Cylinders internal visual inspection

New cylinders and cylinders returned to use after any pressure test should be subject to an internal visual inspection. 

Horoscope. The horoscope enables detailed visual inspection of internal cylinder surfaces and allows for close-up inspection of affected areas through a series of lenses within a tubular assembly. 

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. 

A cylinder must be rejected and held for further evaluation when doubt exists from a visual inspection as to its suitability for continued service. Where the bottom of the defect cannot be seen or where the extent of the defect cannot be measured by various inspection instruments, the cylinder must be condemned. Such internal defects are fabrication irregularities. 

As previously discussed, DOT and TC regulations both specify that the periodic retest must include an external and internal visual examination of the cylinder. It is recommended that these inspections be conducted prior to the hydrostatic retest. 

Requirements concerning the external and internal inspection of low pressure and high pressure cylinders are discussed in the following sections. This material summarizes the inspection procedures provided in CGA C-6, Standard for Visual Inspection of Steel Compressed Gas Cylinders. [13] Except where noted, the focus of this presentation therefore pertains to low pressure and high pressure steel cylinders. While many of the same considerations are also pertinent to the inspection of aluminum cylinders and other types of cylinders made of materials other than steel, the respective CGA technical publications should be consulted for specific procedures and defect limitations concerning such cylinders. See CGA C-6.1, C-6.2, and C-6.3. [14], [15], and [16] Likewise, those concerned with the inspection of steel cylinders should refer to the most current edition of CGA C-6. [13]... 

Regardless of the type of hydrostatic testing method used, DOT and TC regulations both specify that the periodic retest must include an external and internal visual examination of the cylinder. It is recommended that these inspections be conducted prior to the hydrostatic retest in accordance with the applicable Compressed Gas Association standards. See references [13] through [16] and [20]. External and internal inspection considerations were discussed more thoroughly in previous sections of this chapter. 

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