PortalStorage tanks
API 650 and NBR 7821 atmospheric tanks, from bottom and shell plates to the roof.
Quality in Assembly & Welding
Quality Tools Applied to the Assembly and Welding of Tanks and Equipment
Failed tests, rework and weld repairs are expensive and delay delivery. We apply Ishikawa, Pareto, 5 Whys and 5W2H right at the assembly front to find the real cause of defects and remove it, with traceable records in the databook.
4-step method
From the defect found to the action plan carried out
The four tools work in sequence. The example below follows a real job: the field erection of an API 650 storage tank.
01
Ishikawa Diagram
Find the root of the problem
Also called the fishbone or cause-and-effect diagram. It sorts every possible cause of a defect into six families (6M), so the team does not jump straight to the first suspect.
When to use it on site
- Recurring porosity, cracks or lack of fusion
- Distortion and misalignment of shell plates
- Leaks in the hydrostatic or tightness test
Manpower
Welder not qualified (WPQ) for the vertical position
Material
Low-hydrogen electrodes left out of the oven, picking up moisture
Method
WPS parameters not followed at the work front
Machine
Loose ground clamp and power source with unstable current
Measurement
Clamp ammeter out of calibration
Environment
Wind and humidity on site with no protective screen
Porosity in the shell weld
02
Pareto Chart
Decide which problems to solve first
Ranks defects from most to least frequent and shows the cumulative percentage. A few causes usually account for most of the rejections (the 80/20 rule).
When to use it on site
- Consolidate the job’s NDT reports (RT, UT, PT, MT and visual)
- Choose where to invest in training and inspection first
- Compare before and after a corrective action
Share of each defectCumulative percentage
Porosity, lack of fusion and undercut add up to 76% of the rejections. Tackling those three causes removes most of the rework.
Pareto chart data table
| Defect | Share | Cumulative |
|---|---|---|
| Porosity | 38% | 38% |
| Lack of fusion | 24% | 62% |
| Undercut | 14% | 76% |
| Slag inclusion | 10% | 86% |
| Crack | 6% | 92% |
| Misalignment | 5% | 97% |
| Spatter | 3% | 100% |
03
5 Whys
Understand what caused the problem
Asks "why?" in sequence until it moves past the symptom to a process cause that can be removed. It avoids fixing only the effect, such as repairing the weld without stopping the defect from coming back.
When to use it on site
- Investigate a specific non-conformance report (NCR)
- Dig into the most likely cause from the Ishikawa
- Answer a complaint from the client or the inspector
Problem: rejection for lack of fusion in the bottom joint
- 1Why?The weld was made with current below the WPS range
- 2Why?The welder set the machine by experience
- 3Why?The WPS work instruction was not at the work front
- 4Why?There is no control for distributing documents to the field
- 5Why?The document-control procedure does not cover field jobs
Root cause: a failure in the documentation system, not in the welder
04
5W2H
Build an action plan to solve the problem
Turns the root cause into a clear action plan: each action has an owner, deadline, place, method and cost, so it can be followed up and checked.
When to use it on site
- Close an NCR with corrective and preventive action
- Plan the release of a new welding front
- Track how effective the action is in later inspections
- What
- Make the laminated WPS instruction available at every welding front, with a per-pass parameter checklist
- Why
- Eliminate lack-of-fusion rejections caused by parameters outside the WPS
- Where
- Assembly fronts of tank TQ-12: bottom and first shell course
- When
- Before the next welded joint, within 5 working days
- Who
- FortSolda welding inspector, together with the erection foreman
- How
- Revise the document procedure, hold a 30-minute toolbox talk and measure current with a calibrated clamp meter
- How Much(How much)
- About R$ 800, against a repair and re-test cost per joint many times higher
Where we apply it
Quality at every stage of fabrication
Pressure vessels
ASME Section VIII and NR-13 equipment, with material and welder traceability.
Industrial piping
ASME B31.3 spools and lines, with joint control by isometric.
Steel structures
AWS D1.1 structures, from walkways and supports to equipment bases.
Stages covered
- 1Receipt of materials and consumables
- 2Joint fit-up and assembly
- 3Welding and parameter control
- 4Non-destructive testing
- 5Hydrostatic and tightness testing
- 6Databook and final release
What you get
Analysis deliverables
- Non-conformance report (NCR) with root-cause analysis
- Ishikawa and Pareto diagrams built with your job’s data
- 5W2H action plan with owners and deadlines
- Effectiveness check in the following inspections
- Records attached to the databook and available in the client portal
- ART issued by the responsible engineer, where applicable
Does your job have defects that keep coming back?
Send us the reports or describe the problem. Our engineers will tell you where to start the analysis and which tool fits your case.