What is inch-dia?

The calculation

For each weld, the nominal size in inches is counted. A weld on NPS 4 (DN 100) counts as 4 inch-dia, a weld on NPS 2 (DN 50) as 2 inch-dia. The total of a line is the sum over all its welds.

Example: 10 welds on NPS 4 and 6 welds on NPS 2 give 40 + 12 = 52 inch-dia.

From inch-dia to hours

An hour norm per inch-dia, multiplied by the total inch-dia, gives the welding hours. The norm comes from experience and differs per material, wall thickness and welding position. Stainless steel, thick walls and field welds usually get a higher norm than carbon steel, thin walls and shop welds.

Related measures

• Inch-metre: the nominal size in inches multiplied by the length in metres, used for handling and installing pipe.
• Number of welds per type: butt welds, socket welds and branch welds, from the weld list.

Limits

Inch-dia does not include access, working height, preparation or testing. The norms are specific to each company and are best checked against completed projects.

In FlowCAD3D

The cost estimate calculates installation hours with inch-dia, together with the material from the bill of materials, the article file and the price list of the company, and surcharges. The norms and rates are indicative and are checked by the user. More: Cost estimate and quotation for piping.