China is the world's largest coal producer, with coal output accounting for 30% of the world's total. As China's main energy source, coal has always accounted for more than two-thirds of the energy production and consumption structure. Therefore, the safety of coal resources production is a major event related to the sustained and stable development of national economy and society and national energy security. For the coal industry, gas explosion accidents caused by static electricity occur frequently, and the relevant departments of the state have raised the technical standards of plastic pipes for coal mines several times.
1. General dual-resistance PE Pipe (now mainly MPE100)
The requirements of coal mine pipe are relatively high and the performance of PE80 is relatively low, so the main raw material for production is PE100 resin.
PE dual-resistance pipe has gradually become a substitute for steel pipe since it was widely used. The characteristics of PE100 are light weight, good comprehensive performance, unlike nylon and PVC pipes, which have fatal defects, but at the same time, the main indexes of PE100 are not outstanding: the impact strength of PE100 is too low, only 25 kj/m^2, the impact resistance of PE100 drops sharply to 13 kj/m^2 at - 10 C, and the impact strength of PE100 after double-resistance modification is only 15-20 kj/m^2, which is easily destroyed after crossing the bottom line. Tensile strength is not as good as PVC and ABS, and even worse than nylon. It does not have the ability to resist rapid cracking. Wear resistance is general. The creep resistance (fatigue resistance) is poor, and the pipeline often breaks at the flange plate due to stress concentration.
At present, the market share of common PE dual-resistance pipes in China is about 50%. On the one hand, the product consumption is huge, on the other hand, almost all manufacturers have underground cracking and joint fracture accidents of dual-resistance PE pipes. Therefore, manufacturers are very cautious about the supply of pipe materials in coal mines. Mining PE pipes can be divided into the following categories according to their different uses:
A. Underground water supply and drainage pipes. For mines with large drop, considering the pressure bearing capacity of pipes, the current dual-resistance PE manufacturers are very cautious, only in the low drop mine application.
B. Negative pressure duct and pressure duct. When the working pressure is very high, the production enterprises are very cautious. Now PE pipes in coal mines are only popular in ordinary pressure environment.
C, Shotcrete pipe. Due to the general wear resistance of PE100 materials, manufacturers are more cautious in the field of sales.
D. Gas drainage pipe. PE dual-reactor tube is more mature in application at low pressure difference, and its safety factor is relatively high.
When PE is used as raw material for underground pipeline in coal mine, the flame retardant and antistatic indexes are easy to guarantee, but the characteristics of PE itself affect its popularity in underground coal mine.
In view of its own material properties, there are serious defects and potential accidents in the use of MPE100 underground. It is understood that the origin of PE dual-resistance pipeline is mainly concentrated in Shandong Province. There are many production enterprises and the production technology is very mature. But if the safety problem of PE dual-resistance pipeline in coal mines can not be solved, the production enterprises of such pipelines will face fierce competition and after-sales customer service problems at the same time.
In a word, PE plastic pipes used in coal mines are huge in consumption, but performance bottlenecks need to be solved urgently in order to expand the use area and reduce the use safety cost.
2 UHMWPE Pipeline
Ultra-high dual-resistance tube is a kind of material which has been studied by relevant research institutes or production enterprises. Especially in recent years, it has developed rapidly in China. Recently, it has been reported that a Shanghai Institute has successfully developed ultra-high dual-resistance tube, and some other manufacturers have successfully developed their own ultra-high dual-resistance tube.
The tensile strength of super-high double-resistance pipe is 25 MPa (equal to that of unmodified PE100). The impact resistance and cracking resistance of super-high double-resistance pipe are much higher than that of MPE100, and its excellent wear resistance (wear resistance is 4-7 times that of steel), self-lubrication and non-stickiness make it an ideal material for wear-resistant and impact-resistant pipes. The development and application prospect of super-high PE are very broad. In addition, the fatigue resistance of super-high PE is dozens of times that of that of PE 100.