b31.3 process piping course - 09 reactions

7/29/2019 B31.3 Process Piping Course - 09 Reactions

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ASME B31.3 Process Piping Course 9. Reactions

BECHT ENGINEERING COMPANY, INC. Reactions -1

ASME B31.3 Process Piping

Charles Becht IV, PhD, PE

Don Frikken, PE

Instructors


1. Establish applicable system standard(s)2. Establish design conditions3. Make overall piping material decisions

Pressure Class Reliability Materials of construction

4. Fine tune piping material decisions Materials Determine wall thicknesses Valves

5. Establish preliminary piping system layout & support

configuration6. Perform flexibility analysis7. Finalize layout and bill of materials8. Fabricate and install9. Examine and test

Piping Development Process


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9. Reactions

General Considerations Fabricated Equipment

Rotating Equipment

Supports

Cold Spring


The Material in This Section isAddressed by B31.3 in:

Chapter II - Design


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General Considerations

Main purpose is to provide sufficientsupport and flexibility to prevent the pipingfrom exerting excessive reactions onequipment and restraints

The calculation methods are different forfabricated equipment than for rotatingequipment or supports

Reaction limits are determined differently

for fabricated equipment than for rotatingequipment or supports


Fabricated Equipment Calculation Methods

Reaction Limits

Nozzle Flexibility


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Calculation Methods

Usually the accuracy of a formal analysisusing a computer stress analysis programis required

Both sustained loads and displacementloads are considered

Failure modes for fabricated equipmentinclude:

Gross deformation or collapse

Fatigue


Calculation Methods In order to evaluate fatigue, the entire

range of loads must be considered, so thetemperature range for this calculation isthe same as for calculating thedisplacement stress range


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Reaction Limits

Reaction limits fornozzles are calculatedusing

Welding ResearchCouncil Bulletin 107Local Stresses inShells due toExternal Loadings

Finite element analysis


Reaction Limits Allowable stresses values used in the

calculation are taken from the applicable Code,and stress evaluation is usually done using thestress evaluation criteria described in ASMEB&PV Code Section VIII, Division 2, AlternateRules for Pressure Vessels

Advantages to doing these calculations yourself

Cycle time is reduced considerably Easier to decide between reinforcing the

nozzle and lowering the reactions


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Rotating Equipment

Calculation Methods Reaction Limits


Calculation Methods Usually the accuracy of a formal analysis using

a computer stress analysis program is required

Failure modes for rotating equipment include:

Detrimental misalignment

Rubbing interference

In order to evaluate failure modes, only themagnitude of the loads during operation needs

to be considered, so the temperature rangefrom the installed condition to the operatingcondition is used


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Temperature Range Examples

Outdoor cooling tower water line: Minimum water temperature is 45F (7C)

Maximum water temperature is 90F (32C)

The piping is installed during February,which has an average daily temperature of53F (12C)

Minimum average daily temperature is 30F(-1C)

Temperature range is _______ to ________


Temperature Range Examples Outdoor compressed air piping

Minimum compressed air temperature isambient

Maximum compressed air temperature is150F (65C)

The piping is installed during J uly, which hasan average daily temperature of 64F (18C)

Minimum average daily temperature is -30F(-35C)



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Temperature Range Examples Outdoor steam traced water line:

Minimum water temperature is 40F (4C)

Maximum water temperature is 60F (16C)

The piping is installed during September,which has an average daily temperature of76F (24C)

Minimum average daily temperature is 30F(-1C)

Calculated maximum temperature for no flowcondition with steam tracing on is 280F(140C)



Reaction Limits Limits are specified by the equipment

manufacturers

Manufacturers of certain types ofequipment are required to at least meetthe allowable reaction requirements inapplicable industry standards, so

Many manufacturers refer the users tothese standards


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Reaction Limits

API 619Positive DisplacementCompressors

API 617Centrifugal Compressors

NEMA SM-23

API 611

API 612

Steam Turbines

ASME B73.1

API 610

Centrifugal PumpsIndustry StandardEquipment


Supports Calculation Methods

Reaction limits


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Calculation Methods

Usually the accuracy of a formal analysis usinga computer stress analysis program is required

The failure modes of concern for supports iscollapse and excessive deformation

The structural codes dont recognize thedistinction between displacement and sustainedloads, so only the magnitude of the loadingextremes needs to be considered, so

The temperature range from the installedcondition to the operating condition is used

Some codes differentiate between normalloads and occasionalloads


Reaction LimitsReaction limits are determined by either themaximum stress or the stability limit of thestructure.


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Cold Spring

Cold spring is the intentional deformation of pipingduring assembly to produce a desired initialdisplacement and stress. (319.2.4)

Cold springing:

Does not change the stress range

Does not change the reaction range

Is not helpful for reducing reaction ranges at fabricatedequipment

Can be helpful for reducing reactions rotatingequipment and supports

Can be used to control displacements


Cold Spring

Neutral Neutral

Cold Cold

Hot Hot


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Cold Spring

Because cold spring is difficult to achieveaccurately in practice, B31.3 permits onlypartial credit in calculating reaction forces

For two anchor systems with no intermediaterestraints, B31.3 gives equations for estimatingreactions giving 2/3 credit for cold spring(319.5.1)

For other systems, B31.3 requires that each

case be studied to estimate reactions (319.5.2)


Cold SpringNote that unintentional cold spring(misalignment) has the same effect asintentional cold spring.

The Code says Any distortion of piping tobring it into alignment for joint assembly whichintroduces a detrimental strain in equipment orpiping components is prohibited. (335.1.1)

Some owners are more restrictive than theCode on misalignment.

b31.3 process piping course - 09 reactions

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