SECTION VIEW DRAWING AND DESCRIPTION –
SERIES 746-LPA DRY ACCELERATOR
The Series 746-LPA Dry Accelerator is a quick-opening device, which
exhausts air from Series 767/776/798 Actuators 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/21 kPa.
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/21 – 34 kPa, 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.
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
Check Valve
7
Compression Spring
To Pressure
Gauge
Air Inlet
13
1
12
11
10
9
7
6
5
8
3
2
4
CROSS SECTION WITH UPPER CHAMBER ROTATED
45° AND BOLT REMOVED FOR CLARITY
Exaggerated for clarity
IMPORTANT INFORMATION
WARNING
WARNING
Read and understand all instruc-
tions before attempting to perform
maintenance on any Victaulic
piping products.
Wear safety glasses, hardhat, and
foot protection.
Failure to follow these inst ructions
could result in serious personal
injury, property damage, and/or
product failure.
•
•
Depressurize and drain the piping
system before attempting to
remove, adjust, or perform main-
tenance on any Victaulic piping
products.
Failure to follow this instruction
could result in serious personal injury
and/or property damage.
•
The following information is a guide for proper installation of Victaulic Series 746-LPA Dry Accelerators. Always refer to the installation,
maintenance, and testing manual for the applicable valve for detailed system setup, operation, and maintenance instructions.
I-746.LPA_1
Series 746-LPA
INSTRUCTIONS FOR INSTALLING AND REPAIRING SERIES 746-LPA DRY ACCELERATORS
I-746.LPA
INSTALLATION AND REPAIR KIT INSTRUCTIONS
www.victaulic.com
VICTAULIC IS A REGISTERED TRADEMARK OF VICTAULIC COMPANY. © 2006 VICTAULIC COMPANY. ALL RIGHTS RESERVED. PRINTED IN THE USA.
REV_A
