Dipesh H Dahanuwala Date : 25-June-2013
Agenda
Aim
Key Objectives
Aspects of Pipe racks
Optimization Idea
Summary
Aim
To present different aspects of pipe rack
Key Objective
Purpose of Pipe rack
Materials of Construction
Execution Stages
Analysis and Design Concepts
Purpose of Pipe rack
To support group of parallel pipes running at different elevations with emerging or merging branches
Materials of Construction
Concrete
Cast-in-situ
Precast
Application : Concrete Pipe racks are
made in case of corrosive environment
Materials of Construction
Structural Steel
Structural Steel has been used for pipe rack in all projects executed by NPCC
Reason :
FEED requirements
Other advantages are :
Speed of Construction
Better Quality Control
Execution Stages
Preliminary sizing of Pipe rack based on geometry and loading firmed up by Piping
Raise PR for procurement of items
Detailed Engineering
Construction Engineering
Fabrication / Painting
Erection of Pipe rack at site
Analysis and Design Concepts
Geometrical Planning
Loading
Structural Design
End Connection
Base Plate and Anchor Bolt Design
Foundation Design
Analysis and Design Concepts
Geometrical Planning
Grid Location
Tier Elevation
Planning of Beams
Planning of Elevation Bracings
Planning of Plan Bracings
Expansion Joint
Geometrical Planning
Grid Location : by Piping Discipline
Basis :
Width of pipe rack : No. of pipes to be routed with future allowance.
Grid distance :
Based on Piping Support requirements.
Road crossing horizontal clearance
Geometrical Planning Grid Location
Geometrical Planning
Geometrical Planning
Tier Elevations : by Piping Discipline
Basis :
To maintain the minimum headroom for the pipes crossing the roads
Tie-in elevation
Sloping lines
Geometrical Planning Tier Elevation
Geometrical Planning
Planning of Beams : Location of main beam as per Main Grid distances
provided by Piping
Location of secondary beam between Main Grid beams depends on support for small bore pipes provided by Piping
Longitudinal beams to stabilize the Grid Frames, transfer longitudinal forces to vertical braced bay and support secondary beam.
LARGE BORE PIPES
SMALL BORE PIPES
Geometrical Planning
Planning of Elevation Bracings In the middle of pipe rack to allow thermal expansion of
pipe rack on either side thus minimizing thermal restraint in longitudinal direction
To transfer longitudinal forces to foundation
To provide stability to pipe rack in longitudinal direction
Avoid multiple braced bay on same pipe rack to avoid thermal forces in longitudinal beams and braces
Geometrical Planning
Planning of Plan Bracings
Purpose :
To effectively transfer horizontal forces to column
Make better use of structure by introducing truss action instead of bending.
Geometrical Planning
Expansion Joint
Purpose :
To account for thermal expansion of structure
Basis :
As per Company requirement
Methods :
Provide slotted hole connection in the longitudinal beam at all levels at identified location
Pipe rack with slotted joint as expansion joint
Loading
Loads Generated by Civil Discipline
Dead Load (DL)
Live Load (LL)
Temperature Load on Structure (TL)
Earthquake Load (EQ)
Wind Load (WL)
Contingency Load (CL)
Miscellaneous Load (ML)
Loading
Loads Furnished by Piping Discipline
Pipe Empty Load (PE)
Pipe Operating Load (PO)
Pipe Hydro test Load (PT)
Pipe Anchor / Guide Load (PA)
Pipe Friction Load (PF)
Loading
Dead Load (DL)
Weight of Structure
Weight of Fireproofing
Weight of Grating and Handrail in case of platforms on pipe rack
Loading
Live Load (LL)
Applicable in case platform on pipe rack
Normally LL = 5 kPa, but depends on platform use defined by Piping.
Loading
Temperature (Thermal) Load on structure (TL) Due to difference between highest and lowest mean
temperature and based on Design Basis. Typical value for UAE is taken as 60 deg C.
Thermal loads can be minimized by providing Flexible Structure i.e. reduce structural redundancy.
Note : Length of slotted hole connection is based on deflection due to thermal expansion / contraction of structure.
Loading Thermal Load
Good Design
Release of thermal stresses (free to move in both directions)
Loading Thermal Load
Bad Design
Thermal stresses are arrested (restrained by bracings at ends)
Loading
Pipe Empty & Cable Tray Load (PE)
< 12 Pipes : ~ 1.2 kPa
>=12 Pipes : concentrated load (as per Pipe Stress Analysis)
Empty Equipment Load, if any
Cable Tray Load : 1 kPa for each level of cable tray
Critical for checking uplift on foundation
Loading
Pipe Operating Load (PO)
< 12 Pipes : ~ 2 kPa
>=12 Pipes : concentrated load (as per Pipe Stress Analysis)
Operating Equipment Load, if any
Loading
Pipe Hydro Test Load (PT)
To account for pressure testing of pipes
As per Pipe Stress Analysis
Hydro-test weight of equipment
For larger dia pipes (>12) only one pipe hydro tested and other pipes empty (To be confirmed by Piping Discipline and reflected in piping isometric and hydro-test specification)
Loading
Pipe Anchor / Guide Load (PA)
Load to be defined by Piping Discipline
Anchoring lug configuration to be confirmed by Civil in case of high anchor loads
Only Top flange effective Both Flanges effective
Anchor Lug
Loading
Pipe Friction Load (PF)
Cause : Hot lines sliding across beam
Loading Pipe Friction (PF)
For Global Check Longitudinal direction = 5% of Pipe operating Load
Transverse direction = 5% of Pipe operating Load
0.05 P
0.05 P
P = Piping Operating Load
Loading Pipe Friction Load
For Local beam check
1
2
3
4
5
6
8
7
0.3 P
0.1 P
0.2 P 0.1 P
P = Piping Operating Load
Loading Pipe Friction Load
For Local beam check
In Longitudinal direction :
10% of the operating weight (no of pipes >= 7)
20% of the operating weight (no of pipes = 4 to 6)
30% of the operating weight (no of pipes
Loading
Earthquake Load (EQ)
As per project geotechnical investigation and design basis
Earthquake load to be generated for following conditions
a) Erection : DL + PE
b) Operating Case : DL + PO + LL
Loading Earthquake Load (EQ)
As per IBC 2009 & ASCE-7-10, typical parameters for ZADCO site is as follows : Site Class = D
Ss (Short period Spectral Acceleration) = 0.32
S1 (1 sec Spectral Acceleration) = 1.32
I (Importance Factor) = 1 (depends on occupancy category)
R (Response Reduction Factor)
= 3.5 (for ordinary moment resisting frames)
= 7.0 (for special truss frames)
Earthquake Load is generated in STAAD-Pro as per parameters defined in Design Basis.
Loading
Wind Load (WL) As per project design basis
As per ASCE-7-10, typical parameters for ADCO site is as follows :
Basic wind speed (V) = 44.7 m/sec
Importance factor (I) = 1.15
Exposure Category = C
Wind Directionality Factor (Kd) = 0.85
Topographic factor (Kzt) = 1.0
Velocity Pressure Coefficient (Kz) = depends on height of structure
Velocity Pressure (qz) = 0.613 x Kz x Kzt xKd x V2 x I
Loading Wind Load
Gust effect factor (G) = 0.85
Force coefficient Cf = 2 for flat surface members
Cf = 0.8 for tubular members
Wind Force on members = qz x G x Cf x size of member
Wind Load on Pipes = qz x G x Cf x (Pipe Dia)
Pipe Dia = D1+D2+D3 for pipe rack width 4m
D1, D2, D3 and D4 are largest pipe dia in descending order.
Loading
Contingency Load (CL) To account for accidental load on members (e.g.
maintenance load)
Shall be considered for the design of local member
For Beam Design = 10 kN at midspan
Loading
Miscellaneous Load, if applicable (ML) Crane Load
Dynamic Load (considered as equivalent static load)
Blast Load
Structural Design
Member end releases
Support Condition at base plate level
Load Combinations
Design Parameters
Support reactions
Structural Design
Member end releases Main Grid members transverse direction : fixed
Main Grid members longitudinal direction : pinned
Vertical bracings : pinned (to account for local bending due to fireproofing load)
