Scott, 4500 PSI, 30 min. Breathing Air Tanks (expired)

Description

What I have for sale are Scott Air-Pak, breathing air storage cylinders. These are 30 minute, aluminum with a carbon-fibre/fiberglass overwrap air tanks with a 4500 psi. WPR (working pressure rating). These were made in the USA and were taken out of service because they have exceeded their “supposed” 15 year “service” life expectancy, according to “older” DOT regulations at the time of their conception. These tanks have not been recertified for commercial use, the key word here is commercial use.. as of this date, but can be recertified and burst pressure tested at any certification facility that is familiar with the newly established DOT regulations and certification guidelines regarding this type of pressure vessel.
You will receive one (1) randomly selected UNCERTIFIED/UNTESTED tank. These tanks have been painstakingly inspected for any possible exterior damage that would be pertinent to their re-certification. The last inspection/certification date and appearances may vary, but these pressure vessels have virtually unlimited uses in many areas other than the fire protection industry.
The possibility of them holding other gases is possible with the installation of the proper adapter and “content labeling requirements” denoting the contents whether it be carbon dioxide, nitrous oxide, propane or other pressuried gases, and can be used as portable air supplies for impact wrenches, tire refilling tanks, CO2 paint ball refill tanks, propane tanks, or nitrous oxide systems on cars (pressuried at only 900 psi), etc., just to name a few of those possible uses.
What you do as an end-user of these tanks is totally up to you... so do your due dilligence and research any possible application of these tanks for other than for compressed breathing air service.
https://www.airgunnation.com/topic/has-anyone-had-there-tank-fail-the-hydro-testing/
Cylinder Specifications
:
These carbon-fibre composite, 30 minutes (rated), 4500 psi., cylinders and included valve assembly were used for storing atmospheric
breathing air under very high pressure to provide firefighters with a source of breathable air during their firefighting activities
..
Cylinder Dimensions
:
a. Cylinder size = 19.6” × 5”
b. Internal water capacity = ~285 cubic inches
c. Air capacity @ rated pressure of 4500 psi. = 45 cubic feet (1,280 L) for a 30 minute air supply (1274 liters)
d. Weight = 11 pounds (5.0 kg)
e. Cylinder connection to adapter assembly is a single 7/8" by 14 IPT (straight thread with “O” ring seal and seating boss).
Cylinder construction
:
These carbon fibre composite cylinders are made up of an aluminum alloy inner shell with carbon-fibre composite wrappings and a fiberglass and epoxy resin over-wrappings to protect the carbon-fibre wrapping from handling damage.
These aluminum cylinders, when manufactured, are first burst-tested to 6,500 psi PRIOR to being wound with the high strength carbon-fibre material. Then the fiberglass overlay is applied, cured and then they are again resubjected to another burst test. This time to 12,000 psi. (as sited in NFPA 1981: Standard on Open-Circuit self-contained breathing apparatus (SCBA) for Emergency Services)
RDT (random destructive testing), that is, purposely subjecting these cylinders to excessive pressure until failure occurs, usually at approximately 16,000 PSI.
As you can plainly see, the uncovered/unwrapped aluminum cylinder GREATLY EXCEEDS the normal operating pressure of the tank’s specifications which should give you some kind of idea of the over-rating and safety design margins that are built into these cylinders when Scott Air first designed and manufactured them, let alone, then wrapping them with carbon-fibre and then a fiberglass and resin overlay to insure their durability against catastropic failure when subjected to the radiant heat during fire fighting prodedures..
Aluminum (depending on it’s alloy), by itself has a tendency to start losing structural strength at elevated temperatures over 400 °F, so you can see why the need for the additional use of carbon-fibre wrappings to maintain containment of very high air pressures contained within these tanks while being exposed to the radient heat of structure fires.
Outlet Valve Assembly
:
The included cylinder valve assembly is the appliance which makes the connection between the contents of the cylinder and the transport hose (which will send the air to a pressure reducer/regulator for breathing purposes). It is constructed of a forged aluminum alloy and is angled to reduce stress at the connection made between the high-pressure female coupling and that of the high pressure hose.
The valve assembly contains a "tri-lobe”, ergonomically designed hand wheel.
This hand wheel is a one-way, ratcheting type knob which has a “push-to-close” feature style knob. This feature protects the fire-fighter/user from an unwanted accidental shutoff during use.
Also included in this valve is an upstream connected “frangible disc safety relief device" located on the valve assembly which is known as the "tri-dimensional burst disk". This burst disk senses the tank’s internal pressure and temperature and protects the wearer/user against a situation where the pressure in the tank should increase with exposure to heat during a fire. It is designed to prevent an unwanted failure somewhere else in the bottle.
It is also considered to be "tri-dimensional" in that, if this relief is activated, it would disperse the contained air in the bottle in three equal directions so as not to throw the user off their balance.
Typically these burst discs are usually set to release at 7200 psi, or 400 °F, whichever occurs first.
The burst disc pressure relief for these valves, as used in these Scott cylinders, is set to release at 4800 psi or 400 °F , whichever occurs first .
The high pressure male coupling, included in high pressure bottle connection,  meets the Compressed Gas Association Standards #346 and #347.
Reason for being expired
:
These pressure vessels are considered to be “expired” by older DOT standard regulations in that these cylinders were to originally have a 15 year life expectancy and be tested every three (3) years.
https://www.nationalfireinc.com/inspection-testing/scba-scuba.html
At one time, both steel and aluminum pressure vessels also had this same “limited life expectancy” regulation, but that policy was changed by DOT regulations to them having an “unlimited life expectancy” as long as they are “burst tested” every 5 years at 1.5 times RWP (rated working pressure) and as long as they also fall within the REE  (rejection elastic expansion) specification for expansion at rated test pressure, they can be recertified for indefinite use.
The DOT is presently in the process of issuing certificates to have the same effect for “composite pressure” vessels, now that these vessels have had a proven track record for operational safety for 20+ years and they also must be recertified every 5 years as well, with the same expansion limit (REE) conditions as previously mentioned.
(F.W.I.W.) the DOT regulations ONLY APPLY to the commercial transportation of pressurized gas cylinders..., the Compressed Gas Association (CGA) rules apply to construction, maintenance and storage of them.
Whether you choose to use these composite pressure vessels for compressed air or any other compatible gas, the CHOICE IS STRICTLY UP TO YOUR CHOOSING... provided that they have the proper identification signage and adapter attached to their outlet neck for that particular gas’s application.
The adapters for those gases are available from any reputable industrial gas supplier (or even eBay for that matter) and they should be able to recertify these cylinders for your continued usage at that time.
The requirement for that adapter is to be compatible with these cylinder’s is 7/8" x 14 IPT (28.225 mm x 1.81 mm) straight thread, with an “O” ring seal boss.
All full metal “diving cylinders” (SCUBA) built for 300 bar (4500 psi and above) working pressure, and ALL composite cylinders
must use parallel threads
, so as not to induce structural strains into the cylinder’s base material while tightening the “O” ring seal to 20 Nm. (approximately 15 foot/pounds).
Either a 25 x 1.5 mm or 18 x 1.5 mm thread pitch is used for SCUBA cylinders. (These SCBA cylinders have a larger and different thread pitch on purpose to prevent them from being used as SCUBA tanks)
The outlet valve/tank connection is sealed by an elastomeric “O” ring pressurized by the gas, has a bed-stop, and needs only about 20 Nm (15 pound feet) of torque which is compatible with all three types of composite cylinders in use today.
Your shipping cost is only the amount required to ship these “unpressurized” cylinders SAFELY through USPS Priority Mail service and since they might travel on aircraft and
MUST BY USPS REGULATIONS
be unpressurized to be shipped.
I will also ship these cylinders to overseas countries with proper customs declarations with advanced shipping payment received or by shipping collect..
If you have any concerns or questions, please contact me for any clarifications before purchasing.
Orders for multiple cylinders can be bundled together as one (1) package when shipped through USPS Priority Mail as long as the combined total weight is less than 70 lbs... saving you $$$$ on shipping charges.