SECTION VIEW DRAWING AND DESCRIPTION –
SERIES 746-LPA DRY ACCELERATOR
The Series 746-LPA Dry Accelerator exhausts air from the actuator to
speed valve operation.
A diaphragm separates the Series 746-LPA Dry Accelerator into two
chambers. The closing chamber contains a compression spring, which
maintains the chamber in the closed position. The closed position is
maintained as long as the pressure differential between the opening and
closing chambers is less than 0.2 Bar.
When the system introduces air pressure into the dry accelerator, air
enters the closing chamber and passes through a built-in check valve
to t
he opening chamber. The built-in check valve, which allows flow into
the opening chamber, prevents pressure from escaping the opening
chamber. Therefore, air can escape only through the restrictor.
When a rapid loss of system air pressure occurs, such as an open
sprinkler, air escapes from the closing chamber faster than it escapes
fro
m the opening chamber. As the sprinkler system’s pressure continues
to decay, a differential pressure develops across the diaphragm. When
this differential pressure reaches 0.2 – 0.3 Bar, the opening chamber’s
pressure overcomes the compression spring’s closing force, causing
the closing chamber to open to the atmosphere. The closing chamber
opens immediately and releases pressure from the actuator, resulting in
valve operation.
Manufacturer’s Recommended Pressures:
Minimum Water Supply Pressure = 2.0 Bar
Min
imum Air Supply Pressure = 1.4 Bar
Maximum Air Supply Pressure = 1.6 Bar
Exaggerated for Clarity
13
1
12
11
10
9
7
6
5
8
3
2
4
To Pressure
Gauge
Bill of Materials
1 Opening/Air Chamber 8 Seal Support
2 Piston 9 Button-Head Cap Screw
3 Restrictor 10 Closing Chamber Seal
4 Diaphragm 11 Washer
5 Closing Chamber 12 Adjustable Seat
6 Actuator Shaft 13 Built-In Check Valve
7 Compression Spring
I-756LPA.VDS_7
FireLock
®
European Dry Valve Stations
SERIES 756
WITH SERIES 776 LOW-PRESSURE ACTUATOR
I-756LPA.VDSINSTALLATION, MAINTENANCE, AND TESTING MANUAL
www.victaulic.com
VICTAULIC IS A REGISTERED TRADEMARK OF VICTAULIC COMPANY. © 2006 VICTAULIC COMPANY. ALL RIGHTS RESERVED. PRINTED IN THE USA.
REV_B
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