This document addresses common questions about differences between PASS/START-PROF and CAESAR II. Watch the START-PROF Overview Video for feature demonstrations.
PASS/START-PROF uses an object-oriented approach where pipes, fittings, and nodes are distinct objects with specific properties. For example, you can place a bend object within a node object or connect pipes between nodes.
Multiple Pressure/Temperature Scenarios
High-Temperature Creep Analysis
The material database includes a "maximum f=1.2" flag for applicable materials.
A3 and system design factors calculate automatically where required. Temperature factors A1 are pre-applied to al() and hl() values in the database. All material properties are stored in the material database, while pipe and fitting properties are managed in their respective dialog windows.
The database contains complete data for FRP/GRP/GRE analysis. Select the material and analyze as you would with steel piping. Watch the FRP Analysis Video.
No CAESAR II equivalent. The database contains all required data for HDPE piping analysis. Select the material and proceed as with steel piping. Watch the HDPE Analysis Video.
Different temperatures, pressures, and other parameters (via the "L" button) can vary across operation modes. Pipe weight calculates automatically based on material density. Weld quality factors W are retrieved automatically from the database.
PASS/START-PROF automatically handles high-pressure ASME B31.3 Chapter IX requirements (different wall thickness checks, occasional load factor k=1.2, modified allowable stress calculations).
Additional pipe properties vary by selected code. Examples shown for B31.1, B31.4, B31.8, ISO 14692, and Thermoplastic Piping:
PASS/START-PROF displays SIF and k-factors for all fittings directly in property dialogs and stress tables.
Default bend properties match the connecting pipe, but you can override material, weight, wall thickness, and other parameters.
ASME B16.9 and ASME B31 codes don't regulate bend, tee, and reducer wall thickness—only pipe wall thickness is specified. However, fittings typically have greater wall thickness than matching pipes to maintain pressure rating.
Elbows may have 10%-40% greater wall thickness than connected pipes. Manufacturers often produce bends with increased thickness, but actual dimensions require manufacturer data or physical measurement.
ASME B31 codes specify that bend flexibility factors depend on actual bend wall thickness, not matching pipe thickness.
PASS/START-PROF includes a feature to calculate approximate "real" bend wall thickness according to ASME B31.3 304.2.1 and equivalent requirements in other codes. Click the "C" button next to the Wall Thickness field for automatic calculation.
For custom bends, manually specify SIFs and k-factors.
No CAESAR II equivalent for these elements:
Long Radius Bend - Pipe section bent with large radius (typically R>40DN). No initial forces or stresses. Used in long pipelines.
Prestressed Long Radius Bend - Elastically bent pipe with very large radius (R>1000DN). Includes initial stress. Used in long pipelines.
Miter Joint - Single miter joint for modeling widely spaced miter bends as standalone elements.
PASS/START-PROF tee models include internal hidden nodes. The tee run automatically models with potentially greater wall thickness than connected pipes (tn). The "L" and "H" fields define dimensions. Flexible connections insert automatically on header and branch when required (for ASME B31J or ASME BPV Section III Class 1 NB-3686 methods). ASME B31J implementation is embedded—no additional software required.
1 - rigid element, 2 - tee header with user-specified wall thickness,
3 - pipe connected to tee header with different wall thickness
SIF and k-factors calculate automatically for standard tees.
For custom tees, specify SIF and k-factors for header and branch: out-of-plane, in-plane, torsion, and axial.
Each tee type displays only properties relevant to the selected code.
Reducers are node objects, not pipe elements. Deleting them doesn't affect geometry.
Valves are node objects, not pipes. Deleting them doesn't affect geometry. Model as rigid elements with specified weight.
Rigid elements are specialized pipe objects.
Special objects for modeling ballasting on underwater buried pipelines.
Flange pairs model as rigid elements. Includes leakage check capability.
PASS/START-PROF includes common "standard" supports plus "Custom Restraint" for special applications. Specify allowable loads—exceeded loads highlight in red in the support loads table with warnings in the errors and warnings window.
Guide supports include vertical and horizontal restraints with gap and friction settings. Define allowable loads for each direction.
Spring selection tables defined in project settings. PASS/START-PROF includes a variable spring database with products from multiple manufacturers (expanding regularly).
Two spring types: Hangers and Supports. Specify rod length for hangers, friction factor for supports. Leave operating load or stiffness blank for automatic selection. Software suggests when to replace variable springs with constant supports. Final decision remains with the designer due to cost considerations.
Includes constant spring database with automatic selection. Leave vertical force blank for automatic calculation.
Used for model segmentation and special applications. Define allowable loads.
Create any restraint configuration using custom restraints.
PASS/START-PROF uses an Operation Mode Editor approach for load management.
Additional weight loads apply to all operation modes, including seismic.
Non-weight loads apply to all operation modes except seismic.
Additional force-based loads apply only to specified load cases (typically occasional loads like relief valve, waterhammer, slug flow).
Uniform loads follow the same methodology as node loads. G-loads calculate automatically via static seismic load generator.
No CNODE required. Add fixed anchors and specify "deformation" directly—PASS/START-PROF models support movements automatically.
Create complex expansion joint models, though standard models typically suffice. Software automatically checks allowable axial, rotational, and lateral deformations. Expansion joint reports provide comprehensive verification.
Includes expansion joint database for standard components.
Commonly used in buried district heating networks for cold spring effects.
Generate wind, snow, and ice loads automatically. CAESAR II lacks snow and ice load generators.
Wave load analysis not currently available. Development in progress.
Common questions: "How to specify multiple pressures and temperatures?" and "How many can be defined?"
Specify unlimited pressures and temperatures. PASS/START-PROF automatically generates load cases—no manual setup required. See the Operation Mode Editor and related article.
PASS/START-PROF features a high-level Operation Mode Editor with template-based approach. Provides equivalent functionality to load case editors with faster, more intuitive operation.
Common question: "Is there a CNODE equivalent in PASS/START-PROF?"
CNODE functionality not required. CAESAR II uses CNODE for:
Nozzle connections to vessel models using pipe/rigid elements. PASS/START-PROF handles this without CNODE. See Equipment Modeling.
Anchors/supports with displacements. Specify movements directly in fixed anchors or other supports. See Displacement Handling.
Pipe-to-pipe connections or jacketed piping. Model directly without CNODE. See Jacketed Pipe and Pipe-to-Pipe Connections.
Common question: "Can I use different codes (e.g., ASME B31.1 and B31.3) in one project?"
No—load cases and safety factors differ between codes. Load cases generate automatically based on selected code and conditions. To analyze different model sections with different codes, create separate project files with identical geometry but different code selections.
Load cases vary by code. For example, ASME B31.3 includes alternative sustained load cases while ASME B31.1 does not.
PASS/START-PROF always considers Bourdon Effect (translation and rotation). Occasional load factors follow selected code requirements specified in the operation mode editor. SIF multipliers for sustained stress always comply with the selected code.
See ASME B31.3 302.3.5 equation (1c). When enabled, maximum stress range factor f=1.2 for materials with "Maximum f=1.2" flag in the material database. Otherwise, f=1.0.
Enable more accurate SIF and k-factors by activating this option. All calculations and model modifications occur automatically—no additional software (B31J Essentials, FEATools) required.
Convert units anytime—before or after analysis. No model conversion required.
Watch the Buried Piping Analysis Video.
No separate underground pipe modeler required. Soil springs add automatically during analysis. Modify the model and re-run immediately—no need to revert to non-soil-spring models.
Considers creep effects (stress relaxation and self cold-springing) for high-temperature piping. Applies to both operating and cold modes—cold mode often proves most critical due to self cold-springing effects.
START-ELEMENTS module checks wall thickness and allowable pressure for pipes, bends, tees, reducers, caps, and flanges. Before analysis, PASS/START-PROF verifies all components meet pressure requirements for all operation modes.
PASS/START-PROF includes multiple buckling analysis functions: Upheaval Buckling of Buried Pipeline, Upheaval Buckling of Buried Long-Radius Bends, Lateral Buckling of Above-Ground Pipes, Vacuum Piping Local Wall Buckling from external pressure and combined external pressure, axial force, and moment.
PASS/START-PROF experiences no iterative convergence issues. No user adjustments required—convergence handles automatically.
Modify single or multiple object properties easily. Select piping segments and copy/paste, mirror, rotate, or split them. Insert nodes on pipes or bends, move nodes along elements, or delete nodes (select and press DEL).
Modify multiple object properties using the properties float window. Includes full functionality for working with independent piping segments.
Interactive analysis reports: Code Stress, Spring Selection, Expansion Joint, Flange Leakage, Insulation Stress, Internal Forces, Support Loads, Local Wall Buckling, Node Displacements. Export to Excel, Word, txt, or html.
Comprehensive errors and warnings window includes engineering alerts: pressure failures, buckling, support lift-off, spring hanger variation >25%, exceeded allowable loads, sustained/fatigue stress failures—not just stress exceedances.
Graphics display hot/cold/installation positions with clear, intuitive deformation visualization.
The project tree displays temperatures, pressures, color diagrams. Select object groups to modify properties, delete, or copy. View all object properties including bends, tees, reducers, etc.
Free PDMS and E3D interfaces available: Interface Video.