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As a standard, the valve is supplied in the following types:
WAFER-Type:
• For insertion between pipeline flanges
LUG-Type:
• For installation with bolts between pipeline flanges
• As end-of-line valve with flanged connection to pipeline flanges
and with the following operation pressures
- DN 50 - 300: 16 bar
- DN 350 - 400: 14 bar
- DN 450 - 600: 10 bar
Wafer-Type
Figure 3: Types of VAG CEREX
®
3.2 Applications
In the standard "Water" version, VAG CEREX
are equipped with EPDM profiled seals and can be used with the
following media:
• Water
• Raw water and cooling water
• Weak acids and alkaline solutions (with adapted corrosion
protection)
If the valve is used in oil- or gas-containing media or in domestic
sewage systems, this may lead to the destruction of the EPDM
seals, the rubber coating and O-rings and is therefore not admis-
sible.
If the valve is used in gaseous media or filtered waste water, NBR
is to be used as material for the seals.
The VAG CEREX
300 Butterfly Valve should only be used in me-
®
dia in which where there is no risk of clogging.
For information about the corresponding temperature limits,
please refer to the product-related technical documentation (KAT
-A 1331).
In case of deviating operating conditions and applications, please
consult the manufacturer
3.3 Performance limits
3.3.1 Cavitation
VAG CEREX
300 Butterfly Valves are mainly used to shut off flow.
®
If a VAG CEREX
300 Butterfly Valve is used to control flow, the
®
operational limits of the maximum flow velocity as well as the cavi-
LUG-Type
300 Butterfly Valves
300 Butterfly Valves
®
tation limits must be observed.
The operational limits can be calculated either using the VAG
UseCAD
or the following calculation rules:
®
Cavitation limits
After the upstream and downstream pressures of the valve as well
as the flow rate have been determined, the cavitation value is cal-
culated as follows:
sigma
Closed
Figure 4: Sigma values to establish the degree of cavitation in butterfly valves
Calculation of the σ-value:
H1
=
Inlet pressure
H2
=
Outlet pressure
HAt
=
Atmospheric pressure
Hd
=
Evaporation pressure
v
=
Flow velocity in the pipe
g
=
Gravitational acceleration [m/s²]
The VAG CEREX
300 Butterfly Valve has the correct dimensions
®
when the computed σ - value lies above the limit curve of σ k .
The recommended control range lies between 10-100% opening
degree. Below that no reasonable control can be guaranteed. If
cracking noises or vibrations occur while the valve is being put
into operation, the actual operation conditions should be checked.
In case of changed operation conditions, the equipment may have
to be recalculated. If the computed σ - value lies below the limit
curves of σ k cavitation will occur.
no cavitation
low cavitation
intensive cavitation
Angle of the disk
[mWS]
[mWS]
[mWS]
[mWS]
[m/s]
VAG Operation and Maintenance Instructions • 5
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