- Email: [email protected]
Polyurethane lining technology for pipes
Technical Report Polyurethane Lining Technology for Pipes Frank E. Johns ECLP Engineering, English Clays Lovering Pochin & Co. Ltd, John Keay House SL AustelL Cornwall PL25 4DJ Favourable experience with lined pipesfor transmission of abrasive slurries made at ECLP Engineering has encouraged the firm to extend a manufacturing service to all industry. Introduction Since the late 1960's The Clays Division of E C C Plc., English Clays Lovering and Pochin (ECLP), has been seeking ways to improve the massive materials handling problem in its 19 km long pipe installation, which conveys the highly abrasive micaceous waste generated during the production of 2,500,000 metric tonnes of high grade kaolin at the world's largest kaolin production facility in Cornwall. When E C L P Engineering built the pipeline they sought a transfer system that could be installed largely underground with the promise of a working life of at least 20 years. E C L P Engineering devised a realistic evaluation programme to find a suitable cost-effective lining material able to withstand the most highly abrasive slurry likely to be encountered in service. The aggressively scouring action they sought was best simulated using 0.5 mm quartz sancL
Fig. 1
One in a vast complex of recovery pits operated by English China C l a y s - world leaders in the production of China Clay for applications ranging from paper coatings and ceramics through fillers to cosmetics. Pipes lined with urethane rubber based on Du Pont's "Terathane" polytetramethylene ether glycol (PTMEG) successfully handle the transfer of several million metric tonnes per annum of highly abrasive waste and look good to last to the year 2000.
MATERIALS & DESIGN Vol. 5 N a 6 D E C E M B E R / J A N U A R Y 1 9 8 5
Predictably, unlined steel pipe was worn through in only 12 weeks of testing while linings of conventional rubbers did rather better with between 18 and 24 months of service before failure. In contrast, pipes protected with a polyetherbased urethane rubber applied in thicknesses of 0.9 and 1.3 mm were still functioning well after 3 years of simulated service. This narrowed the field of investigation and extrapolation of the wear figures predicted that a 6 mm thick liner of urethane could be expected to provide the 20 year service required. Plant Development As a direct result of the successful test programme, ECLP elected to develop a urethane lining facility in-house. A plant was designed and built with the ability to cast rotationally the urethane liner in steel pipes up to 6 metres in length. A patented process was used that ensured a tolerance of-O to -t-2 mm in liner thickness at bore diameters up to 320 mm as standard (even larger if required). An added advantage was that the liner was extended over the face of the pipe flange to act as an effective, integral joint gasket. To date, the promised performance of the early urethane systems has lived up to expectations - not one length of pipe in the 19 km network has failed in service. Any damage was confined to the odd accident where buried sections of pipe have been inadvertently excavated by earth moving equipment, However, in its search to improve quality and extend even further the lifetime of the coating, E C L P Engineering has introduced more up-to-date mixing and dispensing equipment, and included in its product range a newer, uniquely formulated, abrasion resistant urethane - developed by a specialist U K company based on a quasiprepolymer system incorporating Du Pont's "Terathane" ( P T M E G ) as the soft segment. Furthermore, the primer and adhesive systems which complement this urethane, locked the liner to the metal substrate with such tenacity that no satisfactory method has yet been devised to test the adhesive bond to destruction: the urethane itself ruptures ahead of delamination from the metal. ECLP's best expectations for the performance of the improved systems are entirely justified: this new breed of polyurethanes is fulfilling its promise to give longer, maintenance free service in aggressive on-site evaluation trials than any other materials tried previously. The success of the work is due to the elegant combination of the novel engineering skills brought to bear by ECLP Engineering on
281
Fig. 2
A stack of urethane lined pipes awaits at ECLP Engineering in St. Austell. The excellent physical and mechanical properties of the resilient liner ensure long, maintenance free service in contact with highly abrasive slurries. The smooth, unobstructed bore does not induce turbulence and aids free flow.
the application process, coupled with the best that the modern polyurethane producer can offer. These urethanes owe their outstanding performance, in no small part, to the role played by Du Pont's "Terathane" polytetramethylene ether glycol (PTMEG). This essential glycol, now commercially produced for the first time in Europe at Du Pont's new SM30 plant in the Netherlands, gives tastable and thermoplastic urethanes the performance needed to resist the extreme conditions where more conventional polyester based materials would fail:- notably, outstanding hydrolytic stability: resistance to both abrasion and to attack by micro-organisms: higher resilience: good low temperature flexibility and small hysteresis. The performance of ECLP's in-house polyurethane
282
Fig. 3
Examples of a wide range of solid cast, lined and covered wear parts of polyurethane produced by ECLP Engineering. In addition to in-house applications, the company, on behalf of industry at large, has experience, technical expertise and production facilities to cast, line, coat and spray apply wear resistant urethane to equipment used in mining process and refining operations.
application facility has proved so successful under the rigorous conditions experienced in Cornwall that ECLP Engineering now actively offers lining and casting services to outside users. Products range through pipework and associated bends, elbows and tees through solid cast impellors, pump casings, cyclones, classifier shoes and other wear parts to spray-applied linings and coatings of all types. Satisfied users include Rio Tinto Minera, who have successfully employed lined pipes to handle ore slurries at the Cerro Colorado Mine in Spain since the early 1970's. More recently, 5000 metres of a 150 mm diameter lined pipe was supplied to the National Coal Board for use at Gedling Colliery.
MATERIALS & DESIGN VoL 5 No. 6 DECEMBER/JANUARY 1985
Fig. 1
One in a vast complex of recovery pits operated by English China C l a y s - world leaders in the production of China Clay for applications ranging from paper coatings and ceramics through fillers to cosmetics. Pipes lined with urethane rubber based on Du Pont's "Terathane" polytetramethylene ether glycol (PTMEG) successfully handle the transfer of several million metric tonnes per annum of highly abrasive waste and look good to last to the year 2000.
MATERIALS & DESIGN Vol. 5 N a 6 D E C E M B E R / J A N U A R Y 1 9 8 5
Predictably, unlined steel pipe was worn through in only 12 weeks of testing while linings of conventional rubbers did rather better with between 18 and 24 months of service before failure. In contrast, pipes protected with a polyetherbased urethane rubber applied in thicknesses of 0.9 and 1.3 mm were still functioning well after 3 years of simulated service. This narrowed the field of investigation and extrapolation of the wear figures predicted that a 6 mm thick liner of urethane could be expected to provide the 20 year service required. Plant Development As a direct result of the successful test programme, ECLP elected to develop a urethane lining facility in-house. A plant was designed and built with the ability to cast rotationally the urethane liner in steel pipes up to 6 metres in length. A patented process was used that ensured a tolerance of-O to -t-2 mm in liner thickness at bore diameters up to 320 mm as standard (even larger if required). An added advantage was that the liner was extended over the face of the pipe flange to act as an effective, integral joint gasket. To date, the promised performance of the early urethane systems has lived up to expectations - not one length of pipe in the 19 km network has failed in service. Any damage was confined to the odd accident where buried sections of pipe have been inadvertently excavated by earth moving equipment, However, in its search to improve quality and extend even further the lifetime of the coating, E C L P Engineering has introduced more up-to-date mixing and dispensing equipment, and included in its product range a newer, uniquely formulated, abrasion resistant urethane - developed by a specialist U K company based on a quasiprepolymer system incorporating Du Pont's "Terathane" ( P T M E G ) as the soft segment. Furthermore, the primer and adhesive systems which complement this urethane, locked the liner to the metal substrate with such tenacity that no satisfactory method has yet been devised to test the adhesive bond to destruction: the urethane itself ruptures ahead of delamination from the metal. ECLP's best expectations for the performance of the improved systems are entirely justified: this new breed of polyurethanes is fulfilling its promise to give longer, maintenance free service in aggressive on-site evaluation trials than any other materials tried previously. The success of the work is due to the elegant combination of the novel engineering skills brought to bear by ECLP Engineering on
281
Fig. 2
A stack of urethane lined pipes awaits at ECLP Engineering in St. Austell. The excellent physical and mechanical properties of the resilient liner ensure long, maintenance free service in contact with highly abrasive slurries. The smooth, unobstructed bore does not induce turbulence and aids free flow.
the application process, coupled with the best that the modern polyurethane producer can offer. These urethanes owe their outstanding performance, in no small part, to the role played by Du Pont's "Terathane" polytetramethylene ether glycol (PTMEG). This essential glycol, now commercially produced for the first time in Europe at Du Pont's new SM30 plant in the Netherlands, gives tastable and thermoplastic urethanes the performance needed to resist the extreme conditions where more conventional polyester based materials would fail:- notably, outstanding hydrolytic stability: resistance to both abrasion and to attack by micro-organisms: higher resilience: good low temperature flexibility and small hysteresis. The performance of ECLP's in-house polyurethane
282
Fig. 3
Examples of a wide range of solid cast, lined and covered wear parts of polyurethane produced by ECLP Engineering. In addition to in-house applications, the company, on behalf of industry at large, has experience, technical expertise and production facilities to cast, line, coat and spray apply wear resistant urethane to equipment used in mining process and refining operations.
application facility has proved so successful under the rigorous conditions experienced in Cornwall that ECLP Engineering now actively offers lining and casting services to outside users. Products range through pipework and associated bends, elbows and tees through solid cast impellors, pump casings, cyclones, classifier shoes and other wear parts to spray-applied linings and coatings of all types. Satisfied users include Rio Tinto Minera, who have successfully employed lined pipes to handle ore slurries at the Cerro Colorado Mine in Spain since the early 1970's. More recently, 5000 metres of a 150 mm diameter lined pipe was supplied to the National Coal Board for use at Gedling Colliery.
MATERIALS & DESIGN VoL 5 No. 6 DECEMBER/JANUARY 1985