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Freespan correction

Pipeline Freespan correction

OCS owns and operates a full suite of pipeline free span correction equipment. Pipeline free spans occur where bottom roughness on the seabed creates a situation where the pipeline spans between high points. Such spanning beyond certain prescribed limits creates over stressing during hydrotest or operations. Spans are corrected by placing grout bags underneath the pipeline and filling them with liquid cement or grout. Excessive unsupported spans have to be corrected prior to pipeline pre-commissioning (flooding) so it is often advantageous to combine free span correction and pipeline pre-commissioning contracts.

OCS operates all the required equipment in-house and our technicians are multi-skilled enabling the customer to take advantage of the natural synergies and enhancing efficiency and cost effectiveness with a single contract award covering both services.

Principle Equipment involved with free span corrections:

  • Cement Storage Silos.
  • Air compressor to transfer cement to grout
  • Grout Mixer.
  • Grout Pump.
  • Hose Spooler with Chiksan.
  • Grout bag deployment turntable equipped with a quick connect box.
  • A frame or crane for deployment of turntable

OCS provides grout bags specifically configured for the pipeline diameter and span height.

The deployment vessel must be equipped with divers or an ROV to handle turntable operations or deploy the bag direct.  Grout is mixed in prescribed quantities on the surface and pumped into the bag while monitored by the ROV or divers.

The grouting distribution systems provide a delivery and recovery of HP grout hoses in water depths to 600m. This delivery system comprises of a hydraulically powered hose spooler incorporates a chiksan that allows grout to be pumped continuously while the hose are still on the reel.

OCS’s cement silos’ are in gauge 20ft standard ISO configuration. They are easily transported by conventional shipping container lines and well suited to intermodal transportation. The silos are provided with TIR, CSC certification.

OCS is equipped to handle the full range of free span correction activities utilizing grout bags to water depth up to 1400m and span heights to 3.0m. For spans height in excess of 3m,an alternative span correction method may need to be employed from the standard grout bag system as other technical challenges, eg, soil foundation stability; grout volume will need to be considered.

OCS is equipped to handle large projects or discrete project elements depending on the specific needs of the customer. During the preparation for free span correction or any offshore work, the safety of personnel, equipment and environment plays a vital role in the success of a project and as such, HAZID’s shall be conducted prior to any operations. These meetings are attended by key engineers and supervisors and all potential risks are identified and mitigation measures put in place to ensure they are as low as reasonably practicable.

OCS has undertaken eleven (11) major free span correction projects for different customers;

Year Client Project Scope
PTSC / Shelf Subsea
Sao Vang – Dai Nguyet (SVDN)
Free span correction for 26” spur line
PT TimasSuplinda / Sapura Offshore
Free span rectification for i. 18inch x 13.347km pipeline for Shallow Water (WD 70m to 100m) and ii. 18 inch x 32.9km pipeline for Deep Water (WD 150m to 1500m)
OPHIR Energy Plc (Madura Offshore)/PT TimasSuplindo
Free span correction for 10” pipeline x 11 km
Shell / Technip
Free span correction for 10” and 8”piplelines
Free span correction for 110 km x 12” pipeline
Leighton Offshore
12” Pipeline X-Ray field to Balongan pipeline
Hess Carigali / EmasHessCarigali / Emas
FPSO Flexible Riser Supports
Pertamina EP / Timas
Pipeline Hot tap and Gas Diversion
Zawtika (Phase 1A)
2 x 18” pipelines (10km each)
Conoco Phillips/Timas
8” x 150m tie-in spool from Tembang Tee to T8 Well
Conoco Phillips/Timas
14” pipeline x 40 km and tie-ins

Pipeline Free-span Correction: Pre-Qualification Document: Download