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Weld inspection on LNG tanks
- How to reduce costs?
- What kind of NDT method will provide maximum flexibility during construction, supplies accurate information and at the same time helps to reduce costs and is environmentally friendly?
These are questions every executive and design engineer faces when a LNG project is in process. To find out the answer to these question you should know more about our state of the art inspection method.
The weld material of LNG tanks -because of using 9% Ni steel alloy- has a coarse grain structure on which an advanced method can be used.
Applus-RTD has developed a fast, safe, accurate and cost effective solution, especially for those construction companies who are dealing with one or more of the following problems
- Coarse grain structure, hindering proper interpretation of film and subsequent (possible) misinterpretation and needless repairs
- Radiation hazard and construction down time
- Reduction of chemicals in the environment
- Slow inspection speed
- Lack of flexibility
Our automatic ultrasonic inspection (AUT) system called 'LNG scan®', using special probes was developed to be fast and reliable. The inspection can take
place during construction and welding activities.
The characteristics of this versatile inspection method tell their own tale:
- Reduces costs
- Flexible, no downtime for inspection
- No radiation hazards
- Fast; 60-100m per shift possible
- Instant online results (prevents repairs)
- Use of ECA, acceptance criteria possible
- No chemicals, films, darkroom
- Digital storage/archiving
AUT brings increased accuracy allowing sound decisions on acceptance of defects as per API 620 addendum 1, June 2004 (see table U2).
The owner knows his tank has been inspected with the latest state of the art technology which is good for the owner but also for the contractor and the general public (good quality standards, PR positive). Also in a later stage, the AUT inspection results stored digitally on CD-ROM or DVD, can be used as a zero point to do a remaining life assessment of the installation and to allow longer life.
What about other tanks?
Other storage tanks, including atmospheric cylindrical tanks and spherical storage tanks also can be inspected by this method.
This method can be convenient specially for heavy wall tanks which have the inspection problem by means of Radiography because of their wall thickness which does not allow the inspectors to get accurate results from RT because they have limitation on their radioactive source power. If increase the power, the hazards will increase and if reduce it, the sensitivity will be decreased and many defects may be ignored.
AUT technique has no restriction on thickness and material settings and as this method is tailor made and could be adopted to client's needs so can be best suited the job limitations.