Corrosion under insulation (CUI) is one of the greatest problems faced by the ammonia refrigeration industry.
Massive industrial facilities like petrochemical refineries and food processing plants rely on large-scale refrigeration systems for their day-to-day operations. Ammonia is the most trusted refrigerant since 19th century. Everyone involved in food preservation and industrial process plants know ammonia as the refrigerant of choice because of its unparalleled thermodynamic properties.
Because ammonia’s properties are so well suited to large refrigeration systems and the physics of vapor-compression refrigeration require using enough pressure to compress the gas into a liquid mean that systems are likely to contain large amounts of high-pressure ammonia. Any water in large refrigeration systems can freeze and obstruct piping, therefore they must use anhydrous ammonia (without water or other impurities). As a result, any ammonia-based refrigeration system is going to present a risk of accidental exposure to high concentrations of ammonia—a major health and safety issue—must be prevented at all costs through the use of non-destructive testing (NDT).
The NDT techniques most commonly used to find and assess CUI are radiometric profiling and real-time tomography (RTR), but both have their limitations. Other technologies exist now to assess CUI, but without the shortcomings of the former. One of these technologies is pulsed eddy current or PEC, for short. PEC technology has been around for some time, but was recently vastly improved upon, finally taking the shape of Lyft® (patent pending), a revolutionary solution for the ammonia refrigeration industry.
Reinvented PEC Technology
Pulsed eddy current is an advanced electromagnetic inspection technology used to find defects and corrosion in ferrous materials typically hidden under thermal insulation. A PEC probe creates a magnetic field. When the probe is on the surface under test, the field goes through all the layers present—including sheeting—and stabilizes in the thickness of the component under test. The electrical current in the probe is cut off, which causes a sudden drop in the magnetic field. As a result of electromagnetic induction, eddy currents appear in the component wall. These eddy currents diffuse inward and decrease in strength. This decrease is monitored by the PEC probe and used to determine the component’s wall thickness. The thicker the wall, the longer it takes for the eddy currents to decay to zero.
High-Performance CUI Inspection System
Lyft reinvents PEC in several ways. The instrument is capable of real-time C-scan imaging, acquiring data at up to 15 readings per second, and a dynamic scan mode. The solution also features probes of different sizes for various situations and conditions, as well as many accessories for even more flexibility:
- Extension pole up to 4.6 m (15 ft)
- Extension cables for rope access inspections
- Clip-on stabilizer
- Ergonomic clip-on handles
Powerful Embedded Software
The user-friendly multi-touch software includes several innovative features, including real-time C-scan imaging, complete wall thickness measurements (ID and OD corrosion), as well as complete inspection management and reporting capabilities.
Reliable, Repeatable Results
The Lyft software is packed with automation and advanced algorithms that remove operator-specific dependence, thanks to the power of SmartPULSE™ technology. It automatically optimizes pulser and receiver parameters (gain, duration, time gates, filters, etc.). SmartPULSE also optimizes wall thickness measurements, which ensures optimal performance and repeatability, while limiting the need for advanced knowledge of PEC.
The Lyft instrument is sealed and designed for IP65. Its magnesium alloy casing is tough, water and dust resistant, and cools without any external air exchange. The adjustable stand, the top handle, and the four corner anchor points make it practical for on-site inspections. The system also features standard, connect-anywhere capabilities and advanced productivity tools for optimal field tests.
The premium-quality 26.4 cm (10.4 in) LED display is optically bonded and non-reflective, comes with 3 mm (1/8 in) strengthened glass, and is designed to be operated with gloved hands under any lighting conditions. The system also comes with two, hot-swap batteries for extended autonomy.
The Lyft solution includes three standard probes of various sizes for the right balance between the component wall thickness, the insulation thickness, and the weather jacket. The probes support component wall thicknesses up to 102 mm (3 in); insulation up to 305 mm (12 in); and composite, stainless steel, aluminum, or galvanized steel weather jackets. The probes also feature a keypad for easy remote operation and can be equipped with a universal clip-on encoder enabling dynamic scans. The sleek mechanical design enable inspecting closely packed pipes.