...The plastic pipes have standardized outer diameter and wall thickness. Pipes of identical material with different wall thickness have different service parameters (service pressure / service temperature / service life). The pipes were divided into pressure series designated “PN” according to wall thickness originally. As the plastic material properties gradually improved, the PN designation relevance, particularly as far as the hot water systems are concerned, was increasingly lower and the individual series were named S or SDR.
- PN (pressure nominal): service pressure value at which the equipment can be operated at 20 °C temperature and with 50 years’ service life.
- S = (SDR-1)/2; SDR equals approximately to D/t where D is outer pipe diameter and t is pipe wall thickness. ...
