MIL-DTL-24416 Extinguishing System, Fire, Fixed, Wet ChemicalThis specification covers requirements for pre-engineered wet chemical fixed fire extinguishing systems for protection of deep fat fryers, and doughnut fryers onboard U.S. Navy ships and submarines. The systems covered under this specification are intended for use in new applications, and for backfit into existing wet chemical extinguishing system installations. The current wet chemical extinguishing system utilizes aqueous potassium carbonate \(APC\) extinguishing agent, in a concentration of 42.4 percent K2CO3 and 52.8 percent water.

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MIL-DTL-24416C(SH)

3.4.2.1 Construction. Cylinders shall be constructed so the pressure gauge and/or visual indicators of

operational status can be read.

3.4.2.2 Pressure gauge. A pressure gauge shall be provided for the extinguishing agent cylinder, showing the

pressure within the cylinder. The pressure gauge face shall indicate the operating pressure range of the cylinder.

Dial pressure gauges shall be in accordance with ASME B40.100. The pressure gauge shall be calibrated and

provided with a certificate of calibration in accordance with ANSI/NCSL Z540-1-1994.

3.4.2.3 Cylinder rating. Extinguishing agent cylinders shall be rated for water capacity and service pressure of

the wet chemical system. Extinguishing agent cylinders that do not use an external expellant gas cylinder for

charging, shall meet the requirements of A-A-59666 when shipping of the cylinder is required in the charged

condition. Extinguishing agent cylinders using an external expellant gas cylinder for charging, shall meet the

requirements of ASME Boiler and Pressure Vessel Code Section VIII, when cylinders are not shipped in the charged

condition.

3.4.2.4 Extinguishing agent discharge valve. Internally pressurized extinguishing agent cylinders shall be

outfitted with a discharge valve that controls release of extinguishing agent. Discharge valve shall be designed to

provide rapid actuation and discharge of agent. Discharge valve shall be made of corrosion resistant, non-

combustible material. The discharge hose or piping shall be made of corrosion resistant, non-combustible material.

Discharge valves shall withstand the extinguishing agent cylinder hydrostatic test pressure specified in A-A-59666

or the ASME Boiler and Pressure Vessel Code Section VIII, as applicable, without rupture, damage, or permanent

distortion.

3.4.3 Expellant gas. Dry nitrogen or dry air shall be used to facilitate the discharge of the extinguishing agent.

Expellant gas may be contained within an internally pressurized extinguishing agent cylinder, or provided through

an external self-contained pressurized source integral to the wet chemical extinguishing system.

3.4.4 Expellant gas cylinder assembly. External expellant gas cylinder capacity and pressure ratings shall be as

specified in the manufacturer's wet chemical fire extinguishing system installation manual, and shall be provided

with a valve assembly to regulate the discharge of expellant gas.

3.4.4.1 Construction. An enclosure or other means shall be provided to protect the expellant gas cylinder from

damage. Expellant gas cylinder shall be accessible for inspection, maintenance, and recharge or replacement. The

cylinder assembly shall be constructed so that the pressure gauge and/or visual indicators of operational status can

be read without removal of the enclosure or guards, and without securing the extinguishing system.

3.4.4.2 Pressure gauge. A pressure gauge shall be provided for the expellant gas cylinder, showing the pressure

within the cylinder. The pressure gauge face shall indicate the operating pressure range of the cylinder. Dial

pressure gauges shall be in accordance with ASME B40.100. The pressure gauge shall be calibrated and provided

with a certificate of calibration in accordance with ANSI/NCSL Z540-1-1994.

3.4.5 Extinguishing agent release mechanism. The wet chemical fire extinguishing system shall have an

extinguishing agent release mechanism that activates the extinguishing agent cylinder discharge valve and the

external expellant gas cylinder discharge valve (when applicable) to release the extinguishing agent through the

piping distribution network. The release mechanism actuation modes shall be automatic actuation by fusible link

detectors, manual actuation by remote devices, and manual actuation at the release mechanism.

3.4.6 Pressure switch. Pressure switches shall be provided to operate on low extinguishing agent cylinder

pressure (minimum operating pressure) and shall provide an interface to de-energize fryer heating elements and an

interface to activate audible and visual alarms if the pressure drops. Pressure switch shall incorporate a manual reset

or require recharging of the extinguishing agent cylinder before the pressure switch can be reset. Pressure switch

components exposed to extinguishing agent shall be corrosion resistant.

3.4.7 Fusible link. Fusible links shall meet the requirements of NFPA 17A and be in accordance with the wet

chemical fire extinguishing system configuration for which NFPA approval was granted.

3.4.8 Vent plug. A device shall be provided to safely relieve pressure and to prevent a slow, unwanted build-up

of pressure in the discharge (distribution) piping.