Must I include a safety factor when calculating an acceptable reduced operating pressure [per 192.933(d)(1)] for the interim period until immediate conditions can be repaired?
Yes. Since temporary pressure reductions may remain in place for up to 365 days, this provides a reasonable amount of safety margin to compensate for defect growth for one year until the defect can be repaired. There are three options for calculating reduced operating pressures: Operators can use B31.G or RSTRENG to calculate Psafe. This calculation, in either case, includes a safety factor of 0.72. Operators can reduce pressure to 80 percent of its level at the time the defect was discovered. OPS considers that a reduction of this magnitude includes sufficient safety margin. Operators can use B31.G or RSTRENG to calculate Pfailure and can then apply safety margins to determine a new safe operating pressure. Operators that can demonstrate and justify reliable defect growth rates using empirical data may be able to justify higher temporary operating pressures, if they can show that the defect will not grow to a size that results in the predicted failure pressure being less than 1.1 time
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