What do you understand about GRP Pipe?
In the last couple of years, we have received repeated questions from our clients: Is GRP and FRP pipe the same? What does the terms RTRP, GRE, RPMP, etc. mean? What are the advantages of GRP Pipe? In this article, we will answer these questions and provide you with a comprehensive understanding of GRP Pipe.
What is GRP Pipe?
There are several terms used in the industry to describe the same product, which leads to mass confusion for those who don't understand. Thus, we firstly want to briefly explain these terms. GRP stands for Glass Reinforced Thermosetting Plastic, while FRP stands for Fiber Reinforced Plastic. In prinicple, GRP and FRP are referring to the same entity. It is one of the existing composite materials that is made from thermosetting resin and utilized fiber glass as its strengthener. However, why there exist two terms that refer to the same entity? Well, GRP is typically used by standards issued by the European standards organization, such as ISO, EN, BS, DIN, DFS, etc. Whereas, the term FRP is more widely used` in the standards released by the American standards organization, such as ASME and API.
Types of GRP Pipe Based on American Standards Organization
According to American standard, fiberglass pipe can be classified into two groups based on the materials used for reinforcement. RTRP (Reinforced Thermosetting Resin Pipe) is a type of pipe that only used fiberglass as its reinforcement material. Various resin can be used for this type of pipe, such as unsaturated polyester, vinyl ester, epoxy, furan, and phenolic. Whereas, RPMP (Reinforced Polymer Mortar Pipe) does not only use fiberglass but also utilizes aggregate material, such as silica sand, as its reinforcement material. However, the choice of resin is limited. Generally, unsaturated polyester would be used and only a few used a higher grade resin.
Types of GRP Pipe Based on European Standards Organization
Meanwhile, European standard have different conventions to name types of fiberglass pipes. Their convention is based on the type of resin used in manufacturing the pipe. GRE (Glass Reinforced Epoxy) Pipe is a type of pipe that uses epoxy resin as its matrix. Another type is GRVE (Glass Reinforced Vinyl Ester) Pipe which uses vinyl ester resin as its matrix. The last type is GRUP (Glass Reinforced Unsaturated Polyester) Pipe which uses unsaturated polyester resin as its matrix. Additionally, the reinforced material used is usually either fiberglass or a combination of fiberglass and material aggregates.
Advantages of GRP Pipe
GRP Pipe offers many advantages over traditional materials such as steel, concrete, and PVC. It is lightweight, corrosion-resistant, has a long service life, and is easy to install. It is also cost-effective and requires low maintenance. GRP Pipe is used in various industries such as water and wastewater, oil and gas, chemical, power, and marine. It is suitable for both above-ground and underground applications.
Construction of GRP Pipe
According to its function, the construction of a GRP pipe can generally be illustrated as follows:
- Liner
- Reinforced wall
- Outer layer
Generally, it is called the corrosion barrier where it protects the pipe from chemical attacks from the fluid that flows inside the pipe. Liner is composed of thermosetting resin that was reinforced by C-glass / Synthetic glass surfacing veils that has a minimal thickness of 0.13 mm. FRP engineer will determine the level of liner’s thickness based on the type of fluid and level of corrosiveness. Furthermore, FRP engineer will generally add several layers of chopped strand mat, stitch mat, chopper roving as the baking layers to boost the chemical resistant performance of GRP pipe.
It is the middle layer that is also called mechanical barrier / structure layer because it provides mechanical and physical resistance to GRP pipes, such as pressure class, hoop stiffness, temperature, etc. Consequently, FRP engineer will take into account the requirements and specifications needed to properly design the pipe. The type of reinforcing material and the composition of this layer are determined based on the fabrication method. For RPMP type, reinforced wall are divided into three layers: internal structural layer, core layer, and external structural layer, while RTRP type only needs one layer.
Generally called the weather barrier, it not only functions as the visual but it also provides resistance to the surrounding environment. It is common to add several materials additive to this layer, such as UV absorber, moisture inhibitor, pigment (if requires colour), etc. If the environment is very corrosive, it is required to add reinforcement C-glass veil, similar to the liner layer.