This notice informs users of SCBA
that certain aluminum seamless and composite hoop-wrapped cylinders are
susceptible to sustained load cracking (SLC). If such cracks are not
detected during visual inspection, cylinder rupture can occur, especially
during filling.
DOT and NIOSH are aware of 12
cylinder ruptures from SLC in the U.S.A. Additional failures
have occurred in other countries. Most failures occur during the
fill process. NIOSH has determined that in order to reduce the risk
of death, serious injury, or property damage, the following safety
precautions should be taken with all DOT 3AL and composite cylinders
manufactured of 6351-T6 alloy.
- Increase the frequency of
internal visual inspections. Perform inspections on an annual basis
by a qualified inspector in accordance with comprehensive inspection
guidelines using mirror and light.
- Inspections should be
performed by qualified individuals. Individuals inspecting for SLC
or other cylinder damage must be able to follow visual inspection
guidelines and should be trained by accomplished instructors experienced
in visual inspection of cylinders. These inspections are only
effective when properly performed. Therefore, emphasis should
be placed on inspector training and diligence. The
inspection should be conducted by trained, qualified, and competent
visual inspectors.
- Submit cylinders for
non-destructive testing at regular intervals between the required
requalification testing.
- Do not refill any cylinder
that has lost internal pressure for no apparent reason.
Unexpected loss of pressure (or sound of leaking air) may indicate a SLC
defect has developed. Immediately remove from service, discharge and
visually inspect interior.
- Cylinders should only be
refilled in a manner that limits risk to personnel and property.
Recommend filling in a suitable enclosure.
- Use proper cylinder filling
equipment and procedures and refrain from fast-filling. SLC
develops over several years but such growth and the likelihood of
cylinder rupture are accelerated when cylinders are over-pressurized, or
fast filled. Recommended fill rate is below 600 psig per minute.
(Over 90 percent of all cylinder explosions occur during the fill
process). Never fill above stamped service pressure.
- Check for valid re-test date
before filling. NO cylinder, regardless of construction type
should be filled or used if it has exceeded the valid service life or
re-test dates specified by DOT (seamless aluminum cylinders re-test at 5
year intervals with no life limit. Composite cylinders retest at
3year intervals and are limited to 15 years maximum life).
Training and information on
inspecting high pressure SCBA and SCUBA cylinders can be obtained by
contacting
PSI, Inc.
16932 Woodinville-Redmond Road, Suite A201, Woodinville, WA 98072
telephone 425.398.4300 e-mail
psi@psicylinders.com
web site:
www.psicylinders.com
PSI, Inc. is the ONLY worldwide
full service SCBA/SCUBA visual inspector training company recognized by
cylinder manufacturers, government agencies, fire and dive industries.
We are the industry standard.