Hart Mini Pipe Design Guide Hart Mini Pre-Engineered Pipe Design Guide Manual No: TM0086 It is important to select suitable pipework for the environment requiring protection. This must be designed and installed specifically for each site condition to meet the performance specification that is required. Kidde Fire Protection recommends and supplies Red ABS SnifferPipe and fittings. Other pipe types may also be used dependant upon the type of application being monitored.
Transcript
Hart Mini Pipe Design Guide
Hart MiniPre-Engineered
Pipe DesignGuide
Manual No: TM0086
It is important to select suitable pipework for the environment requiring protection.This must be designed and installed specifically for each site condition to meet theperformance specification that is required.
Kidde Fire Protection recommends and supplies Red ABS SnifferPipe and fittings.Other pipe types may also be used dependant upon the type of application beingmonitored.
Hart Mini Pipe Design GuideTABLE OF CONTENTS
Para Page
1 Aspirating Pipework Design1.1 Pipework Layout1.1.1 Response Time1.1.2 Ventilation of the Area1.2 Air Sampling Systems1.2.1 Duct Sampling1.2.2 Installation of a duct sampling pipe system1.2.3 Air Handling Unit Sampling1.2.4 Installation of Air Handling Unit (AHU) Sampling Pipework1.2.5 Distributed Air Sampling1.2.6 Closed Ended (Balanced) Distributed Pipework Systems1.2.7 Hole Sensitivity Of Balanced Systems1.2.8 Pipework Junctions1.2.9 Remote Sample Points
2 Special Design Considerations2.1 Elutriator2.2 Stratification2.3 Pressure Differentials
3 System Examples3.1 System Design D3.2 System Design I
4 Installation4.1 Pipe Warning Label4.2 Sample Point Labels4.3 Mini Sample Point Label
FIGURE TITLE Page1-1 Single Pipe System 2-11-2 Two Pipe System 2-21-3 Four Pipe System 2-21-4 Duct Sampling 2-41-5 Duct Sampling Installation 2-51-6 Air Handling Unit Sampling 2-61-7 AHU Installation 2-71-8 AHU Typical Installation 2-81-9 Distributed Air Sampling 2-91-10 Remote sample points 2-112-1 Elutriator 3-12-2 Stratification 3-23-1 System Design D 5-13-2 System Design I 5-23-3 Alternative System Design I 5-34-1 Sampling Pipe Support 6-1
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1. ASPIRATING PIPEWORK DESIGN
HART Mini has been designed to provide many years of service with minimalmaintenance. However, an HSSD system is only effective if the sampling pipework has been designed and installed correctly.
1.1 PIPEWORK LAYOUT
The sampling pipe network is the most crucial aspect of the design of an HSSDsystem and there are two important factors to consider: -
• Response time• Ventilation of the area.
1.1.1 Response Time
The response time of the detector is the means by which the overall HSSD system isassessed. It is affected by the environmental conditions and the design of the pipenetwork.
The response time is separated into two parts - the time allowed for the smoke toreach the sampling point and the transport time, which is the maximum time forsmoke to be carried from the furthest sampling point to the detector. For systemsdesigned to BFPSA code of practice for design, commissioning, installation &maintenance of HSSD systems, the transport time should be within 120 seconds.The maximum transport time can be directly affected by the installed pipe design(see figures 1-1, 1-2 and 1-3). The 4 pipe branch design will provide the shortesttransport time (fig 1-3).
Figure 1-1 Single Pipe
DetectionUnit
SamplePipe
DetectionUnit
SamplePipe
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Figure 1-2 Two-Pipe System
Figure 1-3 Four Pipe System
Note: Should the transport time be greater than 120 seconds, an acceptable timeshould be agreed with the client prior to commissioning.
1.1.2 Ventilation of the Area
The ventilation of the protected area affects the time it takes for smoke to reach thesample points. In applications without ventilation detection can be carried out atceiling level using the Secondary Detection principle, ie the air sampling points aresited and spaced to satisfy BS5839 part 1 or BS6266 requirements.
In areas with forced ventilation, air handling units (AHUs) or some other form of airextraction system, smoke may be prevented from reaching ceiling level samplepoints. In this instance it is recommended that Primary Detection be used, ie thepipework and air sampling points are mounted directly in the airflow. This type ofsystem is usually regarded as supplementary to other forms of detection due to itslimited response capability once the air movement ceases.
1.2 AIR SAMPLING SYSTEMS
There are three basic types of sampling system design:
1. Duct Sampling (Primary Detection).2. Air handling unit sampling (Primary Detection).3. Distributed air sampling (Secondary Detection).
1.2.1 Duct Sampling
Within this type of application there are a number of issues to be considered indesigning the HSSD system. These being:
• Pressure equalisation• Maintenance accessibility (eg flexible joints to allow the pipe to be removed)• Monitoring upstream or downstream of filters
Duct detection is considered as primary detection. However, the area should also bemonitored by secondary detection to provide protection in the event of the ductairflow shutting down. Monitoring is achieved by installing sample pipe within the
DetectionUnit
SamplePipe
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duct. To maintain the pressure balance, the exhaust air is returned to the ductdownstream of the monitoring sample pipe.
The use of a union socket is recommended to allow easy access for commissioningand maintenance purposes. Typically, as ducts have different pressures, it isrecommended that only a single HART Mini is used to monitor a single duct.
Where possible the sampling pipe should be installed in the centre of the airflow andaway from bends. It should also be installed close to inspection hatches formaintenance purposes. Due to the use of high efficiency particle filters within HVACsystems, it is recommended that monitoring be carried out before the filter as it mayremove smoke particles.
Fig. 1-4 Duct Sampling
1.2.2 Installation of a duct sampling pipe system
1. The sampling pipe must be inserted approximately half of the height into theduct and should be supported and sealed. It should penetrate at least 80% ofthe width of the duct.
2. In order to be able to maintain and test the HART Mini, the sample pipeshould span the width of the duct, protrude the opposite side and be closed-off using a removable end cap.
3. The sample points should be positioned at an angel of 45O off centre in theairflow. There should be one sample point for each 0.4m2 of the duct’s crosssectional area.
DetectionUnit
SamplingPipe
ReturnAir Pipe
Airflow
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4. Exhaust air from the HART Mini should be returned to the duct by fitting theoutlet adaptor, which is supplied as standard with the detector.
5. The return holes into the duct should face downstream and be inserted atleast 1 metre downstream of the sampling pipe and be positioned at 1/3height of the duct.
Fig 1-5 shows the set-up required for duct sampling.
Fig. 1-5 Duct Sampling Installation
UnionSocket
End Cap
GrommetSeal
SamplePipe
ReturnPipe
Direction ofAirflow
Direction ofAirflow
Sample Hole
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1.2.3 Air Handling Unit Sampling
For applications that include AHUs, a number of issues to be considered in designingthe HSSD system. These are;
• High Airflow• Lack of smoke energy• Resultant low smoke temperature• Dilution caused by airflow velocities• Addition of clean air by ventilation systems
Sampling the air inlets of AHUs is a highly effective way of detecting small levels ofsmoke quickly. Fig 1-6 shows an example.
When monitoring AHUs:
1. Ensure that external air velocities are less than 6 metres per second toprevent venturi effects occurring at the sampling holes.
2. Sample only over the air inlets, as many AHU's have HEPA filters which willremove smoke particles.
3. A maximum of 2 AHU's (dependent upon air movement and size) can becovered by one HART Mini.
Fig. 1-6 Air Handling Unit Sampling
DetectionUnit
SamplingPipe
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1.2.4 Installation of Air Handling Unit (AHU) sampling pipework.
When the pipework is to be installed to monitor an AHU:
1. The sampling pipe should be fitted across the middle of the air grille.
2. There should be one sample point for each 0.4m2 of the grille’s area.
3. The sample points should be positioned in the airflow at an angel of 45O offcentre.
4. A union socket should be used to allow easy access for maintenance.
Fig. 1-7 AHU Installation
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Fig. 1-8 AHU Typical Installation
1.2.5 Distributed Air Sampling
A distributed sampling system consists of a pipe network throughout the area - seefig 1-9. This is typically combined with AHU sampling to provide extra cover in theevent of failure in the AHU by providing secondary detection. In small areas a singledetector is capable of providing both primary and secondary detection.
Ceiling and floor void monitoring should also be considered. The system should bedesigned so that the sample point spacing meets the design requirements ofBS5839 part 1 or BS6266 or any other local requirements, depending upon theapplication.
Fig. 1-9 Distributed Air Sampling
Detection
SamplingPipe
False Floor
Union
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1.2.6 Balanced (Closed Ended) Distributed Pipe Work Systems
A balanced system is one in which the sampling points are sized such that they allprovide the same airflow. The sampling pipe network may be configured to matchenvironmental conditions, holes may be spaced at critical intervals and at unevenspacing. This will provide maximum protection at risk locations. If necessary differentpipe diameters may be combined to decrease transport time and so increase theresponse of the system. All pipe segments should be capped. Typically the lastsampling point will be within 150mm from the end cap.
The pipe designs provided in the appendices have been pre-engineered to producea balanced system.
1.2.7 Hole Sensitivity of Balanced System
In a balanced system design the sensitivity at each sample point hole is the same.The effective sensitivity can be determined by multiplying the sensitivity of thedetector by the number of sampling holes in the system.
Example: - The Relative sensitivity of a sample point with a detector headsensitivity setting of 0.1%/m, which is connected to a sampling pipenetwork using 40 sampling points can be calculated as follows:
0.1%/m x 40 = 4% relative sensitivity per hole
1.2.8 Pipework Junctions
HART Mini has an air inlet for a single pipe connection. For systems requiring morethan one branch to the pipework the network can incorporate Tee pieces and bends. The pre-engineered systems in the appendices have been designed specificallyusing a maximum of 2 branches. If more than two branches are needed, pleasecontact Kidde Fire Protection.
1.2.9 Remote Sample Points
If the area being protected has ceiling voids or false ceilings, run the main pipenetwork within the voids out of sight. To do this, drop a small length of pipe throughthe ceiling into the protected area with the sampling hole drilled in the end cap orsampling point. These are known as extended sampling points and varyingdiameters of pipe can be used, e.g. from 10mm capillary to 25mm OD pipe.
The type of extension would depend upon application requirements. Figure 1-10shows typical examples.
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Fig 1-10 Remote sample points
2. SPECIAL DESIGN CONSIDERATIONS
2.1 ELUTRIATOR
The HART Mini has been specifically designed to operate in most environments fromclean rooms to underground railway stations. However, in areas where the detectormay be subjected to large particles such as dust or fibres or to atomised liquids orsteam, a build up of contamination can occur in the detector or false alarms mayoccur.
The Elutriator is an optional item and can be used if the protected area is expectedto have heavy amounts of non-combustion particulate. An Elutriator should beinstalled to prevent build-up of material within the Detector. The Elutriator is aninertial particle separator that allows air to flow freely through it while separating outlarge particulate by allowing them to accumulate on an impact plate. It has anoptional foam insert that can be fitted in place of the impact plate and screens forapplications where if the detector is likely to be exposed to any atomised liquids orsteam.
The airflow travels into the Elutriator and hits the impactor momentarily slowing theairflow. This slowing of the airflow causes the larger, heavier particles to drop outallowing the smaller, lighter smoke particles to travel through the slots to thedetector.
FlushSample Point
Mini SamplePoint
End CappedSample Point
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Fig 2-1 Elutriator (union adaptors omitted for clarity)
The main benefit of the Elutriator is to allow the HART Mini to operate within areaswhere background contamination may be a problem. It should be checked andcleaned regularly to ensure correct operation.
2.2 STRATIFICATION
Stratification is an important issue, which needs to be considered when designing thepipework layout. It occurs were there are differing temperature gradients within aprotected area and it is commonly associated with high ceiling rooms, atria orwarehouses - particularly where above ground heating or sky lighting are installed.
The air temperature within the area increases with height and this can create athermal barrier preventing the smoke rising up to the sampling point. Aspiratingsystems can compensate for this by sampling at various levels within the room. Thisis done by dropping vertical sample pipes, having sample points spaced at 3 metres,see figure 2-2.
Consideration needs to be given to the practical installation of vertical pipework.Ideally sample pipe should be within the racking. Care needs to be taken to ensurethe pipework is not obstructed or damaged. Alternatively, horizontal pipes can be runat different heights within the racking.
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Fig 2-2 Stratification
2.3 PRESSURE DIFFERENTIALS
It is important when installing a HART Mini to take the pressure within the protectedarea into consideration particularly where the unit is installed outside of the area ofprotection or where more than one area is covered by one detector.
The HART Mini unit should always be installed in an area where the pressure is thesame or negative with respect to the protected area. Where the unit is located in apositive air pressure relative to the protected area, the detector should be exhaustedback into the protected area.
3. SYSTEM EXAMPLES
This manual has covered the design information and applications for the HART MiniHSSD system. This chapter details examples of typical system designs. Theexamples used here are taken from the pre-engineered designs shown in appendixA.
3.1 System Design ‘D’
System D is a typical standard sampling pipe network used in ceilings and roof andfloor void applications. The example design has been configured using a single pipedesign with three sampling points.
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Fig 3-1 System Design D
SamplePoint
Location
SamplePoint size
1 6mm2 7mm3 7mm
NOTE
• For ceiling, roof and floor void sampling, the sample holes need to be positionedfacing down.
• All sampling pipe and sample points should be identified using an appropriatelabel such as provided in Kidde Fire Protection’s SnifferPipe range.
3.2 System Design ‘I’
System I is based on a double pipe design complete with 3 sampling holes on eachsample pipe run covering an area of 150m².
Sampling Pipe
Sample Point Location
DetectionUnit
2.5M
1
2
3
5M
5M
2.5M
5M
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Fig 3-2 System Design I
SamplePoint
Location
SamplePoint size
1 6mm2 7mm3 7mm
NOTE
• For ceiling, roof and floor void sampling, sampling holes need to be positionedfacing down.
• All sampling pipe and sample points should be identified using an appropriatelabel such as provided in Kidde Fire Protection’s SnifferPipe range.
Alternatively a two pipe system design, such as System I, can be used to cover aroom and a floor void, as shown below.
Sampling Pipe
1 2 3
2.5M
5M 5M 2.5M
DetectionUnit
2.5
5M
2.5
Sample Point Location
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Fig 3-3 Alternative System Design I
4. INSTALLATION
The sampling pipe network is an arrangement of pipes within the protected areathrough which air is drawn back to the HART Mini to be sampled. Piping may bemetallic or non-metallic. The designs provided within this design guide are based onusing 25mm pipe such as Kidde Fire Protection’s red ABS SnifferPipe, fittings andaccessories. Pipe and fittings in 32mm ABS are also available.
It is important to ensure that all joints are airtight and cemented to prevent anyleakage, as this would affect system performance. Joint integrity is greatly reduced ifsurfaces are not properly prepared and absolutely clean before cementing.
The pipework must be supported by appropriate pipe clips. The supports must bespaced to give adequate support to the pipework and long, straight sections must besupported at least every 1.5 metres. Short straight lengths of pipes between bendsmust be supported at least once. Pipework supports must not penetrate the pipewall.
DetectionUnit2.5
M1
2
3
5
5M
2.5
5M
Floor Void
Sampling
Sample Point Location
Sampling Pipe in Floor Void
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Figure 4-1 Sampling Pipe Support
4.1 Warning Labels
All sampling pipe and sample points should be identified using appropriate labels,such as provided in Kidde Fire Protection’s SnifferPipe range. If the pipe is notalready pre-printed, identification labels should be applied every 2 to 3 Metres. Asample point warning label should be attached at each sample point.
1.5 Metres
Pipe Clip Pipe Socket Pipe Clip
Sample Pipe
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Total No of
Sample Holes
Single or Double
Pipe
Sample holes / pipe
1 2 3 4 5 6 7 8 1 2 3 41 S 1 8.52 S 2 8.0 8.52 D 1+1 7.0 7.03 S 3 6.0 8.0 8.53 D 2+1 6.5 7.0 7.04 S 4 5.0 6.0 7.5 8.04 D 3+1 5.5 6.5 7.0 4.54 D 2+2 6.5 7.0 6.5 7.05 S 5 4.0 4.5 5.5 6.5 7.55 D 4+1 4.5 5.5 6.0 7.0 3.55 D 3+2 5.5 6.5 7.0 4.5.55.06 S 6 3.0 4.0 4.0 5.0 6.0 6.56 D 5+1 3.5 4.0 5.0 6.0 6.5 3.06 D 4+2 5.5 6.5 7.0 8.0 5.0 5.06 D 3+3 5.5 6.5 7.0 5.5 6.5 7.07 S 7 3.0 3.0 3.5 4.0 4.5 5.0 6.07 D 6+1 3.0 3.5 4.0 4.5 5.5 6.0 3.07 D 5+2 4.5 5.0 6.0 7.0 7.5 4.0 4.07 D 3+4 4.5 5.5 6.0 7.0 4.5 5.5 6.0 7.08 S 8 3.0 3.0 3.0 3.5 4.0 4.0 4.5 5.08 D 7+1 3.0 3.0 3.0 3.5 4.0 4.5 5.5 3.08 D 6+2 4.0 4.5 5.0 5.5 6.0 7.0 3.5 3.58 D 5+3 4.5 5.0 6.0 7.0 7.5 4.0 4.0 4.58 D 4+4 4.0 5.0 6.0 7.0 4.0 5.0 6.0 7.0
