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Module 13 plant piping design
1.
2. Manual Drafting Method
Piping Design Model Method
CADD Method
CADD Model Combined with Physical Scale Model
3. Involves determination of detailed piping with the use
of drawings
Process scheme transposed from flow diagrams onto
Equipment Location Plan
Designer then produces detailed drawings in form of
Piping Plans and Piping Sections called Piping
Arrangement Drawings
Drawn to a scale of 3/8” = 1’0” (imperial) or 1:30 (metric)
Isometrics are then developed from the Arrangement
Drawings
4. Plastic Scale Models
Lay out piping and valves directly on model
Arrangement and isometric drawings developed from
model
scale of 3/8” = 1’0” (imperial) or 1:30 (metric)
Advantages
Accurate and reliable
Points out costly interferences & construction problems
Produces better plant layout
Improves communication between design disciplines
5. Better indication of progress to management
Reduces construction costs by eliminating “ignorance
contingencies” used by bidders
Assists in the writing of better operation manuals
Reduces amount of time spent training plant operators
6. Speed up drawing function and enhance design
function
Allows production of “intelligent” flow diagram
Reports line & instrumentation list and prelim M.T.O.
Reports inconsistencies in pipe sizing and specs
Major strength: data storage and retrieval capability
which allows massive amounts of design information
to be available for checking and reporting
7. Designer produces plant design using following steps:
Set up section of plant as computer model in isometric
Insert foundations and structures
Construct vessels and equipment
Route piping between nozzles
Add fittings, vales and instruments
Report interferences
Report inconsistencies re: size, specs or space
Produce double line plan or section views
Automatically produce isos incl. M.T.O.
Link all sections of plant together
8. Combined to produce faster, more efficient and effective
design with cleaner construction
Early design – plastic model
Plastic model data fed into CADD database which:
Allows for interference checks to be made
Allows Structural load verification to indicate supports and hangars
and interface with stress analysis programs
Provides easy access to drawings of each area
Aids with MTOs and spec compatibility checking
CADD designs related back to physical model
CADD develops Isos, arrangement drawings, MTOs and
inventory lists for use during construction
Physical model available during approvals, construction,
operator training and as basis for revision
9. Positive Pressure Head must be present at piping outlet
Produced by pump, gravity, displacement or static head, suction
Friction loss
Keep piping runs short as possible with few fittings
Viscosity (internal friction of fluid)
Design piping and valving for minimum liquid hold-up during shut-down
Vents and drains
Properly placed to allow filling and draining of vessels during testing and purging
Turbulence is required
Avoid dead spots in piping and use bends of 5 pipe diameter
Control valves
Commonly one pipe size smaller than line size
Points of sudden pressure drop causing “flashing”
Provide sufficient N.P.S.H.
Vapour lock
Slope the line or vent high point
Condensable vapours like steam piped to avoid liquid pocketing
Special pipe materials
may be needed when transporting hazardous liquids
10. Economics
Minimize length of lines and number of fittings
Carefully consider design changes due to increasing operation costs
in facilities
Maintenance
Adequate space must be provided for assembly, disassembly,
adjustment and lubrication of equipment
Utility stations should be readily available
Special lifting or rigging devices may be required
Breakout flanges may be required to aid equipment removal
Vibration
Air chambers may be required for quick valve opening & closing
Reciprocating equipment requires surge tanks or pulsation bottles
plus sufficient piping support