CNS Certified Safety Shoe OEMCNS 20345 SRC slip resistance, a 200 J steel toe and one-piece MD+RB construction

1. What SRC actually requires

Describing SRA, SRB and SRC as "three slip grades" is misleading. They are not parallel options. SRA tests one surface, SRB tests another, and SRC means every one of the four decision states across both surfaces has passed. A shoe marked SRA alone may find no grip at all on an oily steel floor — which is why asking a supplier whether a shoe "is slip resistant" is not a specification.

The choice of two different lubricants is deliberate. Soapy water is a surfactant that forms a film which is hard to break, testing whether the tread can drain and make contact. Glycerol is a viscous oil, testing the molecular grip of the rubber compound itself. The two are defeated by different mechanisms, which is exactly why a shoe can pass SRA and fail SRB.

Note that the SRB thresholds are markedly lower than SRA — 0.13 against 0.28. That is not because SRB is easier. It reflects the physical ceiling of a glycerol environment: on heavily oiled steel, the coefficient any outsole can reach is fundamentally lower. If anything SRB is the harder demand on the rubber compound.

2. CNS 20345 against EN ISO 20345:2022

If you sell both domestically and for export, this section is the one that causes paperwork problems. Taiwan still works to CNS 20345:2015, so domestic safety footwear continues to be marked SRA, SRB and SRC. The European revision, EN ISO 20345:2022, consolidated all three into a single SR marking, with a tile-and-glycerol slip test built into the base certification.

3. What 200 J and 15 kN look like on a real floor

The two headline numbers of a safety shoe convert into scenarios anyone on site recognises. Under the EN ISO 20345 protection requirements the toecap must pass both:

• 200 J impact — after a 200 joule impact the internal clearance must remain above the specified height. By E = mgh that is roughly 20 kg falling from one metre.
• 15 kN static compression — about 15 kilonewtons, or roughly 1,530 kg of sustained load, without collapsing to zero clearance.

The conversion matters because it is how the requirement gets communicated. "200 J" means nothing to someone loading a truck; "about 20 kg dropping from waist height" immediately explains why trainers are not acceptable in a materials yard.

Puncture resistance is the second line. S3 requires a puncture-resistant midsole, verified with a probe test that models standing on a nail. We build either a high-strength steel plate or a composite-fibre puncture textile: the plate is locally very strong but heavier and covers a smaller area; the textile covers more of the footbed, is lighter and flexes, but its performance against very fine probes has to be established by actual test values rather than assumed.

4. S1 / S2 / S3: what to write in the specification

The S series is not a quality ladder — it is a cumulative checklist of protection features. Each level keeps everything below it and adds one more thing, so writing S3 automatically includes every S1 and S2 requirement.

Layer the slip code on top and the specification is complete. The most useful wording on a purchase specification is "CNS 20345 S3 + SRC" — it locks down structural protection and full-coverage slip resistance at once, and stops a supplier satisfying the slip requirement with SRA alone.

5. The SRC rubber outsole: compound and drainage

Slip resistance does not come from cutting the tread deeper. SRC performance is the product of two things: the molecular grip of the rubber compound, and the drainage efficiency of the tread geometry. The first decides behaviour on a glycerol film, the second decides behaviour on a soap film. Neither substitutes for the other.

The logic of the drainage channel is widely misunderstood. Its job is not to "let water flow away" but to give the water film an escape path at the instant the sole meets the floor, so that rubber can actually touch ground. That means the channel must run through to the edge of the sole as an open path. A deep groove cut into the middle as a closed recess does the opposite: it locks the liquid in and creates a hydroplaning pad.

6. One-piece MD + RB: why conventional safety shoes open at the toe

Delamination is not a glue quality problem; it is a structural inevitability. Failure analysis in footwear puts separation at the interface between dissimilar materials — an EVA midsole against a rubber outsole, for example. The two have different thermal expansion coefficients and elastic moduli, so under sustained flex, perspiration and heat the bond line fatigues and eventually parts. As long as the structure contains two pieces moulded separately and glued afterwards, that interface is a permanent weak point.

The fix is not stronger adhesive. It is eliminating the interface.

Precision tooling and a high-pressure process fuse the two materials directly inside the mould, so the outsole and the shoe structure form as one piece. Because cushioning is carried by the light MD layer, the rubber only has to be the outermost ground-contact layer, and overall shoe weight drops considerably with grip and abrasion resistance intact.

Tooling development, the dual-density fusion process and tread design are covered in All-Material Outsole Manufacturing.

7. The PU insole: protection for the ordinary day

The certification protects against the accident. The insole protects against the shift. What a worker actually absorbs every day is eight to twelve hours of standing and walking. The literature is clear that high BMI, prolonged standing and heavy physical workload are associated with foot and ankle musculoskeletal symptoms and plantar fasciitis, and that prolonged standing raises plantar pressure, degrades postural stability and accumulates fatigue.

On the intervention side, research supports insoles with structural arch support and full footbed cushioning as a practical, evidence-supported measure for workers who stand. That is why our high-density, high-rebound PU functional insole is standard rather than an upgrade.

PU beats ordinary EVA specifically on resistance to compression set. Comparative material data puts EVA at roughly 3–6 months before it flattens noticeably, against roughly 6–9 months for higher-density PU foam, with PU about 40% better on ASTM D4060 abrasion. Full material analysis is on PU Functional Insole ODM.

8. Why falls lead the injury statistics

Slipping ranks higher in occupational injury data than most people assume. According to Bureau of Labor Insurance statistics, from 2023 through the first half of 2025 falls were the leading cause of approved occupational injury benefit claims. Over a longer window, falls have accounted for more than 15% of all occupational accidents in each of the last five years, placing in the top three across all industries.

Workforce age is the second trend that has to be designed for. Over the same period, workers aged 45 and over averaged 65% of fall cases (17,577 in total), and the share is rising. The specification implications are direct:

A safety shoe cannot simply be built "hard enough". A heavy, stiff shoe whose insole has flattened within three months will stop a falling object while raising the daily risk of tripping and of fatigue-driven error. That is the reasoning behind the technical route here — one-piece MD+RB for low weight, high-density PU for lasting support. Protection specification and daily comfort are not a trade-off; both have to hold at once.

9. Frequently asked