Use the following procedure to check computer calculations that have been made to verify the design of a floating head. This procedure is generic in that it may be applied to calculations that have been done using most computer programs. However, because the CODECALC program is used for all calculations that are done in this course, the parameter names that are used in the CODECALC program are identified in parentheses where appropriate.
The program input must be checked to ensure that it conforms to the floating head design requirements. The program output must be checked to ensure that it verifies the design that has been used for the floating head.
In using this procedure, refer to Figure 23 for floating head geometry and nomenclature.
Floating Head Geometry and Nomenclature
Figure 23
1. Verify that the specified floating head type is consistent with what is shown in the detailed drawing. The most common type is Type (d) as described in Appendix 1-6 in the ASME Code.
3. Verify that the specified tube-side design pressure (P.S.) is equal to the pressure listed on the specification sheet.
4. Verify that the specified shell-side design pressures (PSS) is equal to the pressure listed on the specification sheet.
5. Verify that the specified tube-side corrosion allowance (CATS) is equal to the corrosion allowance listed on the specification sheet.
6. Verify that the shell-side corrosion allowance (CASS) is equal to the corrosion allowance listed on the specification sheet.
7. Verify that the materials for the head, flange, bolts, and backing ring are the same as the materials listed on the specification sheet.
8. Verify that the allowable stresses for the head, flange, bolts, and backing ring conform to the allowable stresses specified in the ASME Code. Note that many programs such as CODECALC have the ASME allowable stress tables built into them and automatically use the correct allowable stress.
9. Verify that the crown radius of the head (CR) is consistent with what is specified on the detailed drawing.
10. Verify that the inside diameter of the flange (FID) is consistent with what is specified on the detailed drawing.
11. Verify that the outside diameter of the flange (FOD) is consistent with what is specified on the detailed drawing.
12. Verify that the inside diameter of the backing ring (DR) is consistent with what is specified on the detailed drawing.
13. Verify that the actual thickness of the head (TH) is consistent with what is specified on the detailed drawing.
14. Verify that the actual thickness of the flange (TC) is consistent with what is specified on the detailed drawing.
15. Verify that the actual thickness of the backing ring (TR) is consistent with what is specified on the detailed drawing.
16. Verify that the number of splits in the backing ring (NSPLIT) is consistent with what is specified on the detailed drawing.
17. Verify that the distance between the centroid of the flange and the attachment point at the head centerline is consistent with what is specified on the detailed drawing.
18. Refer to the detailed drawing to determine whether the flange is or is not slotted and verify that the appropriate detail is specified in the calculations. The flange will normally not be slotted.
19. Verify that the diameter of the bolt circle (DB) is equal to the diameter shown on the detailed drawing.
20. Verify that the bolt diameter (DBOLT) is equal to the diameter shown on the detailed drawing.
21. Verify that the thread series is identified as "TEMA."
22. Verify that the number of bolts is equal to the number shown on the detailed drawing. 23. Verify that the gasket type and material that is used is consistent with what is shown
on the detailed drawing.
24. Verify that the gasket outside diameter is equal to the diameter shown on the detailed drawing.
25. Verify that the flange face outside diameter (FOD) is equal to the diameter shown on the detailed drawing.
26. Verify that the gasket inside diameter is equal to the diameter shown on the detailed drawing.
27. Verify that the flange face inside diameter (FID) is equal to the diameter shown on the detailed drawing.
28. Verify that the gasket factor, m, is equal to the factor that is specified indicated in the ASME Code, Section VIII, Division 1, Appendix 2, Table 2-5.1, for the specified gasket type.
29. Verify that the gasket design seating stress, y, is equal to the stress indicated in the ASME Code, Section VIII, Division 1, Appendix 2, Table 2-5.1 for the specified gasket type.
30. Verify that the sketch number that is specified for the flange facing agrees with the sketch number listed in ASME Code, Section VIII, Division 1, Table 2-5.2 for the type of flange facing that is shown on the detailed drawing.
31. Verify that the column number (I or II) for the facing sketch agrees with the column number listed in ASME Code, Section VIII, Division 1, Table 2-5.2 for the specified gasket type.
32. Verify that the gasket thickness is equal to the dimension shown on the detailed drawing.
33. Verify that the nubbin width (when a nubbin flange face is specified) is equal to the dimension shown on the detailed drawing.
34. Verify that the length of the pass partition gasket is equal to the gasket inner diameter, multiplied by the fraction Npp/Ng, where Npp is the width of the pass partition gasket
and Ng is the width of the girth flange gasket. This only applies for channel covers
when there is a pass partition plate in the channel.
35. Verify that the actual thickness of the head is at least equal to the minimum required thickness (considering the corrosion allowances) and is consistent with what is shown on the detailed drawing.
36. Verify that the actual thickness of the flange is at least equal to the minimum required thickness (considering the corrosion allowances) and is consistent with what is shown on the detailed drawing.
37. Verify that the actual thickness of the backing ring is at least equal to the minimum required thickness (considering the corrosion allowances) and is consistent with what is shown on the detailed drawing.
WORK AID 3: PROCEDURE FOR EVALUATING CONTRACTOR-SPECIFIED DESIGNS FOR AIR-COOLED HEAT EXCHANGER TUBE BUNDLES AND HEADERS
The procedures in this Work Aid may be used to evaluate whether the tube bundle and header designs that are specified in a Contractor Design Package for an air-cooled heat exchanger meet Saudi Aramco, API-661, and ASME requirements. This Work Aid is divided into three major parts as follows:
• Part 1 provides a general procedural-type checklist that should be used in all cases.
• Part 2 provides a procedure for checking compliance with the requirements that are contained in 32-SAMSS-011 and API-661.
• Part 3 provides a procedure for evaluating whether the mechanical design calculations are in accordance with the ASME Code. It is assumed that a computer program has been used for these calculations.
Part 1: General Requirements
The following procedural items should be checked in all cases.
1. Confirm that the specified dimensions are consistent in all drawings, specifications, and calculations that are provided in the Contractor Design Package. This will be done while checking the design details and dimensions in accordance with Parts 2 and 3 of this Work Aid.
2. Confirm that the dimensions and design details are in accordance with requirements specified in 32-SAMSS-011, API-661, and the ASME Code. Further details on this check are provided in Part 2 of this Work Aid.
3. Confirm that all calculations are done in accordance with ASME Code procedures. This may involve verification of the computer program that is used by the exchanger manufacturer. For the purposes of this course, it may be assumed that the CODECALC computer program that is being used has been verified.