A reinforced pre-insulated polymer pipe system capable of operating at temperatures normally reserved for steel pipes has been used for the first time in the UK. The system has been installed at a St Helier heat network serving Jersey’s largest resort hotel, The Merton.
During upgrades to the site's aging oil-fired HTHW heating and hot water system - including the replacement of a 6MWt steam plant with a 2MWt packaged energy centre - the project's consulting engineer Ramboll was faced with the task of replacing the existing steel distribution pipe system to feed the various properties around the site.
Sue Follows, building services engineer with Ramboll, explained:
We looked at the available pre-insulated pipe systems on the market and whilst pre-insulated steel pipes are a proven solution, we were drawn to the corrosion-free characteristics of polymer systems and the opportunity to lay the systems directly underground.
Needing to operate the new primary distribution system at flow temperatures up to 95°C in order to satisfy the loads from the secondary systems in each of the connected properties, we were concerned that materials such as PEX and PP would not achieve an acceptable design life at the continuous temperature rating and also be beyond the upper limits of what would be considered safe.
During our research into viable options, we were introduced to a new flexible pre-insulated composite polymer system that has a polymer service pipe reinforced with aramid fibres, meaning that it can safely operate at temperatures of up to 115°C and pressures of 16 bar, comfortably above our requirements.
Clearly this system, known as Hiline FibreFlex Pro, offered the design life we required, plus being polymer based meant it had none of the corrosion risks associated with steel.
Mark Whettall, managing director of CPV Ltd said:
Aramid fibres are commonly used in items such as bullet-proof vests and are renowned for their mechanical strength and ability to withstand high temperatures – making them perfect for use in this application.
With the service pipe being reinforced with a mesh of this material, it enables the wall thickness to be reduced when compared to normal PEX pipes, which provides additional space inside the casing for a thicker layer of bonded PUR insulation and greater flexibility during installation. This results in improved thermal performance, with heat loss levels lower than alternative systems using Series 3 insulation thickness for sizes up to 80mm diameter and lower than Series 2 for larger sizes.
In total, some 683 metres of Hiline FibreFlex, ranging in dimensions from 50 to 160 mm, was installed – rolled out directly from coils into pre-prepared trenches excavated in parallel to the existing concrete ducts to minimise disruption to the hotel’s supply. Where required, service pipe joints were made using a unique hydraulic press fitting that negates the need to expand the service pipe end as normally found with press fittings for PEX systems.
The upgrade to the hotel's heating and hot water systems will substantially reduce operating costs for the hotel’s owner, Seymour Hotels of Jersey, and annually prevent around 613 tonnes of carbon emissions – equivalent to taking around 383 family cars off the road (*).
* Comparison based on 100gCO2/km emissions and annual distance travelled of 10,000 miles.