HOBAS Pipe Classification

HOBAS Pipes can be classified according to:

  • Stiffness
  • Pressure
  • Resistance

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 suitable for buried installation, but are mainly used for relining.
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 For special cases pipes can be produced with stiffnesses up to well over 500,000 N/m², e.g. for landfill or well pipes.
Please contact your local HOBAS Sales Representative for more information.

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. A HOBAS Pipe’s mean failure pressure must be at least four times the nominal pressure for a short time. This ensures adequate reserves over the pipe’s entire service life. HOBAS Pipe Systems are available in pressure classes from PN 1 to PN 32.

Resistance Classes

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.