What Are The Common Inspection Methods In Pipeline Application?

As we all know, pipelines play an indispensible part in oil and gas transporting market. Thus, it is crucial to ensure the integrity and good performance of pipelines in real practice. In addition to strict manufacturing process, thorough and professional inspection is also a decisive factor in pipeline performance. Now let’s get to know some key inspection methods.

What is NDT (Nondestructive Testing)

Nondestructive Testing, shorted for NDT, is a widely-used method in pipeline inspection. It is a process of testing, inspecting and evaluating the quality and characteristics of the material without damaging the pipeline itself or affecting the later regular work of the pipe. In other words, after NDT testing, the part can still be put into practical use. NDT utilizes the changes in heat, sound and magnets caused by abnormal inner structure or flaws to inspect the internal and external defects of the material.

The common inspection methods of NDT are visual testing (VT), ultrasonic testing (UT), radiographic testing (RT), hydrostatic testing. Anson International co, ltd uses ultrasonic testing (UT) and hydrostatic testing to inspect its line pipes.

Hydrostatic Testing

What is hydrostatic testing?

Hydrostatic test is an inspection method to reduce the risk of flaws in the pipe that might threaten its ability to withstand the maximum operating pressure. Hydrostatic testing inspects the integrity of pipelines by filling in the pipe with a non-compressible liquid (often water, dyed) to increase the pressure level above the normal pressure to see if there is any defect exists. It can either carried out on pipes prior to being put into service or on existing pipes that are already in service.

Things to notice in hydrostatic testing

In order to carry out hydrostatic testing, the following rules should be strictly stuck to:

• Testing with air is dangerous and not recommended. Therefore, the first step is to release the air in the pipe.
• In the testing process, all the valves and vents should be shut to observe whether there is pressure loss.
• Hydrostatic test should be performed after all the hot work has been done to the pipe, including welding, heat treatment, etc.

Ultrasonic Testing (UT)

What is UT and how does it work?

Ultrasonic testing, also known as UT, enjoyed wide application in the flaw detection and quality control of metallurgy and manufacturing industry. It is able to precisely detect, inspect and diagnose the flaws in the material.
In an ultrasonic test, the ultrasonic transducer connected to a diagnostic machine is put on the pipeline to be inspected. High frequency sound waves can directly travel through the metallic material. If the sound waves hit a defect, normally with a different acoustic obstruction, some of the waves will reflect back to the sending unit and inspectors can see the results in the form of signals on the visual display. By analyzing the reflection, inspectors can locate and test the crack or other hidden defects.

What are the advantages of UT?

Ultrasonic testing bears a number of benefits in the application of pipeline inspection:

• Non-destructiveness is the most important advantage. On one hand, the inspected pipe doesn’t need to be cut or exposed to damaging chemicals, which means the inspection won’t interfere with its future use. On the other hand, it does no harm to operators, leaving no potential risk for them.
• Strong penetrating power makes sure it has a wide detection range.
• High sensitivity allows it to quickly and precisely determine the exact position of the pipe, providing accurate and dependable testing result. 
• Immediate result displayed—The ultrasonic testing equipment makes it possible to get the instant flaw testing result.

In contrast to NDT, there are some destructive inspection methods. They are always carried out on samples of the material instead of on material itself. Destructive inspecting methods are normally used to test the physical properties of the material, such as tensile strength, yield strength, hardness and so on. Suppliers can choose the most suitable inspection methods according to your practical needs.