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MAN3041-1 

 

 

 

 

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Orbis IS Adaptor  

An  adaptor  is  available  which  enables  Orbis  detector  heads  to  be  fitted  to  existing  Series  60  IS  bases  in 
order to upgrade systems with minimal disruption. 

The  existing  system  should  conform  to  ATEX  Certificate  No.  Ex97D2054  SYST.  The  IS  Adaptor  is 
distinguished by the 

markings “part of 

intrinsically 

safe fire detector Baseefa06ATEX0007X”.

 

10

 

System Design 

The  design of an intrinsically safe  fire detection system should only be  undertaken by engineers familiar 
with codes of practice for detection systems and hazardous area electrical systems. The relevant standards 
are BS5839: Part 1, BS EN 60079-14:2003 respectively. 

The fire detection performance of the Orbis I.S. range is the same as that of its standard counterparts but 
some  electrical  parameters  are  different.  Please  use  the  technical  data  given  in  this  guide  for  Orbis  IS 
devices. Performance information given in the Orbis Product Guide is applicable to the Orbis I.S. range. 

The  BASEEFA certification of the  I.S. devices  covers their characteristics as components of an intrinsically 
safe system and indicates that they can be used with a margin of safety in such systems. 

10.1

 

Types of safety barrier 

The  certified  system  configurations  allow  for  two  types  of  safety  barrier,  each  of  which  has  its  own 
advantages and disadvantages. A brief outline of their characteristics is given below. 

Single Channel 28V/300

Ω 

Barrier 

This  is  the  most  basic  type  of  barrier  and  therefore  the

 

lowest  in  cost.  Being  passive  devices,  they  also

 

impose the minimum of restrictions on the operation of the fire detectors. Thus, single channel barriers are 
available  either  as  positive  or  negative  polarity  where  the  polarity  refers  to  the  polarity  of  the  applied 
voltage relative to earth. The significance of this is that one side of the barrier must be connected to a high-
integrity (safety) earth. Although this earth connection has no effect on the  operation of Orbis IS devices 
and is not needed for their correct operation, it may not be acceptable to the operation of the control and 
indicating equipment. If the earth connection is not acceptable then the isolating barriers should be used. 

Galvanically Isolated Barrier 

Galvanically isolated barriers. These are also referred to 

as “transformer isolated d.c. repeaters”, “isol

ating 

interfaces”  and  “transformer  isolated  current

 

repeaters”.  They  differ  from  conventional  shunt  zener

 

barriers in that they provide electrical isolation between the input (safe area) and the output (hazardous 
area).  This  is  achieved  by  the  use  of  a  D.C./D.C.  converter  on  the  input  side  which  is  connected  to  the 
hazardous area through a voltage and power-limiting resistor/ zener combination similar to a conventional 
barrier. 

The  galvanic isolation technique  means that  the  circuit does  not need a high integrity (safety) earth and 
that  the  intrinsically  safe  circuit  is  fully  floating.  Earth  leakage  problems  for  control  and  indicating 
equipment are therefore eliminated if this type of interface is used. 

Note: Although the circuit does not require a high integrity earth, it is permissible to earth either side of the 
hazardous area circuit if required by other system considerations. 

Summary of Contents for Ampac Orbis IS ORB-OP-52027-APO

Page 1: ...Fire detection and evacuation solutions that save lives Orbis IS Product Guide MAN3041 1...

Page 2: ...nviornmental Performance 11 6 4 Technical Data 12 7 Orbis IS Heat Detector 13 7 1 Where to use heat detectors 13 7 2 Choosing the correct class of heat detector 13 7 3 How does Orbis IS heat detectors...

Page 3: ...detectors which has been developed from the standard range of Orbis smoke and heat detectors Orbis IS is a range with modern styling and a TimeSaver IS base It is electrically compatible with Series 6...

Page 4: ...uipment Regulations 1999 Detectors have been declared as being compliant with the essential requirements of the EMC Directive 98 336 EEC the Construction Products Directive 89 106 EEC and the ATEX Dir...

Page 5: ...tion and cable termination Wide operating temperature range StartUp for fast commissioning DustDefy housing which limits ingress of dirt into detector New optical sensor for high reliability reduced f...

Page 6: ...of optical detectors in the standard test fires described in the European standard EN54 7 2000 The results of these tests are given in Figure 1 The graph shows the acceptable response in terms of smok...

Page 7: ...een Orbis Optical Multisensor How are heat detectors classified EN54 5 2000 classifies heat detectors according to the ambient temperature in which they will be working An additional classification ma...

Page 8: ...MAN3041 1 8 So what is the best way to choose a heat detector To make things easier we have produced a flow chart to help you decide Figure 3 Choosing a Heat Detector...

Page 9: ...ensation for slow changes in sensitivity Extra confirmation of smoke before alarm signal given The algorithms are used to verify signals from the sensing chamber to filter out transients and to decide...

Page 10: ...20 seconds Minimum detector active voltage 12V dc Switch on surge current 105 A at 24V dc Quiescent current 85 A at 24V dc Alarm load 325 in series with 1 0V drop Material Detector and base moulded i...

Page 11: ...reas where the fire risk is likely to include heat at an early stage in the development of the fire As with Orbis IS optical smoke detectors the increased reliability of detection is combined with hig...

Page 12: ...A at 24V dc Alarm load 325 in series with 1 0V drop Material Detector and base moulded in white polycarbonate Alarm Indicator Integral indicator with 360 visibility Dimensions and weight of detector...

Page 13: ...er possible since smoke detection provides earlier warning of fire than heat detection There are however limits to the application of smoke detectors and these are described in the section 4 Choosing...

Page 14: ...midity unless specified otherwise Detector operating principle Measurement of heat by means of a thermistor Sampling frequency Once every 2 seconds Supply voltage 14 28V dc Supply wiring 2 wires polar...

Page 15: ...re positive IN positive OUT negative IN and OUT common terminal remote LED negative connection functional earth screen The terminal screws are captive screws and will not fall out of the terminals The...

Page 16: ...ovided It is not necessary for the correct operation of the detector nor is it provided as a termination point for a safety earth If screened cable is used screen continuity should be maintained and t...

Page 17: ...ts for 4 minutes so it may be necessary to reset or de power the circuit to allow all detectors to be observed The LED status is the same as method 1 above 8 3 Orbis LED Status Indication Feature Desc...

Page 18: ...ng passive devices they also impose the minimum of restrictions on the operation of the fire detectors Thus single channel barriers are available either as positive or negative polarity where the pola...

Page 19: ...max out 93 3mA W max out 0 67W In any safety barrier used the output current must be limited by a resistor R such that I max out Uz R A number of shunt zener diode barriers meet this specification and...

Page 20: ...The connection must be such that the impedance from the connection point to the main power system earth is less than one ohm Intrinsically safe circuits in the hazardous area should be insulated from...

Page 21: ...ulate the total capacitance or inductance for the length of cables in the hazardous area refer to Table 5 which gives typical per kilometre capacitance and inductance for commonly used cables Note All...

Page 22: ...at segregation be provided between the IS and non IS circuits A distance of at least 50mm must be preserved between live conducting parts of IS and other circuits If the enclosure is used as part of a...

Page 23: ...eCatalogue Note that the earth terminal in the base is provided for convenience where continuity of a cable sheath or similar is required It is not necessary for the correct operation of the detector...

Page 24: ...should be carried out as recommended by the code of practice BS 5839 Part 1 or other local regulations in force 17Achnowledgement All Orbis IS detectors and products are manufactured for Ampac by Apo...

Page 25: ...MAN3041 1 25 AMPAC TECHNOLOGIES UNCONTROLLED DOCUMENT NOTE Due to AMPAC s commitment to continuous improvement specifications may change without notice...

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