User's Manual

Design
P/N 81-CO2MAN-001 3-55 September 2013
3-10 EXTENDED DISCHARGE SYSTEMS
An extended discharge is used to provide protection beyond the normal duration. It may be
applied either by increasing the agent supply or by providing a secondary system.
The duration of the extended discharge should be specified and agreed upon with the system
owner and Authority Having Jurisdiction.
Examples of special considerations that will necessitate an extended discharge include:
• Hazards containing a liquid having an auto-ignition temperature below its boiling point,
such as cooking oils, require an extended duration of protection to permit cooling of the oil
• Hazards containing a metal or other material that may become heated and remain a
persistent source of ignition beyond the duration of protection
• Hazards protected by a total flooding system that are not capable of maintaining the
minimum design concentration for the specified duration of protection
3-10.1 Increased Agent Supply
An increased agent supply is used when the carbon dioxide must be applied at the original
design rate. This approach is most appropriate for local application systems, which have no
duration of protection beyond the end of discharge. The agent supply is calculated in
accordance with Paragraph 3-6.1.4, adjusting the liquid discharge time to meet the
requirements of the hazard. It is imperative to verify that the excess carbon dioxide will not
create hazardous conditions in enclosed environments.
3-10.2 Secondary System
A secondary system is used when the carbon dioxide must be applied at a rate other than the
original design rate. This approach is most appropriate for total flooding applications that must
maintain concentration in an enclosure with appreciable leakage and/or forced ventilation. In
such cases, the primary system is designed to discharge at a high rate to achieve the minimum
concentration within 1 minute, while the secondary system discharges at a much lower rate to
compensate for losses. The secondary system flow rate and agent quantity are based on the
Uncloseable Opening (Paragraph 3-5.2.4.1) and Forced Ventilation (Paragraph 3-5.2.4.2)
calculations for total flooding systems. Note that if the primary and secondary systems are
= 1.4 x
= 1.4 x 0.5
= 0.7 min.
= 30
= 0.5 min.
= 20.4 x x ( + )
= 20.4 x 1 x (0.7 + 0.5)
= 24.48
25 lb.
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