Turning vertical challenges into horizontal solutions

In our last newsletter we presented the MDL PVLS - the world’s first road-transportable vertical lay system - and its multi-tasking iteration, the PVLR. Both systems offer a convenient alternative to a pipelay vessel for those smaller or isolated scopes where vertical handling is a must.

But what if we told you that there’s also a way to lay vertically using a horizontal lay system??

Honestly, it makes perfect sense.

The Full Package

An industry-proven alternative to the base case VLS approach is a modular spread of portable equipment that can be installed efficiently on a vessel of choice.

The key benefit of the modular spread is the flexibility it offers to both Operators and Installation Contractors in terms of vessel selection for the execution of the work scope, reducing the ‘all-up’ day rate of an installation vessel. Selecting the correct modular spread for the project is primarily defined by the max top tension foreseen during installation or recovery and the properties of the flexible product.

MDL is a specialist in the delivery and operation of such modular spreads, which can also replicate the functionality of a VLS – in the form of an MDL Horizontal Lay System.

Horizontal Lay Systems (HLS) are not new in the SURF market; what differentiates the MDL design is the packaging of an array of handling aids within the system’s footprint - very much like the PVLS.

There's nothing like seeing it in action, which we captured on this video from APAC operations.

Fixing Friction

These convenient features of the MDL HLS have made it a hugely popular system worldwide, with a track record spanning from China and Western Australia to West Africa - as much for umbilical installation as riser retrieval.?

It has also been the system of choice for a SURF decommissioning programme off South America… until an improvement was identified with regard to recovery loads and tensioner rating efficiency.

Engineering studies with the client's product specifications highlighted limitations on handling the recovered pipes over the HLS chute.

Due to the friction between the flexible and the chute, the system's recovery capacity was dramatically reduced - even when using a high line pull-capacity tensioner.

And so, even though the MDL HLS mobilised with our single-unit tensioner an a 4.5m chute could deliver outboard tension of 100Te, the required load capacity to enable recovery would have to be 185Te.

Did that mean the Contractor was going to be forced down the route of using a costly pipelayer for the retrieval scopes??

We are all about finding leaner approaches to traditional operations, so we couldn’t leave things at that. A bit more engineering together with a look around existing solutions gave us the answer.

We needed a wheel.

MDL Wheeled Horizontal Lay System

The MDL WHLS is our newest technology - and as any MDL innovation, it is built on proven systems, for peace of mind of first-time application success.

The WHLS keeps true to the base HLS design, as the complete package is portable, compact, applicable on vessels of opportunity - in summary, a cost-effective way to kit-out a locally-available vessel to handle high loads and tackle recovery projects.

It still incorporates all the features facilitating recovery of various lengths and diameters of products, including: an integrated hang-off for handling end fittings; davits for overhead handling of products; integrated work platform for over the side or moonpool scopes and an adjustable wheel position to accommodate various product diameters.

By incorporating a wheel into the HLS design, the recovery capacity increases to match the tensioner's capacity without additional space requirements or weight from additional steel structures - along with efficiency surrounding tensioner selection.

The 2-point contact from the wheel profile on the product results in reduced MBR requirements, opening up the OD window for wider application.

The first MDL WHLS has now shipped to its new owner in Brazil - but do you think we should add one to our rental fleet? Do let us know in the comments!

Get in touch with any of our team via LinkedIn or our website if you're interested in the MDL WHLS, or would like to brainstorm how else we can improve the lay, retrieval or mechanical handling operations in the sector you are already in or looking to get into.

Because MDL is not just for SURF - tune back in next month to take a dive through the water column with us.