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I need confirmation that if a diagnostic inst is intrinsically safe, is it also explosion proof?
B
bob peterson
They are two different protection means used in classified areas.
IS means the circuit itself is "safe". Not just the device.
XP refers just to the device.
An XP device could be part of an IS circuit. It might be pointless,
but it is possible.
--
Bob
IS means the circuit itself is "safe". Not just the device.
XP refers just to the device.
An XP device could be part of an IS circuit. It might be pointless,
but it is possible.
--
Bob
B
Bruce Thompson
No. An intrinsically safe component is not necessarily explosion proof.
An intrinsically safe component is a tested piece of equipment of low power that cannot cause an explosion in a hazardous environment.
An explosion proof component is a tested piece of equipment that will prevent an explosion within the component from causing an explosion outside of the equipment.
An intrinsically safe component is a tested piece of equipment of low power that cannot cause an explosion in a hazardous environment.
An explosion proof component is a tested piece of equipment that will prevent an explosion within the component from causing an explosion outside of the equipment.
B
Bruce Durdle
There is no reason why an intrinsically safe device has to be explosion proof. An IS circuit is designed so that it cannot release sufficient energy into a flammable atmosphere to cause ignition - this energy is restricted by limiting voltage and current; and placing upper limits on the total capacitance and inductance in the circuit.
An explosion-proof or flameproof device has no limitations on energy, and this protection method can be used for high-voltage or high-current applications, as well as for devices with high levels of inductance or capacitance. The basic principle of an explosion-proof device is that ignition can occur within an enclosure but the effects are confined to the enclosure and cannot propagate through flange faces or other openings to the outside atmosphere.
So just because a device is intrinsically safe does not mean it will also be explosion-proof. You may find equipment with dual certification which means it has incorporated the requirements of both methods of protection.
Bruce.
An explosion-proof or flameproof device has no limitations on energy, and this protection method can be used for high-voltage or high-current applications, as well as for devices with high levels of inductance or capacitance. The basic principle of an explosion-proof device is that ignition can occur within an enclosure but the effects are confined to the enclosure and cannot propagate through flange faces or other openings to the outside atmosphere.
So just because a device is intrinsically safe does not mean it will also be explosion-proof. You may find equipment with dual certification which means it has incorporated the requirements of both methods of protection.
Bruce.
J
Jerry Miille
What a great, clear and concise explanation! Thank you very much Bruce!
Jerry Miille
Miille Applied Research Co., Inc.
http://www.miille.com/
Jerry Miille
Miille Applied Research Co., Inc.
http://www.miille.com/
J
Jonas Berge
Keep in mind that the system/loop has to be designed for one or the other. If the system/loop was designed for explosion proof you need to use an explosion proof device. If the system/loop was designed for intrinsic safety, you need to use an intrinsically safe device.
You can't put an intrinsically safe device (without explosion proof certification) on an explosion proof system/loop because such an installation has no safety barrier, wiring separation, and cable color etc.
You can't put an explosion proof device (without intrinsic safety certification) on an intrinsically safe system/loop because such an installation does not have conduit, potted seals, armored cable, and explosion proof junction boxes etc.
Cheers,
Jonas
You can't put an intrinsically safe device (without explosion proof certification) on an explosion proof system/loop because such an installation has no safety barrier, wiring separation, and cable color etc.
You can't put an explosion proof device (without intrinsic safety certification) on an intrinsically safe system/loop because such an installation does not have conduit, potted seals, armored cable, and explosion proof junction boxes etc.
Cheers,
Jonas
B
Bruce Durdle
Jonas said:
...
> You can't put an explosion proof device (without intrinsic safety certification) on an intrinsically safe system/loop
> because such an installation does not have conduit, potted seals, armored cable, and explosion proof junction boxes etc.
An explosion-proof device will generally be self-contained and may be certified as explosion-proof (or flameproof Ex d in the IEC world). It cannot be used as part of an Intrinsically Safe system as the energy storage parameters will not be certified. This also applies to Ex e or Ex n apparatus - but connecting non-IS certified components into an IS loop is still a major area of non-compliance.
There is one exception. An explosion-proof switch with no other electrical connections can be treated as "simple apparatus" and connected into an IS circuit on the basis that it will not store or generate sufficient energy to cause ignition. Where both types of protection are in use, this simplifies spares holdings etc. In this case, my recommendation is that the items installed on an IS loop are clearly marked to distinguish them from those where protection relies on the explosion-proof features of the switch.
...
> You can't put an explosion proof device (without intrinsic safety certification) on an intrinsically safe system/loop
> because such an installation does not have conduit, potted seals, armored cable, and explosion proof junction boxes etc.
An explosion-proof device will generally be self-contained and may be certified as explosion-proof (or flameproof Ex d in the IEC world). It cannot be used as part of an Intrinsically Safe system as the energy storage parameters will not be certified. This also applies to Ex e or Ex n apparatus - but connecting non-IS certified components into an IS loop is still a major area of non-compliance.
There is one exception. An explosion-proof switch with no other electrical connections can be treated as "simple apparatus" and connected into an IS circuit on the basis that it will not store or generate sufficient energy to cause ignition. Where both types of protection are in use, this simplifies spares holdings etc. In this case, my recommendation is that the items installed on an IS loop are clearly marked to distinguish them from those where protection relies on the explosion-proof features of the switch.
