19 January 2022
CONTROL LOGIC_ITALY: SPARK DETECTOR SYSTEMS TO PROTECT STORAGE SILO FROM RISK OF FIRE
Dimensioning of Spark Detector Systems The elements to be considered for dimensioning the system are the following:
• Ducting: diameter, length and air speed.
• Safety level required: with or without monitoring station.
• Water: pressure. The duct diameter determines the choice between single detector and pair.
Up to 500 mm diameter, the duct is considered small and a single detector is sufficient (small systems type “A” and “E1”).
Over 500 mm diameter the duct is considered large and a pair of detectors is required (large systems type “B” and “E”).
The safety level required determines the choice between systems that perform detection and extinguishing operations (simple systems type “A” and “B”)
and those that also provide monitoring (complete systems type “E1” and “E”). Four systems are then available:
• SYS-A Small simple system. Extinguishing, single detector.
• SYS-B Large simple system. Extinguishing, double detector.
• SYS-E1 Small complete system. Extinguishing and monitoring, single detector.
• SYS-E Large complete system. Extinguishing and monitoring, double detector. Simple systems type “A” and “B” intercept the spark and automatically extinguish it with a water spray without stopping the production process. For every spark detected the alarm will sound for 3 seconds and the nozzle will spray water for 3 seconds (1-2 liters). Complete systems type “E1” and “E” intercept the spark, automatically extinguish it with a water spray and check that the spark is extinguished. They perform the alarm and the automatic extinguishing function. For every spark detected the alarm will sound for 3 seconds and the nozzle will spray water for 3 seconds (1-2 liters).
They also perform the permanent alarm for missing or not sufficient extinction. Control panel operates and monitors all the functions of the system, TEST included. The system must be powered by an external 24Vdc power supply. The air speed is an important factor for the duct length required.
The usual air speed in wood-processing factories is 20-30 meters per second. In textile and others factories air speed is lower, 15 to 20 meters per second. The duct length must be sufficient to allow positioning of the spray nozzles, and of monitoring detectors if required. If duct length is enough, standard distance of 15 meters, based on 0,2 seconds delay time due to the response delay time of the solenoid valve including water travelling time from the solenoid valve to the nozzles, covers an air speed range from 5 meters per second to 75 meters per second that is highly sufficient for most applications.
The water pressure is very important to a proper functioning of the extinguishing system, a pressure of 3-4 bar on the nozzle is recommended. When the water pressure is not sufficient or unstable, it is recommended to mount a small (10-20 liter) pressurized storage tank. Water consumption is moderate.
A nozzle sprays about 1-2 liters of water in each 3 sec spray, the flow rate through the nozzle is about 30 liters per minute at 4 bar.
For more information contact Mrs Sara Russotto:
CONTROL LOGIC Srl
Via Ennio 25
20137 MILAN / Italy
Tel. +39 02 54100818
Fax +39 02 54100764