GRP pipes – do you really know everything about them?

by May 8, 2019Advanced R&D, Design and Prototyping, Filament Winding

Selling GRP pipes is much like dating.

Here’s what most companies do: they go out into the marketplace, pushing offer to prospects and asking complete strangers to marry them!

If you think about it in this way, it is quite difficult to convince technical offices to change the tenders, or investors to choose your GRP pipes. You need to have a clear approach and build the trust in the product, but,

how can one do this properly?

In the following article you will find some information regarding GRP pipes, some details of which you probably already know, whilst other details will be knew to you.

Read it carefully and think about it from the prospective of the end users, so you will understand their concerns and fears, making it easier for you to hit the target.

There are several reasons why GRP pipes in many countries have been replacing conventional pipes, so one should keep this relatively new product in mind when evaluating a new or revamp pipe project.

In parallel, Engineers involved specifying GRP pipes should have a clear understanding of its nature and properties.

You probably already know the main advantages of the GRP pipes, namely:

  • Elevated corrosion resistance, because of the inert nature of the materials it is composed of, in comparison with cast iron and carbon steel. It is not unusual to design a GRP pipe for a working life of 50-60 years. Nowadays, some producers are estimating a lifetime of over 100 years. GRP pipes can be designed to resist corrosion from the inside and outside. In fact, with the aid of an internal-external barrier, and the use of correct resin barriers, the pipe can withstand varied corrosion environments;
  • Lightweight construction is another major benefit. Typically, a GRP pipe has a weight of 35% of that of a comparable carbon steel pipe, and 10% of a comparable concrete pipe. The cost of handling, shipping, long-haul transport and site installation are significantly lower;
  • Ordinary GRP pipes don’t conduct electricity, and consequently have much better electrical properties than its steel counterpart. However, if electrical conductivity is required, it is possible to add conductive reinforced fiber or fillers during the fabrication process;
  • Due to its composite structure, the GRP pipe can be designed to exactly match the project requirements, therefore leading to cost saving;
  • Surge pressure absorption is another plus of GRP pipe: they are designed to absorb 40% of the surge pressure, without the need to increase the pressure class;
  • GRP pipes possess a natural damping property. The fatigue endurance and strength to weight ratio are key attributes associated with replacement cost and the ability to design lightweight;
  • Thanks to its smooth inner surface, friction loss is at a minimum, and it keeps this characteristic throughout its entire service life;
  • low maintenance is another feature associated with these pipes, because they don’t undergo the corrosive attack that the metallic counterparts have.

Many advantages, right?

In spite of these advantages, the decision makers must also consider some particular characteristics of the GRP pipes.

  • To calculate the investments costs correctly, the investor must also consider the installation, erection and maintenance costs, to be able to compare these with other materials; if only the initial cost is evaluated, the project’s figures will not be realistic;
  • The market of composites is not as big as that of many traditional materials, so you can’t consider a GRP as a commodity. It is a customized product that must be prepared for every single project, thus the delivery times may be longer than traditional materials;
  • The design of a GRP pipe, as I said before, is performance based; in other words, the investor must take care in identifying the project requirements and true operating conditions, and only then share the information with the pipe supplier;
  • The composite pipe manufacture should require that the investor adheres to specific instructions in order to ensure the long-term performance of the pipeline.

It is very important that the Engineers also understand the limitations of a GRP pipe, which also depends on the technology used to manufacture it. I have noticed, during recent years, that some projects have been influenced by strong marketing and miraculous promises from some pipe manufactures, leading to an incorrect use of the product.

For example, the performance of a Continuous Filament Winding pipe is very high on certain applications and lower in some other applications, the same applying to the Discontinuous Filament Wound pipe or the Centrifugally Cast GRP pipe.

Which one is the right one for your application and needs?

As I said before, it depends on your specific project, from the design to the installation method.

As indicated in one of my previous articles, we can generally say that the marine, industrial and oil & gas markets demand small quantities of pipe of medium to high pressures and with particular technical characteristics, so generally the pipes need to be produced with the discontinuous filament winding system. This concept is also applicable to the civil infrastructure market but is related to very small quantities and medium to high pressures.

If extensive lengths of pipelines are needed for civil infrastructure projects (over 1000 km), a CFW production line is recommended, also because the cost of produced pipe is 15-30% lower compared to that produced with a discontinuous or centrifugally cast line.

If small quantities and low pressures are mostly called for by a particular market (for example sewer pipes for small works), a centrifugally cast line can be chosen, even though this system does not offer the flexibility of a continuous or discontinuous system.

All clear until now?

Let’s talk a little bit more about the Raw Materials, because you need to understand their properties if you would like to understand GRP pipes better.

The resin mostly used in the filament winding process are polyester, vinyl ester and epoxy resins.

What’s the role of the resin in a pipe? It serves as the “glue” that binds the fibers together in the pipe after the curing (when the resin sets). The pipe liner resin also provides the most definitive corrosion resistance to the transported fluids. Its chemical properties and physical properties play a key role in the pipe design.

The polyester resins used in the manufacturing of the composite materials may be classified as Orthophthalic, Isophthalic or Terephthalic resins.

The Orthophthalic resins are general-purpose resins, for water conveyance and sewerage applications. They are used for manufacturing laminates, which are not subjected to strong chemical attacks or weathering. From a thermal point of view, these resins are employed at ambient or medium-to-low temperatures. Mention must be made that the Orthophthalic resins should not be used for constructing the internal liner of a fiberglass pipe. Isophthalic resins find their most suitable end-use in the manufacture of pipes conveying waste liquids, drinking water and seawater, above or below ground. In fact, they are more resistant to corrosive substances present in the ground, to most salts and to mildly oxidizing acids at medium concentrations. This type of resin is always used for the internal liner of the pipe.

Vinylester resins combine a greater resistance to chemicals with a high mechanical strength, also at high temperatures. Of course, they are more expensive than Polyester resins.

Finally, Epoxy resins are normally used for smaller diameters and for higher pressures, compared to other resins.

Besides the quality of the resin, decisive factors for obtaining an excellent final result are the types of glass employed, and the use of the same in the most appropriate manner for fully exploiting their structural properties.

Glass fibers are obtained with silica glass-based melting mixtures of inorganic materials, at temperatures varying between 1300°C and 1600°C. Under these conditions, the cross-linked structure of the silica is destroyed, its continuity is interrupted and its structure is modified by the introduction of other oxides.

The form of the fiber reinforcements varies considerably, depending on the pipe manufacturing process and the design load requirements. The major examples include directional fibers (roving), chopped fibers and fabric reinforcement forms (mat, woven roving, etc.). The actual fiber content in a composite depends on the end use design. The fiber orientation, the layup sequence of the laminate and the number of reinforcements determine the actual pipe stiffness, strength and mechanical properties.

The reinforcements used in the manufacturing of the industrial products, such as vessels, silos and pipes, are made starting from three different types of glass compositions:

  • “C” glass which displays very good properties of chemical inertness to corrosive environment;
  • “E” glass which is not so resistant to corrosion but displays a very high mechanical strength;
  • “ECR” glass is similar to E-glass but without boron and fluorine. Due to the absence of these components, the chemical resistance (including water-resistance, acid-resistance and alkali-resistance) is greatly improved. When compared to the E-glass fibers, the ECR-glass shows higher temperature resistance, better dielectric strength, lower electrical leakage, and higher surface resistance.

In many cases, design and manufacturing of GRP pipes incorporate additional components. Many of these, including catalyst and hardeners, are processing aids for the resins and are necessary for the completion of the chemistry and curing of the laminate. Filler may be used to enhance the appearance, economy or performance of the pipe. Another role of the fillers is to increase the stiffness of the pipe structure.

If your intention is to maximize your return on investment in the composites market, utilising a filament winding technology, it is important for you to know that you will need to get the maximum capacities out of your raw materials.

Unfortunately, less than half of the existing manufacturing plants are optimizing their design, using the same pipe design regardless of the type of materials involved in the production.

This happens because many investors who, in good faith, followed the incorrect advice offered by the technology and machine suppliers, now find that they are the ones who have to face the wrath of the competitive market.

We have spent more than 16 years travelling, installing CFW plant (more than 35), helping companies to penetrate the market with the GRP pipes. We have developed and successfully applied our EFFECTIVE FILAMENT WINDING method the first ever which guarantees profit making.

Our secret? Deep knowledge on the Filament winding process, hard work and effective steps to be done through an analytical method.

If you  have a project and are looking for a company that can guarantee the reliability of the pipeline that your end customer deserves, without unpleasant surprises occurring during the installation even if the project is located in remote or complicated locations, thus ensuring you with maximum profits, then you seriously need to consider contacting me and my team.

Contact us by writing to us at [email protected] and together with my staff in TOPFIBRA, we will evaluate together with you to see if and how we can help.

Related Post

TOPFIBRA Effective Filament Winding Proved Successful Once Again When you are dedicated and passionate about investing in a technology, you have a picture in mind and a strong desire for results you could achi...
GRP PIPES – Satisfactory solution in many applications There are several reasons why the GRP pipes are very competitive nowadays, and this material should be considered whenever piping is about to be...
Whoever Needs a Supervisor? Pipe installation is a very straightforward procedure, isn’t it? You produce a pipe, transport it to the site and install it. Most companies thin...
How To Increase The Efficiency Of The Fitting Manufacturing By More Than 50% As you are well aware, the cutting of large diameter GRP pipes for the manufacturing of fittings has always been a complicated and lengthy affai...