Plant Laout Pipeway

Embed Size (px)

Citation preview

  • 8/3/2019 Plant Laout Pipeway

    1/25

    Plant Layout - Pipeway Design

    Table of Contents

    1. General

    2. Information Required3. Evaluation of Information4. Line Identification5. Piperack Width6. Piperack Elevation7. Line Location in Piperacks8. Piping Economy in Piperack and its Influence on Plant Layout9. Piperack General Arrangement Checklist10. Pipetracks11. Trenched Piping (Civil Department)12. Underground Piping (by Civil Department)

    http://www.red-bag.com/cms/index.php?section=66#generalhttp://www.red-bag.com/cms/index.php?section=66#informationrequiredhttp://www.red-bag.com/cms/index.php?section=66#evaluationhttp://www.red-bag.com/cms/index.php?section=66#lineidentificationhttp://www.red-bag.com/cms/index.php?section=66#piperackwidthhttp://www.red-bag.com/cms/index.php?section=66#piperackelevationhttp://www.red-bag.com/cms/index.php?section=66#linelocationhttp://www.red-bag.com/cms/index.php?section=66#pipingeconomyhttp://www.red-bag.com/cms/index.php?section=66#piperackgeneralhttp://www.red-bag.com/cms/index.php?section=66#pipetrackshttp://www.red-bag.com/cms/index.php?section=66#trenchedpipinghttp://www.red-bag.com/cms/index.php?section=66#undergroundpipinghttp://www.red-bag.com/cms/index.php?section=66#generalhttp://www.red-bag.com/cms/index.php?section=66#informationrequiredhttp://www.red-bag.com/cms/index.php?section=66#evaluationhttp://www.red-bag.com/cms/index.php?section=66#lineidentificationhttp://www.red-bag.com/cms/index.php?section=66#piperackwidthhttp://www.red-bag.com/cms/index.php?section=66#piperackelevationhttp://www.red-bag.com/cms/index.php?section=66#linelocationhttp://www.red-bag.com/cms/index.php?section=66#pipingeconomyhttp://www.red-bag.com/cms/index.php?section=66#piperackgeneralhttp://www.red-bag.com/cms/index.php?section=66#pipetrackshttp://www.red-bag.com/cms/index.php?section=66#trenchedpipinghttp://www.red-bag.com/cms/index.php?section=66#undergroundpiping
  • 8/3/2019 Plant Laout Pipeway

    2/25

    1. GeneralThe pipeway conveys all main process lines connecting distant pieces of equipment,

    relief and blowdown headers, all lines leaving and entering the plant, utility linessupplying steam, air, cooling water and inert gas to the plant. Electrical and instrumentcable trays are usually routed in the pipeway. Pipeways are classified by their relativeelevation to grade.

    1.1 Piperack

    Overhead piping supported on steel or concrete bents.

    1.2 Pipetrack

    Above ground piping supported on concrete sleepers at grade level. (Off site areas whereequipment is well spaced out)

    1.3 Trenched Piping ( by Civil Department )

    Below ground piping laid in connection trenches. Costly and usually undesirable; unlesstrenches are wide, shallow and well vented, heavy gases may settle and crea

    te a fire hazard through the length of the trench. For these reasons, only pump out lines,chemical sewers or chemical drain collection systems are sometimes placed in trenchesand routed to a pit or underground collection tank.

    1.4 Underground Piping ( by Civil Department )

    Piping direct buried below ground level. Due to costly maintenance and the usuallycorrosive nature of soil, this method of routing is generally reserved for sewer and drainlines. In some plants, especially in cold climates, cooling water lines are buried below thefrostline. This should be determined at the beginning of a job, is generally a Clientrequest.

    2. Information Required

    2.1 Job Specification

  • 8/3/2019 Plant Laout Pipeway

    3/25

    Job specification SP....C100 contains design criteria, agreed between Company andClient, affecting piperack design:

    Battery limit, valving and spade requirements. Catwalk, platform and ladder access to valves and relief valves in piperack.

    Minimum headroom and clearances under overhead piping or supporting steelwithin areas Pipeways and secondary access ways Main access roads Rail roads Standard to be used for minimum spacing of lines in paperacks Handling and headroom requirements for equipment positioned under piperacks Operating and safety requirements affecting piperack and structure design Location of cooling water lines underground or above ground Trenched piping, if any.

    2.2 Process Flow DiagramsProcess flow diagrams show main process lines and lines interconnecting processequipment.

    2.3 Engineering Flow Diagrams

    Engineering flow diagrams are developed from process flow diagrams and show:

    Pipe sizes. Pipe classes, and line number.

    Valving. Manifolding. All instrumentation. Equipment and lines requiring services, i.e. water steam, air, nitrogen etc.

    2.4 Utility Flow Diagrams

    Utility flow diagrams show the required services:

    Steam Condensate Water Air Gas

    And any additional services peculiar to the plant being worked on, e.g.:

    Caustic Acid

  • 8/3/2019 Plant Laout Pipeway

    4/25

    And refrigeration lines, etc.

    3. Evaluation of Information3.1 Initial Evaluation

    Use plot plan and process flow diagrams to make a preliminary assessment of which portion of process lines will be located in piperack and which lines will interconnectdirectly to nozzles on adjacent items of equipment. Draw lines to be located on piperackson print of plot plan. Some idea of utility piping required must be established andincluded coordinate with Instrument and Electrical Section to assess what additional rack space may be required to accommodate cable trays. This action provides a preliminaryvisual idea of the piperack space required.

    3.2 Development

    With the receipt of engineering flow diagrams and utility flow diagrams, a more completeand accurate assessment of rack space is possible. Utility headers generally run the wholelength of the piperack, so should be taken into account when estimating additional spacerequired. To assist Process Department in sizing utility headers in the pipeway a linerouting on a repro of the plot plan, showing order of take-offs is required.

    4. Line IdentificationCertain types of piping require special consideration:

    4.1 Process Lines

    Lines interconnecting nozzles on process equipment more than 6M apart (closer specedequipment may be directly interconnecting inside piping areas).

    Products lines which run from vessels, exchangers or pump to battery / unit limits Crude or other charge lines entering the unit which run along piperack before

    connecting to process equipment, furnaces, exchangers, holding drums or booster pumps.

    4.2 Relief Headers

  • 8/3/2019 Plant Laout Pipeway

    5/25

    Individual relief lines, blowdown lines and flare lines should be self draining from allrelief valve outlets to knock-out drum, flare stack or to a point at the plant limit. Toachieve this, lines will connect into the top of the header and at 45 degrees in direction of flow. To eliminate pockets, and obtain required slope to knock-out drum some relief headers must be placed above the main piperack.

    4.3 Instrument and Electrical Cable Trays

    Often instrument and electrical cable trays are supported on the piperack track. Spacemust be allocated to accommodate them from the outset. Due to the possibility of inducedcurrent interference instrument and communication cable trays must be located awayfrom electrical and power cable trays. Consult with Instrument /Electrical Department for separation requirements.

    5. Piperack WidthThe width of piperack is influenced by :

    The number of lines Electrical/instrument cable trays. Space for future lines.

    The width of a piperack may be calculated using the following method : First estimatenumber of lines as described. Add up the number of lines up to 18 diameter in the mostdense section of the piperack.

    The total width in meters (W) will be :

    W = ( f x N x S ) + A meters

    Where f, safety factor = 1.5, if the lines have been laid out as described in initialevaluation.

    Where f, safety factor = 1.2, if the lines have been laid out as described under development.

    N = number of lines below 18 diameter

    S = average estimated spacing between lines in millimeters.

    Usually - S = 300 mm

    Usually - S = 230 mm ( if lines in piperack are smaller than 10 )

  • 8/3/2019 Plant Laout Pipeway

    6/25

    A = additional width required meters for :

    Lines larger than 18. Future lines. Instrument and electrical cable trays.

    Any slot for pump discharge lines 500 mm - 1 meter.

    The total width is thus obtained. If W is bigger than 9M usually two piperack levels will be required.

    Note : At the beginning of a job, `W` should usually include 30 - 40% of clear space for future lines.

    The width of the piperack may be increased or determined by the space requirement,and/or access to equipment arranged under the piperack.

    Below figure shows typical piperacks bents with tabulated dimensions. Total available piperack width of each type of support is included. This table can be used for selection.The most commonly used piperack supports are types 2, 3, 4 and 5.

    5.1 Spacing between Piperack Bents

    Normal spacing between piperack bents varies between 4.6M to 6M.

    This may be increased to a maximum of 8M consideration must be given to :

    Smaller lines which must be supported more frequently ( see Company designspecification recommended span between pipe supports )

    Liquid filled lines requiring shorter span than gas filled lines Hot lines which span shorter distances than cold lines of the same size and wall

    thickness Insulated lines; small bore, cold - insulated lines due to weight of insulation must

    be supported at relatively short intervals Space requirements of equipment at grade can sometimes influence piperack bent

    spacing.

    6. Piperack ElevationPiperack elevation is determined by the highest requirement of the following :

    Headroom over main road Headroom for access to equipment under the piperack

  • 8/3/2019 Plant Laout Pipeway

    7/25

    Headroom under lines interconnecting the piperack and equipment locatedoutside.

    The size of steel or concrete beam supporting overhead piping must be taken intoconsideration. Headroom requirements for each job are detailed in Company

    specification no. C100 and coordination procedure.

    6.1 Elevation at Piperack Intersection

    Where two two-tier piperacks meet, it is essential that elevations of lateral piperacks slot between elevations of main piperack.

    Figure 2A illustrates this requirement. Choice of top elevation of lateral piperack midway between the top an bottom main piperack elevation allows turning up or down at theintersection.

    Generally, lines running at right angles to main piperack are assigned elevations 500 mmto 1 meter higher or lower (depending on headroom requirements) than lines running inmain piperack. 500 mm differential between pipe runs is the absolute minimum.

    Figure 2B shows a piperack intersection where the respective main and lateral piperack elevations do not slot between each other. This design complicates routing of lines from

    piperack to the other, especially where lines run on the bottom levels of both piperacks.Avoid this design at all cost.

    Where a single tier piperack turns through 90, and all lines can be kept in the samesequence in both directions, no elevation difference is necessary. When lines sequencechanges, introduce an elevation change at the turn. See below figures.

    7. Line Location in Piperacks

    7.1 One Tier Piperacks

    Below figure shows a cross section of a single level piperack. Heavy lines (very large

    diameter lines, large bore lines full of liquid) regardless of service are placed over or near the piperack columns. This simplifies steelwork or concrete piperack design. Centrallyloaded column and reduced bending moment on the beam will result in a lighter overalldesign.

    Place process and relief lines next to these. Lines serving left hand areas of plant on left,lines serving right hand areas on the right.

  • 8/3/2019 Plant Laout Pipeway

    8/25

    The central piperack portion is reserved for utility lines which may serve both right andleft hand areas on the plant. However, utility lines serving one or two pieces of equipment should be on the same side of the piperack as the equipment to which theyconnect.

    Process lines which interconnect equipment on both sides of the piperack should be placed close to utility lines, and can be on either side of piperack, depending uponlocation of equipment they serve. The position of product lines is influenced by their routing after leaving the unit, right, (left) turning lines should be on the right (left) handside of the piperack.

    If possible, a centrally placed section of the piperack is reserved for future lines. Thissection should run the whole length of the piperack. Should this be impracticable, a seriesof smaller sections, running the whole length of the piperack, are to be provided. (see

    below figure).

    7.2 Two Tier PiperacksWhere the number of lines dictate the use of a two level piperack, utility lines are placedon the top level and process lines on the bottom level. This is not a rigid rule and where

    piping economy dictates certain process lines may be routed on the top level. Linesequence arrangement should follow the philosophy outlined previously.

    7.3 Position of Hot Lines

    It is advantageous for pipe supports to group hot lines requiring expansion loops together,

    preferably on side of the piperack. Horizontally elevated loops over the piperack arecommonly used to minimize the effects of expansion on hot lines, the hottest and largestline being on the outside. See below figures.

    7.4 Line Spacing

    For line spacing use recommended piperack spacing per table in Job SpecificationC100. It should be noted that in certain cases, it is necessary to deviate from the standardsquoted above, e.g., see below figures at point A due to possible differential expansionline spacing may have to be increased to allow for movement of lines at start up.

    To determine expansion of hot lines, use Company engineering guide, Attachmentthermal expansion of pipe materials.

  • 8/3/2019 Plant Laout Pipeway

    9/25

    8. Piping Economy in Piperack and itsInfluence on Plant Layout

    8.1 Piperack LayoutPlant layout determines the main piperack piping runs. The shape of piperack is the resultof plant arrangements, site conditions, Clients requirements and overall plant economy.See below figures.

    Piping economy depends primarily on the length of lines routed in the piperack. Belowfigures shows critical dimensions which influence overall cost. These dimensions dependon overall plant layout and should be carefully considered when the plot is arranged.

    Dimension A, (see below figures) is the total length of piperack and is governed by thenumber and size of equipment, structures and buildings arranged along both sides of the

    piperack. On average, 3 meters of piperack length are required per item of processequipment, good lay-out can reduce piperack length. (Thereby costs).

    Equipment in pairs, stacked exchangers supported from towers, two vessels combinedinto one, closely located towers with common platforms, process equipment located -under piperack - are examples which help shorten piperack length. In a well arranged

    plant, average length of piperack per item of process equipment can be reduced to 2.1meters to 2.4 meters.

    Careful selection of dimensions B and C, below figure will minimize interconnectionequipment on opposite sides of piperack. C is normally no more than 1.8 meters to 3meters.

    Dimensions D and E, (see below figure), minimize. Overgenerous dimensioning here willincrease vertical pipe lengths. Maximize use of available platforms for access to valves.Where air fins are located above the piperack, use associated air fin maintenance

    platforms, modifying their extent if necessary. This method will be cheaper than addingspecial platforms in the piperack.

    9. Piperack General ArrangementChecklist

    Critically review piperack layout against latest information. Some lines should requirererouting for maximum piping economy. Check loops required for nesting. As many

  • 8/3/2019 Plant Laout Pipeway

    10/25

    loops as possible should be combined in a loop bay having due regard to stressrequirements.

    9.1 Vibrating Lines Avoid changes in direction Avoid long overhanging bends without support Use bends where possible (check with job specification) Tees to be avoided as far as possible, flow should enter along run of tee and never

    in the branch.

    Low point pockets to be avoided in the following lines :

    Steam (trap any pockets and dead ends) Slurry Blowdown (these lines must be self-draining) Caustic, acid and Phenol (all these services to be self draining) R.V.s both inlet and outlet Vapour to knock-out pots Heavy products, bitumen, wax Pump suctions Lethal and toxic substances

    High point pockets to be avoided in the following lines :

    Pump suctions Light ends Vapour/liquid mixes (hot tower bottoms - reflux lines) Crude lines

    On hot lines, check shoe requirements and clearances at changes of direction (pipeexpansion).

    Provide vents at high points.

    Provide drains at low points.

    Provide steam traps at : low points, up-stream of loops and dead ends, via condensatedrip legs.

    On steam, air and condensate headers, take-offs to be from top of headers. RV headershigh or low elevation. Before finalizing elevation of RV header consider elevation of allRV discharges and elevation of knock-out drum at flare.

    Bends, if used : (check with job specification).

  • 8/3/2019 Plant Laout Pipeway

    11/25

    Where lines change elevation bends may be used providing difference inelevation is adequate and specification permits

    Header take-offs in piperacks, use elbows Special piping: Catalyst lines 5D (minimum).

    Vibrating piping 5D. Small bore usually below 2 (Client preferred).

    Pipe setting : to be avoided in large bore lines. Small bore lines to be set only whereabsolutely necessary.

    Pipe Stress Department will advise which piping systems require formal stress analysis.

    Supports : avoid long unsupported overhangs.

    Steelwork clearances : check steelwork clearances for addition of fireproofing (lower

    elevation of piperack), brackets, gussets and thermal expansion of lines.

    Concrete support clearances : check for local thickening of concrete columns due tomethod of fabrication adopted (i.e. corbels).

    Valves : check clearances and accessibility. Make full of extending platforms for operation (i.e. air fin maintenance platforms).

    Chain wheels : preferably do not use. However, if necessary, check chain clearances.Spading and valving at battery limit : check for accessibility if necessary, provide access

    platform.

    10. PipetracksThis type of pipeway is generally associated with offsite areas where equipment is wellspaced out, and land space is not a premium.

    10.1 Pipetrack Width

    Pipetrack width may be estimated using the method detailed previously for piperack.

    10.2 Spacing of Pipetrack Sleepers

    Pipetrack sleepers are relatively cheap thus piping economy is dictated by therecommended span of the smallest line in the track.

  • 8/3/2019 Plant Laout Pipeway

    12/25

    Where small bore lines are few, sleeper spacing may be determined by the pipe span of large bore lines provided small bore lines are supported off the larger lines at adequateintervals. An angle with U bolts is sufficient (check with Pipe Support Section).

    For recommended pipe support spans, use Company standard.

    On an average minimum span = 3 meters

    maximum span = 6 meters

    depending on line size and substance carried in pipes, (i.e. gas or liquid).

    All lines must be supported. At changes of direction due to long overhangs, for narrow pipetracks a diagonal corner sleeper is recommended. On wide pipetracks, use alternativemethod of two short sleepers located near corner. See below figures.

    10.3 Pipetrack ElevationPipetrack elevation is set by maintenance access to piping items located underneath the

    pipetrack, i.e. drains and steam traps. A minimum of 12/300 mm clearance betweenunderneath of lines and grade is recommended; where necessary, this may be increased to18/450 mm.

    As pipetracks are generally single tier, no change in elevation is necessary at changes of direction. This is effected by use of a flat turn. See below figures.

    For individual line elevation above sleeper, use Company job specification no. C4elevation of hot insulated lines.

    10.4 Line Location

    Line location with reference to bore and weight is unnecessary, as all pipes are supportedon sleepers which rest directly on the ground. Line routing is all important. All linesinterconnecting process equipment and/or storage tanks located on left-hand side of

    pipetrack are placed to the left-hand side. Similarly, all lines interconnecting equipmentlocated on right-hand side of pipetrack are placed to the right of pipetrack. Linesinterconnecting equipment located on either side of pipetrack are placed near the center

    of pipetrack.

    10.5 Line Spacing

    Use Company job specification no. C100 recommended pipetrack spacing

    10.6 Road Crossings

  • 8/3/2019 Plant Laout Pipeway

    13/25

    The standard method is to provide culverts under access roads. Elevating piping on across-over rack is expensive and introduces unnecessary pockets in the lines thus routed.When determining width and height of culvert, care must be taken to allow sufficientroom round the pipework for maintenance, insulation and painting. Where only one or two lines cross a road, crossing may be by means of sleeves set under roadway.

    10.7 Access Ways

    In areas needing frequent access, platforms may be provided across pipetrack.

    10.8 Valves

    Where possible, these should be grouped at the edge of an access platform for ease of operation. Drain valves where possible should be brought to outside of pipetrack for easeof operation. The same applies to steam trap assemblies.

    10.9 Expansion Loops

    Horizontally elevated expansion loops above pipetrack should be provided wherenecessary. Group all hot lines requiring expansion loops, hottest and largest line on theoutside, on one side of pipetrack. (Generally, the side chosen is that side which has thehighest number of take-offs serving equipment on that side).

    11. Trenched Piping (Civil Department)In most plants, trenches are avoided due to problems associated with this type of

    pipeway:

    High initial cost Fire hazard

    Where trenchers are used to route lines such as:

    Pump out lines Chemical sewers Chemical drains

    Trenchers must be enough to allow sufficient clearance between trench wall and piping.150 mm between outside of pipe and inside of wall is the minimum acceptable clearance.This will allow for installation of piping, painting and future maintenance. See belowfigures. Total width of trench required may be determined by using method detailedabove. Piping Department will advise Civil Department of requirements.

  • 8/3/2019 Plant Laout Pipeway

    14/25

    11.1 Line Spacing

    Use Company job specification C100. recommended piperack spacing.

    Line location in a trench carrying a number of lines should be carefully chosen for maximum piping economy consistent with stress requirements, if any.

    Open trenches require drains to stop accumulation of surface water. Trench bottomshould be sloped towards drain points. In this case, pipe supporting is by means of anglesteel or I beams set into the walls, allowing bottom for free drainage to nearest drain

    point.

    This method allows drainage of a trench by a minimum of drain points between each pipesupport as would be the case of solid concrete pipe supports built up from the trench.Before proceeding on trench drainage check with coordination procedure and CivilDepartment for water table level.

    11.2 Safety Precautions

    Most trenches have either a cover of concrete slabs or a grating.

    Where flammable liquids are carried in trenched lines, a fire break is provided at suitableintervals along a trench and at each intersection. This generally consists of two concretewalls 1 M - 1.25 M apart, with the space in between filled with sand. Where highlyflammable gasses are carried, the whole trench, after installation of piping, is back filledwith sand. Piping will advise Civil Department of requirements.

    12. Underground Piping (by CivilDepartment)

    Keep buried piping to a minimum. Generally only sewer drain lines and fire mains arelocated below ground. In some cases due to Client or climate requirements, cooling water lines are also buried below the frost line.

    With future maintenance in mind, buried lines should be located well clear of foundations, and if running side by side, well spaced out. A minimum of 300 mmclearance is necessary between foundations and lines and between the lines themselves.

    Above ground safe drain-tails will enter below ground drain line via a tundish (concentricreducer normally) or if a sealed system and cooling water lines by a flanged stub raisedabove ground.

  • 8/3/2019 Plant Laout Pipeway

    15/25

    Flanged connections should be a minimum of 300 mm above prevalent grade level. It isadvantageous to set a common level for all these take offs at the outset of the job. Whenlocating tie-in connections to underground systems, especially from elevated drain points,and adjacent to equipment plinths, ensure adequate clearance.

    All buried steel pipes should have applied a corrosion resistant coating and wrapping.

    Deep valve boxes for buried lines should be designed with ample room inside the box for a maintenance man to bend over and use wrenches for tightening flanges of re-packingvalves. Consideration should be given to the use of concrete pipe in lieu of square boxes.

    The criteria for a good underground piping design should be ease of maintenance. Pipingshould be so spaced as to allow easy digging out and replacement of faulty sections; for this reason, never run underground piping under or through foundations.

    Figures - Table

  • 8/3/2019 Plant Laout Pipeway

    16/25

    TYPICAL PIPE RANK BENTS

    TYPE TOTAL AVAILABLE WIDTHW IN mm

    PIPERACK CANTILEVER NUMBER

    No. WITHOUTCANTILEVER

    WITHCANTILEVER

    WIDTH A WIDTH B OF ELEV.

  • 8/3/2019 Plant Laout Pipeway

    17/25

    1 3000 - 3000 - 1

    2 6000 TO 7300 9150 TO 10400 6000 TO7300

    1500 1

    3 8500 TO 9750 11600 TO12800

    8500 TO9750

    1500 1

    4 11900 TO14300

    13700 TO16150

    6100 TO7300

    900 OR 1200 2

    5 16800 TO19200

    18600 TO21000

    8500 TO9750

    900 OR 1200 2

    6 8500 TO 10400 11000 TO12800

    6100 TO7300

    900 OR 1500 1.5

    7 12200 TO13400

    14650 TO15850

    8500 TO9750

    900 OR 1500 1.5

  • 8/3/2019 Plant Laout Pipeway

    18/25

    TYPICAL PIPE RANK INTERSECTION

  • 8/3/2019 Plant Laout Pipeway

    19/25

  • 8/3/2019 Plant Laout Pipeway

    20/25

    SINGLE TIER RACK TURNING THROUGH 90

    CROSS-SECTION OF SINGLE LEVEL PIPE RACK

  • 8/3/2019 Plant Laout Pipeway

    21/25

    EXPANSION LOOPS

  • 8/3/2019 Plant Laout Pipeway

    22/25

    PIPE RACK LAYOUTS

  • 8/3/2019 Plant Laout Pipeway

    23/25

    PIPE RACK LAYOUTS

  • 8/3/2019 Plant Laout Pipeway

    24/25

    SPACING PIPE TRACK SLEEPERS

  • 8/3/2019 Plant Laout Pipeway

    25/25

    TRENCHED PIPING