Technical BulletinTechnical Bulletin

Ultrasonic Examination of Ultrasonic Examination of Ring Joint FlangesRing Joint Flanges

All Tech Inspection can determine the integrity of ring joint flanges (RTJ) without disassembling by the use of this special ultrasonic procedure. Most flanges can be examined while in opera-tion. RTJ flanges are commonly used in re-finery and chemical plants for high-pressure piping. The groove on the flange is very susceptible to stress / stress corrosion cracking. These cracks have been found on both the oval and octagon shaped grooves. Bolting proce-dures utilizing torqing or tensioning are used for making up the flanges to en-sure proper loading on the flanges. Even with the use of proper bolting

OVERVIEW:

REFINING • PETROCHEMICAL • OIL & GAS • MARINE• POWER GENERATIONREFINING • PETROCHEMICAL • OIL & GAS • MARINE• POWER GENERATION

page 1 of 1

Historically RTJ flange inspections are performed during maintenance outages. The flanges are disassembled, the grooves are cleaned and examined visu-ally and with the liquid penetrant inspec-tion method. This procedure is very la-bor intensive. Any cracks have to be re-paired or the flanges replaced if damage is severe. Unscheduled repair or re-placement is always more costly than scheduled maintenance. This procedure gives the owner the chance to examine the flanges well before the maintenance outage. Flanges requir-ing repair can easily be added to the work scope.

Figure 1. Technician examining a flange using a pitch / catch technique.

Figure 2. Ring joint flange. Note, crack in ring groove.

The bottom of the groove is ultrasoni-cally examined for crack initiation. The procedure utilizes a straight beam pulse echo method and a pitch catch method of examination. The ultrasonic technician locates the back-wall signal for the inside diameter of the flange then, examines the bottom of the ring groove for cracks. Cracks can be accurately sized so repair or replacement activities can be sched-uled.

Technical BulletinTechnical Bulletin

Ultrasonic Examination of Ultrasonic Examination of Ring Joint FlangesRing Joint Flanges

REFINING • PETROCHEMICAL • OIL & GAS • MARINE• POWER GENERATIONREFINING • PETROCHEMICAL • OIL & GAS • MARINE• POWER GENERATION

PROCEDURE: page 2 of 2

CONCLUSION:

• RTJ flange inspection with-out disassembly

• On-stream inspection • Accurate flaw sizing • 100% inspection of the

RTJ groove bottom • Schedule maintenance ac-

tivities based on inspection results prior to turnarounds

Figure 3. Ring groove crack found under a bolt hole using special pitch / catch technique.

Figure 4. RTJ cross section and CRT signal response.