Last update: July 1, 2015

Inspection is the act of examining the physical condition of a piece of equipment in order to determine if and for how long it will operate as intended. Inspection plays a vital role in any asset integrity management program. There are several different inspection techniques, some that use advanced instrumentation, others that do not.

Some examples of inspection techniques are:

Visual Inspection

Visual Inspection is the oldest and most basic method of inspection. It is the process of looking over a piece of equipment using the naked eye to look for flaws. It requires no equipment except the naked eye of a trained inspector. Although, equipment can be used to improve the range or accuracy of visual inspection, including things like remote visual inspection techniques and unmanned aerial systems.

Ultrasonic Testing

Ultrasonic testing actually refers to group of related nondestructive examination (NDE) techniques that all use short, high-frequency ultrasonic waves. They generally work by emitting waves into a material and measuring these waves in order to identify the properties of the material and any internal flaws. Some specific ultrasonic inspection techniques include long range ultrasonic testing, phased array ultrasonic testing, and time of flight diffraction.

Hydrostatic Testing

Hydrostatic testing is process where components, such as piping or pressure vessels, are tested for strength and leaks by being filled with pressurized liquid. This is done until until a specific pressure is reached. The pressure is then held for a specific amount of time prior to a visual inspection for leaks. For pipelines, the pipeline is removed from service before testing, all oil or natural gas is vented off, and the line is mechanically cleaned prior to hydrostatic testing.

Liquid Penetrant Examination

Liquid penetrant examination (LPE) is an NDE inspection method that uses fluorescent dye. It is one of the easiest and most common inspection techniques in the industry. The process is able to reveal surface flaws on parts and equipment which might not otherwise be visible. The technique works via the principle of “capillary action.” A process where a liquid flows into a narrow space without help from gravity.

Magnetic Particle Testing

Magnetic particle testing (MPT) is a nondestructive inspection technique for detecting surface and slight subsurface flaws. It works on most ferromagnetic materials such as iron, nickel, and cobalt along with some of their alloys. The process involves magnetizing materials to reveal flaws that would not normally be visible. The process works by running a magnetic current through the component. Any cracks or defects in the material will interrupt the flow of current, create a “flux leakage field.” Metal particles flow over the component and congregate around the fields.

If you're interested in learning more about magnetic particle testing, Inspectioneering has created a free resource on the subject. Click here to download our Asset Intelligence Report: A Primer on Magnetic Particle Testing. 

Magnetic Flux Leakage

Magnetic flux leakage (MFL) is a NDE technique that uses electromagnetism. It works by using magnets to temporarily magnetize a pipe before examining and analyzing the pipe's magnetic field for distortions. If there are any major flaws in the pipe wall then the magnetic field will distort. By identifying these distortions, it is possible to find flaws within the pipe.

Some other common inspection techniques include pulsed eddy current testing, and acoustic emission testing. Each type of inspection has its own strengths and weaknesses. The effectiveness of any inspection technique is dependant on the specific equipment, environment, and situation.

Relevant Links


Special thanks to the following contributors:

Mohammed Aboul Gheit, KNPC, MAA

Recommend changes or revisions to this definition.


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