Visual Plus 3 Eddy Current NDT 

Easytek is the only cylinder testing station in Thailand that uses the Visual Plus 3 Eddy Current NDT Device.

Endorsed by major cylinder manufacturers, including Luxfer and Catalina.

The Visual Plus 3 is the only Eddy Current NDT device recommended  
for use on cylinders made of 6061 alloy (DOT 3AL).

Visual Plus 3 the “smartest” eddy-current device available since it eliminates human error and clearly identifies all types of cylinder damage and defects. 

More than an upgrade of existing technology, Visual Plus 3 offers all-new computerized features that make it the best tool for inspecting cylinders made from all types of aluminum alloys now in use, including popular 6061 alloys favored by major global cylinder manufacturers. 

Visual Plus 3 not only detects cracks… it identifies corrosion, gouges, pits, folds, valleys, tool stops and other types of indications and it shows you the differences among them on five different color-coded graphs, including both linear and three-dimensional views, on a computer screen.

Professionally competent visual inspections are a key element in the proper maintenance of gas cylinders (such as those used for scuba diving and by firefighters) and the inspection of cylinder neck threads is an important part of the process.

Even the best trained and most experienced technician can miss or wrongly diagnose small imperfections, such as hairline cracks and folds in the neck/shoulder area of aluminum cylinders using hydrostatic testing alone. Visual Plus, a non destructive testing device, identifies 100% of these defective cylinders using the latest in eddy current technology... Don't leave it to chance!

Anyone working around aluminum high-pressure gas cylinders knows how reliable they are. In fact, they are so dependable that often we forget they need to be treated with care and respect. Proper maintenance is necessary to make sure cylinders are fit for service, especially when they undergo harsh service, such as scuba diving and firefighting.

Professionally competent visual inspections are a key element in the proper maintenance of gas cylinders, and the inspection of cylinder neck threads is an important part of the process. Yet even the best trained and most experienced technician can miss or wrongly diagnose small imperfections, such as hairline cracks and folds.

Visual Plus is a non-destructive testing (NDT) device which utilizes eddy currents to detect neck and shoulder cracks, folds or other similar imperfections in aluminum cylinders such as scuba, SCBA (all metal, hoop-wrap or full wrap), beverage, medical, industrial gas cylinders, fire extinguishers, etc.

An electromagnetic wave is introduced into the metal of the vessels near the area which is desirable to inspect for imperfections (the threaded area). The wave causes currents to flow in a circular manner in the metal. They are called eddy currents because the flow is circular. An imperfection can increase the path that the currents have to flow and so make the material appear higher in resistance in that region where the imperfection is present. This generates a spike on the computer generated report which alerts the technician to a problem that requires further investigation.

Hydrostatic testing alone does not reveal cracking in the neck/shoulder area of aluminum cylinders unless they are leaking. Visual Plus identifies 100% of these defective cylinders... Don't leave it to chance!

THE FOLLOWING STATEMENTS ARE TAKEN DIRECTLY FROM THE LUXFER WEB SITE. READ THE ORIGINALS HERE.

What is sustained-load cracking?

• SLC is a metallurgical phenomenon that occasionally develops in cylinders made of 6351 aluminum alloy, as well as in other types of pressure vessels and structural components under stress for sustained periods of time.
  
• SLC has occurred in cylinders manufactured by various companies, including Luxfer.
  
• Cylinders that have been mechanically damaged, over-filled or abused are more susceptible to SLC.
  
• SLC is not a manufacturing defect; it is a phenomenon inherent in the metal itself.

How quickly do the cracks grow?

• Very slowly, as extensive research by Luxfer and outside laboratories has shown.
  
• No scientific evidence supports rumors and claims of "fast crack growth."
  
• Cracks typically take eight or more years to grow large enough to cause a cylinder leak.
  
• Because SLC growth is so slow, properly trained inspectors have adequate opportunity to detect cracks during the normal re-qualification process.

How many aluminum cylinders have exhibited SLC?

• Out of a total population of approximately 1,073,000 Luxfer scuba cylinders made of 6351 alloy, only 1.25% have exhibited SLC.¹
  
• Out of Luxfer's total 6.1-million population of 6351-alloy cylinders, the SLC rate is slightly less than 0.37%.
  
• While we do not have complete statistics on cylinders manufactured by other companies, industry experts estimate that out of a worldwide population of more than 30 million 6351-alloy cylinders, far less than 1% have exhibited SLC.

Which types of cylinders are most susceptible to SLC-related ruptures?

• Any type of cylinder manufactured from 6351 alloy could conceivably develop a sustained-load crack over time if subjected to certain conditions.
  
• However, a cylinder is more likely to rupture in applications where pressure is higher and where overfilling and abuse occur more often.
  
• Historically, the applications most susceptible to SLC-related rupture are scuba and SCBA (life support).

Why is it necessary to have my 6351-alloy cylinder inspected with an eddy-current device?

• When properly used, eddy-current devices contribute significantly to early detection of hard-to-see sustained-load cracks.
  
• However, an eddy-current test is not a replacement for a diligent visual inspection by a properly trained inspector.
  
• Eddy-current devices are tools to enhance proper visual inspections.
  
• Eddy-current devices currently approved by Luxfer for use with Luxfer 6351-alloy cylinders are Visual Plus, Visual Plus II, Visual Plus III, and Visual Eddy. (However, the only eddy-current device approved by Luxfer for use with cylinders made from Luxfer’s proprietary 6061 alloy is Visual Plus III.)

Why does Luxfer place so much emphasis on inspection?

• Proper inspection is crucial to scuba tank safety—and it cannot be overemphasized that the quality of inspection is far more important even than the frequency of inspection! An untrained or improperly trained inspector can look at a 6351-alloy cylinder numerous times without detecting SLC. Make sure that your inspector is well-trained and competent.
• Unfortunately, many untrained or improperly trained technicians continue to inspect cylinders, and no uniform standards for inspector training and certification exist among regulatory authorities around the world.
• Luxfer is working with industry groups and government agencies to help establish such standards.

How can I tell if my Luxfer cylinder is made from 6351 alloy?

• The easiest way is to check the original hydrostatic test date stamped on the cylinder crown.
  
• Luxfer manufactured 6351-alloy cylinders during the following periods:
  
• United States: 1972 through mid-1988
  
• England: 1958 through 1995
  
• After these dates, Luxfer began making cylinders from a proprietary 6061 alloy, which is not susceptible to SLC.
  
• In Australia, CIG Gas Cylinders manufactured scuba tanks from 6351 alloy from 1975 through 1990, and then switched to 6061 alloy. Luxfer acquired CIG Gas Cylinders in 1997, by which time Luxfer was manufacturing all scuba tanks with its own proprietary version of 6061 alloy. All Luxfer tanks manufactured in Australia under the names “Luxfer” and “Luxfer Australia ” have been made exclusively with Luxfer’s 6061 alloy.

If Luxfer 6061-alloy cylinders are not susceptible to SLC, why has Luxfer exchanged 6061 cylinders that have been reported to have cracks?

• After the introduction of eddy-current technology, Luxfer received reports of cracking in 6061-alloy cylinders. We accepted returns on about 1,200 of these cylinders to conduct extensive tests. Not a single cylinder was found to be cracked.
  
• On Luxfer 6061-alloy cylinders, eddy-current devices sometimes show harmless "indications" that lead to "false-positive" readings for SLC. 

NOTE:  6061 alloy cylinders can still have cracks in the thread area, a cylinder with a fold in the crown will produce a stress raiser from which a crack may propagate.

(This is not a Luxfer statement but an observation Easytek has found from testing many cylinders.) VIEW VISUAL PLUS 3 6061 CYLINDER REPORT

Without a Visual Plus3 Eddy Current device the cylinder inspector is restricted to using only visual inspection techniques on 6061 alloy (DOT 3AL) cylinders.

Inspection and Testing of Luxfer Scuba Cylinders Manufactured from 6351 Aluminum Alloy.

Luxfer scuba cylinders were manufactured from 6351 aluminum alloy during the following periods:

• United States : 1972 through mid-1988
• England : 1967 through 1995
• Australia : 1975 through 1990

Luxfer requires that every Luxfer 6351-alloy all-aluminum scuba cylinder be visually inspected at least every 2.5 years by a properly trained inspector. As part of this inspection, Luxfer further requires that the cylinder neck be tested with an eddy-current device such as Visual Plus™, Visual Plus 2™, Visual Plus 3™,Visual Eddy™ or equivalent non-destructive testing equipment. When properly used, eddy-current devices contribute significantly to early detection of difficult-to-observe sustained-load cracks in the necks of 6351-alloy cylinders. If the cylinder passes the inspection, the inspector will document that fact. If the cylinder fails the inspection, it must be removed from service immediately. 

Do not use Luxfer 6351-alloy scuba cylinders that have not been both visually inspected and eddy-current tested and then properly documented.

This Luxfer-required visual and eddy-current inspection is in addition to periodic re-qualifications (including retesting and inspections) required or recommended by various regulatory agencies around the world. The intervals between retests and inspections vary from country to country.

In addition to the required inspection and testing described above and in keeping with U.S. scuba industry standards, Luxfer recommends that all Luxfer 6351-alloy scuba cylinders be visually inspected at least once each year by a properly trained inspector.

Inspection and Testing of Luxfer Scuba Cylinders Manufactured from 6061 Aluminum Alloy.

Luxfer began manufacturing scuba cylinders from a proprietary 6061 aluminum alloy in mid-1988 in the United States , in 1995 in England and in 1990 in Australia . The majority of Luxfer scuba cylinders currently in service are made from this proprietary 6061 alloy, which Luxfer is still using.

Cylinders made from Luxfer’s proprietary 6061 alloy are not susceptible to sustained-load cracks. Therefore, Luxfer does not recommend the use of earlier-generation eddy-current devices—e.g., Visual Plus, Visual Plus 2, and Visual Eddy—with Luxfer 6061-alloy cylinders because field experience has shown that using these devices can result in misleading “false-positive” readings and erroneously condemned cylinders.

However, Luxfer does approve the use of the Visual Plus 3™ eddy-current device with Luxfer 6061-alloy cylinders. After laboratory testing, Luxfer has determined that properly calibrated Visual Plus 3 equipment eliminates the “false positive” problem, accurately measures features in the neck area of aluminum cylinders, and generally provides correct pass or fail assessments with cylinders made from Luxfer’s 6061 alloy. As of the date of this Luxfer Policy Statement, Visual Plus 3 is the only eddy-current testing device suitable for use with Luxfer 6061-alloy cylinders.

Luxfer emphasizes that the use of eddy-current devices to improve the quality and accuracy of inspections does not eliminate the need for a thorough visual inspection by a properly trained and qualified inspector.

In keeping with U.S. scuba industry standards, Luxfer recommends annual visual inspection of Luxfer 6061-alloy cylinders by a properly trained inspector. For cylinders in heavy use (for example, those filled five or more times a week), Luxfer recommends visual inspection every four months. 

These recommended inspections are in addition to periodic re-qualifications (including retesting and inspections) required or recommended by various regulatory agencies around the world. The intervals between retests and inspections vary from country to country.

© Samui Easytek Co., Ltd. (Pattaya)