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1. Installation
It is necessary during installation to comply with
local requirements, to follow codes of good
practice and to follow the installation instructions.
The installation location should be protected
against frost and be easily accessible.
1.1 Installation Guidelines
Flush connecting pipework thoroughly before
installation
Install the backflow preventer with good
accessibility and with flow in the correct
direction.
Install the backflow preventer only in horizon-
tal pipework and with the discharge tundish
downwards
A clearance of Amin must be provided above
the backflow preventer for maintenance
purposes
Rp
1
/
" to 1"
1
1
/
" to 2"
2
4
A
100mm
150mm
min
It is recommended that a Y-strainer 2
(e.g. FY 30) be fitted upstream to protect the
changeover valve and backflow preventer
against dirt.
Fit shutoff valves 1 and 5 either side of the
backflow preventer
The shock arrestor 8 supplied should be
fitted in the appropriate position (see illustration)
If valves which open and close rapidly are
fitted in the system, it may be necessary to
fit a larger capacity shock arrestor
Connect discharge pipe (DN 40 plastics pipe
or R1" threaded pipe) to discharge tundish 6
The pressure gauge connection is fitted on
the inlet side of the backflow preventer and
therefore complies with the requirements of
DIN 1988, Part 2, Section 4.3.3.5.
If there is a possibility, that at zero flow the
water in the downstream system may be
heated, then a safety valve must be fitted to
allow for water expansion and prevent the
pressure rising above the permitted level.
If soldered union connectors are used the
backflow preventer must not be connected
to the union connectors during soldering.
GB
1.2 Commissioning
As supplied (i.e. in zero pressure condition) the
hydraulic changeover valve 7 is closed and the
backflow preventer is in the shutoff position.
Commissioning should be in the following
sequence:
1. Slowly open shutoff valve 1 (when the
minimum inlet pressure is reached the
backflow preventer goes to the flow position
so that the whole backflow preventer
assembly up to the outlet shutoff valve fills
with water).
2. After filling, the operating pressure sensor
changes over the hydraulic control valve so
that the backflow preventer goes back to the
shutoff position.
3. Check for leaks at the flanges and pipework
connections.
4. Slowly open shutoff valve 5 , fill the system
and vent.
5. After filling of the system, or when no more
water is being drawn, the operating pressure
sensor changes over the hydraulic control
valve so that the backflow preventer goes
back to the shutoff position.
6. If the differential pressure at the backflow
preventer falls below 0.5 bar when water is
being drawn, for example through pressure
drop of the inlet supply or pressure increase
on the outlet side, then the backflow preventer
automatically opens to provide a minimum air
gap of 20mm.
7. The operating position is indicated on the
spring bonnet 3 .
Shutoff position : Green spring cap 4 is
visible
Flow position: Green spring cap 4 is not
visible
2. Inspection and Testing
According to DIN 1988, Part 8, Appendix A 3
specifies that for Type 2 backflow preventers, the
following inspection and testing is required:
2.1 Testing of Function
Close the valve 1 fitted before the backflow
preventer.
Relieve the pressure in the isolated section
through the small drain off valve 9
Visually check that the backflow preventer
goes to the shutoff position.
4
2.2 Checking for Seal
Visually check that no water is emitted when
backflow preventer is in the flow position.
These inspections and tests should be carried out
at least once a year by the user or by a specialist
(depending on operating conditions, it may be
necessary to carry out these tests and
inspections more frequently).
3. The Correct Opening Pressure
The hydraulic changeover valve on the R 295 H
automatically controls the opening pressure to
suit the downstream system conditions. Determi-
nation of the highest likely non-potable water
level to be protected against (and therefore
backflow preventer opening pressure to select) is
not necessary.
4. Contruction Type
Installation areas and construction types are
specified in DIN 1988, Part 4 „Protection of
drinking water, maintenance of water quality".
7. Technical Data
Scope of application
Cold water
Operating pressure
Maximum 16.0 bar
Minimum inlet pressure 1.5 bar
Minimum flow rate
1.0 litre/min
Differential pressure
Not less than 0.5 bar, self adjusting.
Connection Size
Rp
/h) at Dp = 0,8 bar
Nominal flow rate (m
3
k
-value (full flow)
vs
z-value
DIN/DVGW-test No.
569 VE
GB
5. Maintenance
Honeywell Braukmann backflow preventers are
safety devices which require very little
maintenance and which are installed to prevent
backflow of uncleaned water into the supply
network, into separate systems or into other
sections of an installation. Depending on
operating and flow medium conditions, to ensure
trouble free operation it may be necessary at
fixed time intervals to check seal components,
piston guides and rating springs and where
necessary replace them.
6. Method of Operation
Hydraulic backflow preventers are normally in the
shutoff position. When water is drawn from the
downstream system, the differential pressure in
the backflow preventer rises so that changeover
of the hydraulic control valve occurs. This causes
the atmospheric link to the upper side of the
control piston to be broken and connection be
made to the inlet pressure. A force is exerted on
the control piston by the inlet pressure and
pushes the shutoff piston into the flow position.
When water takeoff is completed, the operating
pressure sensor changes over the hydraulic
control valve again. The upper side of the control
piston is relieved of pressure and the setting
spring pushes the shutoff piston back to the outlet
(shutoff) position.
1
/
"
3
/
"
1"
1
1
/
"
1
1
/
"
2
4
4
2
2,2
3,1
3,6
8,9
12,5
2,5
3,5
4
10
14
13
20,9
39
16,8
20,9
570 VE
571 VE
572 VE
573 VE
5
2"
14,3
16
39
574 VE
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