Types of composite pipes (GRP fiberglass)
1. Introduction
Because fiberglass pipes have countless advantages, including very high resistance against all types of corrosion, high hydraulic capacity, long life, low maintenance and operation costs, ease and speed of transportation and installation due to light weight, no need for The inner coating and outer coating are for protection against corrosion and have a variety of production, so there are many different uses for them. It is obvious that the chemical and mechanical characteristics of fiberglass pipes are determined according to the type of application and the conditions of each design, including the characteristics of the passing fluid, the temperature of the fluid and the environment, the chemical characteristics of the soil, the working pressure, etc. The resin and fibers used are determined. This report includes a summary of the comparison of fiberglass pipes from different perspectives for use in the water industry.
General:
A: Fiberglass pipes in the water and sewage industry and chemicals are produced with raw materials including GRP polyester resin or GRV or GRVE vinyl ester resin and with or without silica sand and continuous and cut glass fibers.
B: These pipes are made in three ways: continuous spiral fibers, discontinuous spiral fibers and centrifugal.
The important chapters mentioned in the report are:
1- Comparison of different types of fiberglass pipes in terms of stiffness and pressure
2- Comparing types of fiberglass pipes in terms of resin type (polyester or vinyl ester)
3- Comparing types of fiberglass pipes in terms of using silica sand or not using silica sand
4- Comparison of types of fiberglass pipes in terms of production process, speed of production process and price of production process
5- Comparison of different types of fiberglass pipes in terms of connection type and connection production speed and connection implementation speed at the project site
6- Comparison of the lifespan of vinyl ester and polyester resins
1- Comparison of different types of fiberglass pipes in terms of stiffness and pressure
A- If any type of GRP or GRV pipe can reach the specified stiffness required in the design, they are no different from each other in this regard.
In other words, when a GRP pipe, for example, must provide a stiffness of 5000 pascals, if it reaches a stiffness equal to or higher than 5000 pascals during testing, there is no difference in bearing external loads, including dead, with a GRV pipe that has reached the same stiffness. and is not alive.
B- This issue is also true for hydrostatic pressure, and therefore, if any type of fiberglass pipe with polyester resin or vinyl ester resin, with silica sand or without silica sand, or with any type of production process, including centrifuge, continuous screw fibers or Discontinuous twisted fibers and with any type of fibers, whether continuous fibers or discrete needle fibers, can achieve the nominal pressure desired in the project, the items mentioned above and the types of pipes above have no difference in bearing the pressures.
Conclusion:
1- When a fiberglass pipe reaches the required stiffness and pressure in a project, it doesn't matter which type of resin and which type of process it was used to achieve this stiffness and pressure, and in terms of stiffness, pressure and mechanical properties of all the pipes. are similar and equal to each other, and in this case, only the cost of raw materials and the speed of production will be the criteria for choosing the type of pipe.
2- The aforementioned issue is also true for the type of connection of two pipes to each other.
2- Comparing types of fiberglass pipes in terms of resin type (polyester or vinyl ester)
A- The attached documents and documents from DSM and Ashland companies, as the largest resin producing companies in the world, contain explanations and comparative tables in terms of mechanical, thermal and chemical resistance for two types of polyester and vinyl ester resins. Considering that the mentioned companies have conducted academic studies on the behavior of each type of resin and this information has not been done on domestically produced resins, therefore the results obtained by the above two companies have been used.
B- Polyester resins in DSM company are named Synolite and Palatal, and the rest of the resins of this company are called Atlac, all of them are vinyl ester, and in the strength comparison table prepared by this company, it can be seen that the tensile strength Polyester resins are between 50 and 75 megapascals and the tensile strength of vinyl ester resins is also between 50 and 75 megapascals, which is very close to each other, and this is also true for bending strength.
C- In these resins, only the HDT temperature means the temperature from which the resin starts to change its properties (the temperature at which the properties of the resin begin to lose), in the case of polyester resins between 60 and 90 and for vinyl ester resins between 90 up to 120 degrees Celsius.
D- If we pay attention to the comparisons of Ashland company, the polyester resins of this company named Aropol are similar to the vinyl ester resins of this company named Hetron in terms of tensile and bending strength and bending and tensile modulus. The HDT temperature of vinyl ester resins is somewhat higher than that of polyester resins.
E- Now that it is clear that these two resins do not have a significant difference in terms of mechanical resistance, it is necessary to pay attention to their chemical resistance. Of course, vinyl ester is no different from polyester in front of sea water, but in many cases it is resistant to other chemicals. It is higher than polyester. Although HDT shows a minimum temperature of 65 and 70 degrees Celsius against sea water, but vinyl ester resins also show a temperature of 99 degrees Celsius. (HDT in both resins can be managed and supplied and accessed. )
F- With the above comparison, it is clear that polyester and vinyl ester resins are different in terms of mechanical resistance, chemical resistance, and thermal resistance against sea water.