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| Q:
What is Hydrostatic Testing? |
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Hydrostatic testing is the most common procedure used to qualify cylinders used for the transportation of dangerous goods. Hydrostatic testing is also required periodically to re-qualify these pressure vessels for continued service.
During a hydrostatic test, a pressure vessel is placed inside a closed system, usually a test jacket filled with water, and a specified internal water pressure is applied to the container inside this closed system. The applied internal pressure causes an expansion of the container being tested, and the total and permanent expansion that the container undergoes are measured. These volumetric expansion measurements, in conjunction with an internal and external visual inspection of the container, are used to determine if a pressure vessel is safe for continued use, or has suffered from a degradation in its structural integrity and must be condemned.
Some pressure vessels may be re-qualified by means of a proof-pressure test. This method, also known as a modified hydrostatic test, consists of subjecting a pressure vessel to a specified internal pressure and inspecting the pressurized container for leaks, bulges or other defects. This method is permitted only when the applicable regulations do not require the determination of volumetric expansion measurements (e.g. for certain types of low pressure cylinders such as those used on many portable fire extinguishers).
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| Q:
Do I need to have my cylinders tested? |
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All cylinders must be tested. Some cylinders are tested every 3 years others are tested every 5. Prior to filling any cylinders the last test date is checked, if the tank is past or due for its test then the cylinder must pass a hydrostatic test prior to being refilled.
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| Q:
How can I have my cylinder tested? |
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Simply bring the cylinder(s) in to our Levitt Street location and we will take a quick look at them for you. If the tank(s) are out of test we can tell you within 30 seconds of looking.
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| Q:
What happens if my cylinder fails the test? |
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The cylinder is condemned. In the trade, this is called a "failed hydro", and is one reason that buying used equipment is not always the most economical choice. If the cylinder fails, it may not be refilled. When a cylinder is condemned by a hydro inspector, the DOT markings are stamped out and/or the cylinder is destroyed.
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| Q:
What can I do to pro-long the life of my cylinders? |
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The following will help pro-long the life of your cylinder. Please note: Testing is still required by regulation.
* Always keep your cylinders standing up-right restrained to a wall.
* Always keep the protective cover on unused cylinders.
* Always keep the cylinders away from sources of heat ( including direct sunlight ).
* Have a visual inspection completed every year ( we do this each time we fill a cylinder ).
* Make sure your tank is "in test" ( we check this each time we fill a cylinder ).
* When storing cylinders always leave at least 500 psi in the tank to prevent water from entering the tank.
* Never drain/empty a cylinder before storage.
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| Q:
What are all these markings on my cylinder? |
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The markings on a cylinder include information regarding the date of manufacture, the manufacturers name or registered mark, the serial number of the unit and the specification or exemption to which the container complies. For cylinders that have been re-qualified one or more times, additional markings indicate the date(s) of any previous hydrostatic retests and identification markings of the retest facility.
On steel cylinders, these markings are stamped into the shoulders of the cylinder. On spheres, the markings are stamped into the mounting brackets or the gauge guard, or they may be electro-etched onto the sphere itself. The markings for fiber-wound cylinders are found on a nameplate and retest labels embedded in the epoxy of the cylinder body. The markings on low pressure cylinders are usually found on a label or nameplate.
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| Q:
How do I decode the markings on my cylinder? |
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Cylinder Specifications Markings:
The first group of characters indicate the responsible regulatory agency (e.g. DOT, TC, ICC, CTC). The second group of characters identify the container specification or exemption number (e.g. 3AA, 4DS, E8162) and the third group identifies the rated service pressure of the container (e.g. 1800 psi, 700 psi).
Hydrostatic Test Markings:
Cylinders that have been hydrostatically tested and re-qualified must be marked by the retest facility with the facility retester identification number (RIN), and the retest date. Depending on the age of the container, it may contain none or many sets of retest markings. The oldest date marked on the container is the date of the original hydrostatic test carried out by the manufacturer, and is considered the manufacturing date. Any subsequent dates marked on the container are a record of the hydrostatic tests that the container has undergone.
The manner in which the markings are applied, and the required format for the markings are defined by the applicable regulations.
FORMAT: TEST-MONTH RIN TEST-YEAR
11 D096 02
11 - indicates the month of the retest (Nov.)
D069 - indicates the DOT approved facility RIN
01 - indicates the year of the retest (2001)
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