Victaulic FireLock NXT 769 Series Installation, Maintenance, And Testing Manual

SECTIONVIEWDRAWINGANDDESCRIPTION–
SERIES746-LPADRYACCELERATOR
(OPTIONAL)
The Series 746-LPA Dry Accelerator is a quick-opening device, which
exhausts air from the Series 776 Low-Pressure 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 3 psi/0.2 Bar.
When the system introduces air pressure into the dry accelerator, air
enters the closing chamber and passes through a check valve to the
opening chamber. The check valve, which allows flow into the open-
ing 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
from the opening chamber. As the sprinkler system’s pressure continues
to decay, a differential pressure develops across the diaphragm. When
this differential pressure reaches 3 – 5 psi/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.
NOTE: The Series 746-LPA Dry Accelerator must be used only on
systems operating below 25 psi/1.7 Bar of air. If air pressure higher than
25 psi/1.7 Bar is required, the Series 746 Dry Accelerator should be
used.
Illustration is exaggerated for clarity
* Denotes components that can be replaced in the field
TO PRESSURE
GAUGE
AIR INLET
CROSS-SECTION WITH UPPER CHAMBER ROTATED
45° AND BOLT REMOVED FOR CLARITY
Opening/Air Chamber
Restrictor*
Piston
O-Ring*
Diaphragm*
Closing Chamber
Actuator Shaft
Compression Spring
O-Ring
Seal Support
Button-Head
Cap Screw
Closing Chamber Seal
Adjustable Seat
Washer
O-Ring*
Check Valve*
REV_B
FireLockNXT™AutoConvertPreactionValve
SERIES 769
PreactionElectricAutoConvertDryTrim
I-769P.AC/ELECINSTALLATION,MAINTENANCE,ANDTESTINGMANUAL
www.victaulic.com
VICTAULIC IS A REGISTERED TRADEMARK OF VICTAULIC COMPANY. © 2009 VICTAULIC COMPANY. ALL RIGHTS RESERVED. PRINTED IN THE USA.
I-769P.AC/ELEC_9

Victaulic FireLock NXT 769 Series Specifications

General

Brand	Victaulic
Model	FireLock NXT 769 Series
Category	Control Unit
Language	English