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| Picture 1. Ball valve of Nilo series from RBM Spa |
Ball
valves only perform the locking function, they are not regulating valves. But capacity
is also important for them. There is a characteristic of flow area of the valves.
This term refers to the ratio of the nominal diameter of the pipe to the
diameter of the lock ball. Valves, in which this ratio is 90-99%, are called full-bore.
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| Picture 2. Different types of ball valves depending on the flow area |
Valves with standard passage have a ratio of diameters from 70% to 90%. If this
figure is less than 70%, then such valves are called with a reduced passage.
For
example, consider the assortment of the Italian brand Itap. The photo below
shows three series of valves with different characteristics of flow area -
Ideal, Vienna, Orient.
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| Picture 3. Different series of ball valves of Itap. From left to right: Ideal, Vienna, Orient |
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| Table 1. Characteristics of Itap ball valves |
Almost
all producers make the construction of full-bore valves more reinforced. The
thickness of the wall of the body of such valves is bigger than that of the
standard ones. This is also seen in picture # 3.
Surely
you have a ripe question: why make different valves and which is better? The
answer here is one - it all depends on the system where the product will be
installed. Where it is important to create a minimum of resistance, you need to
mount full-flow valves. In cases where the resistance of the system is not more
important, valves with a standard passage are used. Since they are less
material-intensive and have a lower price. Valves with a reduced (narrowed)
passageway should be installed where additional resistance is necessary.
In order
to properly select a valve, you need to pay attention to the characteristic of Kv.
It shows how much water (in cubic meters) passes through armature in one hour. For
comparison, I showed the characteristics of valves of different manufacturers
in a separate table.
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| Table 2. Characteristics of ball valves of different Italian producers |
It
is also worth noting that the characteristic of flow area of ball valves is not
interrelated with their operating pressure. For example, in the RBM brand, the
standard valve of the Iro series has a maximum working pressure of 50 bar. That
is 10 bar more than his full-bore colleague Nilo.
So
when choosing a ball valve, pay attention to its flow area and the system where
it is installed. Good luck to everyone!
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