Materials Selection

Z-Subsea Materials/Welding/NDT Engineering group provide integrated full life cycle services to the oil and gas industry. The group involvement starts from Concept/Design phase and continues to Construction, Procurement, Fabrication, Installation and Operation phases. Due to the growth in number of aged assets in regions such as North Sea, the group specifically offers specialised services beyond the design life or assets Life Extension (LE).  

As part of successful oil and gas project execution, appropriate materials in various forms such as pipelines, piping system, pressure vessels, subsea structure, etc. should be selected, procured, fabricated and installed. Fit for purpose of the selected materials in terms of the operational condition, resistivity against wear, fatigue, corrosion and protecting requirements (coating and CP systems, etc.) are amongst other Z-Subsea in-depth materials/corrosion offering to the industry. At Z-Subsea, our materials Engineering group has the necessary capability and expertise to deliver the above services starting from high level materials screening/selection during the conceptual phase, provision of procurement specifications especially for the long lead components (Corrosion Resistance Alloys, Clad/lined materials, etc.), support during the operation until the end of the design life and beyond (asset life extension) with aiming at reducing the total life cycle cost. 

Z-Subsea materials group could also assist our client by provision of support on procurement specifications, Component fabrication, Vendor assessment and qualification.


Welding is the most commonly utilised joining process in the oil and gas industry however its quality needs to be demonstrated during the fabrication phase of a project. That said in order to assure integrity of oil and gas welded components; welding procedures specific to each project should be prepared and qualified to recognised standards such as BS4515:2009 and DNV OS-F101 checked by welding

Engineers. At Z-Subsea, we have qualified welding engineers onboard so we screen appropriate welding procedures for each project at the conceptual phase (high level screening) and qualify nominated procedures at the Design stage for application in Fabrication, Construction, Installation and operation (Repair, if applicable) phases.


In case of existing assets, welding experts at Z-Subsea assist our clients by independent/impartial review, audit, and upgrade of existing welding procedure specifications.

Non-Destructive Testing (NDT)

In order to provide assurance to our clients in terms of the quality of the procured and/or fabricated materials/welds, Z-Subsea Non-Destructive Testing (NDT) experts could perform on-site and/or laboratory based NDT services during the Procurement, Fabrication, Construction, Installation and Operational phases of a project. At Z-Subsea we have access to qualified NDT Level II and III experts (qualified to certified to BS EN 473 level II or equivalent) who can deliver high quality services on time and within the project allocated budget.

In conjunction with the integrity engineering offering, Z-Subsea NDT team assists our EPC contractors in developing defect acceptance criteria (Tolerable flaw size) for pipeline girth welds and subsequent adjustment after including inspection sizing tolerances. Moreover, Z-Subsea NDT expertise provide valuable information to the operators during their decision making period for repair and life extension studies for aged assets.

Corrosion Control (Coating, CP Systems)

Corrosion mechanisms modelling as part of the materials selection study or Integrity Engineering services (Fitness for Service (FFS) assessments)

Corrosion protection services such as suggestion of the inhibition strategy, preparation of CP design philosophies, reviewing and upgrading existing CP procedures, performing CP surveys (Offshore/onshore) and coating selection and survey.