At present, there are actually two completely different products on the market that are generally called steel skeleton PE pipes, one of which is steel skeleton plastic Composite Pipe, that is, steel skeleton polyethylene plastic composite pipe (manufactured according to CJ/T123-2004 standard), and the other is referred to as wire mesh skeleton PE pipe. Its full name is steel mesh skeleton plastic (polyethylene) composite pipe (manufactured in accordance with CJ/T189-2007 standard). Although these two pipes are both steel-plastic composite pipes, in fact, from the molding method to the product characteristics, these two pipes have a big difference, the specific comparison is as follows:
1. Molding method and pipe characteristics
Steel skeleton plastic composite pipe:
Steel mesh welding and plastic extrusion are carried out simultaneously, the inner and outer layers of the pipe wall are connected as one through the metal mesh in the middle of the pipe wall, there is no obvious interface between the steel wire and plastic, the overall structure is similar to reinforced concrete, the two materials are completely composite as one, the quality of each part of the pipe is uniform and stable, and there is no delamination hidden danger.
Steel mesh skeleton plastic (polyethylene) composite pipe:
First extrude the inner layer of plastic, then apply a layer of hot melt adhesive on the outer wall of the molded inner layer of plastic pipe, then apply a layer of hot melt adhesive, and then extrude the outer layer of plastic. There is an obvious interface between the pipe layer and the layer, which is easy to delamination. After delamination, the steel wire winding layer inside the pipe is partially separated from the plastic layer, which will cause serious corrosion to the steel wire layer and damage the pressure bearing body of the pipe when conveying corrosive media. Due to the low pressure bearing capacity of the remaining plastic part after the corrosion of the steel wire layer, It is possible to burst the tube even at low pressures. Even if there is no corrosion problem, because the steel wire at the end of the pipe is not fixed (the bonding effect is not good), under the action of pressure, the steel wire will slide between the plastic layers, resulting in the end part of the pipe is no longer reinforced by steel wire, and it becomes a pure plastic tube with a very thin wall thickness.
2. Pipe structure
Steel skeleton plastic composite pipe:
The inner and outer layers of the pipe wall are connected as one through the metal mesh in the middle of the pipe wall (like the structural form of reinforced concrete), and the two materials are completely composite as one, because the surface of the steel wire is very smooth, no edges and corners, and the flow resistance of the plastic in the molding process is small and the extrusion is uniform, so the quality of each part of the pipe is uniform and stable. Because it is welded into a net, the grid spacing of the skeleton is consistent, the structure is stable, and the support effect of the plastic is strong.
The wound molding wire mesh is bonded to the inner and outer layer of plastic under the action of hot melt adhesive, due to the difficult characteristics of polyethylene material itself, the bonding effect is general, because it is multiple molding, the quality uniformity of the pipe is poor. Because the steel wire is only wound together, not welded, the grid spacing of the steel wire mesh is uneven, the structure is unstable, and the local strength of the pipe is very low where the steel wire spacing is large. Due to the poor supporting effect of the steel mesh on the plastic, the contraction of the pipe end is serious.
3. Pipe fitting
Steel skeleton plastic composite pipe:
All pipe fittings, including electric melt sleeve, elbow and tee, have steel skeleton as the reinforcement part inside, good compatibility with the pipe, the pressure resistance and temperature resistance of the pipeline system are consistent, and the size of the pipe and pipe fittings is consistent. The following is the reinforced skeleton photo of the steel skeleton plastic composite pipe part.
Wire mesh skeleton PE pipe:
Generally, pure plastic pipe fittings without skeleton are used to match the pipe, and the pressure level of the pipe fittings is lower than the pipe body or the diameter of the pipe fittings is reduced due to the large wall thickness of the pipe fittings. At the same time, the pressure and temperature resistance of pipe fittings without skeleton (including electric melting sleeve) is obviously lower than that of pipe, and the pipe joints and pipe fittings are easy to break.
4. Welding method
Steel skeleton plastic composite pipe:
The welding is carried out with full wiring fuse sleeve with reinforced skeleton, which has large welding area and high reliability.
Wire mesh skeleton PE pipe:
Generally, the matching pure PE fusion sleeve is used to connect, without reinforcing the skeleton, and the electric fusion is the middle jumper mode, which has a small welding area and low reliability.
5. Size standard
Steel skeleton plastic composite pipe:
The internal diameter is nominal, and the flow rate is calculated scientifically and reasonably. Good inner diameter consistency when connected with pumps, valves, etc. The inner diameter difference between pipe and pipe fittings is small, and the flow resistance is small.
Wire mesh skeleton PE pipe:
The outside diameter is nominal. When connecting with pumps, valves, etc., the inner diameter difference is large, and it is necessary to use more variable diameter pipe fittings, which increases the connection parts and leakage hazards.
6. End processing method
Steel skeleton plastic composite pipe:
The end face of each pipe is processed by injection molding. Because it is mechanically molded, the connection quality of the end end is reliable and the sealing performance is good.
Wire mesh skeleton PE pipe:
The plastic ring used for sealing is first produced by injection molding, and then the sealing ring is connected with the pipe body by gluing or welding. This method has high production efficiency, but it is difficult to guarantee the quality, and it is easy to leak at the seal.
7. Resistance to external pressure and negative pressure
The reinforced skeleton of the steel skeleton plastic composite pipe is a steel mesh welded by steel wire, and the diameter of the steel wire is more than 3mm, while the reinforced steel wire diameter of the steel wire skeleton composite pipe is only about 1.0mm, and it has not been welded, and the two kinds of pipes have poor external pressure and negative pressure resistance compared with the steel wire skeleton pipe. Wire mesh skeleton PE pipe in the construction, especially pay attention to avoid the deformation of the pipe caused by external pressure, especially the deformation of the pipe end, if the deformation is large, will directly affect the size of the fusion sleeve is good or bad, and ultimately affect the welding quality, once the negative pressure situation in the operation process, the wire mesh skeleton pipe is prone to be sucked flat major accidents. (The following is a picture of a pipeline being sucked flat in Sichuan, steel mesh skeleton PE composite pipe)
8. Long-term performance
Due to the reasonable structure of the steel skeleton plastic composite pipe, as well as good temperature resistance, each pipe is sealed by injection molding, because it is mechanical molding, the end of the sealing quality is reliable, good sealing performance, in summary, the long-term performance of the pipe is good, has been in harsh conditions for more than 10 years of application examples, It has been widely used in chemical industry, petroleum, gas, water supply and other fields.
The temperature resistance of the wire mesh skeleton PE pipe is poor because of the graft PE in the middle of the rubber layer, and the temperature resistance of the whole pipe is also low. The sealing ring is connected with the pipe body by gluing or welding. The quality assurance of this method is difficult, the quality is unstable, the corrosive medium is easy to contact the steel wire from the end of the pipe, and the temperature change or pressure fluctuation of the product in use is inevitable, and there is a certain delamination hidden danger in long-term use. In addition, the production history of this pipe is more than 5 years later than the steel skeleton plastic composite pipe, and it is generally used in the field of water supply with relatively low requirements, and there are few examples of application in the field of chemical, brine, oil and gas with more demanding transportation conditions
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