How do you calculate a weld inch risk score?

Multiply severity by 0.40, occurrence by 0.35, and detection by 0.25, then sum them. For severity 6, occurrence 4, detection 3 the score is 6(0.40) + 4(0.35) + 3(0.25) = 4.55.

Why is severity weighted higher than occurrence and detection?

On pressure piping and process skids, the consequence of a weld failure — leak, rupture, loss of containment — dominates risk. The 40/35/25 split deliberately pushes severe-consequence welds up the priority list even when defects are relatively rare.

What is a good weld inch risk score?

On a 1-10 rating basis, scores under about 3.5 are lower-priority welds, 3.5-6 warrant standard NDE coverage, and above 6 call for 100% RT plus tighter procedure control. The 4.55 example sits squarely in the standard-coverage band.

How is detection scored for welds?

Detection scores how hard the defect is to catch — a high score means poor detectability. A lack-of-fusion defect in a socket weld inaccessible to RT scores high; a surface crack readily found by PT scores low.

Is this the same as an FMEA RPN for welding?

It's a weighted variant. A classic RPN multiplies severity x occurrence x detection equally; this weld-inch score weights them 40/35/25 so a single dimension can't unfairly dominate and severe-consequence welds are prioritized.

Can I use this to reduce NDE cost?

Yes — rank all weld packages by score and shift discretionary radiography from low-score joints to the high-score ones, keeping code-mandatory coverage intact. It targets inspection spend without cutting required coverage.

Process Skids, Modular Equipment & Packaged Plants calculator

Weld Inch Estimate Calculator

The Weld Inch Estimate risk score turns three FMEA-style ratings — how bad a weld failure would be, how likely the defect is, and how hard it is to catch with NDE — into one weighted number that ranks weld packages by risk. Welding engineers and QA leads on process-skid and packaged-plant piping use it to decide where to spend limited radiography and PT/MT budget across thousands of weld inches. It matters because you can't 100% inspect every joint on a large skid, so you prioritize the welds that are severe, prone to defects, and easy to miss. The weighting reflects that on pressure piping, consequence and detectability drive risk more than raw occurrence.

What this calculator does

The Weld Inch Estimate risk score turns three FMEA-style ratings — how bad a weld failure would be, how likely the defect is, and how hard it is to catch with NDE — into one weighted number that ranks weld packages by risk.
Use it when weld inch estimate in process skids, modular equipment and packaged plants needs a defensible ranking against other process skids, modular equipment and packaged plants risks for the next review.
It computes a single weld-inch risk score by weighting severity at 40%, occurrence at 35%, and detection at 25%.

Formula used

Weld Inch Estimate risk score = severity × 0.40 + occurrence × 0.35 + detection × 0.25

Inputs explained

Weld defect severity:
Defect occurrence likelihood:
NDE detection difficulty:

How to use the result

Use it when building an NDE plan or ranking weld packages on a skid so inspection hours go to the highest-risk joints first.
It is a relative prioritization tool, not a code compliance check — a low score never overrides ASME/B31.3 mandatory NDE requirements for a given service class.

Current U.S. benchmarks

Steel mill PPI stands at 348.53 (BLS, May 2026), up 6.7% from a year earlier. New factory orders are up 2.3% year over year (Census).

Common questions

How do you calculate a weld inch risk score? Multiply severity by 0.40, occurrence by 0.35, and detection by 0.25, then sum them. For severity 6, occurrence 4, detection 3 the score is 6(0.40) + 4(0.35) + 3(0.25) = 4.55.
Why is severity weighted higher than occurrence and detection? On pressure piping and process skids, the consequence of a weld failure — leak, rupture, loss of containment — dominates risk. The 40/35/25 split deliberately pushes severe-consequence welds up the priority list even when defects are relatively rare.
What is a good weld inch risk score? On a 1-10 rating basis, scores under about 3.5 are lower-priority welds, 3.5-6 warrant standard NDE coverage, and above 6 call for 100% RT plus tighter procedure control. The 4.55 example sits squarely in the standard-coverage band.
How is detection scored for welds? Detection scores how hard the defect is to catch — a high score means poor detectability. A lack-of-fusion defect in a socket weld inaccessible to RT scores high; a surface crack readily found by PT scores low.
Is this the same as an FMEA RPN for welding? It's a weighted variant. A classic RPN multiplies severity x occurrence x detection equally; this weld-inch score weights them 40/35/25 so a single dimension can't unfairly dominate and severe-consequence welds are prioritized.

Last reviewed 2026-05-12.