eSubsea can perform PLEM engineering, procurement and construction (EPC) including 3D modelling and drawings, structural analysis, piping analysis, design and verification of PLEM Pipeline End Modules or Pipeline End Manifolds or PLET Pipeline End Terminations or FLET Flowline End Terminations.

The PLEM, or PLIM, if the structure is located in-line the pipeline, is basically a simple subsea manifold at the end of a pipeline where the flow is split into branches and connected to the production or injection wells located on the subsea templates or manifold via flexible or rigid jumper spools.

eSubsea can through our partners also design, fabricate and deliver complementary subsea connection systems for any subsea pipeline or piping module.

Did you know that eSubsea and our partners deliver engineering and design services and subsea hardware to the North Sea, Gulf of Mexico, Canada, Australia, West of Africa, Brazil and Russia?

PLEM Design, Analysis and Engineering

The pipeline end manifolds consist of a suitable foundation structure based on the soil conditions at the site. If the soil is soft clay, mudmats are included to give sufficient bearing capacity. Skirts may also be required for lateral support and sizing will depend on the penetration resistance and self-weight of the structure. The foundation structure also supports the inboard connection system, valves and piping by the HUB porch and valve and pipe supports. Sliding supports are used to minimise loads from thermal expansion of the pipeline. The static and dynamic structural analysis, including buckling analysis, is performed using structural analysis beam theory software as SAP2000. For local stress and fatigue hotspot analysis, we use Solidworks Simulation or ANSYS. The piping can be analysed using our advanced pipeline analysis software TRIFLEX and to any piping design code, but most common are ASME B31.3 for small bore piping or tubing and B31.8 for large bore piping. Evaluation of flow induced vibrations (FIV) are also part of the piping detail design.

Subsea Pipeline End Modules PLEM PLET FLET - eSubsea

The shallow or deepwater PLEM foundation structures will be designed for all loads as transportation loads, tie-in loads, thermal expansion and flow induced vibrations (FIV). The PLM protection structure, which could be GRP covers, will also be designed for dropped object loads and fishing gear impact if there is fishing activities in the area. The corrosion design will be by cathodic protection using sacrificial anodes as per DNVGL-RP-B401.

Installation of Pipeline End Manifolds

The PLEM PLET could either be installed with the pipeline or it can be installed separately and later tied-in to the pipeline using subsea tie-in systems. The installation could be first-end or second-end installation. Another option is to install the modules using the drilling riser on a drilling rig. The PLEM structure with the lifting and lay down arrangement is analysed for the installation loads using structural analysis. The lay down method of the pipeline could be S-lay or J-lay. A hinged lifting yoke is often used to minimise torsion and bending loads during lay-down.

One important aspect of the PLEM structure design is to optimise both the size and weight as this is often critical in particular if the PLET is welded to the pipeline or flowlines on the pipe lay vessel and is overboard with the pipeline.

The PLEM structural analysis will include the following load conditions: Fabrication, testing and handling at fabrication site, transportation, load-out and installation lifting analysis, in-place operation condition including pressure and temperature expansion, pipeline expansion, earth quake, trawling, dropped objects etc.