Novarc has visited hundreds of fabrication facilities worldwide and one thing we’ve found is that there isn’t a definitive and universal way of measuring pipe welding productivity. Here at Novarc we strive to help the entire industry move forward by helping fab shops measure this critical metric. Examples of how to calculate DI and FDI are provided in the write-up.
Understanding Diameter Inches and Factored Diameter Inches in Pipe Fabrication
In the world of pipe fabrication, productivity is a critical factor in ensuring efficient project completion and cost control. Two commonly used metrics to measure productivity are Diameter Inches (DI) and Factored Diameter Inches (FDI) per shift. These measurements help fabricators, project managers, and estimators evaluate; work output, plan labor, and estimate costs more accurately. In this post, we will break down what DI and FDI are, how they are calculated, and how material type can impact these calculations.
What Are Diameter Inches (DI)?
Diameter Inches (DI) is a basic metric that quantifies the total amount of welding performed based on pipe diameter and the number of joints completed.
Formula for DI:
DI = Nominal Pipe Size (NPS) x Number of Joints
Example:
- A welder completes 5 weld joints on 10 inch diameter pipes in a shift.
- DI Calculation: 10 x 5 = 50 DI/shift
This means the welder produced 50 diameter inches in that shift.
What Are Factored Diameter Inches (FDI)?
While DI provides a simple measurement, it does not account for the complexity of different weld types. This is where Factored Diameter Inches (FDI) come into play. FDI adjusts DI using complexity factors assigned to various weld types. The Pipe Fabrication Institute provides guidelines for the different factors that impact FDI in their Technical Bulletin, TB-10, “Guidelines For Calculating Factored Weld Diameter Inches for Project Reporting”.
FDI Formula:
FDI = Nominal Pipe Size (NPS) x # of Weld Joints x Wall Factor x Material Factor x Weld Type Factor
Wall Factor
Material Factor
Weld Type Factor
Example FDI Calculation:
In one eight-hour shift, a welder completes 4 butt weld joints in the 1G-R position on NPS 6, Standard (0.280” wall) stainless steel pipe, and 3 slip-on flange welds in the 2F position on NPS 8 inch, Schedule 80 (0.432” wall) carbon steel pipe. How many FDIs did the welder complete?
Stainless Steel FDI = 6 in x 4 weld joints x 1.0 (wall factor) x 2.0 (material factor) x 1.0 (weld type factor) = 48 FDI
Carbon Steel FDI = 8 in x 3 weld joints x 1.2 (wall factor) x 1.0 (material factor) x 1.0 (weld type factor) = 28.8 FDI
Answer: The welder completed 48 + 28.8 = 76.8 FDI per 8-hour shift.
Comparison of Manual vs. Novarc SWR
Example: Let’s compare the productivity of a pipe spooling shop that uses manual welding processes to a shop that has implemented Novarc’s SWR for the same job.
Welds to Complete
- Carbon Steel: 1000 Groove Weld Joints, 12-inch diameter, schedule 80
- Wall Factor = 1.6
- Material Factor = 1.0
- Weld Type Factor = 1.0
- Total DI = 1000 x 12 = 12,000
- Total FDI = 1000 x 12 x 1.6 = 19,200
Manual Shop
- Weld Process:
- Root Pass: Manual TIG
- Fill & Cap: Manual FCAW
Automated Shop – Novarc SWR
- Weld Process:
- Root Pass: SWR STT
- Fill & Cap: SWR HyperFill GMAW-P
Conclusion
Understanding and applying Diameter Inches (DI) and Factored Diameter Inches (FDI) helps improve efficiency in pipe fabrication. FDI provides a more accurate measurement by accounting for weld complexity, and material type further refines productivity calculations. By using these metrics, fabricators can better estimate labor requirements, optimize project planning, and control costs.