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