1 aspirating systems training e-series. 2 air sampling system design principle of operation stages...
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ASPIRATINGSYSTEMS TRAINING
e-series
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Air Sampling System Design Principle of operation Stages of Fire General System Design Pipe layout considerations Secondary Air-sampling Systems Primary Air-sampling Systems Referencing – ambient pollution compensation Effect of dilution on sensitivity Response time PipeTracer Adverse Environments
System Components Maintenance
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Air Sampling System Air drawn through pipe network to central system High sensitivity smoke detector Laser detection of particles for very early warning Adjustable alarm thresholds 0.005 – 20%
obscuration/metre Pin-point addressing with sampling from up to 15
channels
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FHSD700 pulls air samples from the sampling channels
simultaneously
Air samples are drawn through a chamber where a laser beam illuminates any smoke particles, with a sensitivity of five parts in
one hundred thousand
Within seconds it will inform the user exactly which channel contained the contaminated sample
When smoke is detected the FHSD700 quickly samples each individual channel
Allowing the user to locate the hazard and prevent it progressing
Principle of Operation
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Obs/metre : 10.0 FULL FIRE
Possible loss of premises, stock and life
Example
Office Chair placed against heater
Obs/metre : 0.1 Est. time to Fire : 45m
Smoke not yet visible.Standard point detectors have not yet
raised alarm
Obs/metre : 0.03Estimated time to Fire : 1 hr
Very fine smoke particlesFHSD700 series sounds alert
Identifying fires within its incipient stages for earliest possible protection
0.01 0.1 1.0 4.0 10 20
Stages of Fire
Obs/metre : 4.0 Est. time to Fire : 0m
Flames appear and the office must be evacuated. The FHSD700 will activate
combined suppression systems
Obs/metre : 1.0 Est. time to Fire : 10m
Smoke clearly be seen.Conventional detectors sound alarm
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General system design Define requirements/expectations at an early
stage. What sensitivity is expected from the system
Two main types of system With Air Handling Units (AHUs) Without Air Handling Units
Special cases include clean rooms, cold rooms, historical buildings
Perform smoke tests to ascertain patterns of air movement and position sampling points where smoke will propagate to.
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Pipe Layout Considerations
Pre-design pipe network, especially for wide-bore pipes
Use a square grid overlay 6mx6m 8mx8m 8mx6m Ensure maximum pipe length is not be exceeded
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Large bore systems - Pico, FT1, FT4, FT6 Use capillary
tubes (8mm id with 2mm end hole up to 6m long) or drop pipes for concealed or cabinet sampling
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Microbore systems - FT15 Flexible nylon 6mm o.d. sampling tube. Fast and simple installation in cabinets or within building structure Outputs and flow monitoring for every sampling point One tube can be used for referencing 2 way split (2m) allowed at end of tubes allowing 30 sampling points
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Secondary air-sampling systems•Air sampling placed in same places as conventional detectors and not relying on air conditioning systems•Designed to BS5839/6266 and EN standards for spacing and placement.
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Primary air-sampling systems•System designed to work in conjunction with an air handling or ventilation system•Only provides optimum performance when air handling system is operational•Detects trace levels of smoke that do not have the thermal energy to rise to the ceiling
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Primary air-sampling systems - AHUs
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Primary air-sampling systems - AHUs
•Cover entry to Air Handling Unit not exhaust as this is filtered•Sampling holes at 200mm intervals across AHU grille facing into airflow•Extract ducts in shallow floor voids have high negative pressure and therefore sampling points should be positioned in front of but at least 2m away from the entry point
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Primary air-sampling - Ducts•Use Probe to penetrate return air duct allowing sampling holes to be directly in air path•Ensure intake and exhaust probes are separated by 300mm and are properly sealed – high negative pressures exist•Ensure probes are diagonally offset to avoid turbulence reaching exhaust probe
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Primary air-sampling - Clean Rooms•Earliest detection possible required to avoid damage from smoke contamination•FT15 ideally suits application by monitoring individual cabinets and processes before the air is diluted and filtered•Conventionally sited air-sampling networks struggle with the high airflows & ultra high dilution
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Referencing - Ambient pollution compensation
Take referencing air-sample from building air inlets
Provides compensation for ambient pollution Use additional detector on RS485 network Use one sampling tube on system for integral
referencing Set parameters for reference compensation and
time delay
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Effect of Dilution on Sensitivity
Smoke entering a sampling hole is diluted by sampling holes closer to the detector
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Table Showing Varying Dilution
This depends on many different factors but this can be used as a rough guide for large bore systems
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Response Times Response times are dependent on several
factors Number of pipes Diameter of pipes Pipe length Distance to first bend Number of holes Hole spacing Aspirator speed and performance
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PipeTracer
Response times are calculated using PipeTracer software
Detailed information about the intended layout is entered
PipeTracer calculates all response times, flow volumes and hole balances together with sensitivity at each sampling hole
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Adverse Environments Cold Stores / Chill Stores
Drill sampling holes in side of pipe Ensure pipes drop along length of store towards detector No vertical pipes Heat air sample outside store before entering FHSD Fit water trap – loop of flexible pipe before detector Keep pipes away from chiller exits
Dusty areas, and Mines Use Filter+ pre-filter
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Adverse Environments Hazardous Areas
Install FHSD in safe areaUse in-line flame arrestors on interface
between safe and hazardous area Atria
Install vertical pipes to cover varying height of smoke stratification layer as temperatures change during day
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System Components Laser Detector Aspirator Fan High pressure pump Rotary Valve Control Panel Control & I/O System Power Supply
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Laser Detector A laser fires radially across optical chamber Any smoke particle is illuminated The scattered light is caught in the wall of the chamber
which acts as a light-guide providing a total integration of the light from the smoke particles
A particle density of 0.005% obscuration/metre is detectable with maximum range of 20% obscuration/metre
Chamber is field removable for ease of service
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Aspirator Fan – Pico, FT1, FT4, FT6 High performance high static pressure
enabling detection over 100m pipe lengths with minimum response times
Full speed control Includes by-pass sampling to preserve
filter life
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High pressure pump - FT15
Allows use of 4mm microbore tubing Carbon rotor & vanes for long life Stainless steel body for long life Vacuum sensor provides flow monitoring
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Rotary Valve - FT4, FT6, FT15 Rotary valve for monitoring samples taken by up
to 15 individual pipes Wide-bore application for ¾ inch pipe Small-bore application for high pressure systems Normally monitors all sectors - when trace level
exceeded rotary valve immediately sequences to pinpoint sector
Individual pipe flow monitoring
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Control Panel
Recognisable symbols for international markets Multi-language display settings Simple interface for easy configuration All alarms and faults clearly displayed to enable
immediate identification Obscuration per metre level constantly visible Programmer RS485 remote interface
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Control & I/O System
Fully programmable system for continuous early warning detection of hazard
Optional web support for remote monitoring using TCP/IP and Ethernet
Optional input/output cards for relay contacts, auxiliary input/output and fire suppression
RS485 connection for remote location of control panel
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Power Supply
Integrated mains power pack in either 230/115 Volt options
Battery compartment for 2 x 17Ah batteries included
Power pack provides 5Amp charge and trickle charge for batteries
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Maintenance Optical chamber and filter cartridge – inspect at
every regular service - clean chamber and replace filter if necessary
Check all internal pneumatic connections for leaks
Check pipe network flow levels Perform smoke test Replace pump vanes annually FT15 only Replace rotary valve seals every 3 years FT4, FT6 and FT15 only