HOBAS Pipe Classification

HOBAS Pipes can be classified according to:

  • Diameter
  • Stiffness
  • Pressure
  • Resin Quality


HOBAS Pipes are manufactured in sizes from DN 150 mm up to 3600 mm in pressure and non-pressure classes.

Classification According to Stiffness

Pipe stiffness refers to the resistance to deflection. The greater a pipe’s wall thickness, the greater is its stiffness and therefore its ability to resist external bending loads or low internal pressure.

HOBAS Pipes of standard stiffness classes are regarded as flexible because pipe deflection has a considerable effect on the load and pressure distribution in the soil, with the result that the soil plays a major role in the overall load-bearing system. From a mechanical point of view, it has proved useful to classify GRP pipes according to their stiffness – as opposed to wall thickness.

Stiffness Classes
SN 2500 These pipes are mainly used for relining or above ground installations, where only minor external loadings occure.
SN 5000 Pipes of this stiffness are selected for minor loads, for example when installed in mixed soil at a depth of 3 m and a live load corresponding to a
60 t truck.
SN 10000 These pipes are designed for high loads, for example for installation in mixed soil at a depth of 4 m or a live load corresponding to a 60 t truck with little soil cover.
SN >10000 Higher stiffness classes for below ground installations can be required especially when combined loadings act on the pipe (eg. negative pressure, external loads).

SN...Nominal Stiffness in N/m²

Classification According to Pressure Classes

The nominal pressure rating (PN) indicates the maximum operating pressure the pipe is designed to handle in bar. Every pressure class can be combined with a stiffness class. HOBAS Pipe Systems are available in pressure classes from PN 1 to PN 32.

Resin Quality

There is a direct correlation between the pipe’s chemical resistance and the resin grade used. The standard grade (VA) is resistant to domestic wastewater and hydrogen sulfide corrosion (H2S). Other resin grades (vinyl ester) for higher demands are available on request.