Presentation on Piperack

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    Pipe Rack Design28-August-2013

    Prepared byEng. Abdussalam Al-Zahrani

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    Introduction Pipe Racks typically support pipes, power cables

    and instrument cable trays in petrochemical,chemical and power plants. Occasionally, piperacks may also support mechanical equipment.

    Main pipe racks generally transfer materialbetween equipment and storage or utility areas.

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    Cont.

    Pipe rack is a structure made of steel, concrete or

    both, i.e. hybrid structure that supporting :-Layer or layers of piping.

    Electrical and instrument cable tray.

    Mechanical Equipment if any.

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    Concept of Design Structural components of the pipe rack must be capable

    of resisting the axial loads, shears, moments, and torsion

    produced by the load combinations given in Section 5.0

    of SABP-M-007.

    The pipe support framing system is designed as rigid

    frame bents with fixed or pinned bases in the transversedirection and as braced frames in the longitudinal

    direction.

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    Steps for Design1. Geometry Modeling. (Dimensions, Section Properties, etc)

    2. Loading. (Application of all possible loads)

    3. Design Parameter (Kz, Ly, Lz, UNL, )

    4. Analyzing & Design. (Check your modal, revise and change as needed)

    5. Connection.By Spread Sheet or by StaadPro if Connection Module is available.

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    Geometry The main components of the Pipe Rack are

    Transversebeams

    Verticalbracing

    Longitudinalbeam

    Columns

    1

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    LoadingTypes of load can be classified as follows:

    Dead Load (Ds, De, Doand Dt)

    Wind Load (W, Wp)

    Earthquake Loads (Eo, and Ee)

    Thermal Loads (T, Tp, Afand Ff)

    Other Loads (O)

    REF: SABP-M-007 Para.4 Page 7

    2

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    Loading Tree

    Ty

    pesofLoads

    Dead

    Self-Weight

    Operation

    Empty

    TestLive

    Wind

    EarthquakeOperation

    Empty

    Thermal

    Temperature

    Anchor

    Friction

    Summarized from SABP-M-007 Para.4

    2.1

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    Piping Loads Operating dead load (Do): A uniformly distributed load

    of 40 psf (1.9 kPa, kN/m2) for piping, product, and

    insulation.

    Empty dead load (De): 60% of the estimated piping

    operating loads shall be used. (To check uplift with Wind or Earthquake)

    Test Load Dt: The test load shall be defined as the gravity

    load imposed by the liquid (normally water) used to

    pressure test the piping.

    2.2

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    Piping Loads For any pipe larger than

    12-inch (304-mm) nominal

    diameter, a concentrated

    load, including the weight

    of piping, product, valves,

    fittings, and insulation shall

    be used in lieu of the 40

    psf (1.9 kPa).This load shall

    be uniformly distributed

    over the pipe's associated

    area.

    SABP-M-007 Page 59

    2.2

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    Cable Tray Loads Operating dead load (Do): A uniformly distributed dead

    load of 20 psf (1.0 kPa) for a single level of cable trays

    and 40 psf (1.9 kPa) for a double level of cable trays.

    *Comment: These values estimate the full (maximum) level of cables in the trays.

    Empty dead load (De): For checking uplift and

    components controlled by minimum loading, a reduced

    level of cable tray load (i.e., the actual configuration)should be considered as the empty dead load.

    Engineeringjudgment

    2.3

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    Wind load

    F = qzG CfAe ASCE 7 (Eq. 6-25)

    qz= Velocity pressure at height z above ground. G= Gust effect factor.

    Cf= Net force coefficient.

    Ae= Projected area normal to wind.

    2.4

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    Velocity Pressure qz

    qz = 0.613 KzKztKdV I (N/m2

    ) Kz is the velocity pressure exposure coefficient per Sect.

    6.5.6.6 & Table 6-3 of ASCE 7.

    Kzt is the topographic factor per Sect. 6.5.7.2 of ASCE7.

    Kzt is equal to 1.0 for Pipe Racks and Open Frame

    Structures located in Saudi Aramco facilities.

    Kd is the wind directionality factor per Sect. 6.5.4.4 and

    Table 6-4 of ASCE 7. When used with load combinationsspecified in SAES-M-001, Kdis equal to 0.85 for Pipe Racks

    and Open Frame Structures.

    Wind Load2.4

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    Wi d L d

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    Wind Load

    Table 3 of SABP-M-006 (Metric Units) provides values for qzatseveral heights for most Saudi Aramco sites. These values areto be used for Pipe Racks and Open Frame Structures.

    SABP-M-006 Page 23

    2.4

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    Thermal Loads Ff = Friction Forces: 10% of total piping loads on

    local supporting beam, 5% of total piping loadsacting on struts, braced, anchor frame, column andfoundation.

    Af = Anchor Forces: Anchor and guide forces andlocations shall be obtained from the piping stressanalysis.

    T = Temperature Force:

    Design tem. = Highest Temp.Lowest Temp. + Metal Temp

    *Highest & Lowest Mean Temp can be taken from SAES-A-112.*Metal Temp can be estimated at 20Co

    2.5

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    Calculation of the Earthquake Base Shear V

    V = Csx W

    Cs: The Earthquake Response Coefficient

    W : The Effective Earthquake Weight.

    Determination of Cs (Ref. ASCE 7-05_Clause 12.8)

    Base Earthquake Response Coefficient

    CS =SDS / ( R / I )

    Maximum Earthquake Response Coefficient

    CS =SD1 / { Tax ( R / I ) }

    Minimum Earthquake Response Coefficient

    Where:

    CS shall not be less than 0.010 (Ref. ASCE 7-05_Eq.12.8-5)

    CSshall not be less than 0.5 x S1/ ( R / I )

    ,when if S1 0.60g (Ref. ASCE 7-05_Eq.12.8-6)

    CSshall not be taken less than 0.030 (Ref. ASCE 7-05_Eq.15.4-1)

    CSshall not be less than 0.8 x S1/ ( R / I )

    ,when if S1 0.60g for non-building (Ref. ASCE 7-05_Eq.15.4-2)

    Earthquake

    2.6

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    Load Combination (ASD)

    Notes: a. Wind forces normally need not be considered in the longitudinal direction because friction

    and anchor loads wil l normally govern.

    b. Earthquake forces shall be applied in both transverse and longitudinal directions, but need notbe applied simultaneously.

    c. 0.6Do is used as a good approximation of the empty pipe condition De.

    d. Full Ds + Do value shall be used for the calculation of E in Load Comb. 4a.

    e. Test Weight + Partial Wind normally is required only for local member design because hydrotest

    is not normally done on all pipes simultaneously.

    # Load Combination Multiplier Description

    1 Ds + Do + Ff + T + Af 1.00 Operating Weight + Friction Force + Thermal Expansion + Anchor Force

    2 Ds + Do + Af + (W or 0.7 Eo) 1.00 Operating Weight + Anchor + Wind or Earthquake3 Ds + Dec+ W 1.00 Empty Weight + Wind (Wind uplift case)

    4a 0.9 Ds + 0.6 Do + 0.7 Eod 1.00 Operating Weight + Earthquake (Earthquake uplift case)

    4b 0.9 (Ds + Dec) + 0.7 Ee 1.00 Empty Weight + Earthquake (Earthquake uplift case)

    5 Ds + Dt + Wp 1.20 Test Load + Partial Winde

    SABP-M-007 Page 15

    Pipe Rack Allowable Stress Design (Service Loads)

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    Load Combination (LRFD)

    Notes: a. Wind forces normally need not be considered in the longitudinal direction because friction

    and anchor loads wil l normally govern.

    b. Earthquake forces shall be applied in both transverse and longitudinal directions, but need notbe applied simultaneously.

    c. 0.6Do is used as a good approximation of the empty pipe condition De.

    d. Full Ds + Do value shall be used for the calculation of E in Load Comb. 4a.

    e. Test Weight + Partial Wind normally is required only for local member design because hydrotest

    is not normally done on all pipes simultaneously.

    # Load Combination Description

    1 1.4 (Ds + Do + Ff + T + Af) Operating Weight + Friction Force + Thermal Expansion + Anchor Force

    2 1.2 (Ds + Do + Af) + (1.6W or 1.0E) Operating Weight + Anchor + Wind or Earthquake

    3 0.9 (Ds + De)+ 1.6 W Empty Weight + Wind (Wind uplift case)

    4a 0.9 Ds + 0.6 Do + 1.0 Eod Operating Weight + Earthquake (Earthquake uplift case)

    4b 0.9 (Ds + Dec) + 1.0 Ee Empty Weight + Earthquake (Earthquake uplift case)

    5 1.4 (Ds + Dt) Test Weight

    6 1.2 (Ds + Dt) + 1.6 Wp Test Load + Partial Wind

    SABP-M-007 Page 16

    Pipe Rack Loading Combinations and Load Factors - Strength Design)

    4

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    Analyses & DesignCheck STAAD Pro output for the following:

    Unity Check: Ensure that unity checks for all

    structural members are less than 1.0

    Beam Deflection: Ensure that maximum beams

    vertical deflection is less than

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