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Pipelines and Weld Inspection

AUT, ToFD, Time of Flight Diffraction, Phased Array, Olympus, Omniscan MX, India, Experience. Advanced NDT using ToFD in lieu of Radiography in Saudi Arabia. TCR Arabia has Saudi Aramco qualified crews.
pipeline baseline study
TCR Engineerig Heat Treatment, Oil Firing, Pre Weld Heat Treatment, Electric Furnance, Stress Relieving. Pre and Post Weld Heat Treatment (PWHT), Stress Relieving (SR)

Time-of-flight diffraction (ToFD) and Phased Array

Time-of-flight diffraction (ToFD) technique is an ultrasonic NDT technique, which relies on the diffraction of ultrasonic energies from 'corners' and 'ends' of internal structures (primarily defects) from the component being tested. Using TOFD, the expert NDT team members at TCR provides amplitude-independent accurate flaw sizing on a wide coverage area. ToFD being an advanced and automated weld examination technique, it assists in Fitness For Purpose (FFP) inspections as well.


ToFD is a fast and effective method of scanning a wide weld area in a very limited time period. While TOFD is a very powerful and efficient technique, it suffers from limited coverage resulting from two dead inspection zones:

  • The first dead zone: Near the surface, as a result of the lateral wave

  • The second dead zone: At the back-wall, resulting from the width of the back-wall reflection.


By combining the use of TOFD and conventional pulse-echo methods, dead zones in proximity to the front and back surfaces can be improved substantially. TCR Engineering offers services of creating ToFD scan plans and procedures in India. This technique has many advantages including: 

  • Wide coverage area using a pair of transducers

  • Accurate flaw sizing; amplitude-independent, Sizing technique using time-of-flight information

  • One-line volume inspection, provides highly efficient scanning

  • Setup is independent of weld configuration

  • Highly sensitive to all kinds of defects with no sensitivity to defect orientation

  • Amplitude-insensitive, acoustical coupling less critical 

ToFD & Phased Array


ToFD is a quick and accurate tool for flaw sizing

Phased Array technology (using a TCG or DAC) and flaw location indicators with experienced analysts is also recommended. The team has done a number of noteworthy ToFD projects:


  • 100% weld inspection of Storage Tanks at Kuwait as per API 650 appendix U

  • Random inspection of pipelines in Rabigh, Saudi Arabia as per ASME Code Case 181

  • Pressure Vessel inspection in India as per ASME Code Case 2235-9 


ASME Boiler and Pressure Vessel Standard Section VIII Code Case 2235-9 states that it is acceptable to use the ToFD for Ultrasonic examination in accordance with ASME Section V, Article 4. ASME Code Case 2235-9 mentions replacing RT with UT and has resulted in incorporating ToFD into pressure vessel work for both detection and sizing of flaws. This now allows ToFD to be used on all Section VIII pressure vessels. TOFD is perfectly acceptable to use as per Code Case 181 and Code Case 179 of ASME B 31.3 for piping products.


API 579 in its current draft form states the Recommended Practice for Fitness-for-Service (crack depth, length, angle and distance to other surfaces) where breaking or embedded cracks are determined using UT examination techniques, either ToFD or angle beam.


Draft-API 580 states the Risk Based Inspection Recommended Practice (Base Resource Document recommends automated ultrasonic shear wave testing as a highly effective inspection technique for crack detection and sizing). The capability of the Automated UT technique/type is evaluated using the probability of detection (POD curves from round-robins in the past where ToFD showed the best performance).


British Standards Institute's welding standards policy committee has created BS 7706 as a guide for calibration and setting-up of the Ultrasonic Time of Flight Diffraction (ToFD) technique for defect detection, location and sizing of flaws. Another well-documented guide is the PrEN 583-6.


The team at TCR with its decades of experience have extensive clues to the characterization of various types of flaws using TOFD with the exception of few instances where definitive conclusions are rare. In the case of Phased Array technology, an experienced analyst has a greater chance of determining flaw type based on the percentage of sound transmitted back to the probe.


TCR uses products from Olympus’s OmniScan technology, which has capabilities to indicate to the operator the exact location of a flaw with respect to the weld centerline and bevel face. An experienced analyst from TCR is able to characterize fusion flaws based on location and amplitude response.

Long Range Guided Wave Ultrasonic Testing (LRGWUT)

The Long Range Guided Wave Ultrasonic Technique (LRGUT) is designed to inspect 100% of a pipe segment from one single location.


Torsional or longitudinal guided waves are induced into the pipe body and propagated along the entire pipe segment under inspection. When these guided waves identify an anomaly or a pipe feature, they convert into laminar waves and reflect back to the tools’ original location. Using a laptop, these signals are digitally captured. The time-of-flight for each signature is calculated to determine its distance from the tool. The cross-sectional area is calculated by amplitude followed by estimating the circumferential extent by the focused beams (broken down into octants) to determine the significance of the defect.


TCR performs LRGWUT in association with its international partner. This partner meets and exceeds the PHMSA 18 points to examine casings and crossings. LRGWUT’s primary application is in the Oil and Gas Refining, Petrochemical, Storage, Offshore and Pipeline Transportation industries among others. More specifically, the tests are used as part of ECDA and ICDA methodologies where access to piping systems are difficult such as:

  • Insulated Pipe in Refineries

  • Offshore Pipeline Risers

  • Cased Road or Railway Crossings

  • Loading Lines and associated Pipework

  • Tank Dyke Pipeline Crossings

  • Above Ground or Buried Flow Lines

  • River or Bridge Pipeline Crossings


Post Weld Heat Treatment (PWHT)

TCR Engineering Services offers a diverse range of Heat Treatment Services including pre-heating, post-heating; stress relieving (SR), intermediate SR, normalizing, solution annealing, water quenching, tempering, step cooling and drying of the refractory material. The experienced technicians at TCR are capable of performing heat treatment on weld joints, piping, regenerators, stripper columns, pressure vessels, boiler headers, modules, deck pipelines and structure, boiler heater tubes, and DOTHERM testing. The team is also capable of carrying out Post-weld heat treatment of carbon steel piping welds (pipe-work, headers, flange joints, valves and branches) by means of the electrical resistance method, in the form of ceramic heater pads. It can design, fabricate, calibrate and run a customized electrical furnace for clients.


Post Weld Heat Treatment Services (PWHT) is performed after welding/machining, to improve the chemical and mechanical properties of weldment / machined surfaces. TCR offers post-weld heat treatment by using electricity as the source of heating for stress relieving of weld joints. All TCR’s heat treatment services are designed to minimize downtime, improve structural integrity and enhance effective plant life. Additionally, depending on the mobility of the required equipment, many of TCR’s heating processes can be applied on-site or at client’s facility.


Conceptually, PWHT covers many different potential treatments:


Stress Relieving: For steel fabrication, the most common procedure used is Stress Relieving where machining and/or welding induces stress in parts. The bigger and more complex the part, higher is the amount of stress. Stress Relieving is done by uniformly heating the fabricated equipment, a vessel or a part of the vessel to a sufficiently high temperature, but below the lower transformation temperature range. It is then subjected to a thermal retardation for a sufficient time depending upon the material thickness and then finally cooled uniformly.


TCR has specialized fully-automatic programmable equipments capable of controlling Heating rate, Holding time and cooling rate as well as carrying out a wide range of heat treatment processes like post-weld heat treatment of PQR test coupons and various components. TCR has at its disposal, well-equipped tools including electrical furnace with 220 and 80 Volts panel, latest 12 point recorder with digital display, coil and pad-type heating element, oil firing systems and extremely skilled technicians. The Heat treatment equipment is supplied with a chart recorder to record up to 8 thermocouples simultaneously to meet the critical requirements of heat treatment.



Oil Firing on Pressure Vessels 

TCR Engineering has a talented crew that uses diesel fuel as the source of heating for stress relieving of pressure vessels with the sole objective of reinforcing process, component integrity, and  high quality. The heat treatment specialists from TCR have all the necessary experience and equipment to develop a custom configuration as per specific processes. Our heating processes include low-Range, Mid-Range & High-Range Temperature Heating.


TCR's high-velocity burners enable excellent temperature distribution and uniformity at all times because of the intense scrubbing action. They are also able to construct temporary furnaces at client sites where internal firing is not a practical or cost-effective option.

The heat treatment operation is affected by the firing of the furnace, using one or more gas/oil high-velocity burners with a nominal rating of 1,500.000 Kcals/HR (6,000,000 Btu/HR) per burner. Each burner is connected by an armored flexible hosing to Combustion Air Fan (s), with a maximum output of 2800/Nm³ per hour via a 150mm diameter outlet, at a pressure of 700mm W.G. The burner is fitted with a (25/20) stainless steel outlet nozzle designed to clear the furnace wall adjacent to the intended opening(s), in such a way that it eliminates the possibility of any direct impingement on components. 

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