EPRS & Subsea Services
Although pipelines are accepted as a safe form of energy transportation, failures can and do occur. Damage sustained to a submarine pipe in particular, can prove challenging to repair. As identified in DNV GL RP F113 Subsea Pipeline Repair, the main cause of pipeline damage is caused by a degradation mechanism such as corrosion, Hydrogen induced stress cracking (HISC) or physical damage such as unstable seabed conditions, anchor strike, dropped objects and trawl gear interference. In cases where pipeline damage has occurred, the damaged section may need to be cut from the pipeline and replaced with a new pipe section or repaired in-situ. As well as pipeline repair, STATS temporary isolation solutions allow safety critical valve replacement, tie-in or re-routing of pressurised pipelines.
STATS has developed a range of subsea pipeline repair solutions which includes inline isolation tools (Tecno Plug), hot tap and plugging equipment (BISEP), mechanical connectors, structural repair clamps and pipeline retrieval tools.
Subsea Pipeline Repair Clamps
Subsea Pipeline Repair Clamps
STATS subsea repair clamps feature a robust design to provide effective leak sealing in the harshest conditions. Subsea clamps are available for diver installation or ROV deployment. The dual seal design provides pressure containment with annulus test capabilities and, where grout filled, radial support to the pipe.
Taper locks can be included in the design where necessary providing axial restraint and structural integrity. The locks are configured as opposing sets which grip the pipe on either side of the defect. The locks are designed to transfer the full axial load of the pipe to the clamp body so allowing the clamp to withstand full pipeline separation loads.
Diver or ROV installed clamps include:
- Structural repair clamps (locks and dual seals)
- Pressure containment repair clamps (dual seals)
- Size range – nominal pipe sizes 4” – 46”
- Pressure range up to 300 Bar
- Seal against pipeline using compression flanges
- Dual seal with annulus test capability
- Taper locks to prevent pipeline separation
- Clamps available for subsea pipelines, risers and caissons
- Optional polymeric grout sealant injection
ROV installed Pipeline Repair Clamp
ROV installed Pipeline Repair Clamp
ROV installed Split Sleeve Repair clamps utilise hydraulics and assembly frames to allow the ROVs to assemble the clamps on the pipe. These clamps are often engineered on a project basis and consist of a hydraulically actuated hinge to fasten the clamp around the pipe. A hydraulically operated taper flange assembly allows the clamp halves to be securely closed and the end compression seals are actuated by an array of hydraulic pistons. The taper flange mechanism and compression seal pistons are retained with ratchets to allow the hydraulic pressure to be vented after clamp installation. ROV clamps can be supplied in single seal, dual seal and structural configurations to repair pipe where fittings restrict access.
- Size range: nominal pipe sizes 4” – 24” as standard
- Pressure range: ambient to 144 Bar
- Hydraulically activated clamp
- Deployed by ROV
- Mechanical lock and elastomer compression seals
- Designed to suit application
Pipeline Retrieval Tool
Pipeline Retrieval Tool
Pipeline Retrieval Tools facilitate the laydown or recovery of subsea pipelines and are designed for lifting large diameter pipe and heavy loads. The laying of subsea pipelines involves the placement of large diameter tubulars in an environment where extreme forces or motions may result in buckling and flooding the pipeline. In this event, the damaged pipe section must be removed and a repair process implemented. The replacement pipe may be tied-in using hyperbaric welding facilities, or the pipeline end may be recovered to the pipe lay vessel for surface repairs.
A Pipeline Retrieval Tool provides the connection between the pipeline and the recovery cable required to handle or manoeuvre the pipeline end. The Pipeline Retrieval Tool engages in the pipeline bore to provide a secure but controllable facility for the connection of the retrieval cable.
Tapered locks featuring the Diamondlock™ tooth profile operate on a wedge principle, improving the connection efficiency as the load increases. Once set, this fail-safe mode of operation enables the mechanical connection with the pipeline to remain secure independent of the tool hydraulic activation system. A seal and vent system within the Pipeline Retrieval Tool assembly enables the pipe to be de-watered prior to the lifting operation.
STATS comprehensive range of Pipeline Retrieval Tools and track record in this highly specialised engineering and manufacturing sector includes tools in a range of 6” to 48” diameter.
- Size range: 6” to 48”
- Taper lock-ring to anchor tool
- Fail-safe design feature; lock & seal energised as load increases
- Seal and vent system enables dewatering prior to pipe lifting
Emergency Pipeline Repair Systems
Emergency Pipeline Repair Systems (EPRS)
Despite good pipeline design and integrity management schemes pipelines can and do get damaged and need to be repaired. The damage could be caused by a number of factors such as, a dragged anchor, landslide, iceberg impact, fatigue or stress cracking. The resulting damage may be unpiggable in the form of a buckle or dent, with or without rupturing the line. Following an inspection of the line and assessment of the defect, repair may require replacement of a section of pipeline.
Emergency Pipeline Repair equipment include
- Tecno Plug, Pipeline Isolation
- BISEP, Hot Tap and Isolation
- Mechanical Connectors
- Structural Repair Clamps
- Pipeline Retrieval Tools
Without suitable double block isolation tools installed locally at both sides of the damaged section; it will be necessary to depressurise the entire section of pipeline to allow safe removal of the damaged section and perform the repair by installing a new section.
Depending on availability of emergency repair equipment the time to return a pipeline to service could be more than 1 year, particularly in a subsea pipeline. However, with appropriate planning and investment in equipment, including isolation tools and procedures this could be reduced to approximately 6 weeks.
A pipeline’s out of service time, following an incident, can be reduced with strategic investment in specific elements of an Emergency Pipeline Repair System (EPRS).
The time to repair can be reduced to approximately 6-8 months, simply by developing detailed procedures for potential repair scenarios and procurement of long lead items; such as large forgings for clamps / mechanical connectors, replacement pipe and flanges all reduce the reaction time.
Further substantial time savings can be achieved if the EPRS equipment has been manufactured and kept in a state-of-readiness for emergency deployment. This could potentially reduce a pipeline’s out-of-service time to less than 100 days.
Even with an Emergency Pipeline Repair System in place, if suitable isolation tools are not available, the time from incident to resumed production can be over 3 months. The decommissioning (flooding and depressurising) and re-commissioning (leak testing / dewatering) stages will be a significant proportion of the out-of-service time, potentially more than 60% of the downtime.
However, with pre-invested isolation tools available the pipeline return to service time will be reduced, potentially down to less than 6 weeks. Additional benefits from this investment include a safer worksite, minimising content discharge to the environment and reducing inventory losses. The prevention of seawater ingress negates the need for a timely dewatering and drying programme, reducing the time to repair and ensuring production outage is minimised.
Abandonment and Decommissioning
Subsea Pipe End Plug
Subsea Pipe End Plugs can be supplied as a temporary or permanent cap to terminate open pipe ends. They provide a robust isolation barrier to prevent seawater ingress or residual hydrocarbon escape to the environment. The Pipe End Plugs are supplied with securing wedge locks to ensure security of the isolation plug in the pipeline at the specified pressures, and the large section elastomeric compression seal provides a leak tight seal, even in corroded and pitted pipework.
These high performance plugs are lightweight and simple to install by diver or ROV. Once inserted into the open pipe end, the plugs are activated and set in position by applying torque to the plug torque interface. To aid installation the Pipe End Plugs are supplied with a handling bracket and buoyancy as required.
The Pipe End Plug lock and seal technology is based on the Tecno Plug™ range of high pressure isolation tools which have an extensive track record covering a range of pipe sizes, pressures and mediums including, gas, crude oil and condensate.