ISO 10952 Glass Reinforced Thermosetting Plastics (GRP) Pipes and Fittings - Determination of Resistance to Chemical Attack Inside a Bent Section

The standard “ISO 10952 Glass-reinforced thermosetting plastics (GRP) pipes and fittings - Determination of resistance to chemical attack inside a bent section” developed by the International Organization for Standardization (ISO) describes a test method for determining the chemical resistance properties of glass-reinforced thermosetting plastics (GRP) pipes and fittings in a deflected condition for nominal sizes DN 100 and above.

Together with the standard “ISO 10928:2024 Plastic piping systems - Glass-reinforced thermosetting plastics (GRP) pipes and fittings - Regression analysis methods and their use”, this standard provides a method for assessing the effect of a chemical environment on the inside of a pipe or fitting after a specified period of time. The test conditions and requirements are specified in the relevant international standard. The standard “ISO 23856 Plastic piping systems for pressure and non-pressure water supply, drainage or sewage - Glass-reinforced thermosetting plastics (GRP) systems based on unsaturated polyester (UP) resin” refers to this standard.

It has been found that the action of chemical environments can be accelerated by stress resulting from deflection, therefore, such effects are often referred to as stress corrosion.

For the purposes of this standard, the following terms and definitions apply:

The average diameter is the diameter of the circle corresponding to the center of the pipe wall cross-section. The average diameter formula is given in the standard.
A leakage failure is a failure condition that is evident when the test fluid passes through the pipe wall. Failures of the test specimen have been observed at the spring line location without leakage of the test fluid. Even if no leakage is observed, this can be considered a test specimen failure because the stress levels in the specimen will change and invalidate the continuation of the test. The test can be discarded or optionally counted as a failure that occurred during the spring line break.

When performing tests, in principle, the inside of a test piece is exposed to a corrosive test liquid at a specified temperature while being kept in a fixed diagonally deflected condition. The test is repeated at several deflection levels, each time using a new test piece and recording the time to leakage failure at each deflection. The results are used to calculate an extrapolated deflection value for a specified time period.

Alternatively, extrapolation can be performed using calculated or measured strains. Strain can be measured using strain gauges. The use of strain allows testing using test pieces with varying thickness and hardness classes. Deflection and strain can be related to each other by calculation.

The following test parameters are assumed to be determined by the international standard that refers to this standard:

Composition of test liquid
Number and length of test pieces
Preconditioning to be applied
Test temperature
If no faults occur, the specified deviation levels and the relevant minimum time intervals
When to extrapolate data

The test liquid shall be as specified in the international standard referred to. The quantity shall be sufficient to achieve and maintain the specified depth in the test piece for the duration of the test.

The loading frame used in these tests consists of two parallel steel sections and threaded rods capable of maintaining a constant deflection of the test piece (a typical test setup is shown in the figure given in the standard). The sections should be rigid enough that no noticeable bending or deformation of the sections will occur during compression of the test piece. Each section should have a length equal to the length of the test piece plus at least 30 mm2 and a width of at least 100 mm.

Dimensional measuring instruments must determine:

Dimensions of test pieces (length, diameter and wall thickness). Instruments shall be calibrated to an accuracy of plus/minus 1,0 percent.
The change in diameter of the test piece in the vertical direction. The instrument shall be calibrated to an accuracy of plus/minus 1,0%.
If used, foil type, single element strain gauges suitable for the maximum expected strain level and of a length appropriate to the pipe diameter.

Strain gauges in 6 mm and 12 mm lengths have been found to be effective for pipe diameters of 300 mm to 600 mm. For gauge length recommendations for other pipe diameters, the strain gauge manufacturer should be consulted.

Among the numerous tests, measurements, analyses and evaluation studies that our organization has carried out for businesses in various sectors, our organization also provides testing services defined in the standard “ISO 10952 Glass reinforced thermoset plastic (GRP) pipes and fittings - Determination of the resistance of the inside of a bent section to chemical attack” with its trained and expert staff and advanced technological equipment.