Many applications require that a pipe is laid out or strung out across the existing terrain. It may simply be placed on the ground surface. Unrestrained installation allows the pipe to move freely in response to temperature change.
The PE Pipe is Snaked along the right of way and the excess pipe allows some slack that will be taken up when the temperature drops and the pipe contracts. The Pipe will terminate at some rigid structure and the transition from free moving PE Pipe to Rigid Pipe is fully stabilized to prevent stress concentration within the connection.
Restrained Pipe Line : Common restraint methods are :
***Earthern Berms *** Pylons
*** Augured Anchors *** Concrete Cradles
The pipeline may be completely covered with a shallow layer of earth cover over its entire length or it may be stabilized at intervals with Earthern Berms between Anchor Locations .
The Earthern Berms Moderate the temperature fluctuations also and due to this the Pipe movement is reduced. These types of installations may be made necessary by any one of several factors such as the economic considerations of a temporary piping system & the ease of inspection and maintenance. Often the prevailing local conditions prevent burial of the pipe. The Properties of Polyethylene pipe which make it suitable for these applications are: Unique Joint Integrity, Toughness, Flexibility, and Low Weight.
Some Widely Used Applications : Temporary water lines. Bypass lines. Dredge lines. Minetailings/ Fines-disposal piping Slurry Transport in many industries, Oil and Gas Collection.
Design Criteria:
Temperature: As a general rule, polyethylene pipe can be used safely at temperatures as low as -75°F (-60°C) and as high as 150°F (65°C).
Chemical Resistance : Unlike many piping materials, polyethylene pipe will not rust, rot, pit, or corrode as a result of chemical, electrolytic, or galvanic action. Please refer to the Chemical Resistance Chart on Page 87.
Ultraviolet Exposure: When Installed outdoors in above-ground applications, Polyethylene will be subjected to extended periods of direct sunlight. However it is sufficiently protected when the Pipe is produced with a minimum 2.0% concentration of finely divided and evenly dispersed carbon black.
Mechanical Impact or Loading : Any piping material that is installed in an exposed location is subject to the rigors of
the surrounding environment. It can be damaged by the movement of vehicles or other equipment, and such damage generally results in gouging, deflecting, or flattening of the pipe surfaces. In Such cases the Pipe is encased in cement concrete.
Supported or suspended Pipelines :
HDPE pipe may also be suspended or cradled in support structures on the Pipeline right of way. Pipe support should be designed to give lateral constraint against movement, while allowing free movement of pipe in axial direction. Support spacing requirements are given below.
For some applications continous support is given throughout the length of the pipeline.
Installation Methods
Note : The values from graph are to be multiplied by: 1.00 for HDPE pipe rated pressure 4 kg/cm² (Class II) 1.10 for HDPE pipe rated pressure 6 kg/cm² (Class III) and 1.25 for HDPE pipe rated pressure 10 kg/cm² (Class IV) Recommended Supports Spacing
Dis tance be tw ee n supports f or 2.5 K g/ cm² pipe
Excavated Trench Width
12” to 18”
Pipe Zone Springline
Haunch Zone
Final Backfill
Secondary Backfill
Primary Backfill
Bedding
Foundation (may not be required) Crown
Invert
Typical Pipe Installation
Installation Methods
HDPE Stay Cable Pipe
Cable Stayed Bridges have galvanized wires strand for supporting cables. These are protected by HDPE pipe in different diameters. We have developed a special type of HDPE pipe in 2-layer construction with the outer layer in diffrent colors like Golden Yellow or Light Blue with UV protection and inner layer in black color. The Ratio of Inner to Outer layer is decided in consultation with the client.
Underground Installations
The care taken during installation will dramatically affect the system performance. In any pipe installation the selection of pipe material plays only 1%, the stiffness of the pipe 2%, the depth of installation 17% and the method of installation 80% role in the performance of the system.
Additional information on pipe burial may be found in the various standards such as : 1. IS 7634 for Installation.
2. ASTM D 2321 - Standard Practice for Underground Installation of Thermoplastic pipe for Sewers and Other Gravity Flow applications.
3. ASTM D 2774 - Standard Practice for Underground Installation of Thermoplastic Pressure Piping.
Typical Trench Size for under ground installation: Generally the pipes are buried at depth of 1 meter depending upon movement of traffic above the ground.
• Trench Width = D + 40 cm. • Minimum Sand Cushion
a. below pipe = (10+D/10) cm, b. above pipe = 15 cm Where D = Outside diameter of pipe in cm.
Buried installations generally involve trench excavation, bed preparation, placing pipe in the trench, backfilling around the pipe, and then placing backfill to the required finished grade. Pipe application and service requirements, size, type, soil conditions,
Installation Methods
backfill soil quality, burial depth and joining requirements will all affect the installation.
Cold Bending of Jain HDPE Pipes: HDPE Pipes can be cold bent to a minimum radius of 20-40 times the pipe diameter as it is
installed. This eliminates the need of elbows for slight bends. The normally recommended radius of curvature is 25 times the pipe diameter to form a bend without kinking the pipe.
Narrow trenching: Since HDPE pipes can either be butt fused in long lengths or it can use in coil form, narrow trench width is sufficient for underground installation. This leads to saving in installation cost. The length of open trench required should be sufficient to bend and lower the HDPE pipes in trench without forming any kinks. The trench width required depends on its depth and type of soil. It should be sufficient to allow the soil to give adequate compaction around the pipe. Generally a trench width equivalent to 50 cm more than the pipe diameter is adequate.
Pipe Embedment: The backfill materials enveloping a buried pipe are shown in the drawing by their function or location. A foundation is required only when the native trench bottom does not provide a firm working platform, or the necessary uniform and stable support for the installed pipe. If a foundation is installed, bedding is required above the foundation.
Bedding: In addition to bringing the trench bottom to required pipe bottom grade, the bedding levels out any irregularities and ensures uniform support along the pipe length. Bedding is required when a foundation is installed, but a foundation may not be required to install bedding.
Haunching: The embedment under the pipe haunches supports the pipe and distributes the load. The quality of the haunching
backfill and its placement are the most important factors in limiting flexible pipe deformation.
Initial Back fill: This is the critical zone of embedment surrounding the pipe from the foundation to at least 150 cm over the pipe. The pipe’s ability to support loads and resist deflection is determined by the quality of its placement. Within this zone are bedding, haunching, primary and secondary zones.
Primary Initial Backfill: This embedment zone provides primary support against lateral pipe deformation. It extends from pipe bottom grade to at least 3/4th of the pipe diameter height, or to at least 6” over the pipe crown if the pipe is installed where the pipe will be continuously below normal groundwater level.
Secondary Initial Backfill: Embedment material in this zone distributes overhead loads and isolates the pipe from any adverse effects from placing final backfill material. Where the ground water level may rise over the pipe, the secondary initial backfill should be a continuation of the primary initial backfill.
Final Backfill: Final backfill is not on an embedment material, however, it should be free of large rocks, lumps, construction debris, stones, stumps and any other material with a dimension greater than 8”.
Recommended Maximum depth of Installation
Type of Load Depth in Meters for various Pressure Classes
2.5 Kg/cm² 4 Kg/cm² 6 Kg/cm² 10 Kg/cm²
Soil Load 4.0 5.0 6.5 10.0