Rawabi Industrial Services

In refining and chemical plants, accurately monitoring and sizing discontinuities continue to become an essential part of operations, even more so when a risk-based inspection is utilized. As the need for techniques to be more accurate, reliable, effective (in time and cost), and straightforward increases, the TOFD, as a method of detecting faults in welds, has become a broadly employed tool across the industry.

It has great advantages in the speed of detection of defects and is very sensitive and accurate in the defect sizing technique in general use. One of the important advantages of using TOFD for weld inspection is the

absence of radiation. In several validation projects, TOFD has shown a proven record of a high detection rate with very high reliability in preservice and in-service inspections.‎

Applications

Two main groups of applications are differentiated as follows:‎

1. Pre-service inspections

• Weld inspection of vessels, pipelines, and plates

2. In-service inspections

• Weld inspection of vessels, pipelines, and plates
• Detection of corrosion underneath reinforcement rings of ‎nozzles
• Cladding thickness measurement
• Determining the depth of cracks

PA allows for the detection of discontinuities that are located in difficult-to-observe configurations, requiring the use of special ultrasonic testing methods. PA combined with a rotating sound beam can reach almost any angle and is the best tool to determine and visualize discontinuities.‎

PA testing has several key benefits; the capability to examine intricate geometries; a fast and efficient speed of inspection; improved accuracy in results; good repeatability, and the ability to visualise signs in base

materials and/or welds through the use of B, C, D, and S-scans (including all A-scans), allowing for data storage and providing a safer method than other NDT testing.

Applications

• Weld inspection of vessels, pipelines, and plates
• Weld inspection of complex geometries such as nozzle-welds
• Flange face corrosion inspection
• Fast corrosion scanning, utilizing 0-degree angled wedges
• Code case inspection in combination with TOFD and/or ‎pulse-echo

Internal Rotary Inspection System (IRIS)‎

Pipes and tubes can be tested using an ultrasonic method known as IRIS, wherein a probe is inserted into a tube flooded with water, and then is slowly released while gathering data. Revealed defects include metal loss from both in and outside of the pipe wall.

Applications

• Boilers
• Feedwater heaters
• Air coolers
• Heat exchangers

Eddy Current Testing (ECT)‎

ECT is carried out to examine non-ferromagnetic tubing and is appropriate for spotting a wide range of metal discontinuities: wall loss, baffle cuts, erosion & corrosion, pitting, and wear.

Applications

Condensers

Feedwater Heaters

Heat Exchangers

Air Conditioners

Magnetic Flux Leakage (MFL)‎

The MFL method is optimal when inspecting ferromagnetic tubes, as it gives a relatively accurate understanding of corrosion-induced metal loss in heat exchanger tubes in a short period.

Applications

• Feedwater heaters
• Air coolers
• Carbon steel heat exchangers

Remote Field Testing (RFT)‎

Two coils are utilized in RFT: the driver coil (also known as the transmit coil) and the pickup coil. A low-frequency AC signal is used to excite the driver coil, and the pickup coil is given a signal which is the vector sum of a small RFT signal that comes from the tube wall, and a direct coupled signal from the diver coil.

Applications

• Boilers
• Feedwater heaters
• Carbon steel heat exchangers

Regular inspection of storage tanks ensures that the walls and bottom plates are sound, as tank floor plates are susceptible to corrosion from the soil beneath them, increasing the risk of hazardous chemical contamination. Using MFL allows for maximum area coverage in a short period so that any indication that exceeds the threshold is verified by the ultrasonic straight beam.

Applications

Used in the bottom plate of tanks.‎