Pipeline Vehicles

VariPig

FTL’s VariPig is a multi‑diameter pipeline pigging solution engineered to navigate complex pipeline systems with exceptional efficiency and repeatability. Designed to run on the true pipe centreline, VariPig is self‑centring to maintain stability across large diameter transitions. Ensuring low friction, low differential drive pressure, and consistent sealing performance. With a proven track record in challenging, “difficult‑to‑pig” pipelines, VariPig delivers reliable dewatering, cleaning, gauging and commissioning across a wide range of offshore and onshore applications.

VariPig - the multi-diameter pipeline pig

To meet the demands of pigging increasingly complex pipeline systems, there is a drive to provide pipeline pigs with increased flexibility, adaptability, operational repeatability and improved efficiency.

FTL developed the multi-diameter capable VariPig to meet these increased challenges and the modular system now has a proven track record of successful project completion in ‘difficult to pig’ pipelines.

Varipig is the name given to our multi-diameter capable pigging system (Varipig is a patented system).

Typically two suspension arm modules are coupled together or a single offset suspension arm module is created to build a Varipig for a given application.

The basic suspension system comprises a number of suspension arms connected to a central piston, so that when one wheel arm deflects, the other arms will also deflect.

A spring loaded piston forces the suspension arms outward.

The basic principle of operation is that the combined total spring force acting on the pistons is greater than the weight of the pig therefore the pig rides on its true geometrical centreline.

Any pipeline feature causing the pig to deviate from the pipeline centreline is immediately countered by the restoring force thereby restoring centreline running.

Repeated testing and field experience has shown that the Varipig suspension system will run within 0.2% of pipe centreline.

VariPig suspension system

The Varipig suspension system is the key to optimising any pigging operation due to the removal of typical key pig performance inhibitors:

Drive pressure differential

With pre-commissioning, commissioning and even for operational cleaning having a low differential drive pressure is considered as beneficial.

The contribution to total pig friction (differential pressure across the pig) from the wheeled suspension modules is negligible in all pipeline diameters, as it is merely rolling friction from the wheels.

Changes in diameter

The changes in a multi- diameter pipeline require careful analysis when looking into seal design for the diameter changes.

When operating in the larger diameter pipeline the seal needs to provide an effective seal (e.g. for dewatering) but must then be able to fold down when entering the smaller diameter pipeline without inhibiting performance.

Drive discs can be sized to give the desired benefit for a pigging operation by minimising the need to oversize to compensate for negotiating bends and pipeline features.

Distance to Travel

One of the main objectives when looking at pigging long distances is seal wear both in constant bore and multi diameter pipelines.

The functional discs will have controlled wear due to induced pig rotation by the suspension which in arduous or long operational runs gives optimum performance.

Utilisation and repeatability

The vehicles can be quickly re-configured around the basic Varipig platform to perform multiple roles in a single run.

The same vehicle can be used for different functions as the suspension can be tuned to account for different load carrying requirements.

Previous Experiences

The Varipig system has been shown to provide both a stable centralised rotating platform, to allow optimised seal design/reduce seal wear, as well as requiring a low drive pressure. The Varipig system has been successfully deployed within dual/multi-diameter pipeline systems and over long operational distances.

Application