Simplify Flange Design With COMPRESS

Flanges provide the primary means of connecting pressure vessels and heat exchangers to process piping. Because of the number of variables involved, designing a custom Appendix 2 flange can be a difficult task. Designing a pair of flanges introduces even more complications as does adding consideration of flange leakage.  Even the seemingly simple task of specifying standard ASME B16.5/16.47 flanges involves considerations beyond the rating tables.  For example, how do you take piping loads into account? It should come as no surprise that engineers have spent their entire careers looking into ways of dealing with flanged joints. Fortunately,  COMPRESS provides intuitive tools to help with these tasks.

Comprehensive ASME Flange Design in COMPRESS
A heat exchanger in COMPRESS displaying flange pairs

Designing Flange Pairs to Appendix 2-5(a)(2)

COMPRESS automatically considers mating flange bolt loads as required by ASME VIII-1, Appendix 2-5(a)(2). When would a designer run into this situation you might ask? Heat Exchanger designs are where this situation is most often encountered.

Tube side and shell side flanges share common bolting, may have different gasketing and are simultaneously subject to different pressures. The question is which side and condition governs the joint?  Appendix 2-5(a)(2) addresses this situation directly.  Bolt loads from gasket seating and operating conditions are determined for each flange and the controlling load is used for the design of both flanges.

COMPRESS can also determine Appendix 2 flange maximum allowable working pressures (MAWP).  As there is no direct solution, COMPRESS iterates the pressures of the shell side and tube side until one of the allowable stresses is reached.

Obviously flange design (or analysis) is much more complicated when performed on a pair of mating flanges. In this case, the flanges have a common link, the bolting. The MAWP (or MAP) of a flange may be restricted so as not to overstress the bolts or to prevent one of flanges from being overstressed. There is some judgment required here as well.  In certain cases the MAWP of one flange will be directly controlled by the maximum pressure of the mating flange. In other words, increasing the MAWP of one flange may reduce the MAWP of the mating flange.

External Flange Loadings (Piping Loads)

Making sure all mechanical loadings are considered on the flange design is critical in ensuring a tight joint. Applied external loadings introduce yet another layer of complexity in flange design. COMPRESS automatically handles this in multiple ways:

Appendix 2 Flanges

If a body flanges are attached to a vertical cylinder or cone and Wind or Seismic has been specified, COMPRESS calculates the loading and applies it automatically. In addition, the weight supported by the flanges is taken into account. Alternatively, a User defined Moment/Radial Load may be specified.

When attaching flanges to a conical section without a knuckle or flare radius, the superposition of the discontinuity stresses is unknown. In this case, COMPRESS calculates the discontinuity stresses as if the cone were attached directly to the adjacent cylinder.

B16.5/16.47 Flanges

COMPRESS uses the rules from UG-44 to account for external loadings on B16.5/16.47 rated flanges. Essentially, an equivalent pressure is determined based on the moments from the applied external loads. These are commonly nozzle (piping) loads taken from the COMPRESS WRC-107/537 dialog which must accounted for on the flange as well.

PCC-1 Appendix O – Flange Assembly Rules

COMPRESS provides the ability to assess bolted joints per ASME PCC-1 Appendix O. This procedure provides guidance on determining the appropriate assembly bolt torque\stress with due consideration for joint integrity.

Two approaches are available, the simple approach and the joint approach.

With the simple approach, an appropriate bolt stress is determined based on the target gasket stress. This is then converted to a target bolt torque.

With the joint approach, the following conditions are considered before arriving at a target bolt torque:

  • Sufficient gasket stress to seal the joint

  • Damage to the gasket

  • Damage to bolts

  • Damage to the flange

ASME PCC-1 Appendix O Variables

Appendix Y Flange Design

A new feature in COMPRESS 2021, Build 8110, is the ability to design flanges that comply with ASME VIII-1, Appendix Y.  The stress analysis for Appendix Y flanges differs from Appendix 2 flanges in that they have metal to metal contact outside the bolt circle. Gasket sealing is usually provided by a self energizing (soft) o-ring type gasket material for Appendix Y flanges.

Appendix Y Flange Design in COMPRESS

Gasket Library Included

COMPRESS comes with a convenient library of gaskets for users to choose from. Gasket suppliers listed include Flexitallic, Garlock, Lamons, and Teadit. Need a gasket from a supplier that isn’t on the list? Simply add the gasket to the library for future use.

Gasket Dialog in COMPRESS

Automatic Flange Design

COMPRESS provides a Flange Wizard to help automatically select flange dimensions and optimize flange designs. The Flange Wizard provides several options  to guide the Wizard including maximum bolt count and minimum bolt diameter. From here users can choose to direct COMPRESS to adjust the gasket, make bolt hole clearance changes or maintain gasket position and bolt hole clearance.

Automate Flange Design With the COMPRESS Flange Wizard

UG-34 Bolted Covers

Flat bolted covers designed per UG-34 are not independent components like cylinders or transitions. They are dependent on the attached flange with respect to bolt circle, gasketing, flange facing details and so forth. COMPRESS addresses this by allowing bolted covers to be designed in conjunction with Appendix 2 or ASME B16.5/B16.47 standard flanges. This sharing of information between flanges and bolt covers saves time and prevents mistakes.

UG-34 Bolted Covers in COMPRESS automatically share flange design details with the attached flange

U-2(g) Flange Analysis

Do you need to perform special U-2(g) assessments on flanges? COMPRESS makes it easy to model and export solid model files to 3rd party FEA software such as SOLIDWORKS or ABAQUS. No need to worry about getting the flange hub dimensions right or the bolt circle correct. The built-in COMPRESS 3D solid model takes care of the geometry for you so you can focus on your Engineering analysis.

COMPRESS Pressure Vessel Design Highlights

 Pressure vessel nozzles Nozzles Simplify the detailing of nozzle attachments with flexible and intuitive nozzle design capabilities. Finite Element Analysis Built-in Finite Element Analysis (FEA) for Nozzles and TEMA Flanged and Flued Expansion joints. FEA Nozzle API 650 Storage Tanks Modeling storage tanks is easy as COMPRESS guides you through an intuitive design wizard. API 650 in COMPRESS Vacuum Rings Drag-and-drop vacuum rings and quickly see how the external pressure rating changes. Vacuum Rings in COMPRESS Quick Design Speed up the process of pressure vessel modeling with Quick Design mode. COMPRESS Quick Design Mode Productivity Software packages like COMPRESS exist to increase productivity and save Engineering hours. Heat Exchanger Perform ASME UHX and TEMA calculations and transfer these designs to your estimating and drafting departments. Heat Exchanger designed in COMPRESS Division II Many companies use the alternative rules of Division 2 because of the cost savings, versus Division 1. Division 2 option in COMPRESS MDMT Rules of UCS-66 The rules of UCS-66 guard against vessel failure by brittle fracture, a low probability high consequence event. MDMT Rules of UCS-66 External Pressure Design Simplify the complexity of
UG-28 rules for external pressure of 15psig and greater. Jacketed Vessels Design both conventional and half pipe jacketed vessels as a standard feature in COMPRESS. Vessel Wizard The Vessel Wizard speeds pressure vessel design by creating complete pressure vessel models with minimal input. COSTER Import files from COMPRESS and create user customizable pressure vessel cost estimates in spreadsheet format. Bill of Materials generated from COSTER Flange Design Create optimized Appendix 2/ASME B16.5/16.47 flange designs with minimal time and effort. Flange design in COMPRESS Weld Seams Designers can visually confirm good practices such as staggered longitudinal seams. Weld seam wizard in COMPRESS Lifting & Rigging Use an accurate weight, the correct center of gravity, and apply the actual section properties. Lifting mechanics in COMPRESS Modeling + Drawings The Codeware Interface includes Drafter 3D, a feature that auto-generates 2D pressure vessel drawings. Drafter 3D from Codeware True SOLIDWORKS models created automatically from the Codeware Interface True SOLIDWORKS Models Sketches, operations and drawings can be manipulated as if the model had been created manually in SOLIDWORKS. Related Codes COMPRESS implements a wide range of related engineering methods, codes and standards. COMPRESS includes related engineering methods, codes, and standards Design Mode Save time by reducing the trial and error iterations that would otherwise be required when designing pressure vessels. Design mode in COMPRESS Rating (Analysis) Mode The COMPRESS Rating Mode takes your design and determines the vessel’s MAWP, MAEP and MDMT. Rating mode in COMPRESS Hydrotest Performing hydrotest stress calculations in the design stage prevents equipment damage during hydrotesting. Hydrotesting in COMPRESS Hillside Nozzle COMPRESS saves time by calculating chord openings and governing planes of reinforcement automatically. Hillside Nozzle design in COMPRESS ASME Editions Older ASME Codes are retained in all COMPRESS releases so you can always use the latest software. 2023 ASME VIII Code Edition in COMPRESS Automatic Liquid Levels COMPRESS eliminates the need to manually calculate each vessel component’s liquid static head. Automatic Liquid Levels in COMPRESS Global External Loads The Loads Menu allows designers to easily consider global external loads when sizing pressure vessel supports. External Loads in COMPRESS Clips and Lugs Designers can quickly include the mechanical effects of pressure vessel internals and attachments in their designs. Clips and Lugs designed in COMPRESS Stacked Vessels Certain industrial processes require pressure vessels with multiple chambers operating under different design conditions. Multi chamber pressure vessels in COMPRESS Appendix 46 Produce more economical Div 1 pressure vessel designs with increased accuracy from the Div 2 design by rule equations. Appendix 46 in COMPRESS Manufacturer's Data Reports Simplify the creation, submission and management of ASME Manufacturer’s Data Reports and NBIC Repair and Alteration Forms. ASME Manufacturer's data reports in COMPRESS Support Skirt Openings Specify piping connections to vertical vessels that require additional piping and openings cut out of the support skirt. Support Skirt Openings in COMPRESS Foundation Loads Summary Break down the loads for the specified vessel operating conditions including weight, wind, seismic, and vortex shedding. Foundation Loads Summary in COMPRESS Shipping Saddles Shipping Saddles in COMPRESS COMPRESS provides a shipping saddle option based on the industry standard Zick Analysis. UG-80 and UG-81 COMPRESS automatically provides out-of-roundness tolerances that must be maintained during pressure vessel fabrication. UG-80 and UG-81 design in COMPRESS Nameplate Design Every pressure vessel is required by Code to have a nameplate. COMPRESS handles this by including a convenient nameplate option. Nameplate design in COMPRESS Fatigue Screening Quickly enter fatigue data and make performing VIII-2 or Appendix 46 Fatigue Assessments simple. Fatigue Screening in COMPRESS WRC 537 Nozzle Loads Check stresses on nozzles using WRC 107 and WRC 537 stress analysis for spherical and cylindrical shells. WRC 537 Nozzle Loads in COMPRESS

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