Mechanical, HVAC, Piping & Plumbing

1. Layout Drawing

• Definition:

  • A 2D/3D schematic showing the arrangement of equipment, piping, and structural elements within a facility.

• Key Details:

  • Equipment location (pumps, tanks, HVAC units) with clearance zones

  • Piping routes with flow directions

  • Structural supports (steel beams, foundations)

  • Accessibility for maintenance

  • Compliance with safety codes (ASME, NFPA, API)

• Used in:

  • Plant design

  • Facility expansion

  • Space optimization

2. Isometric Drawing

• Definition:

• A 3D representation of piping systems, showing exact dimensions, angles, and fittings.

• Key Details:

  • Pipe routing with coordinates (North/East/Elevation)

  • Fittings (elbows, tees, valves) with specs

  • Welding points and support locations

  • Material specifications (ASTM, ANSI class)

• Purpose:

  • Fabrication & construction guide

  • Avoids clashes during installation

• Software:

  • AutoCAD Plant 3D

  • SmartPlant 3D

  • CADWorx

3. Requisition

• Definition:

  • A formal request for materials, equipment, or contractor services.

  • Contents:

  • Technical specifications (material grade, pressure rating)

  • Quantity (length, size, units)

  • Delivery schedule

  • Quality requirements (certifications, testing)

• Types:

  • Material Requisition (pipes, valves, insulation)

  • Equipment Requisition (pumps, chillers, boilers)

  • Approval Flow:

  • Engineer → Procurement → Vendor

4. Flexibility Analysis (Stress Analysis)

• Definition:

  • Ensures piping systems can withstand thermal expansion, vibration, and pressure loads.

• Key Checks:

  • Expansion loops vs. expansion joints

  • Pipe stress at anchor points

  • Nozzle loads on equipment

  • Support types (rigid, spring, hangers)

• Software:

  • CAESAR II

  • AutoPIPE

  • ROHR2

• Output:

  • Stress report with acceptance criteria (ASME B31.3)

  • Support adjustment recommendations

5. Information Drawing

• Definition:

  • Summarizes key data for construction and maintenance.

• Includes:

  • P&ID references

  • Equipment datasheets

  • Valve schedules

  • Insulation/thickness details

• Purpose:

  • Quick reference for field teams

6. Test Block Diagram

• Definition:

  • Outlines pressure testing procedures for piping systems.

• Details:

  • Test medium (water, air, nitrogen)

  • Test pressure (1.5x design pressure)

  • Isolation points

  • Safety valves

• Standards:

  • ASME B31.1 (Power Piping)

  • ASME B31.3 (Process Piping)

7. MTO (Material Take-Off)

• Definition:

  • A bill of quantities extracted from drawings.

• Breakdown:

  • Item Specs Qty Unit

  • CS Pipe 4" Sch 40 ASTM A106 150 meter

  • Gate Valve 4" 150# RF 8 ea

• Uses:

  • Cost estimation

  • Procurement tracking

8. HVAC-Specific Documents

• Duct Layout Drawing

  • Shows airflow paths, dampers, diffusers

  • CFM requirements per zone

• Psychrometric Analysis

  • Calculates cooling load (sensible/latent heat)

• Chiller/Pump Schedules

  • Capacity (tons, kW)

  • Flow rates (GPM)