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Piping/Mechanical Design Drawings

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Piping/Mechanical Design Drawings

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Piping-Mechanical Design Drawings
ROUGH COPY
© 1996 Bechtel Corp. Piping/Mechanical Handbook 4-1
Section 4
Piping/Mechanical Design Drawings
GENERAL
The primary drawings that a Piping/Mechanical Field Engineer will use in the course of completing
a field assignment are:
 Piping and Instrument Diagram (P&ID)
 Piping Isometric
 Plot Plans
 Piping Class Sheets
 Piping Support Details and Hanger Drawings
 Vendor Drawings and Manuals
 Instrument and Tubing Drawings
 Standard Instrument Details
 Steam Heat Tracing Drawings
These drawings along with project installation specifications provide quality guidelines for properly
completing the assigned system.
Piping and Instrument Diagram
The single most important drawing for the installation of piping systems is the Piping and
Instrument Diagram (P&ID). It provides the base design description of the required pipe routing
and sizing, flow direction and slope, instrumentation and controls, insulation, heat tracing, and
equipment and/or instrument references. This provides a road map to finding other drawings,
vendor data, and piping information to properly complete the installation. The P&ID does not
however provide dimensional data or physical locations of any commodities.
The Piping Line List and the Instrument Index are issued documents which often provide this
information.
PIPING ISOMETRIC AND PLOT PLAN DRAWINGS
Piping Isometric and Plot Plan drawings provide plant references and physical dimensioning that
are not on the P&ID. Along with dimensioning and locating the pipe itself, the drawings also show
the physical installation guides, including:
 Hanger location references to plant coordinates and piping commodities
 Specific installation details and/or requirements
 Material requirements for both the shop and/or field
 Correct valve orientation
 Existing equipment outlines
Section 4 Piping/Mechanical Design Drawings
4-2 Piping/Mechanical Handbook 1996:Rev.2
 Pull or dismantling space
 Piping class
 Pressure test requirements
 Spools
 Welds (including welded attachments)
 Valves
 Hangers
 Specialty items with unique tag numbers
For bulk piping systems, Engineering supplies a detailed Bill of Material for each drawing listing
the required material including material description, quantities, stock code numbers, flange
gasket, and flange bolting. Other information that engineering provides includes coating and
slope requirements for the detailed piping system, connecting equipment nozzle numbers, tap
orientations, stress relief and NDE requirements for piping welds, and standard details for vents
and drains.
PIPING CLASS SHEETS
Piping class sheets specify the material and code requirements for designated piping system
pressure and temperature ratings. A sample Piping Class Sheet is shown in Attachment 4-1.
HANGER DRAWINGS
Hanger drawings provide a detailed drawing of the pipe support, and include the following:
 Detailed bill of materials
 Building location and elevation reference
 Piping dimensional reference for installation location
 Welding requirements
 Line reference numbers
 Design loads (on some projects, hanger loads are determined from standard load tables
and/or charts based on pipe size, span, and support member size)
VENDOR DRAWINGS AND MANUALS
Drawings supplied by vendors will vary by manufacturer but generally provide:
 Outline drawings
 Material types
 Parts listing
 Weights and Centers of Gravity
 Field test requirements
Piping/Mechanical Design Drawings Section 4
1996:Rev.2 Piping/Mechanical Handbook 4-3
 Operating pressures and temperatures and data (e.g. pump curves)
 Start-up, operating, and maintenance procedures
INSTRUMENT AND TUBING DRAWINGS
Design Engineering provides a standard set of drawings for the Mechanical Field Engineer to use
in the installation process. The Piping/Mechanical Field Engineer will match the instrument
category and service fluid and instruct the craft in which detail should be used. The standard
usually will show routing, vents and drains, manifolds, bill of material and stock codes.
HEAT TRACING DRAWINGS
Heat tracing drawings provide the Mechanical Field Engineer with:
 Heat tracing category
 Plant location
 Piping isometric and line number
 Manifold locations with specific tap numbers for tie-in of both steam and condensate tubing.
Section 4 Piping/Mechanical Design Drawings
4-4 Piping/Mechanical Handbook 1996:Rev.2
SAMPLE PIPING CLASS SHEET
ATTACHMENT 4-1
Class (XXX)
ASME B31.1 Power Piping Code
Primary Rating 150 LB @ 600 oF
Pipe: 26" and larger Seamless ASTM A-672, Gr. B70 SCH. (later
if required).
12" thru 24" Seamless ASTM A-106, Gr. B STD. WALL
2 1/2" to 10" SCH. 40
2" and smaller SCH. 80
Fittings: 26" and larger ASTM A234 GR. WPBW seam weld, butt
weld, wall thickness to match pipe
2 1/2" thru 24" ASTM A234 GR WPB or WPBW seamless
or seamweld, butt weld, wall to match pipe
2" and smaller ASTM A-105 3000# socket weld SCH. 80
Flanges: ASTM A-105, bored to match pipe.
26" and larger 150# welding neck R.F.
2 1/2" thru 24" 150# slip-on, R.F.
2" and smaller 150# socket weld, R.F.
Plate: ASTM A515 GR. 70
Bolting: Bolts Stud bolts, ASTM A-193 GR. B7
Nuts Heavy hex, ASTM A-194, GR 2H
Gaskets: All Sizes SEE NOTE 2
ASBESTOS FREE SPIRAL WOUND
Valves: SEE PS-22
Joints: Welded except at flange equipment connections. Field weld end
preparation and weld end transition (ref. PS-06)
Notes: 1. This piping shall not be used where service temperature exceeds
775 oF.
2. Flexitallic Style CG with Flexite-Super filler or equal for design
temperature not exceeding 1000 oF. Metal Strip used shall be
stainless steel TP304.
3. Pipe minimum walls (pipe schedules) are based on design
conditions of 200 PSIG @ 400 oF.
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