Addition of a Nozzle to an Existing Vessel
File: Samples/Sample 1
Last Updated: June 16, 2010
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A Simple Calculation And Drawing Set
This is one of the simplest pressure vessel drawing and calculation sets possible - the addition of a new nozzle to an existing vessel - a tower in this case. The calculation set re-calculates the tower shell at the location of the nozzle and provides the nozzle reinforcing calculations. Depending on the condition of the vessel and the corrosion allowance, field thickness testing might be required to provide the wall thickness used in the calculations.
The Catch
The catch with alterations to existing National Board registered vessels is that the National Board code must be met as well as the ASME code. For this sample, the tower is assumed to be built to the ASME VIII-I pressure vessel code, 1992 edition, 1994 addenda and NB registered. The National Board code states that "all required design information, applicable drawings, design calculations, specifications and instructions are to be prepared, obtained, controlled and interpreted to provide the basis for an alteration in accordance with the original code of construction" (AISI NB-23 2001 RC-3020 emphasis added).
This alteration is designed to the 2001 code rules, but the 1994 allowable material stress levels are used. The allowable stresses prior to 1999 were lower than the current levels. This calculation set uses these lower stress levels. The shell was recalculated to determine the minimum thicknesses required for the nozzle calculations. The nozzle was calculated using the standard area replacement calculations. No nozzle loads are calculated, so hangers are required to support the pipe from the nozzle.
The Software We Use at PVEng
Three complete sets of calculations are shown here: calculations done in Advanced Pressure Vessel; PVElite; and our in house spreadsheets. We use these different methods to provide flexibility when solving difficult problems. For a real job we would only provide one set of calculations, preferably Advanced Pressure Vessel our favorite. Click on the links to the left to view the different calculation methods and to see the drawing.
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