GFD Overcomes the “Impossible”: Successfully Coil-Cutting DN 250 RTP Pipe for Salt Mining—And We’ve Already Done DN 500

For decades the thermoplastic pipe industry accepted an invisible ceiling: above DN 150 mm, RTP was “too stiff to spool.” GFD has just erased that ceiling. Our newly released DN 250 (10-inch ID) high-performance reinforced thermoplastic pipe—rated PN 100 bar / burst > 300 bar—leaves the production line on a 350 m steel reel, ready to be un-spooled directly into a European salt-cavern brine loop. It is the first time a pipe of this diameter and pressure class has been delivered in continuous form for mining service, and it signals a milestone application for salt-extraction technology.

Why It Matters to Salt Operators

Salt mining is uniquely punishing: halite crystals scour inner walls, brine corrodes steel in months, and every joint is a future leak. Traditional 6- or 12-m stick piping forces hundreds of flanged connections, kilometres of cathodic-protection cable, and weeks of assembly inside tight drifts. By moving to a single, coilable RTP string:

85 % fewer fittings

70 % faster installation (two riggers and a small dozer instead of a full welding spread)

Zero internal corrosion, zero scale build-up, constant 250 mm full-bore ID for the life of the cavern

The Engineering Hurdle We Crushed

Scaling steel-cord RTP from small coils to DN 250 meant re-writing three textbooks at once:

Hoop-stiffness vs. bendability: We moved from a 4-layer to a 6-layer cord architecture, halving individual cord diameter while doubling wrap count. Result: same burst strength, bending modulus dropped by 38 %.

Thermal “memory”: A proprietary post-extrusion anneal relaxes polyethylene chain orientation so the pipe accepts a 14 m spool core without liner wrinkling.

Reel integrity: Our segmented steel “basket reel” carries 45 t of pipe yet keeps ground bearing pressure below 2 bar—safe for salt-floor loading limits.

We validated the coil through 50 full de-spool / re-spool cycles, then hydro-tested to 330 bar—no cord slippage, no ovality loss, liner still glossy.

Field Birth of a New Application

The first 1.2 km string is now operational at 850 m depth in a K+S brine field. After 18 months the pressure drop has increased by < 1 % (compared with 8 % for the previous carbon-steel line), and pump current draw is down 12 %. Mine engineers are already designing the next cavern loop with DN 300 RTP—because they know we can deliver it.

And Yes, We’ve Gone Bigger

While DN 250 is headline news today, GFD’s production line   is already qualified to DN 500 mm (20-inch), PN 40 bar, in 200 m coils. Same steel-cord technology, same coilability philosophy—proving that the “impossible” was only a question of tooling size and courage.

Bottom Line

Coilable large-bore RTP is no longer a laboratory slide; it is a commercial reality that rewrites capex and opex equations for salt-mine operators. GFD’s DN 250 pipe is the opening chapter—DN 500 is ready when your project demands the next leap.