Some design specifications require that nozzle reinforcement calculations are performed for the maximum allowable pressure, new and cold condition, MAPnc. MAPnc for the nozzles is the minimum of the MAPs determined from analyzing the vessel elements using the Shell/Head part of the software.
The software will then check to see if the nozzle is reinforced adequately using the user entered MAPnc. When the area of replacement calculations are made for this case, cold allowable stresses are used and the corrosion allowance is set to 0. Designing nozzles for this case helps the vessel to comply with UG99 or appropriate (hydrotest) requirements. Check your design requirements to see if this case is required by your client.