SCBA Composite Cylinder Life Extension Q&A
Q: Can the life of standard SCBA cylinders be extended past 15 years?
According to DOT-CFFC, the DOT document that controls the design and manufacture of composite SCBA cylinders, the life of cylinders can be extended. To extend the life an additional 15 years, the DOT must verify that the cylinders processed for extension can operate safely for the extended lifetime. In 2017 US Department of Transportation (DOT) approved Life Extension for SCBA cylinders beyond 15 years following special permit SP-16320. According to SP-16320, the only DOT accepted method to prove that the cylinders safely meet this high standard is LEx, which is based primarily on Modal Acoustic Emissions testing technology. The only company certified by the DOT to use LEx today is the company that invented the technology – Digital Wave.
Q: Why do the manufacturers limit standard SCBA cylinder life to 15 years?
A: Old-fashioned hydrostat testing for standard SCBA cylinders only allows a life of 15 years. That’s all they had.
Life Extension with Digital Wave technology is new, and it’s more than just testing. The LEx process has 3 basic parts: it remediates the cylinder liner deterioration, it verifies the liner quality with Modal Acoustic Emissions Testing, and it wraps the outer sidewall to resurface. Before 2017, the LEx process was not available. Before LEx, the US Department of Transportation (DOT) did not allow use of standard SCBA cylinders beyond 15 years. LEx is a proprietary process, and the manufacturers don’t have it. With LEx technology from Digital Wave and Dalmatian Fire Equipment, the US Department of Transportation says life extension is safe up to 30 years.
Q: Can my current hydrostat testing facility extend the life of my standard SCBA cylinder to 30 years?
A: No. Hydrostat testing is not recognized for life extension.
The DOT’s special permit 16320 specifies that cylinder liner remediation, modal acoustic emissions testing and sidewall wrapping are all required to extend the life of a standard SCBA cylinder to 30 years. Digital Wave is the only company recognized by the DOT at this time, and Dalmatian Fire Equipment is the exclusive representative of Digital Wave.
Q: How long does LEx extend the life of my standard SCBA cylinder?
A: 15 additional years (for a total of 30) including requalification each 5 years.
The LEx process extends the life for 15 years after original cylinder expiration, and requalification with a Modal Emissions Test is required each five years. The Modal Emissions Test requirement for Life Extended Cylinders is similar to the Hydrostat Test that is required for standard cylinders. Return your cylinder to Dalmatian Fire Equipment or Digital Wave each five years to get the Modal Emissions test for a modest fee.
Q: If the manufacturers say the cylinders are dangerous after 15 years, shouldn’t they be removed from service?
A: Cylinders with LEx are safe, and those do not need to be removed from service.
When cylinders meet the US DOT-CFFC manufacturing requirements, they also meet ISO test requirements of infinite life. Failure testing completed by Digital Wave scientists proved that long life. And the DOT validated it. The manufacturing requirements in DOT-CFFC make them the safest high pressure cylinders in the world. To safely extend the life beyond the original equipment manufacturers’ 15 year specification, the DOT requires: liner remediation; proof that it was done correctly using Modal Acoustic Emissions Testing; and wrapping the side walls. To keep cylinders in service beyond the original 15 year service live, the DOT requires the checks and balances built into LEx.
Q: What are the safety specifications and measures that the DOT used to evaluate LEx?
A: Design Safety Factor of 3.4 minimum, and (for 4500 PSI cylinders) a Design Burst Pressure of 15,300 psi.
The DOT-CFFC document requires standard SCBA cylinders to have a design factor of safety of 3.4. Thus, a cylinder that has an operating pressure of 4500 psi has a minimum design burst pressure of 15,300 psi. DOT/PHMSA funded research shows that carbon fiber cylinders withstand closer to 20,000 psi before bursting. The manufacturing requirements in DOT-CFFC make them the safest high pressure cylinders in the world, and their operating statistics support that claim. The service to burst pressure ratio also results in fatigue life performance that meets the ISO test requirements of infinite life. Even with these measures, the DOT still requires LEx, including side-wall wrap, liner remediation and Modal Acoustic Emissions Testing to prove it was all completed correctly.
Q: How did the scientists at Digital Wave discover the SCBA Life Extension process?
A: The US Navy hired them to invent this process.
In 2011 the U.S. Navy had SCBA cylinders coming up on their 15 year life, and they wanted to know if there was a way to use them beyond their life. Digital Wave was contracted by the Navy to perform testing to provide DOT the needed data for life extension. The work was successful. Digital Wave proved conclusively that the cylinders met, or exceeded, the operating requirements of brand new cylinders, and received a DOT special permit for life extension of cylinders.
Q: How long does the standard SCBA cylinder carbon fiber composite overwrap last?
In performing the life extension testing, Digital Wave discovered that the composite overwrap is stressed so little at operating pressures that it will easily last forever.
Q: How long does the aluminum liner of a standard SCBA cylinder last?
A: 24,000 refill cycles.
With LEx conditioning, the cylinders should last an additional 24,000 refill cycles, which is considered infinite life according to ISO.
Q: Why do cylinder liners need the reconditioning that LEx provides?
A: To heal the small areas of corrosion that could be caused by moisture in the cylinder.
After years of use and hydrostatic testing, small amounts of corrosion can occur in an aluminum cylinder liner. The corrosion comes from moisture in improperly dried breathing air, or from improper cylinder drying after the hydrostatic testing required every 5 years. Digital Wave scientists developed a proprietary method that reconditions the aluminum liners, effectively healing the corroded areas.
Q: How do we know that LEx reconditioning really works?
A: Testing shows they last 24,000 refill cycles after life extension processing.
After the reconditioning, cylinders were cycled to developed pressure (e.g., for a 4500 psi operating pressure, this would be a 5192 psi developed pressure) for an additional 24,000 cycles after the 15 year life of the cylinder. At this number of cycles, ISO states that the cylinder has infinite life.