Shearwave Weld Inspection

Ultrasonic volumetric (shear wave) inspection works on the same basic principles as ultrasonic thickness, however angles are introduces. This allows the sound pulse to travel from a smooth base metal into a weld in a controlled manner.

The most commonly occurring defects in welded joints are porosity, slag inclusions, lack of side-wall fusion, and lack of root penetration, undercutting and longitudinal; or transverse cracks.

With the exception of single gas pores all the defects listed are usually well detectable by ultrasonics. Most of the applications are for low-alloy construction quality steels; however welds in aluminum and stainless steels can also be tested. Ultrasonic flaw detection has long been the preferred method for the nondestructive testing of welds. It is a safe, accurate and cost effective method for inspecting these types of weldments.

Ultrasonic weld inspections are performed using a straight beam transducer in conjunction with an angle beam transducer in contact with a plastic wedge. A straight bean transducer is first used to locate any laminations in or near the weld’s heat-affected zone. The angle beam transducer may not return a signal if the sound beam is interrupted by an indication such as an adjacent laminar flaw.

After scanning the heat-affected zone, an angle beam transducer is used to inspect the weld. These transducers use the principles of refraction and mode conversion to produce refracted shear waves into the weld material. The inspection area will include the root, sidewall, crown and heat-affected zones of the weld. The technician will scan the surface of the material around the weld with the transducer. The refracted sound will bounce off a reflector (discontinuity) in the path of the sound beam. By using the proper angle beam, echoes returned from the weld allow the technician to calculate the location and type of discontinuity.

Shear wave is commonly used as an alternative to Radiography, although there is no permanent record of defects.

See the cost comparison between shear wave and radiographic weld inspections of 70 water wall tubes located in a large commercial boiler

Shear wave

Ultrasonic volumetric weld inspection (shear wave) is an accepted method of inspecting boiler tubes per ASME Section I. At least three inches must be cleaned above and below the weld (including membrane) for proper inspection. This inspection can be performed while other work is being performed, allowing more time to make any necessary repairs and eliminating loss of production.

• Duration of six shifts
• One inspector per shift
• Minimal equipment charge
• No loss of production during inspection

Inspection cost: $4,830.00
Welder standby cost: $0.00

Total Cost: $4,830.00

Radiography

Radiographic inspection (X-ray) requires at least two personnel for all jobs; one radiographer, and one radiographer’s assistant. X-ray allows you to have a permanent "photograph" of the weld for records but work areas must be vacated to perform the inspection.

• Three four-hour shot windows (eight hours total production for setup and film development
• Two personnel per shift (radiographer & assistant)
• Expensive equipment and film charges
• Three losses of four hours @ $734.43 per hour for welding company (estimated)

Inspection cost: $3,075.00
Welder standby cost: $8,813.00

Total Cost: $11,888.00   Shear wave inspection would save $7058