Quality Control Tests In PE Pipes

Quality Control Tests In PE Pipes

1. Determination of Internal Pressure Resistance (TS EN ISO 1167-1 / TS EN ISO 1167-2):

         It is the test in which the behavior of pipes against pressure over time is examined by considering the ambient conditions. It is aimed to observe the changes that may occur in a 50-year-old pipe by applying pressure conditions determined according to the PN value and the desired temperature to the pipes.

It is a test method in which the working life of the pipes is determined under high test conditions. When the pipes are exposed to internal hydrostatic pressure under a certain temperature, environmental stress and time given in the standards, there should be no explosion at the end of the test period.

Internal pressure tests in PE pipes vary depending on the material class, diameter, pressure class and wall thickness of the PE pipe to be tested.

General test pressure (Ptest) calculation;

 

 

    

 

 

 

 

2. Determination of Tensile Properties (TS-EN ISO 6259-1 / TS-EN ISO 6259-3):



         It is the test in which the elongation amount of the material at break is determined as%. Tensile elongation test performed with the Universal Tensile Device is performed by pulling the sample tested under constant speed to the breaking point. The elongation amount is measured automatically with the help of the extensometer on the device.


Experimental Procedure :

         Samples cut from the pipe piece spoon sample preparation
It is cut in the apparatus. The pulling device is clamped between its jaws and subjected to elongation.


Result:

         Elongation% according to TS EN 12201 - 2 + A1 standards min. It should be 350%.

 

 

 

3. Mass Melting Flow Rate Determination (MFR) (TS-EN ISO 1133-1 Method A):


         It is done with the aim of examining the behavior of the material against temperature before processing. The samples obtained from the test with the MFR device are weighed with an analytical balance and the results are determined in the unit of gr / 10 min.



Experimental Procedure :

• The device is heated to 190 ° C.
• Pieces of material to be tested (about 3-5 g) are poured into the steel cylinder in the device.
• 5 pieces except 1-2 cut pieces are weighed, averaged and replaced in the formula given in the standard and the MFR value in g / 10 min is found.

Result:

         According to TS EN 12201 - 2 + A1 standards, the deviation in the MFR value of the raw material and the produced pipe should not exceed 20%.

 

 

 

 

4. Determination of Carbon Black Amount by Calcination and Pyrolysis (TS ISO 6964):

        It is the test by which the amount of C atoms in elementary form is determined.

        Carbon black, also known as soot black, is one of the main raw materials of the tire industry. The main purpose of its use in HDPE pipes is that it is used as a UV-stabilizer as well as colorant.

        The amount of carbon black between 2 and 2.5% by weight provides the most effective protection against UV radiation in pipes exposed to sunlight in aboveground applications.

        It is made with the aim of determining the carbon amount in its structure as a% in order to ensure the resistance of the pipe body to UV rays. The amount of carbon, which is the non-combustible part in the sample burned with nitrogen gas in a high temperature furnace, is calculated as%.

Experimental Procedure :

• The device is heated to 550 ° C.
• Nitrogen gas is opened and brought to the desired flow rate.
• 1 gr of material is weighed into the porcelain boat and put into the heating zone. It is kept for about 45 minutes.
• The porcelain boat is taken out, weighed and placed in a desiccator.
• The device is heated to 900 ⁰C.
• The boat is put back into the device and carbon black is blown in the material.
• The porcelain boat is taken out and left in the desiccator until it reaches a stable weight, then it is weighed.

Result:

        According to TS EN 12201 - 2 + A1 standards, the amount of carbon black should be 2 - 2.5% by mass.

 

 

5. Oxidation Induction Time Determination (OIT) (TS EN ISO 11357-6):

        Thermal stability is the period in which the antioxidant additive in the PE material prevents the material from oxidizing in an oxygen environment under high temperature conditions. This test is a measure of how well the material stabilizes under manufacturing, welding and long-term strength conditions. If the material does not stabilize well, it will start to deteriorate in extrusion, welding or high temperature applications, and as a result, pipe life will decrease. It is the test that examines the deterioration in the polymer structure with thermal and oxygen effects in the long-term performance of the pipe. Decomposition time is determined by creating shock conditioning conditions by supplying oxygen to the material under high temperature.


Experimental Procedure :

• A test piece is placed in the test piece container. Meanwhile, there should be as good contact as possible between the test piece and the container.
• If the test pieces are cut out from the inner or outer surface of the pipe or fitting, the test piece is placed in the container with this surface facing upwards.
• An open or ventilable aluminum container containing the test piece and an empty aluminum reference container are placed in the device.
• Nitrogen flow is provided at a rate of 50ml / min ± 10% in the DSC device. When the transition from nitrogen to oxygen is made, it is checked whether the gas passes in the same flow. Then, oxygen is passed through the device at a rate of 50ml / min ± 10%.
• Oxygen in the system is removed by giving nitrogen gas in the oven of the device for 3 minutes. The device is heated from the initial ambient temperature of 50 ° C to the constant test temperature of 200 ° C at a rate of 20 ° C / min and is expected to stabilize at this temperature. A thermogram in which the energy flow difference (Q) or temperature difference (T) is plotted against time is started to be recorded and the time at the first 200 ° C temperature value reached is recorded as t0.
• Exactly 3 minutes after the t0 value, oxygen starts to be passed through the device and this point is marked as the t1 point in the thermogram. In the thermogram, the recording of the thermogram is continued until an exothermic event is obtained as a result of oxidation (until the sample deteriorates).
• Decay time is recorded.

 

Result:


        According to TS EN 12201 - 2 + A1 standards, O.I.T should be ≥ 20 minutes.

 

 

 

 

6. Pigment or Carbon Black Dispersion Test (TS ISO 18553):

        In case the carbon black is not distributed homogeneously in the material, some regions will be unprotected against environmental conditions such as solar radiation and heat.


        Unprotected areas are weak spots and the material from these points will begin to deteriorate much faster than other places. Additionally, the material loosens and creates a cracking initiation point. Therefore, the homogeneous distribution of the material is of vital importance.

        It is carried out to examine the homogeneous pigment distribution in the structure of the material. Grading is done by examining a section with a thickness of 20 ± 10 µm for black pipes and 60 ± 20 µm for colored pipes under microscope.



Experimental Procedure:

        The material to be controlled is turned into a thin film and examined under a microscope.



Result:

        According to TS EN 12201 - 2 + A1 standards, the degree of distribution should be less than grade 3.

 

 

 

 

7.Density Determination (TS EN ISO 1183-1 Method A):

        It is done with the aim of determining the weight of the material in unit volume. With Analytical Balance, the density is calculated by the calculation method as a result of weighing the material first in air and then in a liquid whose density is known beforehand.



Experimental Procedure:

• Whether the samples prepared are less than 1 gram or not is verified by weighing them one by one.
• It is expected that the test sample and immersion liquid come to ambient temperature (23 ° C ± 2). The ambient temperature and the temperature of the immersion liquid are measured.
• The density of the immersion liquid that reaches the ambient temperature is measured with a pycnometer.
• The sample to be weighed should be placed in the middle of the sensitive balance pan.
• While the weighing process is in progress, the lids of the scale should be closed in all areas.
• The prepared sample is weighed on a precision scale.
• The immersion container is filled with immersion liquid and placed inside the scale. Scale weight value is reset.
• The sample weighed in the precision scale is thrown into the immersion liquid in the scale and the weight is measured. It is checked whether there is air bubble while the sample is in the immersion liquid.
• It is waited until the changing weight remains constant in the scale display.
• All measured weights are made to an accuracy of 0.1 mg.

 

Density Calculation:

It is calculated as g / cm³ with the formula ρS: mS, A x ρIL / mS, A - mS, IL.
ρS: Sample Density
mS, A: Density of Immersion Fluid
ρIL: The weight of the sample placed on the upper pan of the balance (weight in air)
mS, IL: Weight in immersion fluid

 

Result:

        According to TS EN 12201-2 + A1 Standard, it is required to be ≥ 0.930 g / cm3.

 

 

 

 

8. Determination of Volatile Content (TS EN 12099):

        The volatile substance content of PE pipe materials at 105 ° C is determined.


Experimental Procedure:

• The weighing container and its lid are cleaned and brought to a constant weight and left in a desiccator at room temperature for at least 30 minutes.
• By removing the weighing pan and its lid from the desiccator, determine their mass, m0, to the nearest 0.1 mg. The cover is placed in the desiccator.
• By placing approximately 25 grams of sample into the container, the mass of the container, lid and test sample, m1, is determined together.
• The weighing pan is placed in an oven at (105 ± 2) ° C.
• After (65 ± 5) minutes, the weighing container is taken out of the oven and placed in the desiccator and kept at room temperature for at least 1 hour.
• By closing the lid of the container, the content of the substance and its mass, m2, are determined with the approach of 0.1 mg.

Calculation of Volatile Content:

        The volatile matter content, mv, of the mass under test is calculated using the equation given below.

mv: Volatile substance content at (105 ± 2) ° C, mg / kg
m0: Mass of empty weigh bucket with cover, g
m1: The mass of the container and test specimen with its cover, g
m2: The total mass of the weighing container with a lid and the remaining substance content after being kept in the oven at (105 ± 2) ° C, g

Result:

        It is required to be 350 mg / kg according to TS EN 12201-2 + A1 Standard.

 

 

 

 

 

9. Length Restoring Determination (TS EN ISO 2505):

         It covers a method applied in air to determine the ability of thermoplastic pipes to take their former shape. For pipes with a wall thickness greater than 16 mm, it is not appropriate to measure the rate of recovery. A certain length of pipe is placed in an air-heated oven where it is kept at a certain temperature for a certain time. The length of the marked portion of the pipe piece is measured before and after the heating process under the same conditions. The recoverability is the ratio of the change in length to the initial length, given as a percentage.

 

Experimental Procedure:

• The test pieces are placed in the air circulation oven in a suspended manner so that they can move freely. The test pieces in this position should not touch each other, the edge or the floor of the oven.
• The test pieces are kept in the position they are placed for the following period of time. The part between the two marked circles of the test piece is kept at the specified temperature. 60 minutes for e ≤ 8   120 minutes for 8 <e ≤ 16
• The test pieces are taken out of the oven and left free in the same position.
• It is kept hanging in a way to be hung. We cooled to a temperature of (23 ± 2) ° C-
• The distance between the marked parts after L is the curvature on the surface.
• It is measured taking into account the meler.

Calculation:


L0: the distance between the marks along the main axis of the pipe before the oven is placed, mm
L: the distance between the marks after taking out of the oven and reaching the ambient condition, mm

Result:

        It is required to be 3% according to TS EN 12201-2 + A1 Standard.

 

 

 

10. Determination of Dimensions (TS EN ISO 3126):

         It covers the method for determining the dimensions of thermoplastic pipes and fittings. The diameters, lengths, wall thickness, ovality, perpendicularity and geometrical limits of pipes and fittings are measured with appropriate measuring equipment.



Wall Thickness Measurement:

The accuracy of the measuring devices used and the measurement results should be in accordance with the table below.

 

 

Maximum and minimum wall thickness:

        Measurements are made and recorded by observing the maximum and minimum wall thickness in the sections to be measured.


Average wall thickness:

        Average wall thickness is the average of the measurements taken at six points equally spaced on the section. The measured value is rounded according to the table above.



Outside Diameter Measurement:

The accuracy of the measuring devices used and the measurement results should be in accordance with the table below.

 

 

 

Maximum and minimum diameter measurement:

        By moving the measuring device on the cross-section, the maximum and minimum diameter is found and recorded.


Average outer diameter measurement:

        The average outer diameter is calculated from the value of π by direct measurement or is the arithmetic average of the measurement made at regular intervals over the cross section for the number specified in the table below.