FORTIFIED BY HONEYCOMB
StifPipe is unique due to its honeycomb construction material, a material that has been successfully applied in the aerospace, ship-building and automotive industries for decades.
Using this manufacturing method, a layer of fibre reinforced polymer (FRP) is bonded to the exterior face of the lightweight honeycomb panel. This results in a very efficient structure that is much stronger and stiffer than the sum of its constituent components.
The construction of the pipe begins with building a mandrel of the same size and shape as the pipe. A thin sheet of metal is wrapped around the mandrel and coated with a non-bonding material. The collapsible arms of the mandrel allow for the removal of the finished pipe.
Depending on the internal pressure rating design requirements of the pipe, one or more layers of carbonfabric saturated resin is wrapped around the mandrel. For culverts and other gravity flow applications, glass fabric saturated with epoxy are sufficient and offer a lower cost alternative. These fabrics typically have a thickness of less than 0.05 inches per layer.
Next, a layer of honeycomb material is wrapped around the carbon fabric. The thickness of the honeycomb material is calculated based on the overall stiffness requirement of the pipe. Additional layers of glass fabric saturated with epoxy are wrapped on the outside of the honeycomb.
In ambient conditions, the pipe section cures in six to eight hours. This process can be accelerated by heating the assembly to a moderate temperature (e.g. 65å¡C).
THE PROOF IS IN THE LINING
When compared to other carbon-fibre reinforced polymer (CFRP) pipe relining methods, StifPipe has a number of advantages. For gravity flow applications the pipe can be manufactured to virtually any size and shape, minimising loss in flow capacity and post-installation grouting requirements.
The ability to construct pipe segments close to the jobsite can also significantly reduce transportation costs. However, the biggest advantage of StifPipe is seen in the repair of pressure pipes. These benefits include:
- Reduction in cost of materials: StifPipe requires fewer layers of carbon fabric, resulting in savings of up to 50 per cent on most projects.
- Increase in on-site productivity and lower labour costs: As StifPipe requires fewer layers of material, and because the pipes can be manufactured either on-site or in a warehouse setting, projects can see a labour cost saving of up to 60 per cent.
- Improved quality control: StifPipe is often constructed in favourable warehouse conditions, improving overall quality. Contractors also have the option to test pipe segments before installation, ensuring that no faulty segments are installed in the rehabilitation process.
- Reduced on-site repair time: As the majority of the StifPipe segments are manufactured off-site, the on-site repair time is significantly reduced.
- Overall costs savings: A case study examining the rehabilitation of a 1.6 km pressurised sewer main found that where regular FRP would have needed six layers to complete – costing US$7.5 million and requiring 20,000 on-site man hours – the StifPipe alternative could achieve the same result for less than US$4 million and only 3,000 on-site man hours.
StifPipe is also constructed with materials that are NSF certified for the repair of potable water mains, meaning operators can trust the integrity of the finished product.
ALL PIPE LININGS GREAT AND SMALL
StifPipe can be successfully installed using conventional sliplining, cured-in-place pipe (CIPP) lining or continuous on-site installation methods. While conventional sliplining and CIPP lining are best suited to large-diameter pipes that allow man entry, continuous on-site installation can be used with both large- and small-diameter pipes.
Conventional sliplining: Using this method the pipe segments are constructed off-site or in a temporary warehouse close to the job site. The lengths of the segments should be determined based on the size of the access pit while the StifPipe cross section should be custom made to be slightly smaller than the host pipe.
Using the StifPipe method, a 1.2 m, 1,170 mm diameter pipe section should weigh only 22 kg, allowing it to be easily lifted by hand and carried to the host pipe. The segments are positioned sequentially along the pipe and connected together before installation. The annular space between the liner and the host pipe can be filled with resin or grout, joining the two pipes together.
CIPP lining: This installation method is ideal for large pipes with relatively smooth surfaces. Once the pipe surface has been prepared and cleaned, a layer of carbon or glass fabric is applied. Next, the honeycomb core is applied on top of the fabric.
The thickness of the hollow core can be 6 mm or more depending on the design strength requirements. Additional layers of fabric are then applied to the honeycomb core. These layers are designed to resist the internal pressure of the pipe.
Continuous on-site installation: For this technique a mandrel with the cross section the same shape as the pipe or culvert, albeit slightly smaller, is built in advance of the installation. This mandrel is placed outside the culvert or pipe so that its axis is aligned with that of the host pipe.
A portion of StifPipe several metres long is constructed and partially cured on the mandrel before being slipped off and pushed a few metres into the host pipe, leaving a small length still on the mandrel. Additional segments are manufactured, partially cured on the mandrel and pushed into the host pipe.
The result is a long pipe with no joints. Once the pipe is lined the annular space between the host pipe and the liner is filled with a low-viscosity resin or grout.
QuakeWrap’s StifPipe is subject to several US and international patents. The technology has been successfully applied by Building Solutions Brisbane in the Gillies Range Road project. For more information on this and other pipe lining solutions visit www.quakewrap.com