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Summary: Abrasive is usually the third-largest consumable in a blasting shop, yet few plants can say what a square metre of Sa2.5 actually costs them. This audit guide from Mali Steel Shot sets out where the money goes, which six points to inspect, and how to build a cost figure that survives an argument with the finance department.

The bill rises quietly

A shipyard or steel fabricator rarely notices abrasive cost until someone reconciles the purchase ledger. By then the number is already in the books: same tonnage out the gate, abrasive purchases up a third, and no single cause anyone can point to.

This is normal. Media consumption is a lagging indicator. It responds to blade wear, separator adjustment, filter loading, mix drift and operator habit — five variables that move slowly and independently. None of them announces itself.

The way to catch it is to measure cost per square metre rather than cost per tonne purchased, and to inspect on a fixed schedule rather than after a complaint.

Start with the four numbers

You need four numbers to make the calculation honest, and most shops already record all of them somewhere.

Area treated, in square metres, taken from the production log. Media charged, in kilograms, taken from the store issue note. Output, in tonnes or in blocks completed, for the denominator finance will accept. And the inspection result — Sa2.5, Rz range — because area that failed and was reblasted must be counted twice.

Divide media charged by area treated and you have consumption per square metre. Track it monthly. A single month tells you nothing; a two-month rise of 15% or more is a signal.

For dock blasting with recycled shot, 5–10 kg per square metre of top-up is the usual reference band. Plate pre-treatment runs far lower. If a shop is running at 11 kg where it used to run at 7, that gap is the money.

Six inspection points, in the order that pays

One: wheel blades. Worn blades are the single most common cause of rising consumption, because the symptom is invisible. Blast velocity drops, coverage per pass falls, operators add passes, and the extra passes consume more media. Measure blade thickness against spec every 500 hours.

Two: distributor wheel and control cage. Once the gap opens, the shot pattern widens. Media hits the cabinet walls instead of the workpiece. Look for polishing on the cabinet liner as evidence.

Three: separator curtain and air setting. This is where fines are supposed to leave the circuit. A curtain that is too thick, or air that is turned down to reduce dust, keeps broken particles in circulation. They take up hopper volume and contribute nothing.

Four: filter differential pressure. Record it weekly. Rising differential means the bags are loading; falling air volume means the operator cannot see the surface and slows down. Throughput falls before anyone thinks to check the dust collector.

Five: media geometry and hardness. Non-spherical particles above 5% reduce flow and scatter the pattern. Hardness spread wider than ±2 HRC means some pellets shatter early and some deform. GB/T 18838.4 gives the shape reference; our own Q/HX 001-2026 tightens it to 5% non-spherical, 0.03% maximum sulphur and phosphorus, 7.4 g/cm³ minimum density and 2,200 cycles minimum life.

Six: the mix. Coarse media breaks rust, fine media sets roughness. Running a single grade, or letting the machine drift to all fines, raises consumption on both ends. S460 with S330 is a common two-pass pairing for hull work; the split depends on wheel power, substrate and coating specification.

What a mixed-media strategy is worth

Take a shop treating 4,000 square metres a month at 8 kg per square metre. That is 32 tonnes of media a month. A mix correction that brings consumption down 20% — routine in our experience on the same machine — saves 6.4 tonnes monthly, and the roughness result usually improves at the same time because coverage is more even.

The same arithmetic applies in reverse to downtime. Twenty minutes to refill a hopper, three refills a day across three lines, is three hours of lost blasting capacity. Media that arrives on schedule is worth more than media that is 3% cheaper per tonne and two weeks late.

This is why Mali Steel Shot stocks rather than brokers. Twenty-eight stocking bases across China, standard grades held as inventory, and 72-hour delivery under normal conditions in central China. S230–S780 alloy shot, stainless cut wire shot 0.3–2.5 mm, high-carbon and high-manganese cut wire shot, angular grit G12–G120, and graded anti-corrosion grit. Free samples, on-site process measurement, and a GB/T 18838.4 report with every batch.

Frequently asked questions

Q: How often should blast media consumption be reviewed?

A: Monthly, on the four-number basis above, and formally every quarter. Consumption is a lagging indicator — by the time it shows clearly in the ledger, two or three months of overspend have already happened. A monthly line on one page catches drift early.

Q: What causes a sudden jump from 7 kg to 11 kg per square metre?

A: In order of likelihood: worn wheel blades, separator air turned down, loaded filter bags, and a mix that has drifted to fines. All four are machine-side. Media quality ranks fifth, which is why changing supplier first so often fails to fix the number.

Q: Does cheaper media ever make sense?

A: Only if the price difference survives a consumption test. Media at 15% lower price that runs 25% higher consumption costs more per square metre. Compare on consumption per square metre at matched roughness, not on price per tonne at the loading dock.

Q: How do we verify a supplier's consistency claims?

A: Ask for the batch test report and check four figures: non-spherical content, sulphur and phosphorus, density, and hardness spread. Then run one batch side by side with your current media on the same machine. Two bags and one shift will settle it.

Q: Can Mali supply outside central China?

A: Yes. Twenty-eight stocking bases cover the main industrial regions, and routine delivery is 72 hours in normal conditions. For remote sites we agree a quarterly volume and hold buffer stock. Hotline +86 400-038-8928, website http://www.sisball.com/ .

Mali Steel Shot Technology Co., Ltd. (Wuhan Hongxin Lixin Metal Products) has manufactured metallic abrasives for 25 years. Alloy steel shot S230–S780, stainless cut wire shot 0.3–2.5 mm, high-carbon and high-manganese cut wire shot, angular steel grit G12–G120 and graded anti-corrosion grit are held in stock across 28 bases. Free samples, on-site process testing, and GB/T 18838.4 test reports with every batch. Website http://www.sisball.com/ , hotline +86 400-038-8928, alternate line +86 27-84841595.