Analysis of common faults and causes in the construction and installation of PE pipes

PE pipe is a new type of water supply pipe produced by extrusion molding process with polyethylene resin as the main raw material. There are three connection methods: hot melt, electric melt and mechanical connection. PE water supply pipe has corrosion resistance, non-scaling, good hydraulic conditions, light weight, long service life (durable for 50 years), good flexibility, Good impact resistance and seismic performance. And the construction connection is simple, convenient and quick.

Measures should be taken to deal with it in design and construction. Common faults and reasons in construction and installation are as follows:

1. Inadequate material management

(1) PE pipes and fittings are not provided by the same manufacturer, their chemical properties are inconsistent, and the bonding at many hot-melt joints is not reliable.

(2) Mixed using PE pipes from different manufacturers.

(3) PE pipes are improperly stored and deteriorated and become brittle after high temperature exposure. The performance decreases and the quality deteriorates.

2. The internal stress damages the pipe after thermal expansion and contraction of the PE pipe

(1) PE pipe expander: PE pipe has a large coefficient of thermal expansion and contraction, and the backfill is not layered and compact. After the temperature drops, the PE pipe expander may rupture at night.

(2) The shrinkage of the PE pipe causes the socket of the ductile iron pipe to fall off: the shrinkage of the PE pipe in winter causes the socket of the ductile iron pipe to fall off, resulting in pipe leakage.

(3) After the PE pipe is thermally expanded and elongated, it will be twisted and bent from the reduced diameter. Under the impact of high-speed water flow for a long time, cracks and water leakage will occur at the bend.

(4) After the water in the water supply pipe freezes, the water meter joint of the PE pipe will break.

3. Unreasonable pipeline installation 

(1) Excessive welding at the hot-melt joints forms a radial necking of the water supply and drainage, and the pipe has a small accumulation of water, and the pipe is almost blocked, causing the user to be without water for a long time. Pay attention to the heat melting time of PE pipe in summer and winter. If the welding time is too long, it is easy to form a radial neck and affect the flow of water.

(2) The PE main pipe shrinks after cooling, causing the attached fixtures to be misplaced and water leaks at the tee. It is not advisable to use cast iron clamps for connecting the branch pipes with PE pipes. It is recommended to use standard PE three-way pipe fittings and use electrofusion sleeves for connection.

(3) The casing is not tightly sealed, and the high-temperature domestic sewage soaks the PE pipe for a long time, causing the PE pipe to be brittle and broken after denaturation.

(4) There is a little mud and sand adhered to the hot melt joint, causing water seepage in the pipe joint.

(5) Concrete is dumped on one side during the pouring of pipeline buttresses, town piers, etc., causing the pipeline to be twisted and out of alignment.

(6) The valve on the main pipeline is not tightly closed and the water stop is not tight, resulting in a line of water flowing at the three-way interface of the welded electrofusion sleeve, and there is water seepage in the welding seam.

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