FROM DRAWING TO QUANTITY
A piping quantity needs
a measurement basis.
This constructed example shows how route dimensions become reviewable takeoff rows. It is a learning example, not a completed client project or a fabrication instruction.
Step 1: establish the drawing basis
Assume one dimensioned route for a single piping specification. Its centreline segments are A = 12 ft, B = 8 ft and C = 10 ft. The route has two direction changes. For this example, the start and end are defined package boundaries; equipment internals and connections beyond those points are excluded.
Step 2: keep different quantities separate
| Item | Quantity | Basis |
|---|---|---|
| Centreline route | 30 ft | 12 + 8 + 10 ft |
| Direction changes | 2 locations | Geometry identifies changes; fitting type follows design |
| Fittings | Per specified component | Confirm type, size, rating and connection |
| Straight cut lengths | To be developed | Require actual component dimensions and fabrication conventions |
| Support quantities | To be developed | Require support information; not inferred from this schematic |
The 30 ft route is not automatically a 30 ft cut-pipe order. Fitting centre-to-end dimensions, valve lengths and connection allowances can change the straight-pipe quantities. Procurement waste and stock-length rules are another separate step.
Step 3: do not guess the weld total
Geometry alone does not establish all fabrication and field joints. Confirm component end connections, spool limits and terminal conditions, then record the joint-counting rule. A direction change is not a universal one-weld item. Separate shop joints from field joints before applying labor or examination scope.
Step 4: connect the takeoff to pricing
An estimate row should identify its description, specification, unit, quantity, drawing reference and pricing basis. Material unit prices and labor-unit hours belong in separate columns. The project location, rate date and supplier-quote exclusions need to remain visible. This example intentionally supplies no market rates.
Step 5: identify the remaining scope
- Pipe material, schedule and line specification
- Component dimensions and connection methods
- Shop/field split, supports and vendor boundaries
- Specified testing, insulation and coating
- Access and installation assumptions
ASME B31.3 addresses process-piping matters including materials, fabrication, erection, examination and testing. The estimating assignment should follow the requirements supplied for the project, rather than assume every process line has the same testing or material basis.
Scope reference: ASME B31.3 — Process Piping. The diagram and dataset on this page are original explanatory examples.