Hobas Technology:
Centrifugal Casting
Precision‑engineered GRP pipe manufacturing technology for durability, stiffness, and long‑term performance.
GRP pipes produced according to the Hobas centrifugal casting technology are made of chopped glass fibres, thermosetting resins (e.g. unsaturated polyesters or vinyl ester resins), minerals, and silica sand. The centrifugal casting process ensures that the pipes are circular, the wall thickness is uniform over the entire length at exact outer diameter, and the material displays a high longitudinal compressive strength that is particularly important for jacking.
Thanks to the three‑dimensional chemical bonding of the thermosetting resin, the pipe retains its stability even in very warm environments. The sandwich construction of the wall also ensures that the pipes can withstand high loading without any trouble and enables the pipe’s strength to be customised to suit the specific load directions required.
Wall structure of a centrifugally cast GRP pipe
- Inner protective layer
- Inner structural layer
- Core layer
- Outer structural layer
- External protective layer
Hover or click a layer to explore the structure
Wall structure of a centrifugally cast GRP pipe (Hobas technology)
Manufacturing of Hobas GRP pipes
GRP pipes based on Hobas technology are produced by centrifugal casting in a 100% computer‑controlled process. The manufacturing machine’s arm feeds all raw materials – chopped glass fibres, thermosetting plastics (unsaturated polyester or vinyl ester resins), and reinforcing agents – into a fast‑rotating mould. Layer by layer, in a predefined process, the pipe wall is built up from the outside inwards.
The material quantities inserted by the machine are monitored and compared with the desired design values in order to ensure that each product is fully traceable with respect to its raw material types and quantities. Once all raw materials have been inserted into the mould, the speed of rotation is increased. High centrifugal forces of up to 75 g press the materials against the mould wall and compress them to a maximum, creating a high‑quality, very solid and void‑free pipe wall. Cold water is used to cool the mould and, after the pipe is removed, the pipe ends are trimmed and bevelled. Finally, a coupling is mounted onto one end of each pipe.
Technical data GRP pipes produced with Hobas technology
| Main materials | resin, glassfibers, sand |
|---|---|
| Main materials | resin, glassfibers, sand |
| Operating temperature | -50 °C to +70 °C, higher temperatures may be considered for individual projects |
| Standard lengths | 6 and 3 m, other lengths on request |
| Pressure range | PN 1-24 |
| Corrosion protection | none needed, as materials used are inherently resistant to corrosion |
| Hydraulic roughness | k = 0.01-0.016 mm (Colebrook-White) |
| Water jetting resistance | tested according to DIN 19523 |
Key benefits of the
Hobas technology
Centrifugal force compacts all raw materials against the mould wall, creating a void‑free, extremely dense composite structure with consistent wall thickness and excellent structural integrity.
The rotating mould ensures precise circularity, exact outer diameters, and finely controlled wall geometry – essential for reliable jointing and trenchless installations.
The resin‑rich inner layer formed during casting results in a very smooth pipe surface with low hydraulic roughness and outstanding long‑term resistance to abrasion and chemical attack.
The silica‑reinforced sandwich wall design and optimal material compaction provide high ring stiffness, enabling the pipe to withstand soil loads, groundwater pressure, and demanding installation conditions.
Hobas licensee
To strengthen the presence of Hobas centrifugally cast GRP pipe technology in North America, Amiblu works closely with its exclusive manufacturing licensee, HOBAS Pipe USA. Serving the entire U.S. market and English‑speaking Canada, HOBAS Pipe USA ensures high‑quality local production, technical expertise, and reliable customer support.
