The Trench
National and regional regulations and directives for soil covered PE pipelines are to be followed during the construction of the necessary trench. The trench has to allow all parts of the pipeline to be in frost-safe depths and enough widths.
Trench widths
Considering the project and extra effect to the pipelines from the earth, the trench width should be as narrow as possible.
A lists recommended trench widths. These values are consistent with the principles that trench width should be as narrow as possible in order to minimize external loads and installation costs, whilst also affording sufficient space to provide the specified compaction.
The adopted actual trench width will be influenced by the soil conditions, the jointing systems, and whether joints are made in the trench.
A Recommended trench widths
| dn of PE pipes (mm) | Trench width (mm) |
| 20~63 | 150 |
| 75~110 | 250 |
| 12~315 | 500 |
| 355~500 | 700 |
| 560~710 | 910 |
| 800~1000 | 1200 |
Where PE pipes are installed with other services in common trench situations, the trench width may be specified by local authority regulations in order to permit later maintenance activities.
Trench depths
Where the PE pipes grade line is not specified, the cover over the top of the PE pipes needs to be set so that adequate protection from external loads, third party damage, and construction traffic is provided.
Where possible, pipes should be installed under minimum depth conditions and, as a guide, the values listed in below should be adopted.
| Installation Condition | Cover over pipe crown (mm) | |
| Open country | 300 | |
| Traffic Loading | No pavement | 450 |
| Sealed pavement | 600 | |
| Unsealed pavement | 750 | |
| Construction equipment | 750 | |
| Embankment | 750 | |
Above Ground Installation
CHUANGRONG PE pipes may be installed above ground for pressure and non pressure applications in both direct exposure and protected conditions. Black PE pipes may be used in direct sunlight exposure conditions without any additional protection. Where PE pipes of colors other than black are used in exposed conditions, then the pipes need to be protected from sunlight. Where PE pipes are installed in direct exposure conditions, then the increased PE material temperature due to exposure must be taken into account in establishing the operational pressure rating of the PE pipes. Localized temperature build up conditions such as proximity to steam lines, radiators, or exhaust stacks must be avoided unless the PE pipes are suitably protected. Where lagging materials are used, these must be suitable for exposure applications.
Bedding Material & Backfill
The excavated trench floors must be trimmed even,and be free from all rocks, and hard objects. The bedding materials used in both trenches and embankments shall be one of the following:
1. Sand or soil, free from rocks greater than 15 mm,and any hard clay lumps greater than 75 mm in size.
2. Crushed rock, gravel, or graded materials of even grading with a maximum size of 15 mm.
3.Excavated material free from rocks or vegetable matter.
4. Clay lumps which can be reduced to less than 75 mm in size.
In the majority of PE pipe applications, a minimum of 75mm of bedding material is used in both trenches and embankments in soil excavations. For excavations in rock,150 mm bedding depth may be required.
The remainder of the trench, or embankment fill may be made with the previously excavated native materials.
These must be free from large rocks, vegetable matter,and contaminated materials, and all materials must have a maximum particle size less than 75 mm.
Where PE pipelines are installed in areas with high external loads, then the backfill materials must be of the same standard as the bedding and overlay materials.
Thrust Blocks & Pipe Restraint
Thrust blocks are required for CHUANGRONG PE pipes in pressure applications where the joints do not resist longitudinal loads. The thrust blocks must be provided at all changes in direction.
Where concrete blocks are used, the contact points between the PE pipe, or fitting and the thrust block must be protected to prevent abrasion of the PE. Rubber or malthoid sheeting may be used for this purpose.
All fittings and heavy items such as cast iron valves must be supported in order to prevent point loading on the PE materials. In addition, where valves are used, the torque loads arising from the opening/closing operations must be resisted with block supports.
Curving of PE Pipelines
All PE pipes installed on a curved alignment must be drawn evenly over the entire curve length, and not over a short section. This can lead to kinking in small diameter,and/or thin wall pipes.
Large diameter PE pipes (450mm and above) must be joined together, and then drawn evenly to the desired radius. The Minimum allowable bend radius of HDPE pipeline can be found.
Relining & Non-dig Trench
Existing pipelines can be renovated by inserting CHUANGRONG PE pipes into the old pipes. Insertion pipes can be pulled into position by mechanical winches. Relining with PE pipes provides a structural element that is capable of withstanding either internal pressure or external loading without relying on the residual strength of the original degraded pipe elements.
The PE pipes require short length inlet and exit trenches to accommodate the PE pipe radius to lead into the existing pipeline, and the winch assembly used to pull the PE liner along the pipeline. The minimum bending radius of the PE liner can be calculated as described under Pipeline Curvature of the manual.
PE pipes can also be used in non-dig trench projects,such as Horizontal Directional Drilling (HDD). Some of the earliest uses of large diameter PE pipe in directional drilling were for river crossings. PE pipe is suited for these installations because of its scratch tolerance and the fused joining system which gives a zero-leak-rate joint with design tensile capacity equal to that of the pipe.
To date, directional drillers have installed PE pipe for gas,water, and sewer mains; communication conduits;electrical conduits; and a variety of chemical lines.
These projects involved not only river crossings but also highway crossings and right-of-ways through developed areas so as not to disturb streets, driveways, and business entrances.
Repairing and Maintenance
According to different damages, there are kinds of repairing technologies to choose. Repair can be accomplished on small diameter pipe by opening sufficient trench space and cutting out the defect. Replace the damaged section with a new segment of pipe.
Repairing large diameter pipe can be accomplished with a flanged spool piece. The damaged section is removed.Next,the butt fusion machine is lowered into the ditch.Flanged connections are fused to each open end, and the flanged spool assembly is bolted into place. The flanged spool must be precisely made to fit the resulting gap in the pipeline.
PE Electrofusion Coupler Repairing
Flange Repairing
Quick mechanical repairing
CHUANGRONG is a share industry and trade integrated company, established in 2005 which focused on the production of HDPE Pipes, Fittings & Valves, PPR Pipes, Fittings & Valves, PP compression fittings & Valves, and sale of Plastic Pipe Welding machines, Pipe Tools, Pipe Repair Clamp and so on. If you need more details, please contact us +86-28-84319855, chuangrong@cdchuangrong.com, www.cdchuangrong.com
Post time: Jul-16-2025
