Technical article
Running a Monthly Free-Opening Audit and Acting on the Number
Free opening is the one ladle number worth tracking every month. How to count it honestly, what the pattern means, and what to change first.
What a free-opening audit is
A free-opening audit is a monthly count of how many ladles opened on their own when the gate was pulled, expressed as a percentage of ladles tapped. Nothing more complicated than that. It is the single most useful number a melting shop can keep about its ladle practice, and most shops either do not keep it or keep it in a form that cannot be acted on.
Our nozzle filling compound is supplied against a free opening target of 90–98%, and that range is process dependent for a reason: the compound is one input among several. Your own number tells you where you actually sit, and more importantly, it tells you which of those inputs is moving.
1. Define what counts as a free open
Before counting anything, agree the definition in writing and get the crew to sign up to it. Arguments about the number are almost always arguments about the definition.
- Free open. The gate was pulled and steel flowed without any intervention.
- Assisted open. Anything that required oxygen lancing, rodding, or a second attempt. This is not a free open, however brief the intervention.
- Failed. The ladle did not open and had to be handled another way.
The temptation is to count a quick lance as "basically free". Do not. A shop that counts assisted opens as successes will show 97% on paper while the crew knows it is nearer 80%, and every decision made from that number will be wrong.
2. Record it at the ladle, on the heat
The record has to be made by the person who pulled the gate, at the time, on the heat. Reconstructing a month from memory at month end produces a number that flatters whoever is reconstructing it.
Capture six fields per heat. They fit on one line of a clipboard sheet:
- Heat number and date
- Result: free / assisted / failed
- Ladle number
- Holding time from fill to open
- Compound batch reference
- Who filled the well
Those last four fields are what turn a percentage into a diagnosis. Without them you know that something is wrong but not what.
3. Calculate it the same way every month
Free opening rate is free opens divided by total ladles tapped, over the calendar month. Not per shift, not per campaign, not excluding the bad week.
Consistency matters more than sophistication here. A number calculated the same way for twelve months is far more useful than a cleverer number that changed definition in March.
4. Read the pattern, not the percentage
The monthly figure on its own says very little. The distribution inside it says almost everything.
Clustered on one ladle number. That is a well block, not a compound. Erosion has changed the cavity geometry and the fill no longer sits the way it should. Inspect that ladle's well and bore.
Clustered on one operator or shift. Filling practice. The likely candidates are tamping the fill, levelling the cone flat, or filling from a container that has been open all shift. Twenty minutes of coaching is usually the whole fix.
Clustered on long holding times. Sintering depth is driven by time at temperature. If your failures sit above a particular hold duration, the practice has outgrown the grade and that is worth raising with your supplier with the actual times attached.
Clustered on one compound batch. Now you have a material question, and because you recorded the batch reference you can ask it precisely rather than as a complaint.
Rising through the monsoon and recovering after. Storage. The compound is supplied at 0.30% maximum moisture and it is hygroscopic; if your storage practice does not change between March and July but your free opening does, you have found the cause.
Evenly scattered with no pattern at all. This is the hardest case and usually means several small things at once. Fix the cheapest first: storage discipline, then filling technique, then well inspection intervals.
5. Act on one thing at a time
The common failure after a good audit is changing three things at once — new compound, new filling procedure, new storage rules — and then having no idea which one worked.
Change one input. Give it a full month. Compare against the same definition. Then change the next. It feels slow and it is the only way the number ever becomes evidence rather than opinion.
6. Show the number to the people who move it
Free opening is decided by the operator filling the well, not by the purchasing department. A monthly figure reviewed only in a management meeting changes nothing on the floor.
Post it where the filling happens. Shops that do this typically see the number improve before any material or procedure changes, purely because the crew can now see the effect of their own practice. That is the cheapest improvement available in this whole area.
What good looks like after six months
You should be able to say: our free opening rate is X%, it has moved from Y, the remaining failures cluster on Z, and the next thing we are changing is A. Four sentences.
A shop that can say that will resolve a genuine material problem in one conversation with its supplier. A shop that cannot will keep switching suppliers on the strength of a bad week, and will never find out whether the supplier was ever the problem.
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