Welded joints of pressure vessels are tested and inspected by mechanical testing and nondestructive testing as the standards or codes.
Mechanical test is performed with a piece of specimen for only typical testing, while nondestructive test is only for detecting of inner discontinuity of welded joint.
Quality of pressure vessels is required inspection system to form quality of welded joints in the background of such tests. This paper has been examined inspection systems of various countreis and is conesidering consolidately the qaulity of the weleded joints on the system and standard in the aspects of test and inspection.

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The Moss type tank system, in which the spherical tank is supported by its skirt, was originally developed for sea transportation of LNG.
The basic premise of this liquefied gas (LG) containment system, known as “leak-before-failure”, or “fail-safe”, implemented in the form of the small leak protection system proved to be of highly practical value in ensuring the safety of the dangerous cargo transportation and consequently has come to find prevalent marine applications: Today nearly a half of the world's LNG carriers are equipped with the Moss type tank system.
The Moss type tanks have been fabricated for installation in many LNG carriers, with highly successful service results. On the strength of its engineering expertise gained through the construction and the marine service of LNG carriers equipped with this tank system, the authors successfully devised this time a spherical LG containment system for land storage application. The authors were directly involved in the evaluation of tank structural strength required for LG land storage in the earthquake-prone environment, etc.
Accordingly, the authors review in this paper the Moss type tank system as regards its construction, structural design, materials, insulation method, etc., which may be capsulized as follows.
1) The tank as a whole is smooth and continuous in construction.
2) The skirt support system lends itself to increasingly larger LG storage tank installations.
3) The spherical tank configuration enables the tank to accommodate a relatively high internal gas pressure and hence the pressure buildup caused by boil-off gas as well.
4) With the air space created within the skirt supporting the tank, no freezing of the surrounding ground foundation takes place.
5) The spherical tank, being independent by itself in construction, can be fabricated completely in the assembly shop.
6) The thermal insulation required is relatively simple, in both material and method of application.
7) The spherical tank configuration permits the tank to be inspected both internally and externally in the fabrication process for complete examination for any defects.
8) The option for employing the small leak protection system is available to render the storage tank fail-safe as in marine application.

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