How to choose fiberglass pipes: production specifics + review of leading manufacturers
Thanks to a combination of positive characteristics of glass and polymers, fiberglass pipes have almost unlimited prospects for application - from the construction of ventilation channels to the laying of petrochemical routes.
The scope of operation of the composite is largely determined by the specifics of its production and the composition of the binder components. An important role in product quality is assigned to technical capacity and manufacturer's reputation.
Fiberglass: polymer composite characteristics
Fiberglass is a plastic material that contains glass-fiber components and bonding filler (thermoplastic and thermosetting polymers). Along with the relatively low density fiberglass products have good strength properties.
The last 30-40 years, fiberglass is massively used for the manufacture of pipelines for various purposes.
Highways combine the qualities of glass and polymers:
- Low 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 the ease, easier installation work and material transportation.
- Corrosion resistance.The components of the composite have a low reactivity, so they do not undergo 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 parameter of specific strength far exceeds thermoplastic polymers (PVC, HDPE).
- Weather resistance.The range of boundary temperatures (-60 ° C .. + 80 ° C), the processing of pipes with a protective layer of gelcoat ensures immunity to UV rays.In addition, the material is resistant to the wind (limit - 300 km / h). Some manufacturers claim seismic resistance of pipe fittings.
- Fire resistanceNon-combustible glass is the main component of fiberglass, therefore the material is not easily flammable. When burning does not emit toxic gas dioxin.
Fiberglass has a low thermal conductivity, which explains its thermal insulation qualities.
As the internal walls rub off, the fibers become bare and break off - particles can get into the transported medium.
Manufacturing technology of fiberglass pipes
The physicomechanical characteristics of the finished product depend on the production technique. Composite reinforcement is manufactured using four different methods: extrusion, pultrusion, centrifugal casting and winding.
Extrusion - getting frameless composite
Extrusion is a technological process based on the continuous extrusion of a pasty or highly viscous material through a forming tool.The resin is mixed with crushed fiberglass and plastic hardener, and then fed to the extruder.
High-performance extrusion line allows to obtain 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.
Pultrusion - production of small diameter pipes
Pultrusion - manufacturing technology of composite long elements with a constant cross section. Passing through a heated forming die (+ 140 ° C), parts are pulled out of fiberglass material impregnated with a thermosetting resin.
In contrast to the extrusion process, where the decisive influence is pressure, in a pultrusive unit this role is played by a pulling effect.
- Fibrous filaments from the coils are fed into a polymer bath, where they are impregnated with thermoplastic resins.
- The treated fibers pass through the preforming machine — the threads are aligned and take on the desired shape.
- Uncured polymer enters the die plate. Due to several heaters, the optimum mode for polymerization is created and the speed of the pulling is chosen.
The cured product is drawn out by a pulling machine and sawn into segments.
Distinctive features of pultrusion technology:
- polymers admissible to processing: epoxy, polyester resins, vinyls;
- The use of innovative optimized "pultruded" polymers allows speeding up to 4-6 m / min. (standard - 2-3 m / min.);
- run-up of the working zone: minimum - 3.05 * 1 m (pulling force up to 5.5 tons), maximum - 1.27 * 3.05 m (force - 18 tons).
At the exit there is a pipe with ideally smooth external and internal walls, at a high level and strength characteristics.
Disadvantages of the method are not related 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 heavy loads.
Centrifugal casting - Hobas patented technique
The Swiss company Hobas developed and patented the centrifugal formation technique. In this case, the production is carried out from the outer wall of the pipe to the inner one when the rotating form is activated. The pipeline consists of: crushed glass harnesses, sand and polyester resins.
Raw materials are fed into a rotating matrix - the structure of the external surface of the pipeline is formed. As the production proceeds, solid components are mixed in with the liquid resin, filler and glass fiber - under the action of the catalyst, polymerization proceeds faster.
- high accuracy of the dimensions of the original product (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;
- getting a smooth surface outside and inside pipe fittings.
The lack of centrifugal production of fiberglass pipes - energy intensity and high cost of the final product.
Forward winding types
The most popular technique is continuous winding. The pipe is created with alternating alternation of glass fiber mandrel with polymers with cooling processes. The production method has several subspecies.
Spiral ring technology. The stacker of fibers is a special ring, around the circumference of which are dies with threads. The work element is continuously moving along the axis of the moving frame and distributes the fibers along the spiral lines.
The main advantages of the method:
- production of high-strength pipes designed for operation under high pressure (pump-compressor engineering networks);
- uniform strength over the entire surface of the highway;
- excellent tolerability of tensile loads - no cracks;
- the creation of products of variable diameter and cross sections of complex configuration.
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 “ribbon” winding has a couple of significant drawbacks:
- limited performance;
- loose laying of fibers reduces the strength of the pipeline.
The spiral-tape method is relevant in the manufacture of pipe fittings under low, moderate pressure.
Longitudinal-transverse method. Continuous winding is carried out - the stacker places the longitudinal and transverse fibers simultaneously. Reverse movement is absent.
Characteristics of the method:
- it is used mainly when creating pipes with a cross section of 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.
Oblique transverse-longitudinal technology. The development of Kharkov engineers is in demand among domestic manufacturers. When oblique winding the stacker removes the "veil", consisting of a bunch of binding threads. The tape is fed to the frame at a slight angle overlap with the previous round - ring reinforcement is formed.
Upon completion of processing the entire mandrel, the fibers are rolled around by the rollers - the remnants of the bonding polymers are removed, the reinforcing coating is compacted.
Features oblique knurling:
- tightness of glass fibers;
- unlimited diameter of the produced pipes;
- high dielectric properties due to the absence of solid reinforcement along the axis.
The modulus of elasticity of "oblique" fiberglass is inferior to the similar parameter of other techniques. Due to the risk of the appearance of interlayer cracks, the method is not feasible when creating pipelines under high pressure.
GRP Pipeline Selection Parameters
The choice of glass composite pipes is based on the following criteria: stiffness and design pressure, type of binder component, design features of the walls and method of connection. Significant parameters are indicated in the accompanying documents and abbreviated marking on each tube.
Stiffness and nominal pressure
The stiffness of fiberglass determines the ability of the material to withstand external loads (soil gravity, traffic) and pressure on the walls from the inside. According to ISO standardization, pipe fittings are classified into several stiffness classes (SN).
The degree of rigidity increases with increasing wall thickness fiberglass pipeline.
The classification according to the nominal pressure (PN) reflects the gradation of products relative to the safe pressure of the liquid at a temperature of + 20 ° C over the entire service life (about 50 years). The unit for PN is MPa.
Some manufacturers, such as Hobas, indicate the combined characteristics of the 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: polyesters and epoxides
The performance properties of a pipe largely depend on the type of binder. In most cases, polyester or epoxy additives are used.
PEF-binder.The walls are formed from thermosetting polyester resins reinforced with fiberglass and sandy additives. The polymers used have important qualities:
- low toxicity;
- curing in the conditions of room temperature condition;
- reliable coupling with glass fibers;
- chemical inertness.
Composite pipes with PE-polymers are not subject to corrosion and corrosive media.
Epoxy resin.Binder gives the material increased strength. The temperature limit of composites with epoxides up to + 130 ° С, maximum pressure is 240 atmospheres. An additional advantage is the almost zero thermal conductivity, so the assembled highways do not require additional thermal insulation.
The design of the walls of composite pipes
By design, distinguished: single-, two-and three-layer fiberglass pipes.
Single-layer products.Pipes do not have a protective lining coating, due to which they are distinguished by low cost. Features pipe fittings:
- the inability to use in regions with difficult terrain and harsh climate;
- the need for careful installation (excavation of a large trench, arrangement of sand "pillows") - the estimate of installation work increases.
Double-layer pipes.Products are internally lined with film coating - high-pressure polyethylene. Protection increases chemical resistance and improves the tightness of the line under external loads. However, the operation of valves in the oil pipelines revealed weaknesses in the two-layer modifications:
- insufficient adhesion between the constructive layer and the lining - a violation of the solidity of the walls;
- deterioration of the elasticity of the protective film at subzero temperatures.
When transporting a gas-containing medium, lining can be peeled off.
Three-layer pipeline.GRP pipe structure:
- The outer polymer layer (thickness 1-3 mm) - increased mechanical and chemical resistance.
- The structural layer is a structural layer responsible for the strength of the product.
- The liner (thickness 3-6 mm) - the inner shell of fiberglass.
The inner layer provides smoothness, tightness and smoothes the cyclical fluctuations of the internal pressure.
Method of docking fiberglass highway
According to the method of connection, the assortment of pipe fittings from composite is divided into 4 groups.
№1. Pipe-studded docking with sealing ring. Elastic rubber gaskets are mounted in the reciprocal grooves on the end spikes of the pipes. Seating rings are formed on equipment with electronic control, ensuring the accuracy of their location and size.
№ 2. Pipe-studded with seal and stopper. When constructing a land line, it is necessary to compensate for the effect of axial forces on the pipeline. For this purpose, in addition to the seal is placed the stopper. The element is made of metal cable, polyvinyl chloride or polyamide.
No. 3. Flange connection. Docking of the composite pipeline with shaped fittings or metal pipes. Connecting dimensions of fiberglass flanges are regulated by GOST 12815-80.
№ 4. Glue fixation. Non-dismountable method of connection - a composition of reinforcing glass materials with the addition of a polyester component of “cold” curing is applied on the ends. The method provides strength and tightness of the line.
Marking of the protective inner layer
The method of production of tubular products allows you to produce products with different composition of the inner layer, which determines the resistance of the line to the transported medium.
Domestic manufacturers use the following marking of protective coatings.The letter designation displays the valid scope of use:
- And - transportation of liquid with abrasives;
- P - supply and removal of cold water, including drinking;
- X - acceptable use in a chemically aggressive gas and liquid medium;
- D - hot water supply systems (75 ° С limit);
- C - other liquids, including those with high acidity.
The protective coating is applied with a layer up to 3 mm.
Product review leading manufacturers
Among the variety of products presented are reputable brands with many years of positive reputation. Such products include: Hobas (Switzerland), Steklokomposite (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: Poliek (Russia), Arpipe (Russia) and the factory of fiberglass pipes (Russia).
HOBAS - GRT Pipes with Polyester Binder
Trademark factories are located in the United States and many European countries. Products of the Hobas group have earned worldwide recognition for excellent quality. Hobas pipes are made according to the technique of centrifugal casting from fiberglass and unsaturated polyester resins.
Hobas composite pipe specifications:
- diameter - 150-2900 mm;
- class of SN-rigidity - 630-10 000;
- PN-pressure level - 1-25 (PN1 - non-pressure pipeline);
- the presence of an internal lining anti-corrosion coating;
- resistance to acidic environment in a wide range of pH.
The production of shaped parts: knees, adapters, flanged nozzles and tees.
Flowtech - a variety of dimensions
The company Steklokompozit has established a line for the production of Flowtech fiberglass pipes, production technology - continuous winding. Involved equipment with a double flow of resinous substances. High-tech resins are fed to the laying of the inner layer, and a cheaper composition - to the structural layer. The technique allows to rationalize the consumption of material and reduce the cost of production.
Amiantit Flowtite Technology
The main components of Flowtite pipes: fiberglass, polyester resin, sand.Applied technology - continuous winding, ensuring the creation of a multilayer pipeline.
The structure of fiberglass includes six layers:
- outer winding of non-woven tape;
- power layer - chopped fiberglass + resin;
- middle layer - fiberglass + sand + polyester resin;
- repeated layer of power;
- lining glass yarn and resin;
- Sheeting from nonwoven fiber glass.
Studies have shown high abrasion resistance - over 100 thousand gravel processing cycles, the loss of the protective coating was 0.34 mm.
Fpipes - a wide range of pipe products
Poliek LLC produces various modifications of fiberglass pipe products. Manufacturing technology (continuous oblique longitudinal-transverse winding) allows you to create a three-layer pipe up to 130 cm in diameter.
Polymer composite materials involved in the creation of casing, parts of lifting columns, water supply pipelines and heating systems.
Conclusions and useful video on the topic
Manufacturing technology and the feasibility of using fiberglass pipes:
Comparison of the technique of continuous and periodic fiber winding:
In private house building 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 the worn-out metal lines were replaced by fiberglass plastic ones.