Installation of Buried FRP Pipes with Reka Coupling Jointing System

In general the followings provide two commonly used onshore installation methods and several for offshore installation.

Installation Type1


  • Open required trench and level its bottom according to project plan & profile drawings.
  • Provide the pipeline with at least 100 mm thickness of bedding using type B of soil as described in table 1 with minimum compaction of 85%.
  • Lay down the pipes and connect them according to the provided handling and installation procedure.
  • Backfill the pipe zone up to minimum of 300mm above pipe crown using aforesaid backfilling material.
  • For non-pressure (PN<1 bar) part of pipeline the requirement of compacting of soil over the pipe crown does not compulsory and also native soil may provide adequate strength to form soil-pipe mechanism. Using native soil to fill the pipe zone is only allowed following Farassan’s written approval.
Installation Buried  (GRP) with Reka Coupling Jointing System
Fig1- Ope Trench Installation Type 1

Installation Type2

This method is used when trench wall is strong enough to support pipe in terms of not allowing any ovality. The steps are more or less similar to type 1 while there are few changes in backfilling the FRP pipeline.



Installation Buried Pipe - GRP Pipe
Fig 2 -Trench Installation Type 2


  • Open required trench and level its bottom according to project plan & profile drawings.
  • Provide pipe with at least 100 mm thickness of bedding using type B of soil as described in table 2 with minimum compaction of 85%.
  • Backfill pipe zone up to level of 60% of pipe diameter using the specified backfill material and compact to the required relative compaction level.
  • Use approved native soil to backfill from 60% of diameter upward with a relative necessary compaction to achieve a minimum soil modulus of 1.4MPa.


Note: Installation type 2 is not applicable to small diameter pipes.
Note: Installation type 2 is not suitable for high traffic load conditions.
Alternate installations to accommodate a specific field condition include wider trenches, sheet piles, soil stabilization, use of geotextiles and etc. is to be consulted with engineering department of Farassan©.

As FRP pipe  of Faratec™ can be installed in a number of different situations including above ground, sub-aqueous, trench less and sloped applications, then more specifications, detail and planning may be required, therefore it is strongly recommended to contact engineering team of Farassan for consultation.




Trenching

The trench must be wide enough to permit placement and use of compaction equipment. Also depth of trench depends on pipeline profile drawn according to design requirements. In general speaking width of “2A+DN” shown on Fig 10 is approximately 1.5 times DN.
A typical trench detail for FRP pipe shall be as the followings, The trench must be wide enough to permit placement and use of compaction equipment. Also depth of trench depends on pipeline profile drawn according to design requirements. In general speaking width of “2A+DN” shown on Fig 3 is approximately 1.5 times DN.
A typical trench detail for FRP pipe shall be as the followings,

Trench detail for FRP pipe
Fig 3 -General Trench Information


Where rock, soft, loose, unstable or highly expansive soils are encountered in trench’s bottom, it may be necessary to increase the depth of bedding layer to achieve adequate longitudinal support. Minimum depth of trench shall be according to several parameters such as pipe diameter, level of underground water table, traffic load, pipe stiffness, working pressure of pipeline and etc. Please consult engineering team in this regard.



Bedding
Beddin FRP pipe
Beddin grp pipe


As FRP pipes are flexible so bedding should be properly done not to loose this flexibility and also not to extend it to failure of pipeline system. Choosing right material for bedding with right compaction shall be according to geotechnical study of field. In a very common practice, bedding forms of minimum 100 mm thickness of the same material considered for initial backfilling with at least 85% of compaction. It is suggested to provide Farassan’s engineering team with final and approved revision of geotechnical report so best technical and economical solution for satisfactory backfill underground pipelines. Following table gives general information about initial backfill materials.



Initial Backfill Material - FRP  pipe
Table 1- Initial Backfill Material