Making waves with new testing technologies

A yacht surveyor uses the EPOCH 650 flaw detector to examine composite materials
A yacht surveyor uses the EPOCH 650 flaw detector to examine composite materials

Inspection and measurement system specialists, Olympus IMS explains how yacht inspectors can overcome the challenges of unique boat materials, designs, and standards using a combination of the company’s ultrasonic equipment and NDT expertise.

 

Ultrasonic testing (UT) uses high-frequency sound waves to conduct examinations and make measurements without damaging the test material. In the marine industry, this non-destructive testing (NDT) method is used to assess composites as well as other boat materials to check the structural integrity and safety of vessels. However, ultrasonic testing of yachts and other pleasure craft can be challenging due to the unique boat materials, designs, and standards in the industry.

The International Association of Classification Societies (IACS) provides a system to promote the safety, regulation, compliance, and maintenance of ships and offshore units. Each society establishes rules with technical standards.

Despite these standards, NDT is not mandatory in the marine industry, and inspection documentation is not included for a yacht or pleasure craft if an IACS member does not classify it. Due to the artisan background of most yacht manufacturers, many building skills are not standardised, and most yachts are built without inspection in mind. Interiors packed with liners, equipment, tanks, lines, and machinery can prevent access to the hull shell and its reinforcement from the interior. Dismantling is often only justifiable after a flaw or damage is strongly suspected.

Unique challenges

Boat materials can be challenging to inspect. To minimise weight, many modern boats are built from composite materials that combine fibres and resin matrices. Fibres might be randomly arranged, then flattened into a sheet (known as a chopped strand mat) or woven into a fabric. The fibre material is often glass, aramid, or carbon; the matrix is often based on polymers such as polyester, vinyl ester, or epoxy resins. Due to the fibre-reinforced composites commonly used in boats and the decreasing safety margins of boat designs and materials (e.g., thinner hulls in modern yachts), the need to characterise and find flaws in the materials has increased.

A serious flaw in a mast detected using the EPOCH 650 flaw detector
A serious flaw in a mast detected using the EPOCH 650 flaw detector

Hidden internal flaws and defects in a composite structure can have many sources: manufacturing anomalies, applied stresses or weaknesses, accidents, or improper repairs. Flaws and defects can significantly impact a boat’s structural integrity.

This is where ultrasonic testing comes in. UT can be used to detect and evaluate flaws, take dimensional measurements, perform material characterisation, and more. Inspectors can use an ultrasonic flaw detector to accurately locate and size flaws, cracks, voids, delaminations, and other defects in boats, yachts, and other marine vessels. Ultrasonic flaw detection can be applied to almost any engineering material. Most tests involve steel and other structural metals, but flaw detectors are being used with great success on composites, fibreglass, as well as plastics and ceramics. A flaw detector can also measure material thickness reasonably but is not designed for precision thickness.

NDT inspection can be performed during the vessel building process, pre-delivery, pre-purchase, routine surveys, damage inspection, or as a part of post-repair inspection. In the commercial marine craft industry, ultrasonic NDT is regularly performed on steel and aluminium vessels to detect and quantify corrosion. In similar ways, ultrasonic NDT can be used to measure the thickness and integrity of composite structures.

UT for yacht surveys

Yacht surveyors conduct surveys on used and new sea vessels to verify their condition and value, as well as determine and evaluate damages. Without standardised building skills and reference standards for yacht manufacturing, surveyors must use their knowledge and experience to develop effective inspection procedures. For example, yacht surveyor, marineSOLUTIONS set up a small lab to examine different boat materials from multiple composite material types to different metals.

Olympus customer, marineSOLUTIONS uses ultrasonic testing for vessel surveys. The company’s surveys include ultrasonic testing with an Olympus EPOCH 650 flaw detector on composite boats, spars and other boat components. To inspect composite vessel structures and materials, marineSOLUTIONS’ engineers pair the EPOCH 650 flaw detector with an Olympus M2008 delay line transducer (0.5MHz, 1inch diameter). This transducer is ideal for highly attenuative composite structures. 

“Composite materials for yachts are anisotropic, which makes it even more challenging,” states Cem Baykent, a materials science engineer and surveyor at marineSOLUTIONS. “You can tell more about anisotropic materials using the M2008 transducer. The M2008 is very strong to get through thick fibre reinforced polymer (FRP) composite materials.”

In composites, ultrasonic testing can be used to detect uniformity of laminate thickness, presence and type of delaminations, presence of voids and/or porosity, quality and bonding of laminate and integrity of repairs, and inclusions and alien material presence in laminate.

Ultrasonic testing of composite boats and spars has many advantages, including: One-sided access is sufficient; Portable equipment for inspections at remote locations and working aloft; Minimal or no surface preparation; Highly accurate in determining the exact point of a hidden anomaly and its main characteristics, such as depth, size, and shape; Provides instant results and data.

NDT technology, such a flaw detector is a powerful way to determine the integrity of a boat’s components or structure and discover flaws without causing any damage. Since NDT does not harm, stress, or destroy materials, it saves time and costs when inspecting boat structures and components.

www.olympus-ims.com

Company

Olympus IMS

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