How do you find corrosion under insulation (CUI) and what nondestructive testing (NDT) techniques are best? These are questions conscientious system operators should ask when trying to hold off the costly problem of hidden corrosion in their systems. CUI is one of the most difficult corrosion processes to prevent but adoption of proactive measures, such as the development of an inspection program intended to detect early signs of corrosion and mitigate potential piping failures, is critical.

In fact, corrosion is so costly that theNational Association of Corrosion Engineers (NACE)估计，全球腐蚀成本约为2.5万亿美元。那么，限制了系统运营商的腐蚀成本的关键是什么，以及在绝缘下的腐蚀如何？

We wrote about theconditions under which corrosion is likely to be foundunder insulation in a previous blog post. If you’d like to learn about CUI risk factors and where you might find it, you might want to start there. However, if you are wondering how we locate corrosion in an insulated system using nondestructive testing techniques, read on.

Let’s look at the most common methods yourNDT consultantmay consider or rule out when building your inspection program:

目视检查I.E.绝缘清除

Visual inspection is one of the most effective NDT methods to locate corrosion but that comes with a couple big caveats. Removal of insulation is the most expensive and labor-intensive way to find corrosion. The logistics of this process can be made even more complicated by the presence of asbestos. What’s more, if your operation is in service during a visual inspection, it’s possible a system may experience process issues.

虽然非常有效，目视检查最终更有用来建立基线和向前向您的CUI检查前进的行动计划，其将与其他NDT方法配对。

简介射线照相

轮廓造影是一种简单且有效的技术，可以检查易受腐蚀的管道，尽管其检测内壁厚度的减小的能力。该NDT技术具有一些不同的优点，包括高水平的便携性，扫描管道的能力而不消除绝缘，以及相对便宜和快速的结果。

However, this method can be limiting because it can only verify small areas and can be technically challenging when scanning piping greater than 10 inches in diameter. There also are safety concerns due to radiation which prevent others from working in the surrounding area during inspection. Depending on your system, this can lead to downtime or scheduling delays.

Ultrasonic Thickness Measurement

Ultrasonic thickness measurement is a technique that measures the thickness of a solid element based on the movement of ultrasound waves. This is another effective technique that can measure wall thickness through a variety of linings and coatings. One benefit of this technique is that you only need access to one side of the piping under inspection.

However ultrasonic thickness measurement comes with its own set of limitations which include scans being limited to a small area and the complication of needing to cut small holes into the insulation to perform the technique which can be expensive and may compromise the integrity of the insulation (which can increase the CUI issues already under inspection).

Infrared Thermography

Infrared thermography is a technique that can detect moisture spots within the insulation of the piping. This method works by detecting the difference in temperature between the dry insulation and damp insulation. Where there is wet insulation, there likely (but not always) is corrosion. One benefit of this method is that infrared thermography can work without making direct contact with the piping being scanned which enhances safety as well as saving time and money. This method is generally faster and more sensitive than other moisture gauges.

Neutron Backscatter

中子反向散射是用于检测绝缘内水分的另一种技术。该方法使用放射源，该放射源将高能量中子发射到响应可能存在的水粒子的绝缘体中。这些结果指出存在较高腐蚀概率的区域。这个过程相对速度和准确。然而，类似于中子反向散射的方法，该方法是可能的腐蚀区域，可以产生假阳性，因为水分的存在不保证也存在腐蚀。

Real-Time Radiography

This technique, true to its name, provides a real-time look at the pipe’s outside diameter through insulation which produces an image an inspector can see on a TV monitor during inspection. Real-time radiography offers safety and speed enhancements relative to traditional radiography. This method is limited to small structures and requires access to both sides of the pipe under inspection.

脉冲涡流

脉冲涡流是一种NDT检查技术，其使用电磁波来确定将电力与放置在管壁上的探针进行电力的材料的壁厚。在高度准确的同时，该技术通常仅用作筛选方法，因为它仅提供平均壁厚。

Leverage NDT Methods for Your CUI Inspection Program

正如您所能通过典型方法的优势和弱点所说，NDT顾问可以用于检测和测量腐蚀，通常可以利用方法的组合，以筛选用于腐蚀可能发生的区域的系统。然后，该初始筛选点指向需要额外检查和测量的管道的目标区域。虽然Brau雷竞技好Newbee赞助商n Intertec目前没有提供中子反向散射，实时射线照相或脉冲涡流，但重要的是要了解可用的选项范围。

作为NDT检查员，我们之间的经验数十年，我们使用我们的专业知识和经验检查复杂的操作，帮助您指导您对系统，预算和担忧最适合的检查方法。

联系我们的非破坏性测试顾问

如果您有兴趣了解Brauun Intertec如何帮助您开发CUI检验计划或评估您的腐蚀威胁的操雷竞技好Newbee赞助商作，请通过下面的联系我们联系我们，我们将保持联系。