Working closely with our Clients, Vertech can plan for under water inspection programmes during in-service periods such as active drilling operations, during shut down periods, or while producing*. We are experienced in complying with the inspection mandates for the various class societies. Vertech owns and operates a fully certified Zone 2 Diving system that allows Surface Diving operations to be carried out where a Zoned requirement is required.
U.W.I.L.D (Underwater Inspection in Lieu of Dry Docking
These inspections are required to ensure the structural and operational integrity of an offshore asset such as a Mobile Offshore Drilling Units (MODU’s), Semi-Submersible type marine vessels involved in offshore operations.
This type of survey carried out with Divers, while on location, saves the asset owner both commercially and operationally by reducing downtime, limiting time off-contract, and reducing or eliminating the need for costly and limited dry dock space. This type of survey is carried out under Class requirements.
Special Periodic Survey (SPS)
An SPS can be carried out in line with a UWILD Survey and this is unique to each vessel or rig with a class society representative onsite to confirm the requirements of the survey.
Eddy Current Inspection (ECI)
Eddy current testing is an inspection method that can be used for a variety of purposes including the detection of cracks and corrosion, material and coating thickness measurement, material identification.
This method of inspection can be carried out without removing any paint coating to the parent material
Time of Flight Diffraction (TOFD)
A computerised and automated system for weld inspection. Probes are mounted on a buggy which our divers move along the weld under inspection, recording data as it moves. This method uses an ultrasonic pulse to determine the position and size of a reflector.
Magnetic Particle Inspection
A simple-to-use inspection method to identify surface and near surface defects in ferrous materials by applying a magnetic field where lines of flux produces a leakage field around the defect.
Where a defect exists particles within the ink fluoresce when a black light is shone over the area under inspection. This method requires parent metal to be cleaned to SA2.5.
Ultrasonic Thickness Inspection (UT)
A method for measuring the thickness of a material. A probe is placed on the material under inspection where a piezo electric crystal produces a pulsed echo from the unit with the time displacement signal converted into a readout that can be recorded to confirm material thickness or sub surface depth to a defect.
This process requires the area under inspection to be free of marine growth and the removal of any paint coating.
Close Proximity Cathodic Measurement (CP)
The tip of a hand held meter is placed onto the material being inspected where a corrosion cell is set up with the seawater acting as an electrolyte where a measure of any potential difference is measured in mV with a digital readout on the hand held meter.
This process requires the area under inspection to be free of marine growth and the removal of small area paint coating for good tip contact with parent metal.
Proximity Cathodic Measurement
A non-contact method where a Proximity cell connected to the surface and earthed to the asset under inspection is used to record readings on a topside unit.
General Visual Inspection (GVI)
General visual inspection surveys are carried out to determine marine growth coverage, % anode depletion or basic condition of a localised area under inspection.
Close Visual Inspection (CVI)
A more detailed visual survey, usually of weldment areas to determine if any visual defects of a weld can be identified, where defects or known defects such as undercut, localised and general areas of pitting, spatter, porosity and crack like indications are measured and recorded and compared to previous readings. This process normally requires the area under inspection to be cleaned to SA2.5 and carried out prior to MPI.
Our divers record an area under inspection using a head mounted or hand held video camera where known anomalies are recorded digitally.
The Diver carrying out the inspection will give a running commentary throughout and may be asked to confirm items from the Inspection co-ordinator.
Where video grabs may be taken from the Divers video Survey or by means of the diver using dedicated underwater cameras for general stand-off photo’s or close up photos may be taken such as a mosaic of a weldment area for subsequent top side interrogation.
Alternating Current Field Measurement (ACFM®)
Alternating current induces a uniform electro-magnetic field into the surface of the parent metal. This field is disturbed by surface-breaking defects.
Sensors measure the disturbances and locate the defect. The interaction is recorded and modelled using advanced mathematics, allowing sizing for depth and length without the need for on-site calibration.
This technique has been used across a wide range of applications including:
- Node welds on lattice type structures
- Caissons/ Risers
- Welded plate structures
- Chain Mooring Systems Jack-Up spudcans
This advanced method of UT is used to find potential flaws in material (welds for instance).
Whilst non-phased array or monolithic probes emit a beam in a fixed direction and then move, phased array, because of it's multiple elements that can pulse individually, allowing the beam to be controllable. This method is particular beneficial when interrogating larger volumes of material. making the interrogation of larger areas more efficient.