THE STRUCTURAL PERFORMANCE OF THIN-WALLED POLYETHYLENE PIPE LININGS FOR THE RENOVATION OF WATER MAINS

Renovation of deteriorating metal pipe with a close-fitting polyethyle ne lining is now standard practice in the U.K. water industry. Usually a full-thickness pressure pipe is used for the lining. However, here it is argued that capacity to span relatively small gaps and corrosion voids is often the major structural requirement of the lining. Under these circumstances an appropriate thin-walled lining (i.e. thinner th an a full-pressure pipe) will yield both cost savings and a larger ren ovated pipe bore. Performance criteria for these linings are then obta ined from a three-phase programme of research: firstly the creep perfo rmance of medium density polyethylene (MDPE) under the stress states o f interest is determined; secondly a series of short-term tests to fai lure of representative systems is undertaken; finally a finite element model is generated which is initially calibrated aginst the short-ter m test results and then used to predict 50 year creep lives. These pre dictions suggest that at least a two-thirds reduction in material cost s on normal practice is often achievable.