Galvanically isolated barriers (also know as transformer isolated barriers) 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. Galvanically Isolated Barrier

Intrinsically Safe Products

Technical Data

Intrinsically Safe Flame Detector (Polycarbonate Housing) Mechanical 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. Housing Material:
See figure 1 Stainless Steel & Glass Reinforced Polycarbonate Earth leakage problems for control and indicating equipment are therefore eliminated if this type of interface is used. Galvanically isolated barriers are widely used with conventional flame detector systems. If the system is of an addressable type with signal pulses on the supply lines then the response time of most standard barriers will be too slow to allow their use. In these applications special galvanically isolated barriers are required that can freely transmit the required protocol pulses without introducing severe voltage drops. These interfaces are available as single or dual channel versions and are recommended for any application in which direct earth connections are not acceptable. The galvanically isolated barrier is a two-wire device which does not need an external power supply. Current drawn from the detector supply connections by the barrier itself is less than 500µA. Housing Colour: Blue (typical) Housing Dimension: Height = 148mm Width = 110mm Depth = 63mm
(Excluding Mount) Cable gland Entries: 4 X 20mm Fig. 1 Electrical The flame detectors respond to light emitted from flames during combustion. The detectors discriminate between flames and other light sources by responding only to low frequency flickering produced by flames (typically 1 to 15Hz). The detectors ignore fixed light sources and rapidly flickering illumination predominantly produced by lighting. The flame flicker techniques have the advantage of still allowing the detection of flames through a thin layer of oil, water vapour, ice or dust. This makes these detectors particularly useful in industrial applications. Full details of the principles of operation, electrical description, and other detailed technical data are published in the products individual data sheet. Supply In: Voltage Current
Terminals 1(+) & 2(-) 14 to 30Vdc 2 to 30mA
See data sheet for detail Polarity sensitive

Approved Safety Barriers

Optional Input: Voltage Current 14 to 30Vdc 40µA For systems a generic specification for the barriers is as follows. Any shunt zener diode safety barrier certified and approved to meet the ATEX Directives or CENELEC / IEC standards. ATEX group and category
typ. @ 24V IN Having the following or lower output parameters. Max. output volts U
Polarity sensitive Terminals 3(+) & 4(-) Optional Output: Voltage Current
Terminals 3(+) & 4(-) o : = 30V Max. output current I 0V to
Supply In (O/C) II (1) G CENELEC / IEC marking [
o : = 100mA Max. output power P 2.4
mA typ .
Internally Limited o : = 0.65W A number of barriers meet this specification and examples are given below. Shunt 300 EEx ia] II C X 2 Shunt 300 Galvanic X 1 Galvanic X 2 Optional Relays Contact Ratings: Voltage Current 30Vdc. Max. 1 Amp. Max.
(associated apparatus) Resistive Loads Only Terminals 3 to 8 Supplier Type Polarity Mounting Technique Environmental Pepperl & Fuchs Ltd. 77 Ripponden Road, Oldham, Lancs. OL2 8PF UK www.pepperl-fuchs.com Z728 Z779 Z828 KFD0-CS-Ex1.51 KFD0-CS-Ex2.51 + + - DIN rail DIN rail DIN rail DIN rail DIN rail Shunt 300 Shunt 300 Operating Ambient Temperature: -20°C to +40°C(T4) -20°C to +85°C(T3) Shunt 300
Check detector limits X 2 Active 300 ATEX Approval Category , 4-20mA output

II 1 G

CENELEC / IEC MTL Power Court, Luton, Bedfordshire LU1 3JJ UK www.mtl-inst.com MTL7028+ MTL7728+ MTL7779+ MTL7706+ + + + + DIN rail DIN rail DIN rail DIN rail Shunt 300 Marking

EEx ia IIC T4

Apparatus Certificate Number BAS02ATEX1001 Table 5 Examples of safety barriers 8 5