Drainage and Sewerage # 1974 Southampton
The experiences of utilizing uPVC pipes as. pressure pipes for fresh water have been both extensive and favourabie, In recent years uPVC has also been introduced as material for relatively thinwalled’ drain and sewer pipes buried in the ground. In connection with this development a lot of research work has been carried out in many countries concerning both soil mechanical problems as well as plastics material long term strength aspects.
Of special interest is the long term strength and behaviour of injection moulded fittings, as they previously have been manufactured utilizing a raw-material with lower molecular weight (lower K value) and lower softening point (Vicat point) than is valid for the pipes.
The long term practical behaviour of pipes and fittings has been simulated with different test methods, the best of which seems to be the box loading test, ie. the BLT method (BS 4660).
A contribution to highlighting the various problems involved in these subjects was given ina paper entitled “Investigations concerning uPVC water and sewer pipes and fittings” by Lars-Eric Janson and Pentti Valimaa (Pipes & Pipelines International, Jan-Feb, 1973), /1j.
In this paper it was clearly stated that the long term strength of uPVC material is strongly influenced by the K value and the Vicat point in such a way that the strength decreases with the reduction of these values.