How to choose fiberglass pipes: production specifics and an overview of leading manufacturers

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

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

We 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.

General characteristics of fiberglass

Fiberglass - a plastic material, which includes fiberglass components and a binder filler (thermoplastic and thermosetting polymers). Along with a relatively low density, fiberglass products are characterized by good strength properties.

The last 30-40 years fiberglass is widely used for the manufacture of pipelines for various purposes.

A polymer composite is a worthy alternative to glass, ceramics, metal and concrete in the manufacture of structures designed to operate in extreme conditions (petrochemicals, aviation, gas production, shipbuilding, etc.)

Highways combine the qualities of glass and polymers:

1. Light weight. The average fiberglass weight is 1.1 g / cc. For comparison, the same parameter for steel and copper is much higher - 7.8 and 8.9, respectively.Thanks to ease, installation works and transportation of material are facilitated.
2. Corrosion Resistance The components of the composite have a low reactivity, therefore, they are not subjected to electrochemical corrosion and bacterial decomposition. This quality is a decisive argument in favor of fiberglass for underground utilities.
3. High mechanical properties. The absolute tensile strength of a composite is inferior to that of steel, but the specific strength parameter significantly exceeds thermoplastic polymers (PVC, HDPE).
4. Weather resistant. The range of boundary temperatures (-60 ° C .. + 80 ° C), the treatment of pipes with a protective layer of gelcoat provides immunity to UV rays. In addition, the material is resistant to wind (the limit is 300 km / h). Some manufacturers claim earthquake resistance of pipe fittings.
5. Fire resistance. Non-combustible glass is the main component of fiberglass, so the material is hardly flammable. When burning, toxic gas dioxin is not released.

Fiberglass has a low thermal conductivity, which explains its heat-insulating qualities.

The disadvantages of composite pipes: susceptibility to abrasion, the formation of carcinogenic dust due to mechanical processing and the high cost compared to plastic

As the inner walls wear out, the fibers become exposed and break off - particles can enter the transported medium.

Fiberglass Pipe Manufacturing Technologies

Physico-mechanical characteristics of the finished product depend on the production technique. Composite fittings are manufactured in four different ways: extrusion, pultrusion, centrifugal casting and winding.

Technology # 1 - Extrusion

Extrusion is a technological process based on the continuous forcing of a paste-like or highly viscous material through a forming tool. The resin is mixed with crushed fiberglass and a plastic hardener, and then fed into the extruder.

The finished product does not have a continuous reinforcing frame, since the binder is filled randomly with fiberglass. The absence of "armopoyas" affects the decrease in pipe strength

High-performance extrusion line allows you to get frameless composite products at a low price, but the demand for it is limited due to the low mechanical properties. The basis of the polymer matrix is ​​polypropylene and polyethylene.

Technology # 2 - Pultrusion

Pultrusion is a technology for manufacturing composite long elements of small diameter with a constant cross section. Passing through a heated mold-forming die (+140 ° С), the details are “pulled” out of fiberglass material impregnated with thermosetting resin.

Unlike the extrusion process, where pressure is the determining influence, in the pultrusive unit this role is played by the pulling effect.

The main working units of the pultrusion installation: fiber supply complex, polymer tank, preforming device, thermo-mold, pulling tape and cutting machine

Technological process:

1. Fibrous filaments from coils are fed into a polymer bath, where they are impregnated with thermoplastic resins.
2. The processed fibers pass through a preforming unit - the threads are aligned and acquire the desired shape.
3. Uncured polymer enters the die. Due to several heaters, an optimal mode for polymerization is created and the pulling speed is selected.

The cured product is pulled by a pulling machine and cut into segments.

Distinctive features of pultruded technology:

• acceptable polymers - epoxy, polyester resins, vinyls;
• pulling speed - the use of innovative optimized "pultruded" polymers allows you to accelerate broaching up to 4-6 m / min. (standard - 2-3 m / min.);
• run-up run: minimum - 3.05 * 1 m (pulling force up to 5.5 t), maximum - 1.27 * 3.05 m (force - 18 t).

The output is a pipe with perfectly smooth external and internal walls, at a high level and strength indicators.

The characteristics of the fiberglass obtained by the method of pultrusion: breaking bending stress - 700-1240 MPa, thermal conductivity - 0.35 W / m2 ° C, the degree of tensile elasticity - 21-41 GPa

The disadvantages of the method do not relate to the quality of the original product, but to the technology itself. Arguments “against”: the high cost and duration of the production process, the inability to manufacture large diameter pipes designed for significant loads.

Technology # 3 - Centrifugal Casting

Swiss company Hobas developed and patented centrifugal forming technique. In this case, the production is carried out from the outer wall of the pipe to the inner one by using a rotating form. The composition of the pipeline includes: crushed glass tows, sand and polyester resins.

Raw materials are fed into a rotating matrix - the structure of the outer surface of the pipeline is formed. As production proceeds, solid components, filler and fiberglass are mixed with the liquid resin - polymerization proceeds faster under the influence of the catalyst.

As a result, multilayer smooth walls are formed. Thanks to the centrifugal "spraying" technique, the pipe structure is monolithic, homogeneous without delamination and gaseous particles

Additional advantages:

• high accuracy of the dimensions of the initial product (the internal section of the rotating form corresponds to the external diameter of the finished product)
• the ability to cast a wall of any thickness;
• high ring stiffness of the polymer composite;
• obtaining a smooth surface outside and inside the pipe fittings.

The disadvantage of centrifugal production of fiberglass pipes is the energy intensity and high cost of the final product.

Technology # 4 - progressive winding

The most popular technique is continuous winding.The pipe is created by alternating the mandrel with fiberglass with polymers with cooling processes. The production method has several subspecies.

Spiral ring technology

The fiber stacker is a special ring, on the circumference of which there are spinnerets with threads.

The working element continuously moves along the axis of the moving frame and distributes the fibers along the helical lines.

When changing the speed of rotation of the frame and the movement of the stacker, the angle of the glass fibers. At the ends of the pipe, the ring operates in the “reverse” mode and puts the threads with a minimum slope

The main advantages of the method:

• uniform strength over the entire surface of the highway;
• excellent tolerance of tensile loads - cracks are excluded;
• creation of products of variable diameter and cross sections with a complex configuration.

This technique makes it possible to obtain high-strength pipes designed for operation under high pressure (pump-compressor engineering networks).

Spiral tape winding

The technique is similar to the previous one, the difference is that the stacker feeds a narrow ribbon of fibers. A dense reinforcing layer is achieved by increasing the number of passes.

Cheaper equipment is involved in the production than with the spiral-ring method, but a couple of significant disadvantages are inherent in the “ribbon” winding:

• limited performance;
• loose laying of fibers reduces the strength of the pipeline.

The spiral-tape method is relevant in the manufacture of pipe fittings for low, moderate pressure.

Longitudinal-transverse method

Continuous winding is carried out - the stacker places the longitudinal and transverse fibers at the same time. There is no reverse movement.

Under the rotating mandrel, moving coils are used to feed longitudinal reinforcing fibers. In the manufacture of volumetric pipes, it is required to use a large number of bobbins

Method characteristics:

• It is used mainly when creating pipes with a cross section up to 75 mm;
• there is the possibility of tensioning the axial threads, due to which strength is achieved, as in the spiral method.

Longitudinal transverse technology is highly productive. Machines allow you to change the ratio of axial and annular reinforcement in a wide range.

Slanting transverse longitudinal technology

The development of Kharkov engineers is in demand among domestic manufacturers. When cross-wound winding, the stacker displays a “veil” consisting of a bundle of binder threads. The tape is fed to the frame at a slight overlap angle with the previous turn - ring reinforcement is formed.

Upon completion of the processing of the entire mandrel, the fibers are rolled in by rollers - the remains of the binder polymers are removed, the reinforcing coating is compacted.

Rolling allows you to achieve the minimum required plastic content. The proportion of glass in the cured composite is about 80% - an optimal result that provides high strength and low flammability

Features of cross-layer rolling:

• fiberglass tightness;
• unlimited diameter of produced pipes;
• high dielectric properties due to the absence of continuous reinforcement along the axis.

The elastic modulus of the “cross-layer” fiberglass is inferior to the similar parameter of other techniques. Due to the risk of interlayer cracks, the method is not feasible when creating pipelines under high pressure.

Fiberglass Pipe Selection Parameters

The choice of glass composite pipes is based on the following criteria: stiffness and design pressure, type of binder component, structural features of the walls and method of connection. Significant parameters are indicated in the accompanying documents and on each tube - abbreviated marking.

Rigidity and pressure rating

Fiberglass stiffness determines the ability of the material to withstand external loads (soil severity, traffic) and pressure on the walls from the inside.According to ISO standardization, pipe fittings are classified into several classes of stiffness (SN).

The maximum allowable level of working pressure for each of the classes: SN 2500 - 0.4 MPa, SN 5000 - 1 MPa, SN 10000 - 2.5 MPa

The degree of rigidity increases with increasing wall thickness of the fiberglass pipe.

Classification by nominal pressure (PN) reflects the gradation of products with respect to safe fluid pressure at a temperature of +20 ° C over the entire service life (about 50 years). The unit of measurement for PN is MPa.

Some manufacturers, such as Hobas, indicate combined characteristics for two parameters (pressure and stiffness) through a fraction. Pipes with a working pressure of 0.4 MPa (class PN - 4) with a degree of rigidity (SN) of 2500 Pa will be marked - 4/2500.

Type of Binder

The operational properties of the pipe largely depend on the type of binder. In most cases, polyester or epoxy additives are used.

Features of PEF Binders

The walls are formed from thermosetting polyester resins reinforced with fiberglass and sand additives.

The polymers used have important qualities:

• low toxicity;
• curing in room temperature conditions;
• reliable coupling with glass fibers;
• chemical inertness.

Composite pipes with PEF polymers are not subject to corrosion and aggressive media.

Scope: housing and communal services, water intake, the pipeline of sewage treatment plants, the industrial and household sewerage. Operational restrictions: temperature over +90 ° С, pressure over 32 atmospheres

Epoxy Characteristics

A binder gives the material increased strength. The temperature limit of composites with epoxides is up to +130 ° С, and the maximum pressure is 240 atmospheres.

An additional advantage is almost zero thermal conductivity, so the assembled trunk does not require additional thermal insulation.

Pipes of this class will cost more than PEF products. As a rule, fiberglass pipelines with an epoxy binder are used in the oil and gas, petrochemical industry and in the organization of the infrastructure of seaports

Wall design of composite pipes

According to the design, they distinguish: one-, two- and three-layer fiberglass pipes.

Characteristics of single-layer products

The pipes do not have a protective lined coating, due to which they are of low cost. Features of pipe fittings: inability to use in regions with difficult terrain and harsh climate.

Also, these products require careful installation - digging a large volume of trench, arranging a sandy "pillow". But the estimate of installation work is increasing because of this.

Features of double-layer pipes

Products inside are lined with a film coating - high pressure polyethylene. Protection increases chemical resistance and improves the tightness of the line under external loads.

However, the operation of fittings in oil pipelines revealed the weaknesses of two-layer modifications:

• lack of adhesion between the structural layer and the lining - violation of the solidity of the walls;
• deterioration of the elasticity of the protective film at subzero temperatures.

When transporting a gas-containing medium, the lining may delaminate.

The purpose of the two-layer pipeline is the transportation of gas masses. Composite pipes are suitable for pumping wastewater, laying sewer and water mains

Three-layer pipe parameters

Fiberglass Pipe Structure:

1. External polymer layer (1-3 mm thick) - increase in mechanical and chemical resistance.
2. Structural layer - structural layer responsible for the strength of the product.
3. Liner (thickness 3-6 mm) - fiberglass inner shell.

The inner layer provides smoothness, tightness and smooths out cyclic fluctuations in internal pressure.

Physico-mechanical characteristics of three-layer fiberglass pipes allow them to be used in various industries for the transportation of gas-containing and liquid media

Fiberglass Docking Method

According to the method of connection, the assortment of pipe fittings made of composite is divided into 4 groups.

Group No. 1 - socket-spiked docking

Elastic rubber gaskets are mounted in mating grooves on the pipe end spikes. Landing rings are formed on equipment with electronic control, ensuring the accuracy of their location and size.

Depending on the location of the engineering network and the type of transporting medium, the type of rubber sealant is selected. Pipe fittings are equipped with the necessary rings

Group No. 2 - socket-thorn with seal and stopper

When arranging a land highway, it is necessary to compensate for the effect of axial forces on the pipeline. For this purpose, in addition to the seal, a stop is placed. The element is made of a metal cable, polyvinyl chloride or polyamide.

The stopper is installed in the annular grooves through the socket hole on the stud end. The limiter does not allow axial movement of the trunk elements

Group No. 3 - flange connection

Docking of a composite pipeline with fittings or metal pipes. The connecting dimensions of fiberglass flanges are regulated GOST 12815-80.

For flange fixation at the base of the pipe, a special “foot” with holes for fasteners is provided. The width of the connecting flanges depends on the parameters of the pipeline

Group No. 4 - adhesive fixation

Inseparable method of connection - the composition of reinforcing glass materials with the addition of a polyester component of “cold” curing is applied to the tips. The method provides strength and tightness of the line.

Marking the protective inner layer

The methodology for the production of pipe products allows you to produce products with different composition of the inner layer, which determines the resistance of the line to the transported medium.

The variety of goods is divided into 4 groups. HP fiberglass pipes calmly withstand regular pumping of liquids up to +90 ° C, while the ultimate pH should not exceed 14

Domestic manufacturers apply the following marking of protective coatings.

The letter indicates the acceptable use:

• AND - transportation of liquid with abrasives;
• P - supply and discharge of cold water, including drinking;
• X - permissible use in chemically aggressive gas and liquid environments;
• G - hot water supply systems (limit 75 ° C);
• WITH - other liquids, including those with high acidity.

The protective coating is applied with a layer of up to 3 mm.

Overview of products from leading manufacturers

Among the variety of products presented there are reputable brands with many years of positive reputation. These include products of companies: Hobas (Switzerland), Steklokompozit (Russia), Amiantit (a concern from Saudi Arabia with production facilities in Germany, Spain, Poland), Ameron International (USA).

Young and promising manufacturers of composite fiberglass pipes: Polyek (Russia), Arpipe (Russia) and Fiberglass Plant (Russia).

Manufacturer # 1 - HOBAS Brand

Brand name factories are located in the USA and many European countries. Hobas products have earned worldwide recognition for their excellent quality. GRT pipes with a polyester binder are made using the centrifugal casting technique of fiberglass and unsaturated polyester resins.

Hobas pipe systems are widely used in sewers, drainage and plumbing complexes, industrial pipelines and hydroelectric power stations. Allowed ground laying, placement by microtunnel and pulling method

Characteristics of Hobas composite pipes:

• diameter - 150-2900 mm;
• SN stiffness class - 630-10 000;
• PN-pressure level - 1-25 (PN1 - pressureless pipeline);
• the presence of an internal lining anti-corrosion coating;
• acid resistance over a wide pH range.

The production of shaped parts: elbows, adapters, flanged pipes and tees has been established.

Manufacturer # 2 - Steklokompozit company

The company "Steklokompozit" established a line for the production of fiberglass pipes Flowtech, production technology - continuous winding.

Involved equipment with a double supply of resinous substances. High-tech resins are used for laying the inner layer, and a cheaper composition is applied to the structural layer. The technique allows to rationalize the consumption of material and reduce the cost of production.

The range of Flowtech pipes is 300-3000 mm, PN class is 1-32. Standard footage - 6, 12 m. On request production within 0.3-21 m is possible

Manufacturer # 3 - Amiantit Brand

The main components of Amiantit's Flowtite pipes are fiberglass, polyester resin, sand. The technique used is continuous winding, providing the creation of a multilayer pipeline.

The structure of fiberglass includes six layers:

• nonwoven tape outer winding;
• power layer - chopped fiberglass + resin;
• middle layer - fiberglass + sand + polyester resin;
• repeated power layer;
• lining of glass threads and resin;
• nonwoven fiberglass protective coating.

The studies showed high abrasion resistance - for 100 thousand gravel cycles, the loss of protective coating was 0.34 mm.

Strength class of Flowtite products is 2500 - 10000, it is possible to manufacture pipes SN-30000 on order. Operating pressure - 1-32 atmospheres, maximum flow velocity - 3 m / s (for clean water - 4 m / s)

Manufacturer # 4 - Polyec

Polyek LLC makes various modifications of Fpipes fiberglass pipe products. The manufacturing technique (continuous oblique longitudinal-transverse winding) allows you to create three-layer pipes up to 130 cm in diameter.

Polymeric composite materials are involved in the creation of casing pipes, links of water-lifting columns, water supply pipelines and heating systems.

The nomenclature range of fiberglass sewer pipes is 62.5-300 mm, high-pressure products - 62.5-200 mm, ventilation ducts - 200-300 mm, well casing - 70-200 mm

In addition to fiberglass pipes, the market offers a lot of products from other materials - steel, copper, polypropylene, plastic, polyethylene, etc. Which, due to its more affordable price, are actively used in various areas of everyday use - installation of heating, water supply, sewage, ventilation and more.

You can get acquainted with the characteristics of pipes from various materials in our following articles:

• Plastic pipes: types, specifications, installation features
• Polypropylene pipes and fittings: types of PP products for the assembly of pipelines and methods of connection
• Plastic ventilation pipes for hoods: types, their characteristics, application
• Copper pipes and fittings: types, marking, features of the arrangement of a copper pipeline
• Steel pipes: types, assortment, overview of technical characteristics and mounting nuances

Conclusions and useful video on the topic

Manufacturing technology and the feasibility of using fiberglass pipes:

Comparison of continuous and batch winding techniques:

In private housing, fiberglass pipes are used quite rarely. The main reason is the high cost compared to plastic counterparts. However, in the industrial sphere, the quality of the composite was appreciated, and worn-out metal lines to fiberglass are massively replaced.

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