Air supply system shall be in accordance with NFPA 13. The connection pipe
from the air compressor shall not be less than 15 mm 1/2 inch in diameter
and shall enter the system above the priming water level of the dry pipe
valve. A check valve shall be installed in the system supply air piping
from the compressor. A shutoff valve of the renewable disc type shall be
installed upstream of this check valve. The air supply system shall be
sized to pressurize the sprinkler system to [275] [_____] kPa [40] [_____]
psi within 20 minutes.
2.7.1
Air Compressor
Compressor shall be single stage oil-free type, air-cooled, electric-motor
driven, equipped with a check valve, shutoff valve and pressure switch for
automatic starting and stopping. Pressure switch shall be factory set to
start the compressor at [200] [_____] kPa [30] [_____] psi and stop it at
[300] [_____] kPa [40] [_____] psi. A safety relief valve, set to operate
at [450] [_____] kPa, [65] [_____] psi, shall be provided.
2.7.2
Air Pressure Maintenance Device
Device shall be a pressure regulator that automatically reduces supply air
to provide the pressure required to be maintained in the piping system.
The device shall have a cast bronze body and valve housing complete with
diaphragm assembly, spring, filter, ball check to prevent backflow, 1.6 mm
1/16 inch restriction to prevent rapid pressurization of the system, and
adjustment screw. The device shall be capable of reducing an inlet
pressure of up to 680 kPa 100 psig to a fixed outlet pressure adjustable to
70 kPa 10 psig.
2.7.3
Air Supply Piping System
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NOTE: Delete air compressor when not required.
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System shall be configured so that each dry pipe system is equipped with a
separate pressure maintenance device, air compressor, shutoff valve, bypass
valve and pressure gauge. Piping shall be galvanized steel in accordance
with ASTM A 795/A 795M or ASTM A 53/A 53M.
2.7.4
Low Air Pressure Alarm Device
Each dry pipe valve trim shall be provided with a local alarm device
consisting of a metal enclosure containing an alarm horn or bell, silence
switch, green power-on light, red low-air alarm light and amber trouble
light. The alarm device shall be activated by the low air pressure switch.
Upon reduction of sprinkler system pressure to approximately 70 kPa 10 psig
above the dry valve trip point pressure, the low air pressure switch shall
actuate the audible alarm device and a red low-air alarm light.
Restoration of system pressure shall cause the low-air alarm light to be
extinguished and the audible alarm to be silenced. An alarm silence switch
shall be provided to silence the audible alarm. An amber trouble light
shall be provided which will illuminate upon operation of the silence
switch and shall be extinguished upon return to its normal position.
2.8
WATERFLOW ALARM
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SECTION 13935A
Page 19
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