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CPV's District Heating Pipe's on a Roll

A leading British district heating pipe system manufacturer, CPV Ltd, has installed a brand new pipe coiling machine at its Hampshire manufacturing base to help meet the increasing demand for the Hiline Flex pre-insulated PEX pipe system.

District Heating Network Stress Analysis

A key part of our technical support services for the Hiline pre-insulated district heating pipe system range is advanced stress analysis service to ensure that a network’s design is optimised for the day-to-day thermal expansion that a system encounters during its many decades of operation.

stress analysis service screen 400When designing and installing district heating pipe networks, stress analysis is a critical part process and one which should be carried out by default. To illustrate the importance of stress analysis, something as simple as adding in an unplanned branch connection can seriously impair a system’s ability to cope with the huge forces exerted on the pipe from thermal expansion. To put it into context, a 200-metre length of buried DN250mm pre-insulated steel pipe, heated to an operating temperature of 120°C will expand by around 150mm – exerting stress of some 171MPa – the equivalent of 52 tonnes. This clearly needs to be dealt with in a way that does not impede the life expectancy of the network and ensure a long and trouble-free operation in delivering heating and hot water to consumers.

sisKMR Software

CPV Ltd is a certified licensed holder of sisKMR software and our design team has several fully-trained engineers to carry out the calculations, offering expert advice in all aspects of stress analysis.

By evaluating the proposed pre-insulated district heating network and using a combination of our engineers’ experience, rules of thumbs and the sisKMR software, pipe systems can be modelled and stresses calculated to the design principles and parameters according to standard EN 13941, Design and installation of pre-insulated bonded pipe systems for district heating.

pre insulated steel bends 300x450Pipe static calculation against proposed district heating network design and routing:

The service covers the pipe initial static calculation for the entire district heating network including modelling the pipework geometry of buried pre-insulated pipework within sisKMR software and according to the proposed design and routing as provided by our client. CPV will model and undertake the analysis to be able to confirm the proposed design is acceptable. 
Where necessary, CPV will propose pipe arrangements, alternative pipe routing and other measures in mutual agreement with the client in order to establish an acceptable technical design solution. Having finalised the design and completed the analysis CPV Ltd shall issue the full stress analysis report together with supporting pipe route drawings.

During Installation - Pipe Static calculation against variations

CPV can provide technical design support for the duration of the installation of the district heating network making recommendations and providing subsequent qualification through stress analysis.

Variations will be remodelled within the sisKMR software to demonstrate compliance. These services do not cover routing modifications that are not based on static requirements

Pipe static calculation against ‘as installed’ district heating network

On completion of the installation of the pre-insulated district heating network and using ‘as-installed’ drawings, our engineers can again model the installed pipework geometry within sisKMR software and complete a final stress analysis to qualify and demonstrate full compliance of the installed network, issuing the final stress analysis report together with supporting pipe route drawings.

Further Information

To find out more, please contact our technical support team by calling +44 (0)1794 322 884 or emailing This email address is being protected from spambots. You need JavaScript enabled to view it.

Details of the sisKMR software

sisKMR is a software programme designed for the static calculation of buried and above-ground pipe systems. It is able to calculate stresses imposed on hot buried pre-insulated bonded pipe systems as well as all kinds of open-air 3-dimentional pipe systems for district heating applications, due to the loads imposed by thermal expansion. The software is based on a beam-element programme with which the sections of 3-dimensional pre-insulated bonded pipe systems with any number of branches can be calculated taking non-linear reactions of the soil and expansion cushions into consideration

In addition sisKMR contains standard modules for the fast calculation of common practical situations including:

  • L-System
  • Z-System
  • U-System
  • Deviation with expansion cushions
  • Curved pipe
  • Reduced Tee Branch
  • Parallel Tee Branch

Alternatively, the stress analysis can be calculated according to the following standards:

  • EN 13480
  • EN 13941
  • AGFW-Worksheet FW 401
  • ASME : AD-S2
  • ASME : AD2000-S2

The following modules are available for fast pre-dimensioning:

  • Pipe bending (during excavation)
  • One-time (start-up) compensator
  • Strain reduction element (System 4)
  • Maximum admissible laying length

With sisKMR the latest research results are included in the calculations:

  • Cold installation
  • Installation without expansion cushions
  • Superimposed installation
  • Pressure bends
  • Mechanical pre-stressing of expansion cushions
  • Subsequent burial of expansion cushions
  • Horizontal branches

This technology is in line with the German Energy Efficiency Association for District Heating (AGFW) research programme, Innovative Heat Distribution

Typical supports implemented in all types of open air 3-dimensional pipe system design and construction can be considered including:

  • Fixed point (anchors)
  • Axial holding point
  • 3-way axial holding point
  • Suspension or pendulum support
  • Sliding bearing bracket
  • Axial roller bearing support
  • Roller bearing with separate roller tracks for u- and v- directions
  • Single roller bearing
  • Spring bearing effective in w-direction

For calculating admissible system limits using:

  • Fixed points
  • Free system limit with free axial displacement and rotation
  • Free system limit with all displacement and rotation possibilities

Other possible considerations that can be taken into account include:

  • Bearing tolerance
  • End displacement
  • Different friction values for axial and lateral displacement
  • Local pre-stressing

In the calculation of load case histories, pre-displacements in the bedding and bearing points are taken into account so that friction and bedding reversal effects can be registered and included in the calculation of the load variation ranges, which are most important for the fatigue analysis of the system.

Complex 3-dimensional systems, also with one-time compensators and strain reducers (bellows), can be calculated together as one entity

sisKMR features comprehensive pre-installed material databases and nominal dimension tables which can be edited and extended by the user.
New databases for different pipe manufacturers and different pipe materials can be created to suit the user’s requirements.

The system features powerful graphics including:

  • XY-/XZ-YZ-View / 3D-View
  • Contour mapping
  • Crosshair cursor
  • Scale for all axis directions
  • Zoom function with mouse driven frame
  • Display of the expanded system with different coloured loaded cases
  • Either in steps or direct distortion of expansion cushion thickness and systems expansion
  • System geometry can be displayed while entering data
  • Clear output of calculation results with tables and graphics

The design parameters of most commonly used compensators can be calculated including:

  • Axial compensator
  • Angular compensator
  • Lateral compensator
  • Strain reduction element (axial compensator with a limit stop)

The calculation results are summarised in special bearing and compensator tables forming part of the final stress analysis report and is able to calculate:

  • Point mass
  • Single load
  • Additional sectional loading in all directions (including wind and snow loads)

sisKMR at a glance:

  • Static calculation of pre-insulated pipe systems (above and below ground)
  • User friendly interface
  • Leading stress calculation software in the district heating industry
  • Simple to use, quick data input, exact results
  • Any bearing condition calculable
  • Calculation capabilities of branched, topological piping system
  • End point displacements and pre-stressing is feasible
  • Comfortable calculation of loading case history
  • Clear orientation by using a local co-ordinate system
  • Visible graphic result while entering pipe geometry
  • Clear layout of results, either in simple or comprehensive reports


To find out more, please contact our technical support team by calling +44 (0)1794 322 884 or emailing This email address is being protected from spambots. You need JavaScript enabled to view it.


Hiline Range at Nextgen 2015

CPV Ltd, one of the UK’s leading manufacturers of pre-insulated pipes is using its presence at the Nextgen 2015 renewable energy event to showcase the next generation of pipe systems for district heating, cooling and hot water service applications.

Hiline X-Block - District Heating Consumer Interface

The ultimate interface for controlling heated spaces in hundreds of applications when delivering heat from a central source - making it ideal for district heating networks. The Hiline X-Block combines a variable-speed Hydronic control, heat source circulator, system circulator and heat exchanger into a single unit. This combination delivers complete isolation between the heat generation side of the system (central source) and the heat delivery side of the system (wet system, radiators, fan coils and underfloor). In-built Weather Compensation is also included - all in one small package, just four pipe connections and your installation is complete.

New Heat Networks CoP ‘Must Succeed’

After campaigning for the development of industry-wide standards for district heating networks in the UK, Mark Whettall, managing director of CPV Ltd is calling upon his industry colleagues to ensure that they fully-engage with the consultation process in response to the recently-published draft Code of Practice by the Combined Heat and Power Association (CHPA) and CIBSE.

New Services for Pre-insulated PEX system

Following the successful launch earlier this year of its new Hiline Flex pre-insulated PEX pipe system, CPV Ltd, the UK’s longest-serving manufacturer of district heating pipe systems, has announced a selection of new optional services that will make the on-site installation process even easier.


Pioneering Poultry System opts for CPV Hiline

When designing and installing a pioneering biomass CHP system for a large Nottinghamshire poultry farm, renewable energy specialist C&H Biomass chose two of the CPV Hiline range of pre-insulated pipe systems for use in the project’s buried LTHW network.

Reinforced Polymers for Jersey Heat Network

An innovative new reinforced pre-insulated polymer pipe system that can operate at temperatures normally reserved for steel pipes, has been utilised for the very first time in the UK on a St Helier heat network serving The Merton, Jersey’s largest resort hotel.

Shetland DH Scheme Selects Reinforced Polymer Network

Shetland Heat Energy and Power (SHEAP) - the company responsible for the Lerwick district heating scheme - has for the first time in its 20-year history, installed an advanced flexible pre-insulated polymer pipe system to connect a new customer to its buried heat network.

Warning of Two-Tier Heat Network Performance

Mark Whettall - CPV Ltd

With the dash to install heat networks gathering apace, the head of one of the UK’s longest serving manufacturers of pre-insulated pipe systems has highlighted a large disparity in the performance of commonly available flexible pipe systems – underlining the significant impact they can have on the operational costs for buried heat network owners.