heads, according to ASME Section VIII Div. 1. This dimension is usually referred to as IKR in many head catalogs. Even though the head catalogs list these heads as being OD heads, the knuckle radius is given on the inside diameter basis. See the illustration in the catalog and where the arrows for DR and IKR point to (the inside of the head). For more information, see Appendix 1-4 in the Code.
Length of Straight Flange - The straight flange is the cylindrical portion of a torispherical (dished) or elliptical head. This dimension is used to compute the overall volume of the head in the new, cold, and corroded condition, as well as the weight of the head. This dimension does not affect the required thickness calculation.
Attachment Factor for Flat Head - Enter the flat head attachment factor, calculated or selected from ASME Code, Section VIII, Division 1, Paragraph UG-34, Figure UG-34. Some typical attachment factors display below, however consult Paragraph UG-34 before using these values: 0.17 (b-1) Head welded to vessel with generous radius
0.20 (b-2) Head welded to vessel with small radius 0.20 (c) Lap welded or brazed construction 0.13 (d) Integral flat circular heads
0.20 (e f g) Plate welded inside vessel (check 0.33*m) 0.33 (h) Plate welded to end of shell
0.20 (I) Plate welded to end of shell (check 0.33*m) 0.30 (j k) Bolted flat heads (include bending moment). To
compute the required thickness of the bolted flat heads (type j and k), use the Flange module and model it as a blind flange.
0.30 (m n o) Plate held in place by screwed ring 0.25 (p) Bolted flat head with full face gasket 0.75 (q) Plate screwed into small diameter vessel 0.33 (r s) Plate held in place by beveled edge
Large Diameter for Noncircular Flat Heads - If you have a noncircular welded flat head, enter the large dimension in this field, and enter the small dimension as the component diameter above. This value is used to compute the factor Z for noncircular heads. If the head is circular, enter the diameter here.
Diameter Basis - Select the type of diameter from the list. ID - Inside diameter
OD - Outside diameter
Torispherical heads should always be specified on the inside diameter basis. Even though the head catalogs refer to these as OD heads, inspection of the catalog nomenclature reveals that the dimensions listed are inside dimensions. Because of this, the inside dimensions from the catalog can be entered directly when the ID basis is specified.
Normally, for a torispherical head the inside crown radius is equal to the vessel outside diameter.
For flat heads, this value is ignored. Always enter the outside diameter of the flat head. Diameter of Shell/Head - Enter the diameter of the shell or head. For cones, enter the largest diameter of the cone. For flat heads, use the appropriate diameter per the figure UG-34 in the
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CodeCalc User's Guide
ASME Code. The diameter of the head is usually taken as the inside diameter of the cylindrical shell to which it is attached.The program allows you to use either an inside diameter (ID) or an outside diameter (OD). Click Pipe Selection to select a pipe by nominal pipe diameter and pipe schedule.
Minimum Thickness of Pipe or Plate - Enter the minimum thickness of the actual plate or pipe used to build the vessel, or the minimum thickness measured for an existing vessel. Many pipe materials have a minimum specified wall thickness, which is 87.5% of the nominal wall
thickness. You should enter the minimum thickness. Some commonly used thicknesses are:
0.0625 - 1/16 " 0.1250 - 1/8 " 0.2500 - 14 " 0.3750 - 3/8 " 0.4375 - 7/16 " 0.5000 - 1/2 " 0.6250 - 5/8 " 0.7500 - 3/4 " 0.8750 - 7/8 " 1.0000 - 1 "
Nominal Thickness of Pipe or Plate - (Optional) Enter the NOMINAL or AVERAGE thickness of the actual plate or pipe used to construct the vessel.
This thickness is used to calculate the volume and weight of the metal ONLY if it is between 1 and 1.5 times the minimum thickness. If this value is left blank or 0, the program will use the minimum thickness to compute the weight and volume of this shell element.
Corrosion Allowance - Enter the corrosion allowance. The program adjusts both the actual thickness and the inside diameter for the corrosion allowance that you enter.
Type of Reinforcing Ring - Enter the index for the type of reinforcing ring on the cylindrical or conical section. Three options are available:
None - No additional input required.
Bar - Displays the Reinforcing Ring - Bar dialog box. You must enter the width and thickness of the bar. For more information, see Bar Options (on page 62).
Section - Displays the Reinforcing Ring - Section dialog box. You must enter the moment of inertia, cross sectional area, and the distance from the shell to the centroid of the beam. In all cases CodeCalc includes the shell in the calculation of the moment of inertia for the stiffening ring. You can only perform this calculation for external pressure calculations. Also, the detailed analysis for the required moment of inertia and cross section area for cones is contained in the separate CONICAL program. For more information, see Section Options (on page 64).
Minimum Design Metal Temperature - If this component is a carbon or low alloy steel shell or head, the program will compute its Minimum Design Metal Temperature (MDMT). The value to be entered in this field is the user-defined MDMT. This value is for reference only and will not be used by the program.
If this material is not a carbon steel then enter a zero (0) in this field. If a value of zero is entered, the program will not echo this value out during runtime.
Skip UG-16(b) Minimum Thickness Calculation? - Select this option to skip the UG-16(b) calculation. Section UG-16(b) states the minimum thickness for pressure retaining components as 0.0625 in. (1.6 mm). There are certain exemptions from this requirement such as in the case of heat exchanger tubes. Refer to the ASME Section VIII, Division -1, UG-16(b) for more details.