Aspects of Piperack Design

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Steel Piperack analysis

Text of Aspects of Piperack Design

  • Dipesh H Dahanuwala Date : 25-June-2013

  • Agenda


    Key Objectives

    Aspects of Pipe racks

    Optimization Idea


  • 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




    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


    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.



  • 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









    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)