Use of safety Barrier

[ykbhatnagar]

Can anyone tell me , when should we use the IS barrier in intrumentation loop,? if the instrument is EXia then also we can uses this IS barrier?

[kuo]

p+f PEOPLE HELP YOU

[prajule]

The intrinsic safe is a low energy signalling technique that prevents explosions from occurring by ensuring that the energy (i.e. voltage, current and power is restricted) transferred to a hazardous area is well below the energy required to initiate an explosion.

The Ex i (ia/ib/ic) certificate of transmitter ensure that all components of transmitters (i.e. which are capable to store the energy ) and wiring which is incapable of releasing sufficient electrical / thermal energy under normal or abnormal condition to cause ignition of atmospheric mixture in its most easily ignited concentration (i.e. hazardous area classification).

Safety barriers is installed in the non hazardous or safe area between the control room (DCS/PLC system) and field device (transmitters) which blocks dangerous energy from being transmitted from the control room to the hazardous area. This energy could be from a power supply, stored in capacitors, stored in inductors, or some combination of the three. This energy could be released due to some combination of faults (open circuit, shorts, grounds, etc) occurring in the system (complete loop from field device to control room is known as system).

There two types of safety barriers generally as mentioned below

1. Active Barriers: Used for complete signal isolation between the field device and control room and vice-versa. Complete isolation achieved by opto-isolator/couplers or transformers (also called galvanic isolation). Active barrier requires an external power (24VDC, 230VAC) and typically drive larger loads than a loop powered zener barrier. It does not require any IS ground connection (i.e. earth bar). That’s why this preferred choice of barrier where high quality IS grounding point is not available.

2. Passive Barriers: Passive barrier cannot isolate the signals from the field device to the control room and vice –versa. Passive barrier generally contains zener diode and series resistor and fuses circuit which diverts potentially dangerous energy to ground before it can reach the hazardous area. It requires separate IS ground connection to avoid ground loop problem. The zener diodes limit the fault voltage to the hazardous area. There are two such diodes for redundancy. The series resistor limits current to the hazardous area. Passive barrier is powered by the loop (i.e. loop powered) and it has a current limiting resistor, it has a voltage drop across it.

[marcoco]

Muchas Gracias de gran utilidad

[Sufia]

nice explanation. thanks

[hasanbarim]

The intrinsic safe is a low energy signalling technique that prevents explosions from occurring by ensuring that the energy (i.e. voltage, current and power is restricted) transferred to a hazardous area is well below the energy required to initiate an explosion.

The Ex i (ia/ib/ic) certificate of transmitter ensure that all components of transmitters (i.e. which are capable to store the energy ) and wiring which is incapable of releasing sufficient electrical / thermal energy under normal or abnormal condition to cause ignition of atmospheric mixture in its most easily ignited concentration (i.e. hazardous area classification).

Safety barriers is installed in the non hazardous or safe area between the control room (DCS/PLC system) and field device (transmitters) which blocks dangerous energy from being transmitted from the control room to the hazardous area. This energy could be from a power supply, stored in capacitors, stored in inductors, or some combination of the three. This energy could be released due to some combination of faults (open circuit, shorts, grounds, etc) occurring in the system (complete loop from field device to control room is known as system).

There two types of safety barriers generally as mentioned below

1. Active Barriers: Used for complete signal isolation between the field device and control room and vice-versa. Complete isolation achieved by opto-isolator/couplers or transformers (also called galvanic isolation). Active barrier requires an external power (24VDC, 230VAC) and typically drive larger loads than a loop powered zener barrier. It does not require any IS ground connection (i.e. earth bar). That’s why this preferred choice of barrier where high quality IS grounding point is not available.

2. Passive Barriers: Passive barrier cannot isolate the signals from the field device to the control room and vice –versa. Passive barrier generally contains zener diode and series resistor and fuses circuit which diverts potentially dangerous energy to ground before it can reach the hazardous area. It requires separate IS ground connection to avoid ground loop problem. The zener diodes limit the fault voltage to the hazardous area. There are two such diodes for redundancy. The series resistor limits current to the hazardous area. Passive barrier is powered by the loop (i.e. loop powered) and it has a current limiting resistor, it has a voltage drop across it.

As an addition to the clear explanation above ,

If you have Smart Hart IS( Ex i( a/b/c) you should use active isolators which will make HART communication available.

Also there are some Non IS galvanic active isolators which are being used for Non IS I/Os ( like motorized valve digital signals or auxillary circuit field electrical local panels which 400 Vac /690 Vac ) and protecting your system galvanically

You can check also from MTL