Post on 08-Apr-2018
8/7/2019 44116778 Pipe Stress Amp Support (1)
1/24
Piping Stress Analysis
8/7/2019 44116778 Pipe Stress Amp Support (1)
2/24
Overview
What is Flexibility Analysis ?
Analytical Method to calculate Displacement & Stresses
Guidelines for lines connected to Critical Equipment
Fundamentals of Primary & Secondary stresses
Spring Supports
Various Load Cases
Stress Analysis
Expansion Joints
Checking Flexibility using Nomographs
Fundamentals of Buried Pipe Analysis
Stress Analysis using CAESAR-II
Stress Analysis- Responsibilities & Methodology
8/7/2019 44116778 Pipe Stress Amp Support (1)
3/24
Flexibility
Temperature
COLD
HO
T
Stress Analysis
Not Flexible
Flexible
More Flexible
What is Flexibility of the Piping System?
Ability to absorb thermal growth of the piping system
8/7/2019 44116778 Pipe Stress Amp Support (1)
4/24
Overview
What is Flexibility of the Piping System?
Stress Analysis
Piping system shall be designed to have sufficientflexibility to prevent pipe movements from causing
failure from overstress, leakage at joints or detrimentaldistortion of connected equipment resulting from
excessive thrusts and moments
How to provide Flexibility in the Piping system ?
By change in direction using BENDS, utilising
Expansion joints
Ability to absorb thermal growth of the piping system
What code states about Flexibility in the Piping system ?
HOW to conclude whether system is Flexible or not ?
8/7/2019 44116778 Pipe Stress Amp Support (1)
5/24
Sustained (Primary) Stresses
8/7/2019 44116778 Pipe Stress Amp Support (1)
6/24
Types of STRESSES in the Piping SystemPrimary Stresses
Direct Shear and Bending in nature Caused due to-
Dead Weight Internal Pressure Occasional Load
Pipe Fluid Piping Component Snow/ Ice
Wind Seismic Load PRV Thrust
Secondary Stresses
Bending (cyclic) in nature Caused due to- Thermal Expansion Equipment Piping System
Local Stresses
Localised Bending and Shear in nature Caused due to-
Local load like load on welded lug on pipe
Stress Analysis
8/7/2019 44116778 Pipe Stress Amp Support (1)
7/24
Code Allowable STRESSES
Primary Stresses
Checking Criteria
Secondary Stresses
Induced Stresses
8/7/2019 44116778 Pipe Stress Amp Support (1)
8/24
Stress Range- Definition
COLD
HOT
HOT OPERATINGCOLD COLD
AsInstalled
Outer fibre-Tension
At Elbow >>
Thermal exp.
Inner fibre- Compr.
Bending stressesdiminishes due toplastic deformations
Stresses Relaxed
At Elbow >>Outer fibre-Compr.
At Elbow >>
Thermal contraction
Inner fibre- Tension
Stress Loading type - CYCLIC
Failure type - FATIGUE
Failure time - Number of Cycle
Stress Analysis
Conclusion ?
8/7/2019 44116778 Pipe Stress Amp Support (1)
9/24
Allowable Stress Range
Allowable Stress Range ( Sa) = (1.5 x Sh) + (1.5 x Sc) = 1.5 ( Sc +Sh )
Yield Stress ( Sy ) =1.5 x Allowable Tensile Stress ( Sc or Sh)
Provision of Primary stresses = Sh
Reduced allowable = 1.25 ( Sc + Sh) To account for simplification in calcn.
To account for localised stresses
Allowable Stress Range ( Sa) = (1.25 Sc + 0.25 Sh ) x f
f = Stress reduction factor
= 1 For life cycle up to 7000
= 0.9 For life cycle 7001 ~ 14000
= 0.8 For life cycle 14001 ~ 22000 = 0.7 For life cycle 22001 ~ 45000
= 0.6 For life cycle 45001 ~ 100000
= 0.5 For life cycle 100001 & over
Stress Analysis
COLD
HOT
8/7/2019 44116778 Pipe Stress Amp Support (1)
10/24
Stress Evaluation
Temperature
COLD
HOT
L = x L
Linear Coef of thermal expn.( Ref. B31.3, Table C-1 )
Stress = Strain x E
Young Modulus of Elasticity( Ref. B31.3, Table C-6 )
Force = Stress x Area
= 48 (L)2 S / E D
E D / 48 (L)2S =
Guided Cantilever Method
Stress Analysis
8/7/2019 44116778 Pipe Stress Amp Support (1)
11/24
Stress Evaluation-In & Out Plan Bending, SIF
Mi
MtMo
For safe design Se < = Sa
Sb = ( Ii x Mi )2+ ( Io x Mo )2 Z
Ii = SIF factor- In Plane
Io = Sif factor- Out Plane
Z = Sectional Modulus of Elasticity
= 3.142 x ( Do3 - Di3 ) / 32
B 31.3 Table D-1
St = Mt / ( 2 x Z )
Se = Sb2 + 4 x St2
Stress Analysis
8/7/2019 44116778 Pipe Stress Amp Support (1)
12/24
Simplified method to check piping system flexibility
Basis - Code B 31.3 para 319.4.1
COLD
HOT
U
L
D x
( L - U ) 2< = KI F Then Piping is Flexible
D = Pipe OD ( mm )
= Resultant Displacement ( mm )
L = Developed Length ( mtrs )
U = Anchor Distance ( mtrs )
K = 208.3
Limitations
Only two point of fixation
No change in pipe size
No intermediate restraint
Stress Analysis
8/7/2019 44116778 Pipe Stress Amp Support (1)
13/24
Other Methods to check the flexibility
Using Nomographs
To perform quick flexibility check
To estimate preliminary anchor loading for civil structural design
Highly versatile application program
To do preliminary exp.. loop sizing on pipe rack at early stage of the job
To review visual analysis lines to avoid expensive CAESAR analysis
Results are acceptable to world wide Engineering companies
Based on Finite Element Analysis Method
Stress Analysis
Using Computer application - CAESAR-II
8/7/2019 44116778 Pipe Stress Amp Support (1)
14/24
Initial Review
Review Piping Specification Review Piping Study Drawing around critical equipment Identify critical civil structural requirements Review all applicable project standards
Prepare Preliminary Stress Critical Line List
Quick check using Excel spreadsheet for Pipe Wall and Br. Reinf. Calculation
Review Pipe-Rack study layout- Establish preliminary exp.. loop location Establish preliminary Pipe-rack loading for structural design
Detailed Review
Identify CAESAR Stress Models- Include group of lines in single model
Perform detailed stress analysis based on issued stress critical line list
Analyse visual check lines using simplified manual techniques Communicate with civil, Vessel and Mechanical groups for loading
Final Approval
Freeze the stress model based on final isometrics
Documentation of Input and Output Reports
Stress Analysis
General Working Procedures
8/7/2019 44116778 Pipe Stress Amp Support (1)
15/24
Identify StressCritical Lines-
Stress Critical Line
List
ReviewStress
Isometric
Revise thePiping study &
Isometric
FreezeSupporting
arrangement
Approvethe Stress
Isometric
Nozzleloading &
Civil Loading
Acceptable ??
Yes
No
Stress Analysis
General Working Procedures
8/7/2019 44116778 Pipe Stress Amp Support (1)
16/24
Responsibilities of Stress Engineers
Nominated by Chief Piping Engineer Responsible for all Stress and Support related activities
Ensure work carried out per Procedures and Design Basis
Establish the Contract Design Data and Design Philosophy
Issue Stress and Support Design Note
Establish Stress Critical Line List
Stress Group Progress Reporting, Man-hours allocation and
Forecast
Raise the Change order to reflect additional work
Supervise Stress and Support activities
Review Piping Specification for Pipe wall thickness and Branch Calc
Job close-out report for stress and support group
Stress Analysis
Stress Lead Engineer
R
esp
o
nsibil
itie
s
8/7/2019 44116778 Pipe Stress Amp Support (1)
17/24
Nominated by Chief Piping Engineer/Lead Stress Engineer
Carry out Flexibility analysis
Identify all the load cases to be considered in analysis
Review Study Drawing to ensure sufficient flexibility in critical piping
Identify and review all critical piping supports Summarise Equipment Nozzle Loading communicate to others
Perform flange leakage calculation for high pressure piping
Communicate critical support loading to Civil
Prepare Spring Schedule/Bellow Specification for procurement
Identify requirement of reinforcement pad due to stress consideration
Decide on position of Fixed saddle of horizontal Heat Exch.. and Vessels
Review Vendor data regarding nozzle loading etc..
Documentation of Analysis Reports
Stress Analysis
Responsibilities of Stress Engineers Stress Engineer
R
esp
o
nsibil
ities
8/7/2019 44116778 Pipe Stress Amp Support (1)
18/24
SPRING Supports
Spring Hangers/ supports
Why required ? ? ?
Variable Type Constant Force Type
Types of Spring supports
Principle of working
Terminology
Cold Load Hot Load
Spring Rate Travel
Instruction for Field Installations
Technical Specification
Stress Analysis
8/7/2019 44116778 Pipe Stress Amp Support (1)
19/24
Expansion Bellows
Why to use ? ? ?
Instruction for Field Installations
Why NOT to use ? ? ?
Metallic Bellow
Material of Construction Non- Metallic ( Rubber / Fabric )
Axial Types of Metallic Bellows
Universal Tied Swing
Hinged Gimbal Pressure Balanced
Selection Criteria
Technical Specification
Stress Analysis
Back Thrust of Un-tied bellow
8/7/2019 44116778 Pipe Stress Amp Support (1)
20/24
Piping Supports
8/7/2019 44116778 Pipe Stress Amp Support (1)
21/24
Pipe Supports
Purpose of Support
Pipe support Instructions and Design Guide
Type of Supports
Pipe support Standard
Pipe Support - Trunnion Calculation
Pipe Support - Span Table
Overview
8/7/2019 44116778 Pipe Stress Amp Support (1)
22/24
Purpose of Pipe supports
Purpose
To Support dead weight of Piping system
To absorb wind load and Seismic load
To absorb Vibration in the Piping system
To Suppress the Noise level in the Pulsating Piping systems
To take Expansion load in the Piping system
To absorb Hydraulic Thrust in the Piping system
To Support the system during Shut down/ Maintenance Cond.
To absorb the Pressure Thrust of Bellow
To minimise Pipe Sagging
Pipe Supports
8/7/2019 44116778 Pipe Stress Amp Support (1)
23/24
Types of Pipe supports
Based on Functions
Loose or Resting supports Longitudinal Guide Supports Transverse Guide Supports Anchor Supports Limit Stops
Welded Type
Non- Welded Type
Based on Construction
Rigid Support
Adjustable Supports
Elastic Supports
Bolted Type
Welded Type
Constant Type Variable Type Snubber Type
Pipe Supports
8/7/2019 44116778 Pipe Stress Amp Support (1)
24/24
Types of Pipe supports- Details
U-Bolts and Clamps Shoe Rod Hangers
Welded Type Clamped Type
Secondary Supports
Attachment from Steel Structures
Attachment from RCC Structures
Attachment from Equipment
Primary Supports
Attachment from Grades
Other Supports
Trunnion Supports
PTFE Sliding Supports
Pipe Supports