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Ductan

Technical solutions

Ductan

BLUTOP range in DN 90, 110 and 125 features a new internal lining, DUCTAN, deposited on the pipes in the factory. The DUCTAN internal coating lines the inside of the pipe completely from the socket to the end of the spigot.

Protection provided by DUCTAN lining

Since potable water may prove aggressive for pipelines, due to its mineral composition or to treatment products such as oxidizing agents, ductile iron pipelines are lined with an internal coating. Traditionally, the internal lining of cast iron pipelines is blast furnace cement mortar.

For the BLUTOP range, the cement mortar is replaced by an innovating ultramarine blue thermoplastic coating called DUCTAN. It is deposited by a hot powder process on a surface carefully prepared beforehand.

This coating features the same functional characteristics as the powder epoxy coating on gate valves.

Main characteristics :

  • Perfectly adherent, with an average adhesion value of 14 MPa (140 kg/cm2) and a minimum value of 8 MPa, DUCTAN withstands without damage : perforation under load, cuts on site ;
  • Totally smooth, DUCTAN minimizes head losses ;
  • With no discontinuity from socket to spigot, DUCTAN guarantees 100 % protection for the barrel ;
  • Extra-light, DUCTAN reduces the pipe weight by 25 % ;
  • Thinner than the cement coating, DUCTAN increases the pipe's hydraulic cross-section.

In addition, the DUCTAN lining is impact resistant and therefore does not flake in case of point impact.

DUCTAN characteristics

The characteristics of DUCTAN thermoplastic material used for the internal lining of BLUTOP pipes are listed in the following table :

CharacteristicValues
ColourUltramarine blue (similar to RAL 5002)
Density (dry film)0.96 g/cm²
Adhesion (ISO 4624)10 MPa on shot peened steel
Shore hardness D44
Elongation at break (ISO 527)400%
Stress cracking (ASTM D 1693)1000h
Induction time before oxidation at 200 °C (NF EN 728)>10min under 0²

 

Tests on the migration of organic products in the water indicate very low levels of migration and migration rate, reflecting the high purity of DUCTAN.

 Total organic carbon
TOC (mg/l)
Migration rate
mg/dm-2/jour
Chlorine-free water
1st immersion0.06<0.01
2nd immersion0.01<0.01
3rd immersion<0.01<0.01
Chlorinated water (1 mg/L)
1st immersion0.190.01
2nd immersion0.0380.03
3rd immersion0.110.01

 

Durable internal surfaces

The internal surfaces of BLUTOP pipelines consist of DUCTAN for pipes and epoxy for fittings. These 2 coatings uniformly line the inside of the pipelines and the sealing surfaces. Epoxy is renowned as a coating for valves and highly appreciated for its chemical inertia in water. In addition to displaying properties which are similar to epoxy, DUCTAN also withstands impacts, making it more suitable for pipes.

These surfaces are perfectly smooth and inert, thereby limiting the formation of deposits in the pipes.

DUCTAN’s behaviour has been studied for several thousand hours in contact with disinfection products such as :
- Hypochlorite
- Chlorine dioxide.
The chlorine content of the water was 10 ppm, i.e. 100 times the value used. The temperature was 40 °C. These two factors accelerate possible ageing and are used to estimate the protection durability.

Study of the behaviour in contact with hypochlorite and chlorine dioxide

 HypochlorideChlore dioxydePure water
Duration4000h3000h8424h
Temperature40°C40°C40°C
Chlorine content10 ppm10 ppm-
Surface crackingNonNonNon
ErosionNonNonNon
Breaking stress*>15 MPa>15MPa>15MPa

* Initial breaking stress measured, between 15 MPa and 17 MPa

The main conclusions of these studies are given below :
- Good stability of the chemical structure
- No chemical change, confirmed by the absence of surface cracking or erosion
- Mechanical elongation-traction properties are not significantly affected.

Bacterial growth

As regards the water bacteriological quality, the DUCTAN internal lining is inert and durable and therefore does not stimulate bacterial growth (confirmed by Hydrocheck tests in Belgium).

Due to its inertia, the DUCTAN internal lining does not transmit carbon compounds likely to favour the growth of bacterial colonies by providing nutrients.

European approvals

The BLUTOP range plays on a European scale: it has now also obtained drinking water approvals for the DUCTAN internal lining in several European countries:
Conformity with the “Hydrocheck” approval procedure in Belgium, issued by Belgaqua
Conformity with the UBA-Guideline and DVGW-W260 approval procedures in Germany, issued by the Hygiene-Institute of the Ruhrgebiets, Gelsenkirchen
Conformity with standard BS 6920 issued by the WRAS in the United Kingdom
Conformity with “regulation 31 (4)(a)” of the DWI in England, Wales and Scotland, issued by the DWI, on the basis of the WRc report.

Other approvals are in progress in other European countries.

Appendix

Extract from the CSTB Technical Approval draft - Conformity with reference standards

DUCTAN thermoplastic internal lining of pipes is a new product not yet covered by any specific standard. However, the main functional performance characteristics of this coating are equivalent to those of an epoxy type of coating in compliance with EN 14901-2006.

The following epoxy specifications do not apply:
Resistance to indentation: since DUCTAN coating is deposited inside the pipe, there is no risk of perforation by the soil
Resistance to air ageing: during use, DUCTAN coating is only in contact with water. The pipes are plugged before laying, thereby avoiding any exposure to solar radiation.
Cross-linking : DUCTAN coating is a thermoplastic which does not undergo heating treatment to cross-link the material.

Resistance to water and impact strength are not covered by any particular specification.

Performance tests

The average adhesion of the DUCTAN thermoplastic internal lining must reach at least 8 MPa and a minimum individual value of 6 MPa when it is measured according to EN ISO 4624-2003. The minimum number of measurement points is 9. In practice, values in the region of 15 MPa or more are measured.

Performance testCriterion
Non-porosityWhen measured under a voltage of 1500 V, the pipe internal surface must be free from porosity (see note a)
Reverse impact strength (opposite side)No breakdown with Holiday detector under an impact of 10 J (see note b)
Durability - Resistance to thermal ageing in water(see note c)

 

When measured under a voltage of 1500 V, the pipe internal surface must be free from porosity. Porosities are allowed in the designated areas, the ends, i.e. spigot and socket.

The impact resistance of the internal protection is checked with respect to standard EN ISO 6272-1-2004 with impact on the side opposite the coating.
The 1 kg mass with spherical indenter of diameter 20 mm must be dropped from a height of 1 m. The mass must fall perpendicular to this surface.

The durability of the DUCTAN internal anticorrosion protection is measured after a water immersion test according to EN ISO 2812-2-1995, but at a temperature of 50 °C (instead of 40 °C). The exposure duration is 480 h.
On each test specimen, the coating shall be incised down to the metal in the form of an upside-down V, the line to be 1 mm wide, the mark to be incised 50 mm high at least and form an angle of about 60°. 2 areas are evaluated (see the table).

On the damageOff the damage
Width of blistering each side of the scratch:
requirement < 5 mm
Blistering Di<2 and Do<2 according to EN ISO 4628-2
Width of rust propagation each side of the scratch:
requirement < 5 mm
Rusting < Ri1 according to EN ISO 4628-3
 Average adhesion by traction test according to
EN ISO 4624-2003: requirement ≥ 6 MPa
(9 measurement points, see 5.3.2.)

 

See also

The internal protection guarantees that the hydraulic performance of the pipe is maintained long term, prevents any risk of internal attack by the waters carried and maintains the quality of water carried.