Why is fit-up and rework a percentage?

Fit-up and tack welds repeat on every spool, and rework tends to scale with the base work. A percentage keeps the allowance tied to the spool set instead of a flat guess that misses on large jobs.

How do I set the spools per hour rate?

Use completed spools from a comparable job divided by the hours booked to fit and weld them. Include handling and fixture time; exclude painting and inspection if those sit outside this operation.

What causes rework on a skid spool?

Mis-cut pipe, springback after bending and out-of-tolerance flanges are common. Each one adds a fit-up cycle, so track rework hours separately and feed them back into the allowance.

Does the window include painting?

Only if painting sits inside the fabrication window. If coating happens downstream, keep those hours out of the rate and out of the window so this tool covers fit and weld labor alone.

Water, Wastewater & Pump Systems Manufacturing calculator

Skid Piping Labor Calculator

Turn a skid spool count and a fit-and-weld shop rate into labor hours, add the fit-up and rework allowance, then check the total against the fabrication window. The margin shows how much of the window remains.

What this calculator does

Labor hours to fit and weld skid pipe spools at your shop rate, with a fit-up and rework allowance against the window.

Formula used

Base skid piping labor = spools to fabricate ÷ spools fitted and welded per hour
Required skid piping labor = base hours × (1 + fit-up and rework allowance ÷ 100)
Allowance hours = required labor − base labor
Window margin = fabrication window − required labor

Inputs explained

Skid Pipe Spools to Fabricate: Spools on the skid fabrication list for this job.
Spools Fitted and Welded per Hour: Shop rate for fit-up, tack and finish welding.
Fit-Up, Tack, and Rework Allowance: Extra time for fit-up, tack welds and rework.
Fabrication Window: Hours the shop has for this spool set.

How to use the result

Best suited to scheduling a skid fabrication job, quoting rework into a spool set.
Field fit-up can add spools and rework beyond the shop estimate. Welding position, material and inspection level all move the rate; one rate is an average.

Current U.S. benchmarks

The U.S. has 21,668 machinery manufacturing establishments employing about 1,086,146 workers (Census County Business Patterns, 2023).

Common questions

Why is fit-up and rework a percentage? Fit-up and tack welds repeat on every spool, and rework tends to scale with the base work. A percentage keeps the allowance tied to the spool set instead of a flat guess that misses on large jobs.
How do I set the spools per hour rate? Use completed spools from a comparable job divided by the hours booked to fit and weld them. Include handling and fixture time; exclude painting and inspection if those sit outside this operation.
What causes rework on a skid spool? Mis-cut pipe, springback after bending and out-of-tolerance flanges are common. Each one adds a fit-up cycle, so track rework hours separately and feed them back into the allowance.
Does the window include painting? Only if painting sits inside the fabrication window. If coating happens downstream, keep those hours out of the rate and out of the window so this tool covers fit and weld labor alone.

Last reviewed 2026-10-01.