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1. Foreword
BA 294 and BA 298 backflow preventers are available in
various construction types. The following references
apply, with the connection size also being added as a
suffix:
Construction
type
BA 294
BA 294 FB
BA 298 FA
BA 298 I-FA
Diagrams in these installation instructions all refer to type
BA 294. However, the information given is valid for all types.
Wherever this is not the case, it is specifically indicated.
2. Introduction
BA reduced-pressure-zone backflow preventers are suitable
for the protection of drinking water systems against back
pressure and back syphonage. Fluids up to risk class 4 to DIN
1988, Part 4 and DIN EN 1717 are protected. This
corresponds to construction type 2, DIN 1988, Part 4. They
can be used for supplies to buildings and for industrial and
commercial purposes within the limits of their specification.
Category 1
Category 1
Category 1:
Category 1
Category 1
Water for human consumption which is taken direct from a
potable water supply.
Category 2
Category 2
Category 2
Category 2
Category 2:
Liquids which present no health risk to humans.
Liquids which are suitable for human consumption, including
a potable water system, where a change in taste, smell,
colour or temperature (heating or cooling) may occur.
Category 3:
Category 3:
Category 3:
Category 3:
Category 3:
Liquids which, because of the presence of one or more
poisonous substances, present a health risk to humans.
Category 4:
Category 4:
Category 4:
Liquids which, because of the presence of one or more very
Category 4:
Category 4:
poisonous substances or which contain one or more
radioactive, mutagenic or carcinogenic substances, present a
health risk to humans.
Category 5:
Category 5:
Category 5:
Category 5:
Category 5:
Liquids which present a health risk to humans because of
the presence of contagious substances causing illness.
The higher the classification, the greater is the risk
potential. DIN 1717 defines acceptable safety protection
devices for every risk category. BA 294 and BA 298
backflow preventers are permitted without restriction for
all risk categories up to and including class 4. A continuous
bacterial risk must not be present.
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GB
Connection size
Standard type with threaded connections
½" to 2"
Standard type with flanged connections
DN 65
Standard version with flanged connections
DN 65 to DN 150
Industrial version with flanged connections
DN 65 to DN 150
3. Method of Operation
Type BA backflow preventers are divided into three zones. The
pressure in Zone 1 is higher than in Zone 2, which in turn is
higher than in Zone 3. A discharge valve is connected to
Zone 2 and this valve opens when the pressure difference
between Zone 2 and Zone 1 falls to no less than 0.14 bar
minimum. Water then freely flows to atmosphere from Zone 2.
In this way the risk of back pressure or back syphonage into
the supply network is prevented. The supply is interrupted and
the drinking water network is protected.
Zone 2
Zone 1
Inlet check valve
Flow position
Flow position
Flow position
Flow position
Flow position
Shutoff position
Shutoff position
Shutoff position
Shutoff position
Shutoff position
As long as the differential
The discharge valve opens
pressure between zone 1
to atmosphere if the
and zone 2 is greater than
differential pressure
0.14 bar, the discharge
between zone 1 and zone
valve remains closed, even
2 falls below 0.14 bar.
when water is not being
drawn off.
GB
Zone 3
Outlet check valve
Discharge valve
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Two check valves and a
discharge valve divide the
system into three zones.
The discharge valve opens
even if both check valves
do not fully seal.
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