1. Performance characteristics of dredging pipe
PE molecules have no polarity, so the stability is particularly good, no decay, rusting, teleological corrosion phenomenon. The chemical substances present in the soil will not cause any obstacle to the pipe. In addition, it does not win bacteria, does not form dirt, and is an environmentally friendly product.
Due to the light weight of dredging pipe, it is easy to carry and connect, and it can be moved by hand in the process of installation in general. Such as a DN200 dredging pipe can be carried by one person, loading and unloading are very convenient. It not only reduces the labor intensity, but also saves the transportation cost, which is 50% less than the installation cost of steel pipe, especially in the case of tight schedule and poor construction conditions, the advantage is more obvious.
Using dredging pipe, its inner surface is smooth and has higher dredging transmission capacity than other pipes.
PE pipe can be slightly disturbed in the axial direction, so it can be laid directly in a slightly straight trench without fittings, and it is not affected by a certain degree of uneven ground settlement. It also has good low temperature resistance, minus 30 ° construction are not necessary to take insulation measures, winter construction is convenient. There is also good impact resistance, timely 2 times the nominal pressure of the dredging hammer will not cause any harm to the pipe.
PE pipe aging resistance, long service life, under the condition of no direct ultraviolet light service life of 50 years.
2. dredging pipe installation
Before the pipe connection should be noted that the pipe and fittings and ancillary equipment should be checked as required, and the construction should be inspected for appearance and meet the requirements before use. The main inspection items include: pressure resistance level, quality of fit, consistency of material, the use of fusion connection and even the pipe, the use of the same good brand of material pipe, pipe construction. For the performance of the shape must first go through the experiment, qualified before proceeding, according to the different forms of interface using the appropriate thermal processing, shall not use open flame heating pipe and fittings.
PE pipe is most convenient is the hot fusion connection, electric fusion connection, socket connection. Hot fusion connection is also divided into hot fusion socket connection and hot fusion butt connection.
(1) Hot fusion socket connection is to match the inner surface and outer surface simultaneously heated into a fluid state, remove the heating tool and insert the outer surface into the inner surface to form a socket lap joint. Adjust the position of the pipe and fittings so that the pipe and fittings are on the same axis to prevent eccentric welding joints from being weak and gas tight. Since PE street can reach the best heat resistance strength only after all cooling to room temperature, other external forces during the cooling period will make the pipe and fittings cannot maintain the same axis, thus affecting the quality of the fusion joint, therefore, the connected parts should not be moved or external forces applied at the connection during the cooling period.
(2) hot fusion butt connection, that is, two identical connection surface with a heating plate to the powder flow state, remove the hot plate and then apply pressure to the connection surface, and in this pressure cooling fixed, forming a solid connection. The key to this connection is to adjust the three factors of time, temperature and pressure.
(3) different pipe diameter limit dredging pipe connection using dredging pipe reducer pipe fittings after resizing, and then using hot fusion connection. dn>50 above dredging pipe and other pipe piping, valves, expansion devices, fire hydrants and other metal fittings connection, using the same type of flange connection transition dn<50 below dredging pipe and metal pipes, small diameter valve connection, the use of internal and external inlaid metal thread injection fittings for transition. The pressure level of the transition fittings shall not be lower than the nominal pressure of the pipe.
3. dredging pipe in the connection process is prone to quality defects and the measures taken
The nature of dredging pipe material and the quality of the joint is determined by the strength of the fusion joint, the general fusion temperature control between 190-240 degrees. Temperature is too high appears rolled edge size increases, polymer melt adhesion to the tool does not reach the required bond strength, it is very easy to appear.
(1) the rolled edge is not standardized, the rolled edge is too wide is not the correct time to absorb heat, too narrow is the fusion pressure.
(2) misalignment of the tube end, is due to the machine fixture different axis, the tube end is not placed horizontally, the operation error is large.
(3) Cracks easily appear on the pipe around the joint; due to the set temperature is too high, the pipe surface carbonization, mutual fusion of the two ends of the material melt flow rate is different.
(4) Due to fusion is insufficient pressure, or heat absorption, cooling time is too short, the pipe mouth cutting is not parallel, the melt seam is very easy to gap.
(5) Heating plate processing is not clean or the presence of dredging solvent on the heating plate, the fusion surface is easy to produce gaps.
(6) Connected tube end face with pollution, the temperature of the hot plate is too low, the fusion joint is not sufficient easy to produce false welding.
4. the hydraulic test of dredging pipe
PE for the hydraulic test and GB30268 dredging supply and drainage pipe construction and acceptance specifications of the hydraulic test is different, the method of judging the hydraulic test and the standard is also different, should fully understand the dredging pipe in the pressure test during the pressure drop phenomenon, can not be considered a pipe leak.
5. dredging pipe problems in use
(1) Few varieties of raw materials and unstable quality.
(2)PE pipe is plastic pipe, afraid of sunlight, and must be kept in a better closed warehouse.
(3)The hydraulic test is difficult to control.
(4)The price of dredging pipe is relatively cheap, but the fittings are relatively high, such as electrofusion fittings. Although there are certain shortcomings, but as a new type of pipe, there are many advantages, wide environmental adaptability and good connection, construction performance.
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