Non Destructive Testing

ADC Rig Inspection Services recognises that investment in maintenance is as critical in challenging markets as it is in prospering periods. Masts and derricks support enormous loads when drilling and running casing. API recommended practice for mast and derrick inspections is a critical element to avoiding potentially non-productive time or even serious incidents and catastrophic events during drilling operations or following rig reactivation.

Using our own trained, skilled and experienced engineers, ADC Rig Inspection Services is now able to further enhance the quality of their existing rig inspection and commissioning services by providing cost efficient, Non Destructive Testing using liquid penetrate and MPI testing methods, for weld and equipment verification on drilling masts and substructures. These additional services qualify ADC Rig Inspection Services Engineers to complete Category IV inspections as recommended within API Recommended Practice 4G for drilling and well servicing structure inspections.

Non Destructive Testing (NDT)

Welds and equipment therein will encounter design loads and fatigue during product lifetime, however there is a chance that they may fail if not created or maintained to proper specification. During the process of casting a metal object, for example, the metal may shrink as it cools, which may introduce voids or cracks inside the structure.

Some typical weld defects that need to be found and repaired in order to ensure the safe operation of a product are: lack of fusion of the weld to the metal, porous bubbles inside the weld, and variations in weld density, all of which could cause a structure such as a drilling mast and substructure to break or fail.

Tests that reveal defects may indicate flaws that would otherwise cost money, time, and even lives in some cases.

NDT is an analysis technique used widely in the oilfield to determine the state or function of equipment without requiring invasive approaches such as disassembly or failure testing. Therefore it is a highly-valuable technique that can save both money and time in drilling mast and substructure evaluation, troubleshooting, and research.

Benefits

Because NDT does not require the disabling or sacrifice of the drilling mast and substructure, it is a highly-valuable technique that saves both money and time in product evaluation, troubleshooting, and research.

It is noteworthy that NDT methods do not always reveal hidden defects, it is therefore highly beneficial having skilled and experienced NDT Category IV engineers such as are employed by ADC Rig Inspection Services in place of technicians, who are more able to interpret results correctly.

Original equipment manufacturers have recognised the growing demand for API RP4G inspection and recertification. ADC Rig Inspection Services continue to provide qualified and experienced rig inspections which serve to add longevity to equipment, reduce downtime events, and more importantly, provide a safer working environment.

The consequences of inadequate well rig inspection can be catastrophic.

Liquid Penetrant

Liquid or dye penetrant inspection is a method of enhancing the visibility of surface-breaking flaws. Liquid penetrant inspection can be used on any non-absorbent surface such as the drilling mast and substructure to detect surface-breaking flaws, such as cracks, exposed pores, folds or cold laps. Sensitivity is improved greatly by ensuring that the surface to be inspected has been cleaned thoroughly and is free of scale, dirt, grease and other contaminants.

In this method, a brightly coloured or fluorescent liquid is applied liberally to the component surface and left to permeate into any surface-breaking cavities and cracks. The time the liquid is allowed to soak into the material’s surface is normally about 15 minutes. After soaking, the excess penetrant is wiped from the surface and a fine white developer powder is applied. Any penetrant liquid that is trapped in flaws at the component surface is drawn into the developer by reverse capillary action, producing a surface indication. These indications are broader than the actual flaw and are therefore more easily visible. The time it takes for an image to form is no more than a few seconds for a cavity, but over an hour for a fine hairline crack. It is claimed by some that cracks as narrow as 150 nanometres can be detected.

liquid-penetrant

Despite being one of the most widely used NDT methods, liquid penetrant testing is often misused. Test surfaces are often not cleaned adequately, the contact time between the penetrant and the test surface is too short, or the excess penetrant is removed carelessly, i.e. from flaws as well as the test surface.

If applied correctly, the major advantages of liquid penetrant testing are its simplicity, speed, cheapness and ability to cover large areas relatively easily.

Magnetic-particle inspection (MT or MPI)

Magnetic particle inspection (MPI) is used for the detection of surface and near-surface flaws in ferromagnetic materials. A magnetic field is applied to the specimen, either locally or overall, using a permanent or electromagnet. If the material is sound, most of the magnetic flux is concentrated below the material’s surface. However, if a flaw is present, such that it interacts with the magnetic field, the flux is distorted locally and ‘leaks’ from the surface of the specimen in the region of the flaw. Fine magnetic particles, applied to the surface of the specimen, are attracted to the area of flux leakage, creating a visible indication of the flaw. The materials commonly used for this purpose are black iron particles and red or yellow iron oxides. In some cases, the iron particles are coated with a fluorescent material enabling them to be viewed under a UV lamp in darkened conditions.

As previously stated MPI is used to detect surface-breaking and near-surface flaws in ferromagnetic materials. It cannot, however, be used to detect deeply embedded flaws, nor can it be used on non-ferromagnetic materials, such as aluminium, copper or austenitic stainless steel.