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Piping Isometric Drawing-Purpose and necessary information

Isometrics are documents showing a three-dimensional Isometric view of Pipeline. One can say that it is the final outcome of all Piping Engineering activities. Once the Final Isometrics are released it is used at the site and/ or at fabricators for erection or fabrication.
Separate Isometrics will be there for every other line. Isometrics are prepared in A3 Size sheets and shows the profile of a line but the dimensions are not to scale.
Isometrics are made in different stages. The number of stages may vary from consultancy to consultancy. In the very first stage, detailed dimensions won’t be there except locating a valve or showing upstream/downstream straight lengths for flow nozzles etc. These sketches will send to Stress groups and interdepartmental check for their inputs. In the final stage after receiving comments from other departments, the Isos will update and include detailed dimensions, Support mark-up, Bill Of Material and release with the signature of Piping Lead, Stress Lead, and Designer.
The details that should be incorporated in an Isometric drawing are,
1)  Plant North Direction should be mentioned
2)  All Tagging will be present in the Iso as per the P&ID specification. Which includes-Valve Code No, Control Valves Tag, Special Parts Tag, Pressure, Temperature and Flow Measuring instrument details, Safety Valves and bursting Discs.
3) Flow Direction should be Marked
4) An Isometric shall give the details of the starting point and end point of a line Including Elevations, reference Coordinates, etc. Continuation sheet number or matching points shall be clearly identified.
5) If a line is passing through a floor or wall, this has to be indicated on the Isometric drawing along with the elevation of the floor or reference of the wall.
6) The operating floor levels shall be indicated on an isometric near control stations, instruments, isolating valves etc
7) Valve Handwheel directions shall be marked on the border of the Isometric Sheet
8) Weld Points (Excluding field joints) shall be indicated on the Isometric.
9) Reduced size and type shall be identified on the Isometric. For eccentric reducers center line difference and whether installed with the flat side down(FSD) or with Flat Side Top(FST) shall be indicated.
10)  In case of temp Nozzles, the nozzle projection from the OD of the line shall be indicated in the Nozzle table on top of the Isometric along with corresponding representation on the ISO
11)  In the case of offset bends or bends rolled in a plane other than the Isometric plane, hatching lines should be used to indicate the true orientation of the plane on which the bend lies.
12)  The Isos shall be dimensioned continuously without any open dimensions. Duplicate dimensioning is prohibited.
13)  A Flange should be shown on Iso using correct symbol based on its types, such as Weld Neck or Slip on or socket weld or Loose backing flange with stub end
14)  For Flanged joints, the dimensioning shall indicate the distance between the face of one flange to the face of another flange. The distance between two flange faces indicates gasket thickness. When an Item is held between flanges, this thickness will be the sum of the thickness of item and thickness of two gaskets. For Lined pipes, the face of lining is considered as the face of flange. A note to this effect that all dimensions are inclusive of lining thickness should appear on isometric sheet
15)  Isometric include location and Primary Tag number of each point of support. In case a secondary support is also required, the coding for the same shall also be indicated.
16)  On the right-hand side of each Iso.sheet bill of materials is indicated includes-quantity of pipes (size wise), fittings, gaskets, bolts, valves, special parts, primary supports, etc. Should include all items in the Piping Scope of Supply. For Traced/Jacketed lines BOM for tracers/Jackets are indicated separately.



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