Series 756 FireLock
®
European Dry Valve Stations
6
SECTION VIEW DRAWING AND DESCRIPTION – SERIES 753-A DRY
ACTUATOR/ANTI-FLOOD DEVICE
Dry Actuator
The Series 753-A Dry Actuator/Anti-Flood Device is located in the trim of Series 756 Dry Valves and acts as the trigger for these systems.
Diaphragms separate the dry actuator into two chambers. The upper chamber controls actuation, while the lower chamber acts as a
water control valve.
As the system is being charged with air, the upper chamber of the dry actuator also fills with air. Air pressure pushes a seal (attached to
a diaphragm) against a seat in the lower chamber and closes the water control valve. Water pressure then enters the piston charge line
of the valve, which sets the clapper.
When a sprinkler opens, air pressure releases from both the system and the upper chamber of the dry actuator. When the air pressure
in the upper chamber decays to approximately
1
/
8
the pressure in the lower chamber, the seal lifts from its seat. Water escapes from the
piston charge line of the dry valve, thus allowing the piston to retract. The dry valve’s clapper opens, and water flows into the sprinkler
system.
Integral Anti-Flood Device
After the dry valve operates, water from the main water supply enters the air-filled trim. A Series 748 Ball Check is included in the trim,
which prevents water from entering the actuator.
During system charging and normal operation, a seal covers a small vent hole in the top of the upper chamber. During actuation, a shaft
that connects to the diaphragm pushes the seal away from the vent hole and allows air pressure to vent to the atmosphere. In addition,
any system water that passes through the Series 748 Ball Check exhausts without filling the upper chamber of the dry actuator.
From Water
Supply and
Piston
To Drain
Air
Inlet
7
6
5
4
3
2
1
9
10
11
12
13
14
8
BILL OF MATERIALS
Item
Description
Item
Description
1
Upper Chamber Seal
8
Actuator Shaft
2
Washer
9
Diaphragm
3
Button Head Cap Screw
10
Lower Chamber
4
Seal Support
11
Seal
5
Adjustable Seat
12
Seal Retainer
6
O-ring
13
Threaded Rod
7
Upper Chamber
14
Piston
