Cylinder Requalification

Cylinder Requalification Approvals

Carroll Welding Supply, Inc's Cylinder Requalification Facility Approval issued by the United States Department of Transportation for Industrial (high and low pressure) cylinders.

Carroll Welding Supply, Inc's Hydrostatic Testing Certificate of Registration issued by the Texas Department of Insurance State Fire Marshall's Office.

Hydrostatic Cylinder Testing

Carroll Welding Supply is a Department of Transportation authorized Hydrostatic Retester for high and low pressure cylinders and ton tanks. We utilize the very reliable Volumetric Hydrostatic Testing (VHT) method. VHT measures the expansion of a cylinder under pressure using the displacement of water from a test jacket. Cylinders are visually inspected internally and externally for defects. A cylinder that passes both the visual inspection and VHT is then marked with the required information to allow the cylinder to be filled and transported with a hazardous material. Turn around time for hydrostatic testing is a minimum of 5 business days.

Visual Eddy Testing

We also offer Visual Eddy Testing (VET) to determine if a problem exists with Sustained Load Cracking (SLC) in DOT 3AL cylinders manufactured from 6351-T6 aluminum alloy.  Cylinders manufactured with alloy 6351-T6 are susceptible of SLC in the neck and shoulder area over.  VET is a non-destructive test that uses an instrument to measure fluctuations in an eddy current flowing through the threads that may indicate a possible crack due to SLC.  Any faults identified by the instrument are then visually inspected to verify the instrument's results.

As of January 1, 2007 - The DOT requires a specification or exemption cylinder made of aluminum alloy 6351-T6 and used in self-contained underwater breathing apparatus (SCUBA), self-contained breathing apparatus (SCBA), or oxygen service to be visually inspected and eddy current tested for evidence of SLC in the neck and shoulder area when the cylinder is hydrostatic tested.

Turn around time for Visual Eddy testing is a minimum of 1 business day.

The following manufacturers of aluminum cylinders were affected by the DOT requirements and advisory ruling:

  • Luxfer DOT-3AL cylinders were made from alloy 6351-T6 from 1960 to 1988. Luxfer has published the dates they changed from alloy 6351-T6 to 6061-T6 for all cylinder models.
  • Walter Kidde DOT-3AL cylinders are made of alloy 6351-T6. Production ceased in January 1990.
  • Cliff Impact DOT-3AL cylinders were made from alloy 6351-T6 before July 1990.
  • Catalina Cylinders did not produce any DOT-3AL cylinders from alloy 6351-T6.
Information Sources

The DOT maintains a web page on the topic of SLC in DOT-3AL cylinders.

Luxfer has published a FAQ on SLC and their cylinders.

Cylinder Reconditioning

We also offer shot blasting and priming for high pressure DOT 3A, 3AA, 4AA cylinders and 106 ton tanks. Reconditioning is only offered for cylinders that have been hydrotested at our facility.