Trelleborg Forsheda Pipe Seals have proudly supplied elastomeric seals for pipe joints to Polypipe in the UK and Irish markets for more than 10 years. From EN 1401 pipes through to Ridgidrain and structured wall pipes up to DN 1050mm.
We were therefore very pleased when Polypipe became the Krah licensee for the UK and Ireland and asked us to help to develop a ‘push fit’ rubber jointing system for their DN750, 900 1050 & 1200mm Krah pipes. We had previously been involved with other Krah Licensees in Estonia, Italy, Mexico and the US so the Krah pipe technology was not new to us but ensuring a robust joint to meet the demands of EN 1277 is never an easy task.
In the demanding installation environments of today, the main criteria for designing joints are:
In approaching this type of design, and before practical jointing and physical testing can begin, a clear understanding of pipe joint geometry, dimension and achievable tolerance has to be reached. The engineers and technicians at Polypipe have an excellent understanding of the information needed and this allows us to model the joint design options using non linear finite element analysis (FEA) taking into account the maximum and minimum joint conditions. A typical simulation is shown below.
In this modelling we can take into account the stresses generated in the pipe spigot and socket and allow for any stretching or compressing of the pipe material as it reacts to the forces exerted by the seals.
Jointing force and seal behaviour can also be modelled and once the joint is optimised using FEA we then move to physical jointing and finally the joint performance tests.
The European Standard EN 13476 specifies joint performance requirements when tested in accordance with EN 1277 : Plastic Piping Systems – Thermoplastic piping systems for buried non-pressure applications – Test methods for leaktightness of elastomeric sealing ring type joints.
There are 3 basic test pressures, and 3 conditions for determining leaktightness:
At each stage of the test the assembly is inspected for evidence of leakage.
Dn1200mm pipe joint during EN1277 condition B testing at our test laboratory.
After the successful completion of the Dn750 to 1200mm range of pipes we were asked to extend the joints to include Dn1500 and 1800mm. These larger sizes are too big for our test rig and so the Belgian Research Centre for Pipes and Fittings – Becetel performed the final joint tests for us.
Dn1800mm Pipes with welded end plates
In the final stages of the project, the UK certification organisation, WRc witnessed the joint tests before issuing the approval certification to include ”Rubber Sealing Ring Joints for Ridgistorm XL Pipes Dn700 to 1800mm.
Trelleborg Pipe Seals, develop, manufacture and market elastomer based sealing systems for pipeline systems for water, sewerage and drainage applications.