It is a common subject requested by all the standards, from the pipe producer for proving by sampling, the compliance of the pipe with the minimum performance requirements. This minimum performance requirements for GRP pipe are both for short term and long term.

The most important ones are expressed in all the previously described standards as;

  1. JUNCTION
  2. INITIAL RING DEFLECTION
  3. LONG TERM PRESSURE RESISTANCE
  4. CORROSION STRAIN CAPACITY

Alfebor is carefully performing the all mentioned tests in order to control whether the requirements TS 4355, TS EN 1796, TS EN 14364, ASTM D 3262, ASTM D 3517, AWWA C950, DIN 16869, ISO 10467 and ISO 10639.

1- JUNCTION

Coupling Tests
This important performance test is realized in compliance with ISO 10639 Standard with coupling prototypes made with elastomeric gasket sealed sleeves. This is a standard which is valid for the entire pipe industry and which had determined the coupling performancerequirement of the pipes of all types of materials and for each pressure class and diameter.For the simulated laying conditions, flexible coupling is expected to resist against the hydrostatic pressure. The pressures applied in this test are 100kPA (1 bar) for non-pressure pipes and 1.5 times the operation pressure for the pressure pipes. Additional configurations are linear line, maximum angular turning and differential cutting loads. It also includes some fatigue pressure tests.

2- INITIAL RING DEFLECTION

2.1 Initial Ultimate Deflection in the pipes that are laid underground
The allowable deflection value is not specified in ISO Standard system, however, this value can be calculated from ISO TR 10465 - 3: 1999 Standard.
İNTAŞ SYRIA produces GRP pipes in a way to meet;

  • SO/DIS 10639 - GRP Pipe System in Providing Water
  • SO/DIS 10467 - GRP Pipe System in Drainage and Waste Water Applications

Standards and also the mechanical requirements of ANSI/AWWA C950 standard.
The design procedures in AWWA M-45 Glass Fiber Pipe Design Manual for Water Applications should be followed.

2.2 Minimum Axial Strength
ISO initial values are given as N/mm in unit circumference in relation with the pipe pressure class and diameter. Minimum axial strength values in AWWA are given as Ibf/inch in unit circumference correlated with the pipe pressure class and diameter.

2.3 Initial Failure (Burst) Pressure
Initial blasting pressure is based on long term safe blasting pressure and the regression factor is obtained from the long term static internal pressure. This test methods applied by using the static pressure are similar in ISO and AWWA, but long term safety factors are different.

 

3- LONG TERM PRESSURE RESISTANCE

3.1 Hydrostatic design base - HDB
Another important competency test is hydrostatic design base - HDB determination test. This test is realized incompliance with ASTM D2992 Procedure B or ISO and high constant hydrostatic pressure is applied on many pipe samples until they leak. The pressure on which the leaking occurs (or the ring strain resistance) and the time values are extrapolated to 50 years on the logarithmic basis.
Extrapolated damage pressure (strain) value or HDB, should be at least 1.6 times the pressure class of the concerned operation (strain for the related pressure class).
In other words, the design criteria, pressure value of the constant pressure pipe for being resistant for 50 years, should be minimum 1.6 times the maximum operation pressure. On the other hand, since the effect of the internal pressure and the external loads in the pipe design is taken as resultant, the safety of the pipe only against the internal pressure is bigger than 1.6 according to the above condition.
HDB competency test guarantees the long term performance of the pipe for the pressure pipe applications.

3.2 Leak test
Leak test may be realized by two methods in ISO GRP pipe system: The first one is experimenting each pipe with a pressure which is 1.5 times of its pressure class. Here, the test period is not specified.
The second method is based on subjecting a sample to a test for 6 minutes under very high pressure. Test pressure is determined from the regression curved obtained from the long term static pressure test. This way, if the long term safety factor is equal to the value calculated from ISO DTR 104-65 - 3, then there will be a failure risk of 6.5%.

3.3 Long Term Ultimate Deflection
Although there is no requirement in AWWA C 950 related to long term deflection, it requires the producer company to determine the deflection value that is convenient for it and announce it. This value which is shown by Sb symbol is defined as strain (elongation % in breaking off).
In ISO, long term deflection is defined as % and it is as Level A deflection without the formation of pipe crack.Level B is the requested structural strength, values in parantheses are the requirement of AWWA C 950 (e.i. table 4)
The requirements are same on both methods.
The pipes laid underground should operate under nominal pressure.This means that the deflection of the laid pipe should also be taken into account.
This state is explained in ISO in ISO DTR 10465 - 3 Attachment G. The safety factors for the long term average minimum values are given in the following table. The values given above are determined according to 9% deviation coefficient.
For higher deviations, the safety factor should be increased. In AWWA, long term safety factor for aboveground and underground laying is constant and this value is 1.8. the calculation should be made in compliance with AWWA M-45 Article 5.7.4.

4- CORROSION STRAIN CAPACITY

This is the only and important pipe performance requirement test that is applied by subjecting the sample for the non-pressure pipes for sewage water, to deflection in chemicals and it is a special test performed for glass fiber pipes that transport chemical materials.
This test is performed by subjecting at least 18 ring samples taken from the pipe, to be deflected at various levels and by keeping them constant at this position according to ASTM D3681 and ISO 10952. The strained samples under the load are subjected to sulfuric acid of 1.0 N (5% by weight) from their internal bottom surfaces. This way, septic waste water medium is simulated. This state represents the Central Asia conditions where the worst septic waste water medium shown and where GRP applications are realized succesfully. By using the smallest squares analysis method, minimum corrosion strain value extrapolated for 50 years should be equal to the value shown for each stiffnes class. The value obtained this way shows the safe installing limitations during the design of GRP pipes to be used in these type of applications.
As ISO requirement, level A and level B values are used in order to form a regression formula. Calculations for 1.000, 3.000 and 10.000 hours are made from these deflection values. Test samples are kept at this deflection value and they are requested not to encounter any structural damage at the period calculated by the regression formula.

 

The environmental and axial load bearing capacities of the pipes produced are proved by routine tests. Additionally, pipe structure and composition are controlled by tests and approved.
Controls at the stage of production:

  • Visual examination
  • arcol hardness
  • all thickness measurement
  • Pipe length
  • Diameter measurement
  • Hydrostatic leak-proof test

The controls realized by taking sample:

  • Pipe rigidity
  • Deflection test performed without damage and
  • structural damage
  • Ring tensile strength
  • Axial tensile strength

 

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