- Anti-aging problem
- (1) the PE water supply pipe can be blue pipe, or it can extrude blue strip from black pipe. Generally speaking, the latter has better anti-ultraviolet and anti-aging functions.
- (2) polyethylene pipe should not be overlaid, and the real demand should also advocate casing maintenance.
- (3) Polyethylene pipes should be transported and stored in the process of preventing direct sunlight, and the time of placement on the site should be very short.
- (4) the PE tube with anti-aging treatment is also available in violation of the above two points, but the service life is greatly reduced.
- On temperature related issues:
- (1) The main results are as follows: (1) when the medium temperature of PE pipe is higher than 20 ℃, the nominal pressure of the selected pipe should be calculated according to ‘Technical Specification 4.1.1’, which will be greater than the working pressure value of the pipe network.
- (2) Technical specification 4.2.4′ requires that the distance between buried polyethylene pipe and thermal pipe shall not be less than 1.5 m, and the distance shall be calculated according to the condition that the surface temperature of polyethylene pipe does not exceed 40 ℃
- (3) If casing is added to part of the pipe, it is also necessary to check whether the direct sunlight casing can make the surface temperature of polyethylene pipe exceed 40 ℃, otherwise, the heat insulation layer should be added.
- (4) The linear expansion coefficient of polyethylene pipe is more than 10 times higher than that of steel pipe and ductile iron pipe, but the elastic modulus of polyethylene pipe is much lower than that of metal pipe, which indicates that although the elastic degree of polyethylene pipe is relatively high, the stress of elasticity is significantly smaller. Therefore, it is appropriate and important to overcome the axial deformation caused by seasonal temperature difference when laying polyethylene pipe. The fixed method needed to manipulate this elasticity is often simple and economical. It uses the rare advantage of polyethylene-stress relaxation function to control mechanical activity and deformation.
There are two fundamental solutions:
- (1) the pipeline is not fixed, so that the pipeline can move freely with the temperature change, such as the snake laying of the hot melt and electric fusion connection in the planned scale, and the demand for the temperature change of the pipeline.
- (2) after anchoring method to control its scale change, such as hot melt, electric fusion connection pipeline and metal pipeline, cement pressure pipe, polyethylene pipe should be firmly stuck, prevent the axial force of polyethylene pipe temperature change, and affect the sealing of the interface with metal pipeline and cement pressure pipe.
Of course, when each pipe section is closed, the temperature tends to the annual average temperature as far as possible; the unlocked polyethylene pipe with flexible connection can be used to the demand of pipe temperature change.