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Advice
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Well choosing ones valves
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To efficiently select valves according to a specific need,
it is necessary to answer the 7 following criteria.
- Function (insulation or regulation)
- Nature of the fluid
- Physical and chemical characteristics
- Service pressure
- Flows
- Frequency of use
- Type of connection and face to face dimensions
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Correctly selecting a butterfly valve (double excentration)
Double excentration is a primordial characteristic of our butterfly valves.
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Advantages in relation to the centred type:
- Tightness by compression of an elastomer joint and not through deformation of a spool.
- Tightness is obtained on the whole joint; the axis no longer represents a tightness rupture.
- At the first degrees of opening, the butterfly is no longer in contact with its seat.
- Removable gasket in elastomer or in metal mounted on body or on stopper according to diameter.
- Changeability of gaskets without dismantling of the axis and without special
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Consequences in relation to the centred type:
- Feeble operating torque, notably on the operating range in regulation, thus optimising regulation.
- Minimum elastomer volume: better resistance to temperatures and to wear, cost of spare parts optimised.
- Easy and inexpensive maintenance.
- Extreme temperature conditions (250°C): tightness contact metal/metal.
- No premature friction wear of joint , notably in regulation
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Diagram of butterfly valve
at various degrees of opening. |
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Correctly selecting the materials
Grey casting
Also called Flake-Graphite cast iron or FGL, it is an Iron Carbon alloy containing 3 to 3.6% of carbon and the carbon is present in the alloy in the form of flakes.
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Advantages
- Low price
- It is easily moulded
- Very good behaviour to corrosion
- Absorbs vibrations
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SG cast iron
Also called Spheroid-Graphite cast iron or SG, it is an Iron Carbon alloy containing 3.5% of carbon, the carbon being present in the alloy in the form of small spheres due to specific processing.
Advantages :
- Average price
- Easily moulded
- Good behaviour to corrosion
- Possesses good mechanical characteristics (no rupture in case of frost)
- Prolongation before rupture, important for some qualities
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Low risks of rupture
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Moulded Steel
It is an Iron Carbon alloy containing 0.2 to 0.4% of carbon, generally in the form of Ferrite and Perlite.
Advantages:
- Very good mechanical characteristics (particularly important prolongation before rupture)
- More resilience than SG
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