Views: 0 Author: Site Editor Publish Time: 2023-11-30 Origin: Site
What is the Pipe Longitudinal Reversion Test?
The Pipe Longitudinal Reversion Test, also known as the heat reversion test, is a method used to assess the degree of longitudinal contraction of a pipe during the cooling process. It is usually expressed as a percentage, which reflects the shrinkage rate of a material relative to its original length during cooling. Longitudinal reversion is a crucial indicator in pipe material testing, and failure to meet the specified reversion rate can directly impact the pipe's service life.
The specific longitudinal reversion rate of a pipe depends on factors such as material composition, manufacturing process, and cooling conditions. Different materials and processes result in varying longitudinal reversion rates. Generally, polymer pipes (such as plastic pipes) exhibit higher longitudinal reversion rates, while metal pipes (such as copper or steel pipes) tend to have lower rates
To determine the specific longitudinal reversion rate for a particular pipe, reference should be made to relevant material data sheets or technical specifications provided by the manufacturer. These documents typically include longitudinal reversion rate values for different temperatures and cooling times.
It is worth noting that the longitudinal recovery rate is very important in pipeline manufacturing and installation, especially in applications where dimensional stability and accuracy are essential, such as pipeline installations and cable laying. In practical applications, the longitudinal recovery rates should be accurately calculated and considered according to the requirements of specific project and pipeline specifications. During design and construction, adherence to relevant standards and regulations is essential, and consulting with professionals is advisable to obtain accurate data and guidance
How to Test Pipe Longitudinal Reversion?
PVC Pipe Heat Reversion Test
The technology of testing the thermal recovery of PVC pipes includes controlled heating and cooling cycles of the pipes, and then measuring the longitudinal recovery caused by them. This process is essential for assessing the material's behavior under different temperature conditions and ensuring that it meets the required dimensional stability for its intended application.
CPVC Pipe Reversion Test
CPVC (Chlorinated Polyvinyl Chloride) pipes undergo a similar reversion test to evaluate their longitudinal contraction. The test involves applying heat to the CPVC pipe, simulating conditions it might encounter during its lifecycle. By measuring the longitudinal recovery rate, manufacturers and engineers can verify whether CPVC pipes are suitable for specific applications.
In a word, understanding and testing the longitudinal reversion of pipes, especially CPVC pipes, is crucial for ensuring the reliability and performance of piping systems in various applications. Adhering to industry standards, consulting material data sheets, and conducting accurate tests are essential steps in guaranteeing the quality and longevity of pipe installations.
ERA's CPVC Pipe Longitudinal Reversion Rate Testing
ERA carefully selects batches of CPVC pipes every 8 hours for rigorous longitudinal reversion rate testing, meticulously recording the results to ensure that all pipes produced meet the required quality standards. This proactive approach demonstrates our commitment to delivering consistently qualified products.
The longitudinal shrinkage index of pipes is generally 5%~10%, but it will also vary due to different materials and process conditions. For example, the national standard stipulates that the longitudinal shrinkage rate of PVC-U pipes should be ≤5%, while the longitudinal shrinkage rate of PPR pipes is ≤2%.
1. Basic concept of longitudinal shrinkage rate of pipes
The longitudinal shrinkage rate of pipes refers to the ratio of the shrinkage amount of the pipe along the pipe axis during the thermal molding process to the original length under specific conditions. This indicator is a key parameter for measuring the quality of pipes, which can reflect the dimensional stability of pipes under heating conditions. Generally speaking, the longitudinal shrinkage index of pipes is between 5% and 10%, but the specific value will be affected by many factors.
2. Factors affecting the longitudinal shrinkage rate of pipes
1. Pipe material: Pipes of different materials have different longitudinal shrinkage rates. For example, under the same temperature and process conditions, the longitudinal shrinkage rate of PE pipes is usually greater than that of PVC pipes.
2. Process conditions: Factors such as process temperature and extrusion speed will affect the longitudinal shrinkage rate of pipes. Generally speaking, the higher the temperature, the greater the shrinkage rate of the pipe may be.
3. Mold design: The structure and cooling method of the mold will also affect the longitudinal shrinkage rate of the pipe. Reasonable mold design can help reduce the shrinkage rate of the pipe.
3. Longitudinal shrinkage rate standards for different pipes
According to national standards, different types of pipes have different longitudinal shrinkage rate requirements. For example, the longitudinal shrinkage rate of PVC-U rainwater pipes for construction should not exceed 5%, while the longitudinal shrinkage rate judgment standard for PPR pipes is less than or equal to 2%. These standards ensure the stability and durability of pipes during use.
4. Test method for longitudinal shrinkage rate of pipes
In order to accurately measure the longitudinal shrinkage rate of pipes, specific test methods are usually followed. According to the standard "Determination of longitudinal shrinkage rate of thermoplastic pipes", a certain length of pipe samples needs to be taken, baked at a specified temperature, and the length change before and after baking is measured. Through this method, the performance of pipes under heating conditions can be scientifically evaluated.
In general, the longitudinal shrinkage rate of pipes is one of the important indicators for evaluating the quality of pipes. Understanding and controlling this indicator is of great significance to ensure the stability and safety of pipes during use.
The main technical performance parameters of CPVC power pipe:
1. Vicat softening temperature ≥℃ High-pressure protection pipe 93 Ordinary protection pipe 81
2. Ring segment thermal compression force nominal wall thickness en/mm5.0＜8.0KN0.45≥8.01.25
3. Volume resistivity ≥.m1.0×1011
4. Drop hammer impact test 9/10 passed
5. Longitudinal shrinkage rate ≤5%CPVC
Eight characteristics of CPVC power pipe:
One of the technical parameters of power pipe: CPVC power pipe is made of PVC-C resin with excellent heat resistance and insulation performance as the main material. CPVC products are currently recognized as green and environmentally friendly products. Their excellent physical and chemical properties are increasingly valued by the industry. CPVC power pipe is a hard straight solid wall pipe with smooth inner and outer walls, orange-red color, bright and eye-catching color.
Technical parameters of CPVC power pipes: heat resistance: CPVC power pipes have a heat resistance temperature that is 15°C higher than that of ordinary UPVC double-wall corrugated pipes. They can remain unchanged in an environment above 93°C and have sufficient strength.
Technical parameters of CPVC power pipes: insulation: CPVC power pipes can withstand high voltages of more than 30,000 volts.
Technical parameters of CPVC power pipes: compression resistance: After material modification, the ring stiffness of CPVC power pipes reaches 1Okpa, which is significantly higher than the national regulations for buried plastic pipes, which stipulate that the ring stiffness should be above 8kpa. Technical parameters of CPVC power pipes: high impact strength: CPVC power pipes can withstand the impact of a 1kg hammer and a height of 2m at a temperature of 0°C, which fully reflects that the low-temperature impact performance of the material is fully applicable to the requirements of construction environment conditions.
Technical parameters of CPVC power pipes: flame retardancy: Both PVC and PVC-C materials have good flame retardancy and can be extinguished immediately when away from fire. In particular, PVC-C materials, because their chlorine content is significantly higher than PVC, have significantly improved flame retardancy and smoke density index.
CPVC power pipe technical parameters 7 Installation characteristics: CPVC power pipe is light in weight, high in strength, and has a simple construction and laying method. It can be excavated and buried at night, backfilled on the road surface, and can be used as usual during the day; it adopts elastic sealing rubber ring socket connection, which is convenient and fast to install and connect, and has good connection sealing performance, which can prevent groundwater leakage and effectively protect the safety of power cables.
CPVC power pipe technical parameters 8 Long service life: CPVC power pipe materials are corrosion-resistant and aging-resistant, and the service life can be up to 50 years or more.
The longitudinal shrinkage rate of pipes, as a key indicator to measure the quality of pipes, is usually in the standard range of 5% to 10%, but this value is not fixed. In fact, the longitudinal shrinkage rate of pipes is affected by many factors, including pipe materials, process conditions, and mold design.
First, different pipe materials will lead to differences in longitudinal shrinkage rates. For example, under the same process conditions, the shrinkage rate of PE pipes is often greater than that of PVC pipes. Secondly, process conditions such as temperature and extrusion speed will also affect the shrinkage rate. Generally, the higher the temperature, the greater the shrinkage rate may be. In addition, the structure and cooling method of the mold are also important factors affecting the shrinkage rate.
For different types of pipes, the national standard also stipulates corresponding longitudinal shrinkage requirements. For example, the longitudinal shrinkage rate of PVC-U rainwater downpipes for construction should not exceed 5%, while the longitudinal shrinkage rate of PPR pipes should be less than or equal to 2%. These standards are formulated to ensure the stability and durability of pipes during use.
In order to accurately measure the longitudinal shrinkage rate of pipes, specific test methods need to be followed. Usually, we take a certain length of pipe sample, bake it at a specified temperature, and measure the change in length before and after baking. In this way, we can scientifically evaluate the performance of the pipe under heating conditions, thereby ensuring the quality and safety of the pipe.
Test items:
1. Elongation at break
Elongation at break is a manifestation of the good flexibility of PE pipes. By measuring the elongation at break of pipes, the adaptability of pipes to uneven foundation settlement can be ensured to meet the needs of seismic performance.
National standard requirements: elongation at break ≥ 350%. When the company's pipes are actually tested for elongation at break, they reach the range of the equipment without breaking. At this time, the displacement of the extensometer is 350mm, that is, when the sample is stretched 350mm, it still does not break. The elongation at this time is 700%. It can be seen that the elongation at break of our pipes is greater than 700%, which is much greater than the national standard requirements.
2. Longitudinal shrinkage rate
Pipes are prone to deformation after being heated. The determination of longitudinal shrinkage rate is intended to detect the degree of dimensional change of pipes along the axial direction under the influence of heat. The longitudinal shrinkage rate of pipes reflects the dimensional stability of thermoplastic plastic pipe products under the influence of heat. The standard requires a longitudinal shrinkage rate of ≤3%.
3. Oxidation induction time
Oxidation induction time is an important indicator for measuring the thermal stability of pipes. Its length is closely related to the long-term heat-resistant oxidation aging life of PE pipes. By measuring the oxidation induction time of pipes, it is ensured that the pipes can still meet the use requirements during construction, welding and 50 years of service life.
The thermal stability of the sample is evaluated by measuring the time when the sample begins to undergo autocatalytic reaction under high temperature conditions (i.e., oxidation induction time).
Test steps for oxidation induction time:
① Cut a 20-30mm wide ring from the pipe, cut a 20mm long arc segment from the ring, cut a cylinder with a diameter slightly smaller than the thermal analysis sample dish from the arc segment, and then cut a disc-shaped sample weighing 15±0.5mg from the cylinder.
② Turn on the computer and analytical instrument, connect oxygen and nitrogen, turn on the gas switching device, adjust the flow of the two gases respectively, so that they both reach 50±5cm3/min, and then switch to nitrogen.
③Put the sample in an open aluminum dish and then put it on the sample support of the thermal analysis instrument.
④Start the instrument, raise the temperature to 200±0.1℃ at a rate of 20℃/min, keep the temperature constant, and start recording the thermal curve.
⑤After maintaining the constant temperature for 5min, switch the nitrogen to oxygen and continue to record the temperature-heat curve until the oxidation process ends or the specified time is reached.
Test results of oxidation induction time:
On the thermal curve recorded in the test, mark the point A1 where nitrogen is switched to oxygen, give the tangent line of the slope when the curve changes significantly, mark the intersection point A2 of this tangent line and the baseline extension line, and the time between the two points is the oxidation induction time (min) representing the thermal stability of the sample.
