several, so to speak, subspecies. Let's get to know them.

Spiral-ring winding

The stacker - a ring with several impregnated thread feed mechanisms - reciprocates along a rotating mandrel. With each pass, a layer of fibers with a constant pitch is laid; the ring laying scheme, as we remember, allows to achieve maximum tensile strength of the pipe.

Curiously, the pre-tensioning of the thread also has a positive effect on the final strength of the product, preventing the appearance of cracks under bending loads.

Tubing designed for high operating pressures, load-bearing structural elements (including composite power transmission line supports) and even ... rocket engine casings are manufactured using the spiral-circular winding method.

Spiral tape winding

The difference with the previous method is only that in one pass the stacker forms a narrow tape into a dozen or two fibers. Accordingly, much more passes are required to form a continuous reinforcement; the reinforcement itself is somewhat less dense. The main advantage of the method is much simpler and, accordingly, cheaper equipment.

Longitudinal-transverse winding

The fundamental difference from the previous schemes is that the winding is made continuous: the stacker simultaneously lays the longitudinal and transverse threads. It would seem that this should simplify and reduce the cost of technology; however, there is a purely mechanical problem here.

The mandrel on which the future pipe is wound rotates; if so, the coils from which the thread of longitudinal reinforcement is unwound should also rotate. Moreover, the larger the diameter of the pipe, the more coils should be.

Oblique transverse-longitudinal winding

This solution was developed during the life of the Soviet Union in Kharkov and was originally used in the production of rocket shells. Later it became widespread throughout the post-Soviet space.

What is the essence of the method?

The stacker forms a wide ribbon of parallel fibers impregnated with a binder.
The tape before winding on the mandrel is pre-wound with a thread without impregnation, which subsequently forms axial reinforcement. The threads themselves assembled into a tape form, respectively, a transverse reinforcement: the tape is laid across the axis of the mandrel.
After laying, each layer is rolled with rollers, compacting the reinforcement and displacing excess binder.

What is the benefit of such a scheme?

Possibility of continuous production. In one pass, you can form arbitrarily thick walls by simply changing the overlap of the tape.
High performance.
The ability to produce large diameter fiberglass pipes (in theory - without any restrictions on the maximum size). Dimensions are limited only by the size of the mandrel.
Extremely high content of fiberglass in the finished material. It reaches 85% against 45-65% with alternative methods. This affects both the final strength and the flammability of the product.

Oblique cross-longitudinal winding.

Standards

The production of products of interest to us is regulated by two regulatory documents:

GOST R 53201-2008 contains technical conditions for the manufacture of pipes with a diameter of 50-200 mm on threaded connections.
Developed with the participation of LLC NTT (New Pipe Technologies) GOST R 54560-2011 describes the details of pipelines made of "glass fiber reinforced thermoplastics".

Let's study the main provisions of the documents.

GOST R 53201-2008

The mode of operation of pipes provided by the standard looks like this:

Temperature - from -60 to + 60C.
Relative humidity - up to 100%.
The temperature of the transported liquid is up to +110C.
Working pressure - from 3.5 to 27.6 MPa.

The following options for using the products described by the standard are envisaged:

Transportation of oil and gas condensate.
Transportation of salt solutions (including sea water).
Construction of lift columns.
Fixing wells for various purposes.

Maintenance of reservoir pressure during the development of underground deposits.
Technical and drinking water supply.

The standard distinguishes three types of pipes:

Designation	Decryption
NK	Pump and compressor
O	Casing
L	Linear

What can be the diameters of fiberglass pipes produced in accordance with GOST R 53201-2008, and their other characteristics?

Pump-compressor, casing

Inner diameter, mm	Nominal pressure, MPa		Weight of running meter, kg
50	6,9 – 27,6	4,3 – 8,4	1,6 – 3,3
63	6,9 – 27,6	4,6 – 10,7	2,2 – 5,5
100	10,3 – 17,2	8,1 – 12,2	5,8 – 8,2
150	10,3 – 17,2	13,5 – 15,0	14,0 – 14,9
200	10,3	13,6	16,5

In the photo - fiberglass high-pressure tubing.

Linear

Inner diameter, mm	Nominal pressure, MPa	Minimum wall thickness, mm	Weight of running meter, kg
50	10,3 – 27,6	2,79 – 8,10	1,2 – 3,1
63	8,6 – 27,6	2,80 – 9,90	1,4 – 5,2
100	5,5 – 27,6	2,80 – 16,00	2,3 – 12,8
150	5,5 – 13,8	4,57 – 11,20	5,1 – 12,2
200	5,5 – 13,8	5,84 – 14,70	8,6 – 22,6

In addition to pipe sizes, the document contains detailed instructions for the manufacture of fittings, indicating basic dimensions, requirements for appearance, maximum tolerances and marking of all products.

GOST R 54560-2011

The standard describes pipelines operating in much milder conditions than those described above:

Working pressure - up to 3.2 MPa;
Medium temperature - up to 35C;
Transported liquids - water, aqueous solutions and wastewater (domestic and industrial).

Important: GOST does not apply to pipelines for internal water supply and sewerage.

Within the framework of the document, products are classified according to the following criteria:

Diameter (DN). The range of values is from 300 to 3000 millimeters.
Nominal pressure (PN). For non-pressure pipes, the very concept of PN is rather arbitrary and is taken equal to 0.1 - 0.4 MPa; for pressure ones, it takes on the values of 0.6, 1.0, 1.6, 2.0, 2.5 and 3.2 MPa.
Nominal hardness (SN). It is also measured in megapascals and can be equal to 1250, 2500, 5000 and 10000.

Please note: when laying with your own hands, it should be borne in mind that SN 1250 pipes are not recommended for underground laying in principle, and SN 2500 is recommended to be laid in trays.

The document, like the previous one, lists the main dimensions of all types of fittings and the requirements for their appearance, strength, marking and reinforcement methods.

Conclusion

Of course, in our material, we touched on only a small part of a very extensive topic of using fiberglass. We have not found out whether fiberglass pipes can be used for heating or domestic sewage, how good they are against the background of metal-polymer or all-plastic products. Some of these questions affect the video in this article. Good luck!

They are used both for transporting various media along them, and as structural elements (supports, columns, crossbeams, shells).

Story

The appearance and production of fiberglass pipes became possible in the mid-1950s, when the industrial production of thermoplastic binders (primarily epoxy resins) and glass fibers was mastered. Even then, the advantages of these pipes became obvious: low weight and high corrosion resistance. However, during this period, they could not yet win any market share of pipe products due to the low price of "traditional" pipe materials: steel (including stainless steel), copper and aluminum. In the mid-1960s, the situation began to change. First, the price of alloyed steel and aluminum rose sharply. Secondly, the beginning of oil production on the sea shelves and in hard-to-reach land areas required the use of light and corrosion-resistant pipes. Thirdly, the production technology of fiberglass pipes has been improved, and product performance has been improved. During these years, Ameron (USA) mastered the large-scale production of high-pressure fiberglass pipes (up to 30 MPa) for oil fields. The pipes were a commercial success and many manufacturers of fiberglass products appeared in the USA. In the 1970s, US-made fiberglass pipes became widespread in the oil fields of North America and the Middle East.

In the 1980s, interest in fiberglass pipes appeared in all industrialized countries. Their production and application have mastered in Europe, Japan, Taiwan. Experiments began on the use of fiberglass pipes in the USSR.

Production technologies

As of 2013, four fundamentally different technologies for the production of fiberglass pipes are known:

Winding glass reinforcement impregnated with a binder on the outer surface of a technological mandrel (mandrel);
centrifugal casting;
Centrifugal molding from prepreg on the inner surface of the technological mandrel (mould);
Pultrusion in the gap between the outer and inner mandrels;
Extrusion of a binder filled in volume with chopped glass fiber.

winding

The winding (coiling) technology is the simplest to implement and provides high performance. Winding can be both periodic and continuous. The winding technology ensures high quality of the inner surface of the pipe due to its molding on the outer surface of the mandrel, but the quality of the outer surface is low due to the absence of forming elements outside. For pipes used to transport liquids and gases, the latter circumstance is not essential.

Known winding using thermosetting (polyester, epoxy, phenol-formaldehyde and other resins) and thermoplastic (polypropylene, polyethylene, polyamide, polyethylene terephthalate, etc.) polymer binders. When using thermoplastic binders, one-stage and two-stage winding technologies are possible. When using a one-stage technology, the process of combining (impregnating) a fibrous filler with a thermoplastic binder and winding on a mandrel occur sequentially on the same technological installation. When using a two-stage technology, first, as a result of the combination operation, a pre-impregnated material (prepreg) is obtained in the form of a thread, tape, strand. The resulting prepreg is then reheated and applied to the mandrel.

There are many ways of laying reinforcing glass fibers, but spiral-annular, spiral-tape, longitudinal-transverse and oblique longitudinal-transverse methods have found industrial application.

Spiral-ring winding

The method was first proposed and implemented by Ameron (USA) in the 1960s for the production of fiberglass tubing. With spiral-ring winding (SKN), the stacker, which is a ring with dies evenly spaced around the circumference, moves back and forth along the axis of the rotating mandrel. Such a movement ensures that the fibers are continuous along the entire length with an equal pitch along the helical lines. By varying the ratio of the speed of rotation of the mandrel and the translational movement of the stacker, it is possible to change the angle of fiber stacking. At the end sections of the pipe in the reversal zone of the stacker, the laying angle of the fibers is reduced so that they are held on the surface of the mandrel by friction forces. Due to this, the fibers retain the tension given to them by the stacker, and after curing of the binder, the pipe reinforcement becomes stressed, which improves the physical and mechanical properties of the product.

The advantages of spiral-ring winding include:

high productivity due to the laying of a large number of fibers in one pass;
high strength of the resulting pipes;
the possibility of obtaining equal strength in the annular and axial directions;
high value of the axial modulus of elasticity;
due to the pre-tensioning of the reinforcement, the binder tolerates tensile loads well without cracking;
the possibility of forming a generatrix with a complex shape, as well as pipes of variable diameter;
the possibility of laying glass rovings, consisting of a large number of elementary fibers (over 2400 tex);
when using a collapsible or destructible mandrel, the possibility of forming closed shells (cylinders, rocket engine cases).

Due to these advantages, spiral-ring winding has become widespread in the manufacture of high-pressure pipes (in particular, tubing), structural pipes, composite supports for power transmission lines, and housings of solid propellant rocket engines.

However, this technology has its drawbacks:

high complexity of equipment;
the large mass of the stacker, combined with its fast reciprocating motion, leads to increased loads on the drives and guide mechanisms;
the complexity of loading fiberglass into the thread-carrying path;
a significant increase in the number (up to several hundred and even thousands) of fibers to be laid when winding pipes of large diameter, which necessitates the use of a large number of spinnerets and other elements of the thread-carrying path;
due to the need for a reverse movement of the stacker relative to the mandrel, the spiral method is not very suitable for continuous winding.

Due to these disadvantages, spiral-ring winding is rarely used for the production of large diameter pipes.

Spiral tape winding

According to the principle, spiral-tape winding (SLN) does not differ from spiral-ring winding, however, the stacker forms only a narrow tape consisting of several tens of fibers. The continuity of the reinforcement is ensured by multiple passes of the stacker. This technology is simpler than the spiral-annular one and allows the formation of pipes of large diameters, but has a number of disadvantages:

the productivity of the method is significantly lower due to the need for a large number of passes of the stacker;
the laying of the fibers is uneven and loose, which worsens the physical and mechanical characteristics of the pipes.

However, spiral tape winding is widely used in the production of low and medium pressure general purpose pipes.

Longitudinal-transverse winding

With longitudinal-transverse winding (PPN), the fibers reinforcing the pipe in the longitudinal and transverse directions are laid independently of each other. In this case, there is no need for a reverse movement of the stacker and this method is suitable for continuous winding. The advantages of PNP include:

high performance;
the ability to change the ratio of the annular and axial reinforcement in a wider range than with spiral methods;
the possibility of implementing continuous winding;
the continuity of the axial fibers and the possibility of their tension, as a result of which the physical and mechanical characteristics of the pipes are no worse than with spiral methods.

Disadvantages of PPN:

The need to use a rotating longitudinal fiber stacker, which complicates the equipment;
In the case of large pipe diameters, the need to accommodate a large number of spools of fibers in a rotating stacker.

Longitudinally transverse winding has found wide application in the in-line production of fiberglass pipes of small diameters (up to 75 mm).

Oblique longitudinal-transverse winding

The technology was developed in the USSR for the mass production of fiberglass shells for rockets. Little known outside of Russia and Ukraine. In Russia, on the contrary, it was widespread until the mid-2000s. In the case of oblique longitudinal-transverse winding (CCW), a stacker forms a pseudo-tape consisting of a parallel bundle of fibers impregnated with a binder, wound at a slight angle on the surface of the mandrel (forming an annular reinforcement), which is preliminarily wrapped with unimpregnated fibers, which form axial reinforcement after laying. Pseudo-dolent is placed on the mandrel with an overlap on the previous coil. After laying on the mandrel, the pseudotape layers are rolled by rollers, the outer surface of which has helical lines. Roller rolling compacts the reinforcement layer, removing excess binder. As a result, the stacking of fibers is very dense, and the binder layer between them has a minimum thickness, which has a positive effect on the strength of fiberglass and reduces its combustibility. Thanks to rolling, it is possible to obtain a glass content in the cured fiberglass of 75% -85% by weight - a result unattainable for other methods (SKN gives a glass content of the order of 65%, and SKL and PPN - 45% -60%). By varying the overlap, it is possible to change the thickness of the pipe wall laid in one pass. This method makes it possible to implement continuous winding, as well as winding large-diameter pipes with a small number of simultaneously laid fibers.

The advantages of CPP include:

very high productivity, especially when winding pipes of large diameters (over 150 mm);
the possibility of winding pipes of arbitrarily large diameters (theoretically - to infinity);
the possibility of continuous winding;
very high fiber packing density;
low flammability of the obtained fiberglass;
the possibility of varying the ratio of annular and axial reinforcement over a wide range;
the absence of continuous axial reinforcement, which improves the dielectric properties of fiberglass.

The disadvantages of CPP include:

the possibility of interlayer cracking, which does not allow the creation of high-pressure pipes using this technology;
the use of stitching rollers complicates the use of fast-hardening binders;
the lack of pre-tensioning of the axial reinforcement reduces the modulus of elasticity of fiberglass.

Fiberglass winding

Winding with glass cloth is used relatively rarely, due to the higher cost of glass cloth compared to non-woven fibers. In terms of technological properties, winding with fiberglass is close to CPV and is sometimes used for small-scale production of large-sized pipes.

Centrifugal molding

In 1957, in the Swiss city of Basel, the idea was born to use centrifugally cast glassfiber reinforced plastic pipes (CC-GRP - Centrifugally Cast Glassfiber Reinforced Plastic). This technology was first developed, applied and patented by HOBAS

In this method, the materials that make up the pipe wall are fed by a feeder controlled by a digital controller into the interior of a rapidly rotating steel mold.

The composition of the materials is polyester resin, chopped fiberglass roving, quartz sand and marble flour.

The inner diameter of the rotating mold is the outer diameter of the finished fiberglass pipe. This makes it possible to obtain a pipe with an outer diameter accuracy of 0.1 mm.

This method also makes it possible to make the pipe wall more homogeneous and monolithic, to avoid gaseous inclusions and delaminations.

Since it is possible to cast a pipe wall of almost any thickness, composite products of increased ring rigidity

(over SN 12,000 n/m² and high axial load-bearing microtunneling pipes are predominantly produced in this way.

pultrusion

Pultrusion is a high-performance method for the production of fiberglass pipes and ensures high quality of the outer and inner surface. At the same time, pultrusion has a number of limitations:

the complexity of the implementation of ring reinforcement;
the difficulty of obtaining pipes of large diameters;
complexity of technological implementation in comparison with winding;
the need to use special binders with a short initial curing time.

Pultrusion is used for mass production of fiberglass pipes of small diameters of low working pressures for plumbing and heating purposes, as well as in the production of fiberglass rods.

Extrusion

Extruded fiberglass pipes do not have a solid regular reinforcement frame. The binder is filled with randomly oriented chopped glass fiber. This technology is simple and highly productive, but the absence of solid reinforcement significantly worsens the physical and mechanical characteristics of the pipes. Thermoplastics (polyethylene, polypropylene) are mainly used as a polymer matrix for extruded fiberglass pipes.

Application and performance features

The relevance and economic feasibility of using fiberglass pipes is determined by a number of their operational features compared to other types of pipes.

Fiberglass is characterized by a density of 1750-2100 kg/m 3 , while their tensile strength is in the range of 150-350 MPa. Thus, in terms of specific strength, fiberglass is comparable to high-quality steel and significantly surpasses thermoplastic polymers (HDPE, PVC) in this indicator.
Fiberglass has a high corrosion resistance, since glass and cured thermosetting resins (polyester, epoxy), which are part of it, have a low reactivity. According to this indicator, fiberglass is significantly superior to ferrous and non-ferrous metals and is comparable to stainless steel.
Fiberglass is a slow-burning, flame-retardant self-extinguishing material with a high oxygen index, since non-combustible glass makes up a significant proportion in the mass of fiberglass. In this indicator, fiberglass is superior to homogeneous and filled thermoplastic polymers.
Fiberglass is an anisotropic material and its properties in given directions can be easily controlled by varying the fiber stacking pattern. Thus, fiberglass pipes can be made with an equal margin of safety in the axial and annular directions. In isotropic materials, when pipes are loaded with internal pressures, the margin of safety in the annular direction is always 2 times less than in the axial direction.
The yield strength of fiberglass is close to the tensile strength, for this reason fiberglass pipes are much less elastic than steel or thermoplastic pipes.
Fiberglass is not weldable. Pipe connections are made using flanges, couplings, nipple-socket connections, glue.

Based on these features, a number of areas of application of fiberglass pipes have been formed:

Oil production

In the oil industry, fiberglass pipes are used due to their high corrosion resistance in aggressive environments (formation waters, crude oil, drilling and process fluids) compared to steel and high specific strength compared to thermoplastic polymers.

Fiberglass is used to manufacture tubing and line pipes (RPD systems) with a diameter of up to 130 mm for operating pressures of up to 30 MPa, pipes for oil gathering pipelines with a diameter of up to 300 mm for operating pressures of up to 5 MPa, main pipes with a diameter of up to 1200 mm for operating pressures of up to 2 .5 MPa.

coal industry

In the coal industry, there are restrictions on the materials used in closed mine workings. So the safety rules in coal mines establish that products made of non-metallic materials located in closed mine workings must have an oxygen index of at least 28%, be slow-burning, difficult-to-ignite (according to GOST 12.1.044), and their combustion products should not be highly toxic. For these reasons, the use of polyethylene and polypropylene pipes in coal mines is impossible. At the same time, fiberglass pipes meet these requirements. The use of fiberglass pipes in mines is advisable for a number of reasons:

low weight, which is very important, since mine pipelines have large diameters (150 - 1200 mm) and are mounted, as a rule, manually;
corrosion resistance in a mine atmosphere;
smooth inner surface, which reduces the formation of deposits of coal dust and other dust inevitably present in transported media;
safety in methane explosions, since the destruction of fiberglass occurs without the formation of traumatic fragments.

Department of Housing and Utilities

Fiberglass pipes have found application in housing and communal services, mainly as sewer pipes. This is due to the fact that sewerage pipes have diameters of the order of 600 - 2500 mm, they work without internal pressure in conditions of external loads from the soil and groundwater pressure. The high ring stiffness of fiberglass allows you to create pipes for these conditions.

Another application of fiberglass pipes in housing and communal services are garbage chutes. In the last 10-15 years, fiberglass pipes have also been used as smoke pipes in gas boilers and thermal power plants.

Of all the variety of materials that are used for the manufacture of polymer pipes for various purposes, special attention is always paid to fiberglass, as it has truly unique performance properties. As a rule, fiberglass pipes are used more for industrial purposes and are distinguished by the fact that they easily endure any operating conditions and have a fairly high working life. And, despite the fact that this material is relatively expensive, in recent years it has become increasingly popular, including among ordinary private developers.

Fiberglass pipes

What are these pipes?

So, fiberglass is a special composite material, which is characterized by increased strength characteristics. The manufacturers of the pipes described in this article assure that their products, which are impregnated with epoxy / polyester resins, can be used in surface / underground laying of pipelines for various purposes. Such pipes perfectly demonstrate themselves in conditions of increased pressure of the transported substance; with their help, highways are laid in a variety of climatic zones (this even includes the Far North).

Note! If required, a protective coating can be applied to the inner surface of the products, thanks to which they can be used to transport various gaseous or liquid media.

The marking of fiberglass pipes that have a similar coating is as follows.

"P". Such products can be used for pipelines of cold water supply.
"BUT". Pipes with this marking are intended for moving liquid media, including various abrasive impurities.
"G". These are pipes that are used for laying hot water networks.
"X". Products that have this marking are designed for chemically active liquids, including products of the oil refining industry.
"FROM". The last category of pipes, which is intended for all other purposes.

Features of the appearance of fiberglass pipes

The manufacture of this kind of pipes arose back in the 50s of the last century, since it was then that the production of epoxy resins gained an industrial scale. This technology, like any other novelty, was not very popular at first: people had no experience with fiberglass, moreover, traditional materials (such as aluminum or steel) were relatively inexpensive.

However, in 10-15 years the situation changed dramatically. For what reason?

First of all, this is due to the fact that the cost of steel and non-ferrous metals has increased markedly.
Fiberglass tubing had an advantage over steel pipes - they weighed a little and differed in corrosion resistance (the pipes did not suffer from prolonged contact with salt water, which cannot be said about their “competitors”).
Another reason, which is largely related to the previous one, is that the commercial development of gas / oil fields has begun to develop.
And, finally, the production technology itself has changed - now fiberglass pipes were cheaper and became more and more durable.

It is quite obvious that the results did not have to wait long - by the end of the sixties, Ameron from the USA broke into the building materials market with high-quality high-pressure fiberglass pipes. At first, the company's products conquered North America, and therefore moved to the Middle East market. Already in the eighties, European countries entered the game, and some time later, the Soviet Union.

Video - Fiberglass pipes

Varieties of pipes depending on the type of resin

The operational properties of the pipes described in the article may vary depending on which resins they are made of. It is for this reason that at the time of purchase it is imperative to specify what kind of fiberglass you are selling. From this point of view, products are divided into two categories, let's get acquainted with the features of each of them.

Fiberglass, made on the basis of polyester resins. This material is characterized by chemical neutrality, resistance to the influence of various kinds of substances; material is a very important element in the laying of pipelines for the oil refining industry. However, you should know that such pipes are unsuitable for operation at high temperatures (above +95 degrees) or high pressure (maximum - 32 atmospheres).
Fiberglass, made on the basis of epoxy resins. Thanks to the epoxy binder used in the manufacturing process, the finished product is much more durable. Pipes made using this technology and having a larger diameter are able to withstand very high pressure (maximum - 240 atmospheres) and temperatures of no more than +130 degrees. Another advantage of this material is its relatively low thermal conductivity, and therefore there is no need for additional thermal insulation (the products practically do not give off thermal energy). The cost of such pipes is somewhat more expensive when compared with the same indicator of polyester fiberglass.

Where can fiberglass pipes be used?

Immediately make a reservation that they can be used in a variety of industrial and economic sectors. But more specifically, such pipes have proven themselves in the following areas.

Energy. Here, such pipes are actively used when laying highways operating at a high pressure indicator.
Oil industry. In this case, fiberglass pipes are used both for transporting valuable minerals (we are talking about trunk lines), and for providing all other production processes, including gas / oil production.
In the housing and communal services system. And here, the products described in the article are used for laying water pipes (DHW and cold water), as well as for installing heating systems.
Medical, chemical industry. Due to chemical neutrality, as well as resistance to various kinds of aggressive influences, fiberglass pipes are simply indispensable for transporting alkalis, acids and other mixtures/liquids.

Note! Among other things, recently such pipes are increasingly used for domestic purposes. Moreover, this use is fully justified - their trouble-free (that is, without repair) operational life is more than half a century.

Features of the manufacture of fiberglass pipes

How are these pipes produced today? There are four main ways, we will consider each of them. But first, we note that the performance properties of finished products can vary significantly depending on the number of structural layers.

The simplest single-layer pipes are considered the cheapest. And it is not surprising, because fiberglass in this case is practically not protected by anything.
Two-layer products have an outer protective shell that increases resistance to UV radiation and various aggressive environments.
Finally, in products consisting of three layers, one layer is an additional power layer - it is located between the outer and inner. Such pipes are very durable, and therefore can be used at very high pressures. However, it should be remembered that they are not cheap at the same time.

Now let's look at the main manufacturing technologies.

Technology No. 1. Extrusion

In this case, the hardener is mixed with resin, as well as crushed glass fiber, and then the resulting mixture is forced through the hole using a special extruder. As a result, we get a technologically advanced and fairly cheap production, but there is no reinforcing frame, which affects the strength characteristics of the product.

Technology number 2. pultrusion

Here, the products are already formed between the outer and inner mandrels. Thanks to this, all surfaces come out perfectly even, but due to production limitations, such pipes cannot be made with a large diameter or designed for increased working pressure.

Technology number 3. Centrifugal molding

A feature of the method is that the reinforcement in this case is a ready-made sleeve made of fiberglass, pressed against the surfaces of the mold, which rotates due to centrifugal forces. Due to the same forces, the resin is distributed along the walls of the products as evenly as possible. But the main advantage is that you can get a perfectly smooth outer surface. Although there is a minus - the technology is quite energy-intensive, and therefore expensive.

Technology number 4. winding

Here, fiberglass, which is impregnated with a binder, is wound on a cylindrical mandrel. The equipment that is used for such production is most widely used due to increased productivity and simplicity.

Note! This method can be of several types. Consider the features of each of the varieties of windings.

The first variety. Spiral annular

The special stacker moves back and forth parallel to the rotating mandrel. After each such pass, a layer of fibers remains, and the step is permanent. Thanks to a similar winding technique, fiberglass pipes that are extremely tear-resistant are obtained.

Note! What is characteristic, if the thread is pre-tensioned, then the strength of the finished product will also increase because of this, and the risk of cracks during bending will be minimal.

Using this method, pumping and compressing products are produced (they are able to withstand high operating pressures), various load-bearing elements (including supports for power lines), as well as casings for rocket engines.

The second variety. Spiral tape

It differs from the previous variety only in that the stacker after each pass leaves a small tape consisting of several tens of fibers. For this reason (more passes are needed), the reinforcing layer is not as dense. The advantage of the technique is that it uses a simpler, and therefore cheaper technique.

The third variety. Longitudinal-transverse

The main difference is continuous winding - the threads are simultaneously laid both longitudinal and transverse. At first glance, the technology itself in this case should be simpler and cheaper, but there is one difficulty - purely mechanical. So, the mandrel itself rotates, and therefore the coils must also rotate (those from which the threads are wound). Tellingly, the larger the diameter of the pipe, the greater the number of these coils will be needed.

The fourth variety. Transverse-longitudinal oblique

The technique was created in Kharkov in the days of the USSR and was intended for use in the manufacture of rocket shells. Soon the technology was spread to other countries. The bottom line is that the stacker forms a wide tape, which, in turn, consists of numerous fibers that are impregnated with a binder. This tape is wrapped with a non-impregnated thread even before winding - this is how axial reinforcement is created. Each new layer after laying must be rolled with a roller, which squeezes out excess binder and compacts the reinforcement.

This technique has important advantages, we will get acquainted with each of them in more detail.

The production process is continuous, and the wall thickness can be any (requiring only a change in the overlap of the tape).
The finished fiberglass pipes contain quite a lot (this figure can reach 85 percent; for example, for other methods it is a maximum of 40-65 percent).
The performance indicator in this case is also quite high.
Finally, it becomes possible to produce pipes of the largest sizes (theoretically, there are no restrictions at all), which depend solely on the dimensions of the mandrel.

Table. The main varieties of pipes described in the article.

Table. Diameter of casing and pump-compressor products according to GOST.

Table. Diameter of linear products according to GOST.

Key Benefits of Fiberglass Pipes

What is the reason for such a high popularity of such pipes? Below is a list of the advantages of this material - it is not too long, but each of the points is of great importance.

Fiberglass pipes are more than acceptable, especially when compared with stainless / high-alloy steel products.
Thanks to one or another reinforcement scheme (all of them were listed in the previous section of the article), it is possible to obtain products with specific mechanical properties. For example, the first type of winding (spiral-annular) makes it possible to produce pipes that are extremely resistant to high working pressure.
Fiberglass is also characterized by excellent resistance to various aggressive environments and corrosion.
Finally, the material just weighs a little. More specifically, its specific strength is about 3.5 times higher than that of steel. Consequently, pipes made of these materials, having the same strength, will have completely different masses.

Approximate cost of fiberglass pipes

The modern range of products described in the article is quite large, and therefore there are many manufacturers. However, they all manufacture pipes according to GOSTs, and therefore the dimensions and characteristics must be identical. But still, let's get acquainted with the features of several types of pipes, as well as find out today's average market prices. For the convenience of visitors to our site, all the information below is presented in the form of a small table.

Table. How much does fiberglass pipes cost - prices, characteristics.

Name, photo	Short description	Average market value, in rubles
1. Profile pipe made of fiberglass	The dimensions of the product are as follows - 10x5x0.6 centimeters (HxWxT). As for the weight, in this case it is 3.14 kilograms per linear meter.	From 1250 per meter
2. Profile pipe made of fiberglass	A similar product, only the dimensions differ (in this case they are 18x6x0.6 centimeters) and, therefore, weight. The density in this case varies between 1,750 and 2,100 kilograms per cubic meter. Note also that the specific strength of this material is the same as that of stainless steel.	From 2200
3. Corrugated fiberglass pipe	The dimensions of this product are 3.4x0.9 centimeters, and the weight is 500 grams per meter of length. The inner diameter of such a pipe is 2.5 centimeters.	From 200
4. GRP round pipe	Its outer diameter is 7 centimeters, while the inner diameter is 5.5 centimeters. The walls of the product have a thickness of 1.5 centimeters. The mass is 2.8 kilograms per meter of length.	From 1150
5. GRP round pipe	According to the characteristics, this product is very similar to the previous one - its outer diameter is also 7 centimeters, but the inner one is already 6 centimeters. The walls are centimeter thick.	From 800

Note! As you can see, the cost can be different and depends on the specific shape of the products, their dimensions and wall thickness. Still the price can vary depending on the specific manufacturer, but not much. Be that as it may, there are plenty to choose from in any case.

Video - Advantages of fiberglass pipes

Summing up

In the end, it is worth noting that today we talked, of course, only about a small part of such an extensive and interesting topic as the use of fiberglass (in particular, pipes made from this material). We only briefly mentioned whether such pipes can be used in sewer or heating systems, whether they are better than plastic or, say, metal-polymer counterparts. Be that as it may, we will return to this topic later. That's all, good luck with your work!

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