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3.3 Refitting instructions
CAUTION: during the assembly, Silicone grease will have to be applied on O-rings.
Replace the check valve
• Introduce the 1st check valve in its bore (8) (9). Then using a lever (bottom part placed in the relief valve bore) and a plastic
wedge, push the subset to replace it.
• Important: take care that the relief valve seat is removed
• With the same method, mount the second check valve.
Replace the relief Valve
• Mount the relief valve seat in its bore . If necessary, push it using a plastic rod.
• Place the relief valve spring on the seat (5).
Before the final operation, carefully dry the surfaces (body – cover) in contact with the membrane. If the membrane is assembled
for a second time, apply talcum powder on it.
• On the working station, place the relief valve unit in the cover.
Take care of the membrane orientation
• Turn the subset and place the screws on the cover.
• Take the unit and carefully position the relief valve in the spring then in the seat.
IMPORTANT: angular movements have to be as smallest as possible.
Tight the screws to the following torques: DN65 : 80 mN - DN80 : 90 mN - DN100 : 130 mN
Replace the outlet drain holder (2)
• The outlet drain holder is maintained on the casing by bolts and nuts. When replacing it, remove the screws from a groove on the casing.
• Then manually screw it until it reaches the draining valve (10).
Specification for DN200 and DN250:
• Dismantling of the upstream and downstream check valves: insert two screws into the upstream and downstream threaded (M10)
in order to remove the upstream and downstream subset out of their own bore. Then remove them from the body.
• Reassembling of the new subset (upstream and downstream check valve): introduce the first subset in the body bore, then with a
lever into the low part of the body (draining valve seat removed), push the subset to replace it.
• Remark: the upstream seat is equipped with an external notch with must be placed in the low part of the body. Do not forget to
replace the two safety seals (13). Reassembling the draining valve seat (5) and the spring (6).
3.4 Repair kits
Repair kits are available and make it possible to replace the specific defective part on the BA 4760 backflow preventer
DN
A
B
mm
mm
mm
"
2 1/2
65
185
356
3
80
200
440
4
100
220
530
6
150
285
630
8
200
340
763
10
250
395
763
* Maximum torque for tightening bolts of the backflow preventer cover
C
D
E
F
acceptable
torques *
mm
mm
mm
mm
155
326
63
180
173
337
63
200
201
434
80
255
230
456
80
310
272
499
80
390
272
499
80
390
Max.
Nm
40
40
40
110
300
300
BA 4760
7
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