Cylinders hydrostatic testing

At least semiannually, all high-pressure cylinders should be weighed and the date of the last hydrostatic test noted. If, at any time, a container shows a loss in net content of more than 10%, it should be refilled or replaced. 

The laminate compressive hoop strength/stiflness of a filament-wound vessel can be evaluated using the externally pressurized ring test method [44] or the standardized ASTM D2586 test method. In the ASTM D2586 test method a filament-wound FRP cylinder is tested under hydrostatic pressure to simulate the loading conditions of a pressure vessel under an external pressure load. The main drawback of this test method is the influence of the end constraints on the test results. 

The process for manufacturing seamless line pipe is shown schematically in Figure 5.8. In this process, a heated metal cylinder is pierced and then formed into the proper diameter and wall thickness. Seamless pipe is available through 26 in. (660 mm) diameter, but it is normally used only up to 16 in. (405 mmi diameter. Although seamless line pipe is the most expensive (15 to 25% above ERW), it is the most reiitable Even so, failures do occur. Hydrostatic test records reveal that about one failure occurs every 500 mu (800 km) of test. Some mills produce seamless pipe that has a significantly higher failure rate thus, it is important to ensure adequate quality control. 

CGA C-1, Methods for Hydrostatic Testing of Compressed Gas Cylinders, 7 ed.. Compressed Gas Association, Inc., 1725 Jefferson Davis Highway, Arlington, VA... 

Metrication also affects the specified ratio for hydrostatic test pressure, but does not increase the maximum test pressure. While high pressure seamless steel cylinders marked to CTC specifications are still tested to 5/3 service pressure, such cylinders marked to metric standards are retested at 1.5 times service pressure because the marked metric service pressure is 10 percent higher. 

The Hazardous Materials Regulations of DOT and similar regulations of TC require that cylinders be periodically requalified including a visual inspection to determine their suitability for ongoing service. A formal visual inspection is authorized instead of the periodic hydrostatic retest for certain low pressure cylinders dedicated for noncorrosive gas service. Specific details for this allowance can be found in DOT regulations under 49 CFR 173.34, or CAN/CSA B339 and B340 [1, 3, 4]. Otherwise, visual inspection is a mandatory supplement to a hydrostatic test. 

Low pressure cylinders exempt from hydrostatic testing... 

The first category covers cylinders exempted from hydrostatic retesting requirements of DOT and TC by virtue of their exclusive use in non-corrosive gas service. Since they are not subject to internal corrosion they do not require internal shell inspection, and, therefore, can be requali-fied by an external visual inspection. However, if internal corrosion is suspected, cylinders of this type should be internally inspected and hydrostatically tested. 

Interior corrosion is best evaluated by a hydrostatic test combined with careful visual inspection. Ultrasonic thickness-measuring and flaw-detection devices may be used to evaluate specific conditions. Corrosion limits for both low and high pressure steel cylinders were dis-... 

DOT and TC regulations require the hydrostatic testing of compressed gas cylinders by water jacket or other suitable methods that provide accurate data [1, 2]. The hydrostatic test determines the total expansion and permanent expansion under specified test pressure. These expansion readings determine wall thickness, average wall stress, and level of yield strength of the steel. DOT or TC must approve in writing the type and operation of the test apparatus. 

In Canada, CAN/CSA B339 and CSA B620-1987, Highway Tanks and Portable Tanks for the Transportation of Dangerous Goods, should be consulted [3, 19]. In the United States, 49 CFR Part 173 outlines procedures for applying for approval of hydrostatic test equipment. More detailed information is available in CGA C-1, Methods for Hydrostatic Testing of Compressed Gas Cylinders [1,20]. 

Methods used for hydrostatic testing of compressed gas cylinders and tubes are as follows ... 

The pressure recession method consists of rapidly subjecting the cylinder to hydrostatic test pressure, then immediately cutting off the pressure supply and observing the recession of pressure in the cylinder due to permanent ex... 

In addition to hydrostatic testing of cylinders at the time of manufacture, DOT requires the owner or his authorized agent to fulfill periodic requalification requirements for his cylinders. See 49 CFR 173.34(e) [9]. Hydrostatic retest or visual inspection under certain conditions are the accepted methods for requalifying cylinders. Requalifying periods and test pressures for cylinders in ammonia service are shown in Table 6. 

If, as a result of hydrostatic tests, a cylinder leaks or shows a permanent expansion that exceeds 10 percent of the total expansion, it must be condemned. Except for TC/DOT-3AL aluminum cylinders approved for ammonia service. 

The specification 3A, 3AA, and 3AL type cylinders authorized for arsine service must be requalified by hydrostatic retest every 5 years under present regulations. Specification SE 1800 cylinders require no hydrostatic test. 

Under present regulations, the cylinders authorized for carbon monoxide service must be requalified by hydrostatic test every 5 years with the exception of type 3E (for which periodic hydrostatic retest is not required). 

Storage banks of DOT/TC cylinders should be checked for the last hydrostatic test date to ascertain that the cylinders are within the allowable time period between tests. Cylinders in these banks must be retested every 5 years. DOT/TC cylinders must be filled and periodically retested in accordance with appropriate regulations. Retesting is not required for ASME storage tubes. 

Specification 3A, 3AA, and 3B cylinders used in methylamine service must be requalified by hydrostatic retest every 5 years under present regulations. Specification 4B, 4BA, and 4BW must be hydrostatically tested after expiration of the first 12-year period and each 7 or 12 years thereafter depending on the initial hydrostatic test method. Cylinders in compliance with specifications 3A, 3AA, 3B, 4B, 4BA, or 4BW that are used specifically for monomethylamine, dimethylamine, and trimethylamine service and are free from corroding components may also be qualified by an external visual inspection as described in CGA C-6, Standards for Visual Inspection of Steel Compressed Gas Cylinders [10]. Periodic hydrostatic retest is not required for specification 3E cylinders. 

Under present regulations, cylinders of all types authorized for service with neon, krypton, and xenon must be requalified by hydrostatic test every 5 years with the following exceptions DOT-3A and 3AA used exclusively for krypton, neon, and xenon may be retested every 10 years under special requirements as given in 49 CFR 173.34(e)(15), or equivalent TC regulations [5, 6]. DOT-4 may be retested every 10 years and DOT-3C, 3E, and 4C require no periodic retest. 

C4 Methods for Hydrostatic Testing of Compressed Gas Cylinders. U.S. DOT and Transport Canada regulations require certain cylinders to be periodically retested to requalify them for continued service. This standard contains operating and equipment requirements to properly perform these tests (29 pages). 

C-6. / Standards for Visual Inspection of High Pressure Aluminum Compressed Gas Cylinders. A guide for the visual inspection and hydrostatic testing... 

A cylinder must not be filled until the date, of its last hydrostatic test has been checked. If the time allowed between tests has expired, the cylinder must not be filled until the prescribed tests are made. Test intervals, methods of... 

As a supplement to a hydrostatic test and normal filling procedures to ensure the integrity of the cylinder or tube. 

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