Saint Gobain


Cement Mortar Lining

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  The classic Saint-Gobain Canalização internal protection consists of a cured cement mortar lining. It is applied centrifugally ensuring:
  • excellent long term hydraulic flow conditions,
  • the drinkable quality of the water conveyed,
  • effective protection of the pipe wall.

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APPLICATION

The cement lining is applied by a centrifugal process. In this method, used by Saint-Gobain Canalização, the cement is introduced into the pipe and rotated at high speed, giving good lining compaction. The lining is then cured to give it the optimum mechanical strength. The spinning process has the advantage of producing a smooth internal surface, composed of very fine particles, reducing the water / cement relation and favouring flow. The process gives the following properties:

  • high mortar compaction and low porosity,
  • low roughness,
  • good mortar key.
FLOW HYDRAULIC PERFORMANCE

The cement mortar has a very smooth inner surface, which favours flow, reduces head losses and guarantees long term hydraulic efficiency. The roughness coefficient of a single pipe (Colebrook formula) is k = 0.03 mm. However, Saint-Gobain Canalização recomends the use of a value k = 0.1 mm, in designing a pipe system to take any exceptional localized head losses into account. See Head Losses.


PROTECTIVE MECHANISM

The cement lining is an active coating. It is not only a barrier coating but provides chemical protection through the phenomenon of passivation. When the pipe is filled, the mortar gradually absorbs water, which becomes enriched in alkaline substances. Consequently, it does not cause corrosion when it reaches the pipe wall.

Crack plugging

Crack plugging is recognized and is covered in the standards. Small cracks often can be seen in the internal cement mortar lining. However, when the pipes are put into use, these cracks disappear under the combined effect of two reactions:

  • swelling (rapid) of the mortar in water,
  • hydration (slow) of the cement compounds.
MECHANICAL PROPERTIES

Expansion

The linear coefficient of thermal expansion of cement mortar linings is approximately 12 × 10 -6 m/m/°C, a value virtually identical to that of ductile iron (11 × 10 -6 m/m/°C), thus eliminating the risk of cracks forming through differential thermal expansion.

Cement mortar mechanical performance

The excellent adherence of cement mortar to iron gives the lining two important qualities:

  • good resistance to vacuums (pressure losses due to water hammer),
  • good response to deflection and ovalisation,
  • low roughness coefficient.
Longitudinal bending tests on small diameter pipes have demonstrated the ability of cement mortar lining to withstand limited pipe diametral deflection.

In large diameter pipes, which are more susceptible to ovality effects, ring bending tests have confirmed the good performance of the mortar lining under high top loads

Abrasion

Cement mortar has good abrasion resistance, which allows the pipes to be used to carry untreated water containing solid particles.

Consult Saint-Gobain Canalização about this application.


STANDARDS
  • NBR 8682: Cement mortar lining in ductile iron pipes.
  • ISO 4179: Centrifugal cement mortar lining. General requirements.
  • NBR 11828 : Cement mortar for internal coatings for steel, gray iron or ductile iron, pipelines for water conduction.

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Saint-Gobain Canalização

Saint-Gobain Canalização - Tubo,Tubo de ferro fundido,Tubo de ferro dúctil,Ferro fundido,Ferro dúctil,Válvula de cunha emborrachada. Tampao

Saint-Gobain Canalização - Tubo,Tubo de ferro fundido,Tubo de ferro dúctil,Ferro fundido,Ferro dúctil,Válvula de cunha emborrachada. Tampao