About Subsea Inspection

Sonomatic Subsea is a leading provider of ROV and Diver Deployed robotic technologies capable of advanced subsea inspections. With over 30 years of experience in this field, and the ability to adapt existing technologies to suit specific client requirements, Sonomatic subsea are industry leaders in the field of subsea advance inspections.

Sonomatic brought innovation to the Oil and Gas market by introducing Time of Flight Diffraction (TOFD) in the 1980s and has continued to bring world-leading technology to our clients. We are unique amongst other inspection service providers, in that we design/develop, and build our own inspection systems and scanners that can and have been modified over time to meet specific requirements for inspection performance, deployment and in-field reliability.

Sonomatic is committed to providing accurate, proactive inspection solutions that enable clients to manage the integrity of maturing assets, while making informed and cost-effective decisions crucial to the extension and safety of plant life. We pride ourselves on our proven track record in the management and safe delivery of inspection services for subsea operations.

With the support of our internal integrity division, we can assist operators by providing not only the field data but a range of integrity services, including innovative statistical analysis methods that ensure decision making is aligned to the real conditions of subsea assets.

Diver Deployed Inspection Solutions

When scopes require a high level of dexterity and may need on-site adaptability, Sonomatic can utilise divers in a wide array of subsea and splash zone NDT inspections.

Work-Class ROV Solutions

Work-Class ROVs overcome many of the key issues presented when using divers (issues with depth, high cost, risk factor, etc.). Sonomatic has developed a range of ROV tools specifically designed to inspect pipelines, risers, caissons, and structural assets. Many of these tools are adaptable and can operate both horizontally and vertically. Our tools can be used in a range of services including:

  • Verification of ILI tool findings
  • Inspection for internal corrosion and erosion
  • Inspection for preferential weld corrosion/erosion
  • Inspection for fatigue cracking (TOFD)
  • Inspection for wet H2S damage in sour service
  • Inspection for chloride pitting/SCC in corrosion resistant alloys
  • Inspection of subsea fabrication and repair welds
  • Component geometry measurement including ovality inspection

Mini-ROV Inspection Solutions

Mini-ROVs provide clients with a reliable, safe and cost-effective alternative to divers or work-class ROVs. The size and weight of Mini-ROVs make them ideal for jobs that require rapid mobilisation or where access is an issue. The deployment method can also be tailored to each situation, with the Mini-ROVs having the ability to be fitted with front-facing NDT attachments or deploy heavier tools in a payload capacity.


If your project includes the inspection of subsea structures, then there are many reasons to consider an ROV advanced inspection. The benefits of such inspection approaches include, but are not limited to:


Subsea inspections can sometimes seem like a costly venture, needing a team operating manned underwater vehicles to perform such duties. Subsea ROV Advanced inspections come in handy in this situation as they are significantly more cost effective and can be operated below the water for longer periods of time. This in turn makes inspection available at a low cost, saving money across the entire project.

Value of Data

Operating inspections on a project should be efficient and save time that can be used in other areas. Subsea ROV Advanced Inspection encodes all inspections with high precision data and good repeatability; this makes all inspections as efficient with the highest value possible.

Better Safety

Safety is an integral part of any project – big or small, above or below water. Since Subsea ROV inspections can be performed by operators above ground, the risk to workers is significantly reduced. Such high levels of safety are highly sought after, making these inspections a great choice.

Frequently Asked Questions

TOFD is a method of accurately sizing and monitoring the through wall height of in-service flaws.It is effective for weld inspection flaw detection irrespective of the flaw type or orientation. TOFD doesn't rely on the reflectivity of the flaw, but uses diffracted sound initiating from the flaw tips. TOFD main advantage is that it has a through wall height accuracy of +/- 1 mm, and a crack growth monitoring capability of +/- 0.3 mm, on defects of all orientations. 

DRS is a proprietary technology developed by Sonomatic using frequency-based ultrasonic wall thickness measurements. It is a corrosion mapping technique that applies a broad range of low ultrasonic frequencies (<1 MHz) to penetrate challenging coatings such as composite repairs, PE and Neoprene, and excites the natural frequencies of vibration of the underlying steel. The DRS probe raster scans over an area of interest and collects response signals. Advanced signal processing algorithms have been developed to extract the vibration frequencies and map the wall thickness profile.

PEC is a comparative technique whereby advanced processing of the eddy current signal decay and comparison with a reference signal, allows for the determination of the average wall thickness (AWT). This fast-screening method allows for the assessment of the general condition of structural steel and is best suited for general corrosion-type defects in subsea pipelines. A major benefit of PEC is its ability to inspect through challenging coatings such as concrete weight coat, and marine growth.

Cathodic Protection is a technique used to control the corrosion of a metal surface by making it the cathodic side of an electrochemical cell. The simplest method to apply CP is by connecting the metal to be protected with another more easily corroded metal to act as the anode of the electrochemical cell.

Alternating Current Field Measurement is an electromagnetic technique for detection and sizing of surface-breaking indications. It works on all metals, does not require direct contact and works through various thicknesses of coatings. This technique  can accurately detect and size linear indications both length and depth. It is also easier to use on complex geometries such as nodes and nozzles.

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