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OSHA Safety Hazard Information Bulletin (1) - Defective Imported Lap Joint Stub Ends
August 24, 1994
FOOTNOTE(1) The Directorate of Technical Support issues Hazard Information Bulletins (HIB) in accordance with OSHA Instruction CPL 2.65 to provide relevant information regarding unrecognized or misunderstood health hazards, inadequacies of materials, devices, techniques, and safety engineering controls. HIBs are initiated based on information provided by the field staff, studies, reports and concerns expressed by safety and health professionals, employers, and the public. Bulletins are developed based on a thorough evaluation of available facts and in coordination with appropriate parties.
The Federal Trade Commission (FTC) has brought to our attention a potentially serious safety hazard that exists in lap joint stub ends installed in piping systems used in any facility (see attached figure). The defective stub ends were discovered by two corporations as a result of tests performed prior to start-up of their piping systems.
Two types of stub ends were tested: Stub ends manufactured by Ta Chen of single piece construction containing no welds, and ones manufactured by Tru-Flow and Tung Teng of welded construction using materials of different chemistry for the tube and flange sections. The stub ends range in size from 1/2 to 6 inches (1.27 - 15.24 cm) in diameter and are marked with the ASTM A403 specification. The stub ends are free from any visual defects. The following is a list of organizations that performed tests on the stub ends:
* Lehigh Testing Laboratories performed an evaluation and testing for the FTC of stub ends from three Taiwanese manufacturers: Ta Chen, Tung Teng and Tru Flow. The stub ends manufactured by Ta Chen were acceptable. Lehigh, however, found the stub ends from Tung Teng and Tru Flow to be unacceptable because they had an incomplete penetration of the weld. The American Society of Mechanical Engineers (ASME) standard, Section VIII requires the welded connectors between the pipe and flange be a full penetration of the weld.
* Lehigh Testing Laboratories also conducted testing for the Occidental Chemical Corporation. Occidental Chemical Corporation submitted test reports indicating that Tru Flow stub ends were defective.
* The Henkel Corporation, a major manufacturer of chemicals, suspected that the stub ends that it was installing in a new facility were defective. The company radiographed eighteen units and found five to be defective due to lack of fusion or penetration. All were manufactured by Tru Flow and sold as Merit stub ends.
A review of test reports submitted by the above organization revealed the following common findings of the Tung Teng and Tru Flow stub ends:
* Radiographs taken of the welds indicated either lack of fusion or incomplete penetration. All the tested welded stub ends failed the American Society for Testing Materials (ASTM) A403 radiographic requirements. These results were confirmed later when the stub ends were sectioned for metallographic examination.
* The manufacturers' certification (stub ends stamped with ASTM A403) was not reliable. Follow-up quality control must be provided by intermediate suppliers or end users (employers.)
* The stub ends did not meet the fatigue testing required by ASTM A403. The partial penetration welds failed much earlier than those with full penetration. The fatigue life of a stub end with a full penetration weld was 10 to 100 times that of the weld with a lack of penetration.
A midwestern manufacturer contracted outside consultants to conduct tests to determine the life expectancy of the defective fittings. The results are confidential. The manufacturer received fittings from numerous suppliers, some of which may have provided the defective stub ends. These suppliers are: Wilkins Pipe, Robert-James, Central Stainless, Service Pipe, Mutual Manufacturing, Mid-Valley, CTI, RJ Gallagher, Indiana-Michigan Supply, and Industrial Supply.
The in-service failure of these stub ends under cyclic loading would most likely result in a crack leading to a leak. It is not possible to predict if or when a failure will occur because the in-service loads on the stub ends are not known. In applications, such as pump circuits, it is possible that a cyclic loading can occur that may lead to cracks and result in a leak.
These stub ends may be installed in petrochemical and chemical facilities that are covered under the Process Safety Management Standard, 29 CFR 1910.119. 29 CFR 1910.119(j) covers piping systems and requires that the employer establish and implement written procedures to maintain the ongoing integrity of process equipment.
Visual inspection of stub ends will not reveal defects such as lack of penetration or fusion, magnetic particle test can not be used to examine stainless steel stub ends, and periodic dye penetrant inspection of suspected joints detects only surface cracks and near surface defects. Therefore, radiographic examination or other nondestructive testings are recommended.
Please distribute this bulletin to all Area Offices, State Plan States, Consultation Project Officers, and appropriate local and industry groups.
Figure 1. Lap-Joint Flange (with Stub-end)