Advantages of the Ali-tek Aluminium Scuba Cylinders:

• Flat base allows for easy storage and transportation.
• Seamless construction provides for an incredibly strong and safe product.
• Conforms to internationally recognised manufacturing standards.
• Each cylinder is tested and documented at every step of manufacture.
• International inspection authorities independently inspect and approve the cylinders.
• Cylinders produced by a specialist division of Hulett Aluminium in South Africa one of the world's major Aluminium semi fabricators.
• Internationally recognised experts in Aluminium metallurgy, chemistry, design, operations, technology and quality.

Aluminium Alloy 6061

• Light - due to its low density, one-third the weight of steel.
• Highly resistant to most forms of corrosion - The metal's natural coating, Aluminium oxide, provides a highly effective barrier to the ravages of air, temperature, moisture and chemical attack.
• Non-toxic
• Absorbs impact due to its low modulus of elasticity - in other words it does not damage easily.
• Non-magnetic
• Non-combustable
• Non-sparking
• Fills cryogenic needs
• Recyclable - require only 5% of the energy to produce secondary metal as compared to primary metal and generates only 5% of the green house gas emissions.
• No SLC (Sustained Load Cracking) as was inherent in the 6351 alloy
• Reaches full strength.
  

Aluminium Cylinder Cleaning

One of the most common questions asked is, "How do we clean aluminium cylinders which have been in service?" Hulett Cylinders have found the following cleaning practices to be effective in the cleaning of aluminium cylinders. The cleaning practices have been broken down into two groups, external and internal, with different types of conditions requiring listed under each group.

External

General In-Service Soiling
Wash with a mild soap and rinse. Dry the cylinder after rinsing.

Chipping Paint or Minor Corrosion

Removal of loose paint and minor corrosion by-products by scrapping with a scrapper or putty knife is acceptable.

If complete paint removal from a cylinder is desired, Hulett Cylinders recommend that the paint be removed from aluminium cylinders by the use of paint strippers. Hulett Cylinders recommend that gel-type stripper work well in removing old paint and do not remove metal from the cylinder when properly used. Use gel strippers that are compatible with aluminium. Take great care to ensure that the gel-type stripper does not enter the cylinder.

It is not recommended to clean cylinders by means of sanding or abrasive blasting. Removal of paint or minor corrosion from a cylinder by sanding or abrasive blasting can also remove metal thus reducing the wall thickness of the cylinder and reducing the integrity of the cylinder. If sanding or abrasive blasting is used to clean a cylinder, the remaining wall thickness must be checked by suitable means (i.e. an Ultrasonic gauge) to guarantee the minimum remaining wall thickness is greater than the minimum design wall thickness.

Hulett Cylinders strongly recommend against the use of any method of exposure to high heat (i.e. flame, oven, etc.), in excess of 130°C, for any amount of time in the removal of paint from aluminium cylinders.

Internal

Moisture and Light Soils

Steam clean with soft water and blow dry with forced air if possible. If not possible, fill cylinder with hot soft water and tumble the cylinder for a few minutes. The hotter the temperature of the water introduced into the cylinder increases the capability of the hot cylinder to aid in the drying of the cylinder by evaporation. Follow the tumbling with hot soft water by 1 minute of forced air blow-drying. Always make sure the air used in blow-drying a cylinder is dry and free of filtered contaminates. Drying the cylinder completely after cleaning is necessary to reduce the chance of corrosion from occurring.

Grease, Oil and Lubricants

Tumble the cylinder for 5 minutes with a solution of a small amount of dishwashing soap and hot soft water. Make sure the amount of solution is sufficient to wet the entire inside surface of the cylinder. Rinse the cylinder with hot soft water. Several rinses may be required to remove all the soapy solution. Repeat this sequence as often as needed. Drying the cylinder completely after cleaning is necessary to reduce the chance of corrosion from occurring.

Odours

For a few minutes wet the entire inside of the cylinder with a solution of baking soda and soft water, approximately ½ to 1 cup of baking soda to 4.5 Litres of water. Make sure the entire inside surface is wetted by the solution. Next, rinse the cylinder with soft water. Follow this with a few minutes of wetting the entire inside surface on the cylinder with a solution of vinegar and water, approximately on ¼ - ½ cup of household vinegar to 4.5 litres of water. Then rinse the cylinder completely with water until all odour of vinegar is gone. If original odour persists repeat this operation as many times as necessary. Drying the cylinder completely after cleaning is necessary to reduce the chance of corrosion from occurring.

Corrosion

Tumble the cylinder with a slurry of aluminium oxide pellets and water. You may choose to add a little dishwashing soap to the slurry to aid in the cleaning process. The amount of water inside the cylinder should be sufficient enough to wet the entire inside surface of the cylinder. The amount of aluminium oxide pellets to be used is dependent on the condition of the cylinder. Start out with 1 cup of aluminium oxide pellets to 4.5 litres of water and increase the amount of pellets as needed. Most corrosion is removed within 30 minutes of rotating the cylinder at 30 rpm. Always rinse and dry the cylinder after tumbling is complete. Drying the cylinder completely after cleaning is necessary to reduce the chance of corrosion from occurring.

Eddy Current Inspection Of Aluminium Cylinder Threads

The use of eddy current devices to aid in the inspection of the threads of aluminium cylinders is supported by Hulett Cylinders. Hulett Cylinders believes that eddy current devices should be used in conjunction with visual inspection, not as a replacement for visual inspection, in the inspection of the threads of aluminium cylinders.

Eddy current devices have proven themselves valuable in detecting linear defects (i.e. folds, cracks, intergranular corrosion, etc.) in the threads of aluminium cylinders that are hard to detect during visual examination aided by a light source and a 2X dental mirror.
Hulett Cylinders believes that any linear indication that extends two threads is reason for rejection of the cylinder. This is of course being linear indication that appears as a spike on the most commonly used eddy current devices.

Valleys do not cause rejectable linear indications, a spike, on the, most commonly used eddy current devices. Tool stop marks also do not cause rejectable linear indications on the commonly used eddy current devices.

High Temperature Exposure of Aluminium Cylinders

Aluminium cylinders subjected to fire must be removed from service. No testing for acceptance or re-heat treatment is authorised.

In CGA pamphlet C-6.1; Standards for Visual Inspection of High Pressure Aluminium Gas Cylinders, it states that cylinders heated to metal temperatures in excess of 176°C must be condemned.

Common evidence of exposure to elevated temperatures that may heat the metal temperature to 176°C include:

· Charring, blistering, or discoloration of the cylinder paint or protective coatings;
· Distortion of the cylinder;
· Melting of non-metallic (i.e. plastic, etc.) valve components;
· Charring or burning of labels;
· Activation of valve pressure relief device; or
· Activation of the heat indication system.

Hulett Cylinders recommend that if there is evidence, or it is believed, that a cylinder has been exposed to elevated temperatures but the temperature of metal of the cylinder is not believed to have reached 176°C for any duration of time, the cylinder must still be subjected to hydrostatic testing or condemned. A cylinder that has been exposed to temperatures great enough to change the temper of the cylinder could show an increase in total or permanent expansion as measured during hydrostatic testing. Cylinders showing unusually high total expansion or exceeding regulatory limits for the relationship of permanent expansion to total expansion (5%) should be condemned.