Q: Can the life of standard carbon fiber composite SCBA cylinders be extended past 15 years?
A: Yes. In 2017 the US Department of Transportation (DOT) approved Life Extension for carbon fiber composite SCBA cylinders beyond 15 years by issuing DOT special permit 16320.
In DOT-CFFC, the DOT document that controls the design and manufacture of composite SCBA cylinders, life extension is allowed. To extend the life to 30 years from original manufacture date, the DOT must verify that the cylinders processed for life extension can operate safely for the extended lifetime. According to SP-16320, the only DOT accepted method to prove that the cylinders safely meet this high standard is Digital Wave’s LEx™ life extension process, which is based primarily on Modal Acoustic Emission (MAE) testing technology. The only company certified by the DOT to use LEx™ today is the company that invented the technology – Digital Wave Corporation (www.digitalwavecorp.com). Dalmatian Fire Equipment (www.dalmatianfire.com) is the exclusive distributor of the LExTM technology.
Q: Can my current hydrostatic testing facility extend the life of my standard carbon fiber SCBA cylinder to 30 years?
A: No. Hydrostatic testing is not recognized for life extension.
The DOT’s special permit 16320 specifies that cylinder liner remediation and Modal Acoustic Emission testing are both required to extend the life of a standard SCBA cylinder to 30 years.
Q: How long does LEx™ extend the life of my standard carbon fiber SCBA cylinder?
A: To 30 years from the date of manufacture including MAE requalification each 5 years after life extension.
The LEx™ process extends the life to 30 years from the original manufacture date. Requalification with a Modal Acoustic Emission (MAE) test is required each five years after life extension. The MAE requalification test requirement is the required periodic inspection for life extended cylinders. Return your cylinder to Dalmatian Fire Equipment or Digital Wave each five years to get the Modal Acoustic Emission test for a modest fee. The MAE requalification test is different from the MAE life extension test.
Q: What if my SCBA cylinder is not yet at its 15 year end of life? Can I life extend it prior to the current 15 year end of life and how long can it be used for?
A: Yes. For example, if you have a SCBA cylinder that was manufactured in 2004 and you life extend it in 2017, it can be used to 30 years from the original manufacture date. This would be 2034. It would require MAE requalification testing every 5 years from life extension date.
Q: My SCBA cylinder was manufactured in 1998. After 15 years in service, I just stored it in my warehouse. It has been there since 2013. Can I life extend it now and how long can it be used for?
A: Yes. For example if you have a SCBA cylinder that was manufactured in 1998 and you life extend it in 2017, it can be used to 30 years from the original manufacture date. This would be 2028. It would require MAE requalification testing every 5 years from the life extension date.
Q: Does it matter if my cylinder was hydrostatically tested during the initial 15 years of life?
A: No, the LEx™ process is specifically designed to take into account hydrostatic testing that was used for requalification testing.
Hydrostatic testing was the only means to requalify SCBA cylinders prior to Modal Acoustic Emission. If cylinders were not properly dried after hydrostatic testing, the aluminum liner could see corrosion. The LEx™ process inspects the liner and also remediates liners exposed to water during the initial 15 year life.
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 do not need to be removed from service.
Per the DOT-CFFC manufacturing requirements the manufacturers’ could provide the DOT data showing that their cylinder are safe to use past 15 years; several manufacturers tried, and they were unsuccessful (http://www.luxfercylinders.com/press-releases/concerning-life-extension-of-dot-cffc-carbon-composite-cylinders). Failure testing completed by Digital Wave Corporation engineers proved that extended life is safe, and the DOT validated it. The design 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 Emission testing; and re-labeling. To keep cylinders in service beyond the original 15 year service life, the DOT requires the checks and balances built into LEx™.
Q: Are LExTM cylinders warrantied?
A: Yes, the LExTM cylinders carry a limited warranty for ten (10) years or the life of the cylinder, whichever is shorter for protection against manufacturing defects.
Q: The manufacturers say they have a new 30 year cylinder that I should replace my end of life cylinder with.
A: You already have a 30 year cylinder! You have used it 15 years already. You have another 15 years to go if it has been life extended with LEx™. You have 15 years to make the decision of what new cylinder to buy.
Some manufacturers are claiming that they have “30 year cylinders” available for sale. This is somewhat of a misleading statement. In actuality they “may” have a 30 year cylinder available. The DOT has not officially granted approval of 30 years for these cylinders. In the special permit requirements, the manufacturers must supply data at the ten(10) and fifteen (15) year intervals to be granted the 30 years of service life. If you look closely at the fine print on these manufacturers web pages regarding these cylinders you will see that they state “…up to a 30 year life (Cylinders must undergo additional testing before they are fully approved for 30 years.)”. What this means is that they still need to perform the testing required to prove to the DOT that they can be used for 30 years. They DO NOT as of yet have this 30 approval. What you do have is the DOT approval to use your current 15 year SCBA cylinder until 30 years from the manufacture date with LEx™ life extension.
This lack of certainty is explicitly stated in a SCBA manufacturer’s literature (https://www.scottsafety.com/en/us/DocumentandMedia1/QA_30-Year_Cylinder_HS7221A_EN.pdf)
Q: Why do the manufacturers limit standard carbon SCBA cylinder life to 15 years?
A: This life was based off of stress rupture studies by NASA on Kevlar composite cylinders, and does not apply to carbon fiber pressure cylinders.
Life Extension with Digital Wave’s MAE 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 composite overwrap quality with Modal Acoustic Emission Testing, and it wraps fiberglass on 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: 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 cylinders to have a design factor of safety of 3.4. Thus, a cylinder that has an operating pressure of 4500 psi must have a minimum design burst pressure of 15,300 psi. DOT/PHMSA funded research shows that carbon fiber cylinders typically withstand closer to 20,000 psi before bursting, for a factor of safety of closer to 4. The design requirements in DOT-CFFC make them the safest high pressure cylinders in the world, and their operating statistics support this claim. The service to burst pressure ratio also results in fatigue life performance that meets the ISO test requirements of infinite life. For safe life extension, the DOT still requires LExTM .
Q: How did the engineers at Digital Wave Corporation discover the SCBA Life Extension process?
A: The US Navy hired them to see if their cylinders could be used for an extra 15 years.
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 Corporation was contracted by the Navy to perform testing to provide DOT the needed data for life extension. The work was successful. Digital Wave Corporation proved conclusively that the cylinders met, or exceeded, the operating requirements of brand new cylinders, and received a DOT special permit SP-15720 for life extension of Navy SCBA CFFC and FRP-1 cylinders. In addition they received SP-16343 for life extension of Navy life raft inflation cylinders manufactured to the same DOT-CFFC design requirements.
Q: How long does the standard SCBA cylinder carbon fiber composite overwrap last?
A: A long, long time. Maybe forever.
The DOT-CFFC design requirements keep the stress in the fiber to such a low level that the composite overwrap will easily last forever. The durability of the carbon is a blessing and a curse for the environment as well. These cylinders will last a very long time if life extended, therefore not taxing the environment with material and energy demands to manufacture new cylinders. When we just throw cylinders out after 15 years they go in the landfill. They do not decompose or breakdown easily. They will be in their existing state for millennia. This is a waste of money, a waste of resources, a waste of energy and a scar on our environment.
Q: How long does the aluminum liner of a standard SCBA cylinder last?
A: At least 24,000 refill cycles.
With LEx™ conditioning, the test cylinders lasted an additional 24,000 refill cycles, which is considered infinite life according to ISO 11119-2, the international standard for the design and manufacture of composite cylinders.
Q: Why do cylinder liners need the reconditioning with the LEx™ process?
A: To heal the small areas of corrosion caused by hard water exposure of the liner.
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 engineers 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 DOT-CFFC cylinders lasted 24,000 refill cycles after life extension processing.
After the reconditioning of cylinders with highly corroded liners, they were then 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 11119-2 states that the cylinder has infinite life.