AVK established the test procedure for couplings according to EN 14525
Very few manufacturers claim to fulfil EN 14525, and in reality it is up to the manufacturers to test their couplings in accordance with the requirements in the standard. When AVK launched the Supa Maxi™ range there was not even an official KIWA or DVGW testing regulation available to obtain an official type approval according to EN 14525, and consequently the customer could not be sure that the manufacturers’ claims had any substance. Therefore, AVK joined forces with KIWA in Holland and DTI in Denmark to define a valid test procedure and subsequently get the test results verified by KIWA in accordance with the requirements of EN 14525.
The test procedure according to EN 14525 first and foremost ensures a functional and durable product. Even though tensile couplings are typically used for temporary repairs, which may later be replaced by a more permanent solution, many couplings remain installed on the pipeline throughout their service life. Consequently, a long-term reliability is very important.
Test procedure
Scope
Ductile iron wide tolerance couplings and flange adaptors for use with pipes of different materials: ductile iron, grey iron, steel, PVC-U, PE, fibre-cement.
Test items
One small, one medium-size and one large coupling and flange adapter (DN100, DN200 and DN300) are selected, and for sizes 350-600 one random size are selected.
Requirement
No leakage may occur during any of the tests #1 to #4 below. The coupling alone must absorb the full pressure and end-pressure with no external end-support or support rods.
Pipe types:
The couplings are to be tested on the following specified pipes:
- Ductile cast iron, PN16, with pipes of minimum and maximum external diameter respectively (min./max. tolerance dimensions)
- PVC, PN 6 and PN16 nominal diameter pipes
- PE, PN6 and PN16 nominal diameter pipes
Tests on asbestos-cement and steel pipes are not a must, as these are considered to be rigid pipes comparable with ductile iron pipes.
Test #1: Pipe assembly - straight and deflected, rigid pipes
All test items are to be tested on a ductile iron pipe with maximum and minimum diameter with a water pressure of 1.5 x PN16 + 5 bar = 29 bar for PN 16, or 1,5 x PN10 + 5 = 20 bar for PN 10, with the pressure held constant for minimum 2 hours. Side load of 40 x DN (mm) in N (Newton) is concurrently to be applied:
- straight pipe assembly without deflection
- 4° deflection per insert, equivalent to a total of 8° for an assembly of two pipe ends in a coupling.
Test #2: Pipe assembly - other flexible pipes PVC/PE
All test items are to be tested on a straight assembly with a water pressure of 1.5 x PN + 5 bar, with the pressure held constant for minimum 2 hours. PVC pipes are also subjected to concurrent side load of 40 x DN (mm) in N (Newton). To be performed on pipes:
- PVC/PE PN6, water pressure 1.5 x PN6 + 5 bar = 14 bar
- PVC/PE PN10, water pressure 1.5 x PN10 + 5 bar = 20 bar
- PVC/PE PN16, water pressure 1.5 x PN16 + 5 bar = 29 bar
Test #3: Pipe assembly - vacuum test
All test items are to be tested with a pressure of -0.8 bar. Pressure must not change by more than 0.08 bar over 2 hours. PVC pipes are also subjected to concurrent side load of 40 x DN (mm) in N (Newton). To be performed on pipes:
- ductile iron pipe on minimum tolerance diameter
- PVC PN6
- PE PN6
Test #4: Pipe assembly - durability test
All test items are to be tested at 24,000 times pulsing pressure rise and fall between 13 bar and 18 bar respectively. Ductile iron and PVC pipes also subjected to concurrent side load of 40 x DN (mm) in N (Newton). To be performed on pipes:
- ductile iron pipe on minimum tolerance diameter
- PVC PN6
- PE PN6
AVK’s test procedure for Supa Maxi™ exceeds requirements in EN 14525
The test procedure fulfils the requirements of EN 14525. However, throughout the development phase the Supa Maxi™ universal tensile couplings have undergone and passed significantly tougher and more extensive tests, based on AVK’s long experience with the practical applications of tensile couplings. All dimensions in the dimension range from DN40 to DN400 have been tested in accordance with the above, but also on asbestos-cement, steel and thin-walled stainless steel pipes, along with full deflection of all pipe types. A rigid ductile iron pipe has also been exposed to strong weight loading on a free-hanging pipe end to test stability under extreme conditions simulating earth settlement and applying an uneven side load. Furthermore, pure tensile loading was performed in dry and non-pressurised condition equivalent to over 30 bar water pressure, as well as an extremely deflected assembly with uneven bolt tightening. In addition, couplings were mounted in temperatures between -30°C and +70°C, tightened with the specified torques and tested as described in test #1 and #2, to verify usability in very cold or hot surroundings. Finally, testing was performed with air to verify usability for gas applications. The Supa Maxi™ couplings remained tight and tensile throughout all these tests.
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