CONTROL & RELEASE EQUIPMENTThere are two principle parts in the control and releaseportion of the system: (a) the cylinder valve, and (b) thecontrol head. See Figure 1.Halon 1301 is stored in the steel cylinder as a liquidwhich is super-pressurized by nitrogen to 360 psig at700 F.VALVEThe discharge valve operates on a principle whereby thecylinder pressure is used to effect the release of theagent. In a normal standby situation, the pressure onboth sides of the valve piston is equalized by a smallinterconnecting orifice through the piston. This providesa differential force to hold the valve closed (See Figure2). When the extinguishing system is actuated, thecontrol head which is mounted on top of the cylindervalve depresses a pilot check. This allows the pressureabove the piston to vent rapidly to atmosphere, reversingthe differential pressure force. The piston is then drivento the open position allowing the agent to be discharged.See Figure 3.The discharge valve incorporates a safety release burstdisc which is designed to release at 750-900 psigthrough an anti-recoil plug to atmosphere.Where the size or type of hazard requires more than onecylinder of Halon 1301, the cylinders are manifoldedtogether. In these multiple cylinder installations of morethan two cylinders, a pair of cylinders is fitted with controlheads. These are known as control or master cylinders.The other cylinders are called slave cylinders.When the system operates, the Halon 1301 from thesecontrol cylinders pressurizes the manifold connecting allthe cylinders thus releasing the content in the balance ofthe cylinders. The pressure-operated or slave cylindersare identical to control cylinders except they are notfitted with control heads.5
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