Heat Exchanger Inspection Techniques

Many heat exchangers need to be inspected due to malfunction, and a timely inspection is critical. This often means the quickest detection of flaws, allowing for prompt resolution and minimizing expensive losses.

RVI utilizes advanced video borescopes to provide high-resolution images of hard-to-access areas. Combined with established inspection methods like ECT, RFT, MFL, IRIS, UT and radiography, RVI helps operators achieve comprehensive understanding of their heat exchangers’ condition.

Non-Destructive Testing (NDT)

NDT inspections allow technicians to evaluate the integrity of a component without altering it in any way. This helps prevent future equipment failures and reduce maintenance costs.

NDT can detect flaws like corrosion or wall thinning, and it can also locate internal issues such as tube cracking or misalignment. It can even determine the remaining useful life of a machine so that a decision can be made about whether to repair or replace it.

NDT techniques are broadly classified into conventional and advanced methods. For example, straight beam ultrasonic testing (UT) is a conventional technique while phased array UT is an advanced method.

Eddy Current Testing (ECT)

Eddy current testing is one of the most common inspection methods for heat exchanger tubes. Its advantages include a non-contact approach and its versatility. It can detect surface cracks, measure approximate dimensions of cracks, and detect changes in conductivity and permeability.

However, ECT can have difficulty locating very specific flaws such as corrosion and wall thinning. Additionally, the data collected by ECT can be difficult to interpret without proper training and experience. Fortunately, new techniques such as Lorentz force ECT are helping to address some of the limitations that come with standard ECT equipment. These new approaches utilize overlapping coils to enable faster inspection coverage and provide more accurate data interpretation.

Magnetic Particle Inspection (MPI)

Magnetic particle inspection is a fast and relatively inexpensive nondestructive testing technique that can detect surface and slightly subsurface flaws in ferromagnetic materials such as steel. It requires minimal preparation of the test piece and can be performed in almost any environment.

MPI is an effective method for detecting cracks in heat exchanger tubes. This is important because a missed crack could lead to further downtime, expensive repairs and system loss.

This method involves spraying the test part with magnetic particles and then examining it for signs of defects. Various contrast coatings are available to increase the visibility of indications. A wide range of accessories is also available to help ensure that the magnetization process has been carried out effectively.

Ultrasonic Testing (UT)

Ultrasonic Testing (UT) involves using sound waves to scan a product for internal flaws. UT can be used on any type of metal, including aircraft components and industrial equipment. Oil or gel is usually applied to the probe to smother rubbing and provide clearer data. A transducer converts electrical pulses into high-frequency ultrasonic sound waves that propagate into the test object. If the test object has any flaws, they will reflect the waves back to the probe and be displayed on the equipment display.

Airlines and manufacturers use UT to identify any minuscule cracks or imperfections that could compromise flight safety. They also use it to inspect welds in manufacturing, so vehicles meet stringent quality standards.

Radiography (RT)

Heat exchangers are susceptible to many types of surface and subsurface flaws including cracking, pitting, and general corrosion. These can deteriorate over time and lead to compromised performance and unplanned shutdowns.

To avoid such issues, proactive inspections should be performed regularly. This can prevent costly repairs and unplanned shutdowns.

Radiographic inspection uses X-rays or g-rays to reveal internal structure and defects. Radiation passes through the test piece and is reflected by the material, creating an image on the radiographic film. This can detect the location of welds and other discontinuities. The process is fast and accurate. It is also relatively inexpensive, especially when compared to more advanced methods such as ECT and internal rotary inspection.

Remote Visual Inspection (RVI)

RVI is a non-destructive testing method that applies visual aids like video cameras and robotic crawlers to assess infrastructure and components in places too dangerous or remote for direct human intervention. It’s used in a variety of industries, including aerospace, petrochemical, power generation and healthcare.

In safe environments, this process involves someone on-site using an inspection camera to show an expert around technology or equipment. The assessor takes notes and screenshots to form the basis of an inspection report. Alternatively, drone footage can be recorded to allow an expert to conduct a visual assessment remotely. The process is faster, more cost-effective and safer than on-site assessment.