Conveyor Fire Detection – Using Patol Flame Sensors To Prevent Fire
Published 25 Sep 2016
T&D thank Steve Wilder of Patol for this Guest Blog contribution on the benefits of installing Patol 5610 Conveyor Fire Sensor Detectors to prevent fires and plant downtime.
Conveyor Fire Detection With Patol 5610 Infrared Flame Sensor
There are thousands of conveyor systems all around the globe, all needing a specialist heat and fire detection system capable of stopping any product at the combustion stage from getting further into any plant, holding hoppers, blending/crushing areas or causing damage to the belt itself.
Many products including biomass, black and brown coal, industrial confetti with Energy From Waste plants (EFW), recycling products and even sulphur are extremely combustible.
The flame sensor is ATEX certified to Ex d iiC T5 Gb Ex tb iiiC T95C Db – suitable for hazardous area location installation.
Employing solar blind infra-red technology with a wide frequency of 5-14 micro metres will detect anything above 100° Celsius set at the most sensitive of 4 settings in a 250mm square area or 400° Celsius in a 50mm area, way before spark or ember point.
The fire detection system is perfectly suitable for hazardous areas and dusty environments using 10mm inlet compressed air at 2.5-10 pounds per square inch (PSI) in order to keep the lens clean. A water trap after the compressor should be considered to make sure any moisture in the system is not transferred across the lens.
Patol 5610 Infrared Flame Sensor
Product System Setup
A typical installation would be 1 metre above the conveyor close to a 30 degree angle, 5 metres after the start of the loading end of each conveyor system. Consideration should be taken into account every 100m, transfer towers or after inlets for each sensor.
Conveyor speeds from 0.5-6 metres per second and can be powered by 20-30 Vdc supply in relay mode or low power operation from a trigger circuit addressable loop system.
A recent live test was initiated at the commissioning stage with a Power Station’s Lead Maintenance staff using a roasting tray full of wood pellets (biomass), scorching them to 100° Celsius. The Engineer then added a cold layer of pellets to perform a mock buried heat test.
The Patol 5000 series infra-red detector triggered the alarm immediately.
Relays can be connected to enable the conveyor to stop in the event of a fire outbreak on the conveyor. A fire extinguishing panel could be connected to operate a mist or sprinkler deluge system at the activation point determined by the weight of the product, speed of the conveyor and momentum.
If this system is not put in place, a lack of housekeeping and wash down can result in the entire conveyor housing going up in flames in seconds. A regular maintenance schedule should be arranged to confirm that correct pressure PSI from the regulator is connected to the compressor, the lens is clean and the system is tested with a heat platen or test wand (Patol 721-002) after isolation to the control room.
This will be required to make sure a positive air pressure around the unit’s solar blind sensor window is present. This is a continuous airflow out of the optical visor which essentially stops any dust settling.
Patol also produce a stainless steel 5712 infrared transit flame sensor version perfect for the food processing industry and hygiene applications which includes the sensor head, a 5020 controller and multi core cable. The lens employs an air knife using a compressed air 10mm inlet to again keep the lens clean – applications include pop corn, Doritos, Corn Flakes, etc.
Using a different spectral narrow frequency of 4.2-4.7 micro metres which will enable the Patol 5712 flame sensor to alarm at a higher temperature. For example at flame/ember point with the product already hot after exiting the oven.
A polycarbonate flame sensor is also available, Patol 5410 which includes the sensor head, an air purge blower and 2 metre section of air hose. This would be a suitable for non-hazardous applications when compressed air is not readily available – contact T&D for hazardous area flame sensors.
In this case regular checks should be made to change or wash the filter attached to the blower. Clean air should be transferred in a PVC pipe to the blower from a clean air source.
In the event of a static heat or fire condition Linear Heat Detection Cable (LHDC) should be installed either side of the conveyor using knock-on clips at every 1 metre roller frame brace and/or above using a catenery wire. If the conveyor has stopped and a problem has occurred with stuck rollers any smouldering product could cause damage.
Patol 5610 InfraRed Transit Heat Sensor
Correlation Between Temperature & ‘Hot Spot’ Anomalies
Optional monitoring can also be installed using distance location or 4-20mA output to a scada system in the main control room of any plant. A consideration should be taken into account for mechanical protection with Patol stainless steel braid (order code 700-071/091). The rest of a typical system included an end-of-line termination box housing the resistor or an optional fire/fault test switch end of line.
Patol’s fire detection solution is essential at keeping property damage and insurance premiums to a minimum – not to mention how much plants can lose during downtime.
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- Patol 5610 Heat Sensor – Infrared Transit Heat Sensor (Patol 5000) – Data Sheet Size: 555.59 KB
- Patol 5710 Heat Sensor – Infrared Transit Flame Sensor (Patol 5000) – Data Sheet Size: 532.90 KB