Pressure vessel and piping codes have used the area replacement concept for at least 50 years. This concept requires that the metal cut out by an opening be replaced by reinforcement within a prescribed zone around the opening. The concept is relatively simple and the vast majority of vessels and piping with openings conforming to this concept have given satisfactory service. During the past 20 years@ a substantial amount of information has accumulated which indicates that the area replacement concept@ in some applications@ is excessively conservative. This excess conservatism increases costs in two ways: (1) the reinforcements contain more metal than needed and thus cost more@ and (2) more welding is required. The added welding is probably the more significant; not only in the welding itself but in subsequent inspections (e.g.@ radiograph@ ultrasonic) and repairs of unacceptable flaws.
BULLETIN 335-1988 history
1988BULLETIN 335-1988 A REVIEW OF AREA REPLACEMENT RULES FOR PIPE CONNECTIONS IN PRESSURE VESSELS AND PIPING