Inspection of Compressed Gas Cylinders

The inspection procedures are intended to identify cylinders that should be condemned due to  

The basic elements involved in performing a visual inspection of a compressed gas cylinder include  

In 49 CFR 173.34 of the U.S. Code of Federal Regulations and equivalent Canadian regulations, DOT and TC state that results of required five-year (or when applicable, ten-year) periodic inspections of a cylinder be recorded and that a record be kept by the owner or the owner s authorized agent either until the expiration of the retest period or until the cylinder is again reinspected or retested, whichever occurs first. [1] and [2] Also, a cylinder which passes the inspection prescribed must have the date recorded on the cylinder in the manner currently prescribed for recording the retest date. Note that an E is to follow the date (month and year) when requalification by the visual external inspection method is allowed in lieu of hydrostatic retesting. 

Definitions for terms commonly used with respect to the visual inspection of compressed gas cylinders are as follows  

High Pressure Cylinders—High pressure cylinders are those with a marked service pressure of 900 psi (6205 kPa) or greater. 

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Employers must visually inspect compressed gas cylinders to determine that they are in safe condition under 1910.101. Visual inspections must be conducted as prescribed in the Hazardous Materials Regulations of the Department of Transportation (49 CFR Parts 171-179 and 14 CFR Part 103). Where those regulations are not applicable, visual inspections must be conducted in accordance with Compressed Gas Association, Inc. (CGA) Pamphlet C-6-1968, Standards for Visual Inspection of Compressed Gas Cylinders. ... 

C-11 Recommended Practices for Inspection of Compressed Gas Cylinders at Time of Manufacture, Outlines U.S. DOT inspection requirements for cylinders as interpreted and practiced by manufacturers and inspectors. Qualification of certifying inspectors is covered as well as inspection requirements for seamless, welded, and brazed and nonrefillable cylinders. (20 pages)... 

Chapter 9 covers specific essential information for anyone who has day-to-day involvement with compressed gas cylinders. The topics of marking, labeling, inspection, testing, filling, and disposition all contribute to ensuring the continued safety of the many millions of compressed gas cylinders currently in use. In the United States and Canada, there are approximately one-half as many compressed gas cylinders of various types as there are people. 

Every five years, all hoses should be tested to 1 times the container pressure at 130°F (54.4°C). Also, every five years the cylinders should be inspected per DOT requirements. For containers in continuous service, a visual inspection per CCA C-6, Standard for Visual Inspection of Steel Compressed Gas Cylinders may be conducted. The cylinder does not need to be emptied and cylinder should not be stamped. 

CGA C-6.19. Standard for Visual Inspection of Steel Compressed Gas Cylinders. Compressed Gas Association, Chantilly, VA. 

This discussion may not cover all conditions, sizes, types of defects, or methods of inspection. More complete and specific coverage of the subject is found in CGA C-6, Standards for Visual Inspection of Steel Compressed Gas Cylinders, and 49 CFR 173.34 and 173.301 [10, 1]. For cylinders made from materials other than steel, see CGA C-6.1, Standards for Visual Inspection of High Pressure Aluminum Compressed Gas Cylinders , CGA C-6.2, Guidelines for Visual Inspection and Requalification of Fiber Reinforced High Pressure Cylinders , CGA C-6.3, Guidelines for Visual Inspection and Requalification of Low Pressure Aluminum Compressed Gas Cylinders , CGA C-8, Standardfor Requalification of DOT-3HT, CTC-3H, and TC-3HTM Seamless Steel Cylinders , and CGA C-13, Guidelines for Periodic Visual Inspection and Requalification of Acetylene Cylinders [W, 12, 13, 14, 15]. 

The following sections summarize the inspection procedures provided in CGA C-6, Standards for Visual Inspection of Steel Compressed Gas Cylinders [10]. Except where noted, the focus pertains to low pressure and high pressure steel cylinders. While many of the same considerations apply to the inspection of aluminum cylinders and 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, andC-6.3 [11, 12, 13]. 

Due to the vast diversity of exposures during the use of a compressed gas cylinder, a prefill inspection of each cylinder is a necessary precaution. This inspection identifies any damage or repairs that are required prior to filling. The following describes inspections included in the prefill inspection process. 

CGA C-6.1, Standards for Visual Inspection of High Pressure Aluminum Compressed Gas Cylinders [11]... 

CGA C-6.3, Guidelines for Visual Inspection and Requalification of Low Pressure Aluminum Compressed Gas Cylinders, ed., Compressed Gas Association, Inc., 1725 Jefferson Davis Highway, Arlington, VA 22202. 

External visual inspection as described in CGA C-6, Standards for Visual Inspection of High Pressure Aluminum Compressed Gas Cylinders, is permitted in lieu of the periodic retest provided cylinders used exclusively for ammonia of 99.95% purity. Subsequent inspections are required at 5 year intervals [12]. ... 

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. 

C-6 Standards for Visual Inspection of Steel Compressed Gas Cylinders. A guide for establishing cylinder inspection procedures and standards to meet cylinder inspection requirements of DOT. Covers all types of steel compressed gas cylinders including those that may be visually inspected in lieu of hydrostatic retest. Current edition cited in 29 CFR and 49 CFR (16 pages). 

C-6.3 Guidelines for Visual Inspection and Re-qualification of Low Pressure Aluminum Compressed Gas Cylinders. Provides data and details as a guide for the periodic inspection of aluminum cylinders with a service pressure of 360 psi (2482 kPa) or less. Contains color photos of defects. Current edition cited in 49 CFR (9 pages). 

P-15 Filling of Industrial and Medical Nonflammable Compressed Gas Cylinders. Covers prefill inspection procedures and describes the steps necessary to ensure cylinders of air, argon, carbon dioxide, helium, nitrogen, nitrous oxide, and oxygen are filled in a manner that is safe (19 pages). 

AV-3 Filling of Industrial and Medical Nonflammable Compressed Gas Cylinders. Covers numerous aspects and considerations with respect to prefill inspections and filling procedures. Includes a leader s guide and study materials. Available in VHS or PAL format. (23 minutes)... 

Cylinder neck threads must be examined whenever the valve is removed from the cylinder. When manufactured, cylinders have a specified number of full threads of proper form as required in applicable thread standards. More information on this can be found in CGA V-1, American National, Canadian, and Compressed Gas Association Standard for Compressed Gas Cylinder Valve Outlet and Inlet Connections. [21] When inspected, cylinders must be rejected if the required number of effective threads has been reduced so that a gas-tight seal cannot be obtained by reasonable valving methods. Common thread defects are worn or corroded crests and broken or nicked threads. 

Compressed Gas Cylinders, provide details on the requirements for inspection of aluminum cylinders. [14] and [16] Other publications, such as CGA C-6.2, Guidelines for Visual Inspection and Requalification of Composite High Pressure Cylinders, provide similar information for cylinders made of other materials. [15]... 

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