Several years ago, MSA (Mine Safety Appliances) and
Interspiro, manufacturers of SCBA cylinder systems, introduced policies
that encourage extraordinarily rapid fill of their brands of fully wrapped
composite SCBA cylinders. The potential value of filling a cylinder
in a minute or less is obvious. Emergency personnel can get back on
line much more quickly than either having to change out cylinders or wait
for a air fill that conforms to the more common gas industry standard of
600 psig or less. The disadvantages are less apparent and, in some
cases overlooked.
MSA in a well-written guideline, points out that its
cylinders are well made and thoroughly tested. Selected new
cylinders are even cycled at much faster fill rates to hydrostatic test
pressure thousand of times with no ruptures. Temperature sensing
devices affixed to the aluminum liner of a composite cylinder show that
internal temperatures, generated by rapid compression of air, at about 116
degrees F. are well within the allowable limits for safety. Even
in-service use of the fast filling methods for several million fills
contributes to the view that fast filling techniques are safe.
The process of fast filling, that is charging a
4,500 psig full-wrap composite cylinder in 45 seconds, is reported to be
so routine that it can be used for non-emergency filling as well as
emergency fills even though the original purpose was for emergency fills.
That rate of fill may also be used on steel SCBA according to MSA and
Pressed Steel Tank Co.(PST).
PSI, Inc. personnel are neither metallurgists nor
engineers. We do not dispute the policy statements made that
indicate new and otherwise well maintained full wrap composite SCBA
cylinders can safely withstand such rapid fill and resulting expansion.
Apparently they can and emergency conditions may well support the need for
such speed. We do however know something about in-service cylinder
condition and their level of care.
We know that within the 15year life of a composite
cylinder many receive unusually harsh treatment. Some are not
hydrostatically retested at the required three-year interval. And, there
is some question as to the actual value of the hydrostatic retest to
determine the overall quality of the cylinder. A few fire departments have
been found using composite cylinders past the mandatory retirement age of
15 years. A small percentage of SCBA cylinders are kept like new in
storage cases at factories, aboard vessels, and at other locations where
they are not regularly used. Most SCBA in fire department
inventories are used regularly and often harshly.
We at PSI, Inc. are concerned that many operational
SCBA are in far less than Ideal Condition. OSHA (Occupational Safety
and Health Act), DOT (Department of Transportation) and NIOSH (National
Institute for Occupational Safety and Health) all direct or
recommend frequent visual inspections. NIOSH places considerable
emphasis on both the quality of the inspection and the qualification of
the inspector. In a December 7, 1999 NIOSH notice signed by Richard
W. Metzler, Chief Respirator Branch, seven policy statements are made.
In that document, NIOSH recommends filling cylinders (without regard to
type) at a rate below 600 psig per minute and refrain from
over-pressurizing or fast filling. Cylinders are to be inspected
frequently, at least annually, by trained inspector conducting proper
inspections. Inspections should be conducted by trained, qualified
and competent visual inspectors. Unfortunately, many government
officials and fire department technicians don’t know what constitutes a
proper inspection. OSHA requires the employer to be responsible for
safe cylinders based upon visual inspection and directs that SCBA shall be
inspected every 30 days and after each use. DOT in its notice
RSPA-99-5143 (notice no. 99-11) advises those who own or fill certain 3AL
or aluminum lined composite cylinders to have annual technical internal
and external visual inspections. The notice further advises,
“for additional information on SCBA/SCUBA cylinders contact PSI, Inc. and
Luxfer Gas Cylinders”.
The problem with fast fills is that there are a
great many cylinders in use that have not had frequent inspections by
trained, competent technicians with a technical protocol to follow.
So, while there appears to be nothing wrong with the concept of rapid
cylinder filling, even while the cylinder is on the fire fighter’s back,
many cylinders may not qualify for the dramatic stresses generated by a 45
second fill to 4,500 psig. Since 90 percent of cylinder failures
occur during the fill process and, every year numerous cylinders of
various designs rupture, great care should be given to ensure the
cylinders are not damaged. Technical visual examinations
should only be conducted by trained inspectors who understand the
significance of various damage types. Fire fighters in Detroit
didn’t understand the effect of damage nor did the fatally injured New
York fireman or the California department that filled chemically damaged
cylinders. It is interesting that several agencies recommend all
fills take place in some form of protective container which contradicts
the logic of routine fast fills on the back of a fire fighter.
A policy of routine fast fills might also prompt
technicians to fast fill other cylinders that have not been recommended
for filling faster than 600 psig per minute. Many fire departments
use solid wall 3AL SCBA and SCUBA. One manufacturer specifies these
cylinders are not to be filled faster than 600 psig per minute.
While Pressed steel Tank Co. states that its steel cylinders may be fast
filled, we know that many of those cylinders used by divers have
significant damage and might not withstand a fast fill protocol.
All fill station operators who chose to fast fill
cylinders should be trained and qualified to identify any questionable
cylinders and to ensure the cylinders they fill receive frequent,
technical visual inspections, the cylinders are in excellent condition and
eligible for fill rates beyond 600 psig per minute.
Professional training for
cylinder inspectors is offered throughout the U.S. and Canada and at
some international locations. Contact PSI, Inc. at 16932
Woodinville-Redmond Road, Suite A201, Woodinville, WA 98072. Telephone 425-398.4300, fax
425.482.0160 e-mail:
psi@psicylinders.com