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04/95

Screwed FittingsBackground

Screwed piping connections can have unseen dangers due to the risk of crevice corrosion of the threads. Crevice corrosion of piping threads can result in a loss of strength and integrity along the threads. Leaking fittings should not be tightened under pressure as the connection may fail completely.

It is important that all production operators, maintenance crews and their supervisors are aware of the dangers of screwed piping fittings. Pressurised systems transferring corrosive gases are particularly dangerous.

Recommendations

Equipment with a leaking screwed fitting should be shut-down and depressurised. The fitting should be removed and inspected. Re-tightening under pressure could be dangerous as the condition of the fitting is unknown.

Learning Points

There are a number of screwed piping connections in PDO in many locations. It is important to inform personnel of the hazards and to alert them of the dangers of tightening screwed fittings that are pressurised.

For more information on this topic, please contact AOS/4 at 67-7867.