Technical data

Classification of pipes
FLOWTITE pipes are identified by nominal diameter (DN), pressure rating (PN), and stiffness class (SN).

The pipe dimensions are outside diameter controlled, with thickness varying according to pressure and stiffness. FLOWTITE GRP-pipe can be supplied in nominal diameters from 100 mm up to 4000 mm. The most common diameters are in the range 300 – 3000 mm.

Pressure classes of FLOWTITE pipes range from PN1 to PN32 (1 to 32 bar). Not all pressure classes are available in all diameters and stiffnesses. Pipes are pressure rated at full operating pressure even when buried to the maximum depth recommended. Due to the exceptionally high short-term strength, occasional surge pressure allowance is 40% above the pressure class.

Stiffness Classes
When tested in ring bending standard stiffness classes for FLOWTITE pipes are SN2500, SN5000, and SN10000, with the numerical expressed in N/M2. Custom-designed pipes with stiffness tailored to the needs of a project are also available from FLOWTITE.

Pressure pipes with or without end-thrust
FLOWTITE pressure pipe systems are designed to withstand internal pressures with high safety margins, with fibre reinforcements placed in the direction of the principal stresses. For pressure pipes without end-thrust (uniaxial pipe) the reinforcement is mainly in the circumferential direction. Double bell couplings for such pipes do not transfer longitudinal load from one pipe section to the next. Unbalanced thrust at elbows or tees must be resisted by concrete thrust blocks. Such systems can be used both buried and above-ground for operating pressures up to 32 bar. Details for such installations are provided in the appropriate manuals under the Downloads tab on this web page.

Pressure pipes with end-thrust (biaxial pipe) are reinforced for full axial thrust as well as in the circumferential direction. Joints for such systems are designed to transfer load in the longitudinal direction, thereby eliminating the need for thrust blocks. Such systems can be used both buried and above ground.

The standard length of a FLOWTITE pipe is 12 meters for diameters 300 mm and larger. Lengths of 6 and 18 m are also available. Smaller diameters (DN < 250) are only available in 6 m standard lengths. FLOWTITE pipes can also be supplied in other lengths for special orders.

Fittings and Accessories
All commonly used fittings or accessories can be supplied, such as bends, tees, wyes and reducers.

Flow velocity
The generally accepted economic flow velocity for water supply pipelines is in the range of 1–3 m/s. Maximum recommended flow velocity for FLOWTITE pipes is 4—6 m/s. Depending on conditions (velocity profiles, vortices at fittings, misaligned joints, etc.) velocities of up to 6 m/s can be used if the water is clean and contains no abrasive material. For storm drains in straight alignment a flow velocity of 8 m/s has been observed.

Flow coefficients
Based on tests carried out over a three year period on FLOWTITE pipes, the Colebrook-White coefficient may be taken as 0.029 mm. This corresponds to a Hazen-Williams flow coefficient of approximately C=150.