Super anti-abrasive composite pipe
I. Structure of the New Type Super Abrasion Resistant Plastic Pipe
In the rapid development of the economic construction, there are lots of powdered solids, liquid and slurry solid-liquid mixtures that need to be conveyed by pipe in many industries, which results in abrasion, corrosion, scaling and other problems of the pipe. This should be urgently solved. In the face of demands in broad markets, recently, some abrasion resistant pipes have been applied in electric power, metallurgy, coal, petroleum, chemical engineering and building materials industries etc. with a trend of rapid development. Quick abrasion is a common problem for conveying of ash, pulverized coal, ore fines, tailings and cements etc. by abrasion resistant pipe, especially by bend pipe. In addition, the abrasion resistant pipe can be corroded and thus rapidly damaged when it is used to convey highly corrosive gases, liquid or solids.
This series of products, with the inner layer made of the new type modified polyolefin abrasion resistant material (elastomer structure for abrasion resistant material), are divided into super abrasion resistant composite pipe and high pressure super abrasion resistant multilayer composite pipe, according to the production structure. For super abrasion resistant composite pipe, its thickness and strength meet to the requirements specified in standards GB/T13663-2000 and Q/0881DHB003-2015, and its PN is 0.8-1.6MPa. For high pressure super abrasion resistant multilayer composite pipe, its thickness and strength meet to the requirements specified in standards CJ/T189-2007 and Q/0881DHB001-2014, and its PN can reach 7.0MPa
For the structure of the super abrasion resistant composite pipe, please refer to the Fig. 1:
Fig. 1 Double-layer super abrasion resistant composite pipe
For the structure of the high pressure super abrasion resistant multilayer composite pipe, please refer to the Fig. 2:
Fig. 2 Steel wire-wound reinforced super abrasion resistant composite pipe
The use of the abrasion layer greatly improves the abrasion resistance of the pipes during slurry and solid medium conveying and thus prolongs the service life of the pipes. It is recognized that UHMW PE pipe has super abrasion resistance performance. Compared with the UHMW PE pipe, this series of products have the much more excellent abrasion resistance performance and reduce the mortar abrasion rate by more than ten times. Thus, this series of products can be widely used for conveying the solids, liquid-solid mixtures, gas powder and slurry etc., which may severely corrode the pipes and result in acid, alkaline and salt corrosion.
I. Performance Features of the New Type Super Abrasion Resistant Plastic Pipe
1. Good abrasion resistance:
1.1 Mortar abrasion test
The mortar abrasion test is carried out according to the “mortar abrasion rate test methods” in Appendix B in QB/T 2668–2004 Ultra-high-molecular-weight polyethylene pipes. The test method is shown as follows: put the specimens with the same dimension and made of different materials in the mortar and make them rotate at high speed to rub with mortar; after several hours, take out of the specimens, measure the weight loss proportion of the specimens and obtain the abrasion rate of different materials in the mortar. The test data of different pipe materials under the same conditions are shown in tables 1 to 3.
Table 1 Mortar abrasion resistance test result 1
Table 2 Mortar abrasion resistance test result 2
Table 3 Mortar abrasion resistance test result 3
1.2 Darmstadt test of finished pipe
The principle of the Darmstadt test is shown as follows: mix the gravels with different particle sizes to a scale, put them into a test pipe section with a length of 1m, add a certain amount of water into the pipe section and seal the pipe end. Make the pipe section clamped at the wobbler and let the wobbler swing back and forth at a certain angle and speed to make the gravels in the test pipe section rub with the pipe wall. Change gravels once and measure the wight loss (abrasion loss) of the pipe section once every 100,000 times of rubs. Fig. 3 shows the working principle of the wobbler. Fig. 4 shows the abrasion results of different pipe materials.
Fig. 3 Schematic diagram of wobbler
Fig. 4 Abrasion results of different pipe materials
1.3 Ring pipe abrasion test by slurry
The test conditions of the ring pipe test basically simulate the actual conditions of industrial pipe conveying. The test system is a complete ring pipe, including slurry tank, slurry pump, variable-frequency speed governor, test pipe section, flowmeter, adjusting valve, concentration and speed calibration device and pipe cooling system etc. Fig. 5 is the schematic diagram of system for pipe wall abrasion test by ring pipe method. Fig. 6 is the photo of the test site.
Fig. 5 Schematic diagram of system for pipe wall abrasion test by ring pipe method
Fig. 6 Site photo of pipe wall abrasion test by ring pipe method
For abrasion test, the average density of the iron ore concentrates is 4722kg/m3; the mass concentration of the slurry is 60%; the flow velocity of the slurry is 1.8-2.0m/s. The inner diameter of the test pipe is 50mm; the total length of the ring pipe is 30m. The slurry should be changed once and the abrasion resistance capacity of the test pipe section should be detected once every 60 test hours. The slurry temperature should be controlled below 40℃. The total test duration is 600h. The test results are shown in Fig. 7.
Fig. 7 Results of ring pipe abrasion test by slurry of different pipe materials
2. Good corrosion resistance:
With double-sided corrosion resistance performance, it not only is acid-resisting, alkali-resisting and chemical corrosion-resisting, but also can resist electrochemical corrosion and cannot produce the galvanic cell effect with the stray current of the environmental soil. Thus, it is safe and reliable for conveying solids and liquid that will rub and corrode the pipe.
3. Good weather resistance:
When it is used underground, its weather resistance is equivalent to that of the PE pipe. At the low temperature of -40℃, no physical property change and no frost crack occur. It can be used all year round, with no moisture condensation in summer and with no need for heat protection of outer wall in winter (the thermal conductivity is 1/200 of that of steel).
4. Good hydraulic performance
The equivalent roughness of its inner wall is 0.0015 - 0.015ram. While, that of the steel pipe is 0.19nHn in general (after 3 years, the hydraulic performance of the steel pipe will be poor due to corrosion and scaling, thus the equivalent roughness of the inner wall of the steel pipe will be calculated at 0.6mm after 3 years). So, compared with the traditional pipes such as steel pipe, this series of pipes have the smoother inner wall without scaling, smaller conveying resistance and better energy saving effect, thus increasing the conveying capacity by 20%-30%.
5. Easy installation
Due to its light weight and few joints, it can be installed easily and quickly. It has sufficient capacity to resist underground movement and end load, thus, anchoring that requires too much money is unnecessary during installation. The requirements for the bottom of the pipe ditch is low and the volume of earthwork is few, thus the installation cost is low.