What does CAESAR II do?

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Session overview

Taking the task from piping design to piping engineering. What questions does CAESAR II answer? A brief CAESAR II “design” sequence. Should conclude within the hour.

Please use the Webinar dialog box to post your questions.

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Piping designer responsibilities

Designer locates equipment and then routes pipe between these positions using an established “pipe” specification

– The piping system is a unique pressure containment.

Givens:– Pipe size is based on pressure drop, flow rate– Pipe specification (e.g. wall thickness) is based on design pressure & temperature– Material based on service requirements

Designer has established rules for basic layout – Hydraulic issues– Spans between supports (deadweight sag)– System stability – Access / clearance

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So what’s left for the piping engineer?

Many systems require analysis to evaluate strain– Sources of thermal growth

Pipe Equipment connections (vessels and equipment)

– Other sources of strain Support settlement Support movement in marine piping

Strain Load Stress– Evaluate pipe load as stress due to this strain– Evaluate load on equipment directly

Except for simple layouts, the system response due to this strain is difficult to estimate Analysis yields a better estimate of pipe deflection, loads on pipe supports and equipment

connections, and stress in the piping; and not only for strain.

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100 feet @ 170F

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Designer “handoff” to engineering

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A sample “Critical Line List” from PROCESS PIPING: The Complete Guide to ASME B31.3, by Charles Becht IV, ASME PRESS, New York, 2002========================================• In the case of general piping systems; according to the following line size/flexibility

temperature criteria:• All DN 50 (NPS 2) and larger lines with a design differential temperature over 260°C

(500°F)• All DN 100 (NPS 4) and larger lines with a design differential temperature exceeding

205°C (400°F)• All DN 200 (NPS 8) and larger lines with a design differential temperature exceeding

150°C (300°F)• All DN 300 (NPS 12) and larger lines with a design differential temperature exceeding

90°C (200°F)• All DN 500 (NPS 20) and larger lines at any temperature• All DN 75 (NPS 3) and larger lines connected to rotating equipment• All DN 100 (NPS 4) and larger lines connected to air fin heat exchangers• All DN 150 (NPS 6) and larger lines connected to tankage• Double-wall piping with a design temperature differential between the inner and the outer

pipe greater than 20°C (40°F)

Design by Rule vs. Design by Analysis:

Design by Rule:Minimum pressure thickness = (PD)/(2(SEW+PY))

Design by Analysis:Maximum stress due to pressure = Sh = (2/3)(yield stress)Stress due to pressure = PD/2tIs PD/2t < Sh ?Yes: OKNo: Redesign required

Many shops develop a “critical line list” to determine which piping layouts require additional engineering evaluation

So, a move is made from “Design by Rule” to “Design by Analysis”

This is where CAESAR II enters the picture

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Four typical interests in “pipe stress analysis”

Selecting and sizing supports Checking pipe deflection under load Verifying loads on connected equipment Evaluating pipe stress

And not only for those strain-based loads…– Deadweight– Pressure– Wind & wave– Earthquake– Hydraulic transients– Vibration

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Creating a CAESAR II Model

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(the analog) Start with a stress isometric or similar concept Mark up the drawing for analysis Create the piping input model (a digital representation of that analog)

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Analog to digital

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Analog Digital representation

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CAESAR II Results

1. Hanger selection, restraint load

2. Pipe sag, horizontal deflection

3. Equipment check

4. Stress check

– A few examples will illustrate…

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1. Size Support

Size this spring…

…to minimize this pump load

What is the load on this steel?

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2. Check Deflection

How much does this elbow move when the system heats up?

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3. Evaluate Equipment Load

Is this compressor overloaded?

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Compressor

Thermal Growth

Anchor

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4. Evaluate Pipe Stress

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This stub in connection is overstressed and will fail

by fatigue over time.

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Analyze and review TURBO

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Document Results

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Conclusion

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