What is Intrinsically Safe?
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- เผยแพร่เมื่อ 22 พ.ค. 2024
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⌚Timestamps:
00:00 - Intro
01:10 - Risk assessment
01:48 - Intrinsically safe levels
02:44 - How to apply standards
02:51 - Barriers
03:56 - Examples
05:48 - Decreasing the dust
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In this video, we will explain what it means to be intrinsically safe. We will explain why being intrinsically safe is important to an automation professional.
We will also explain where intrinsic safety should be considered. Then we will provide a few examples of how to design intrinsically safe circuits.
Intrinsic safety has to do with preventing fires that could occur because of sparks or heat sources.
Being intrinsically safe in an electrical sense means restricting the current flow or preventing sparks in a hazardous environment.
An intrinsically unsafe environment could cause a fire or even an explosion by something as simple as a wire being cut. We need to be aware of the environment we are working in, especially when working in potentially hazardous environments.
If you are working in or around hazardous environments, it is imperative that a risk assessment is done to help identify the risks. Knowing the risks in any environment will help you mitigate those risks and keep you and others safe.
There are two main types of classifications:
- ATEX,
- NEC (NFPA70).
We will focus on the UL (Underwriters’ Laboratories) standard for intrinsic safety.
There are three main types of NEC 70 intrinsically safe levels: Class I, Class II, and Class III.
- The Class I environment has to do with flammable gasses and vapors. These vapors could be gasoline, hydrogen, natural gas propane, ethanol, or methane. These gasses exist under normal operating conditions and abnormal operating conditions.
- The Class II environment has to do with combustible dusts. Some possible dusts include metal and metal alloys, charcoal, carbon black, flour, plastics, grains, and wood. These dusts exist under normal operating conditions and abnormal operating conditions.
- Class III has to do with flying objects or fibers.
In intrinsically safe environments it is necessary to use special circuits to help protect from explosions and fires. Electrically speaking we do this by using optic isolation or by current-limiting devices. The industry term is a barrier.
Barriers come in many shapes and sizes but they all optically isolate the sensor in the environment from the electrical cabinet.
An optic isolator is a set of electrical components that connect two circuits optically. The components of an optic isolator are a diode and a light-sensitive transistor usually packaged in a chip.
Because of optic isolation different voltages can be used, which helps in an environment that needs intrinsic safety devices.
In some situations, there will need to be more done with the electrical panel than just installing barriers.
The panels in the room with the flour conveyor will need to be pressurized with some sort of compressed gas. This is usually compressed air, which causes positive pressure on the panel and decreases the likelihood of the flour dust getting in the panel.
Because of the compressed air, each panel will need to be sealed with some sort of putty or sealant.
To follow the Class II, DIV 2 standard pressure switches will need to be installed.
When a panel is opened, the switches will turn on a red strobe light, alerting those working nearby that the room is unsafe.
When designing a Class II, DIV 1 panel there are more restrictions. DIV 1 refers to the presence of a hazardous atmosphere under abnormal operating conditions.
Just like the Class II, DIV 2 environment, a Class II, DIV 1 will need pressure switches for loss of pressure and they will additionally need to remove line power to every panel in the room when the pressure is not safe.
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#RealPars #IndustrialSafety #IntrinsicSafety
Clear, simple and straightforward basic explanation of the main aspects and concepts of intrinsic safety. Congratulations!
Just a small conceptual comment: Both "classified" and "unclassified" areas need to be considered and deemed as "SAFE".
Electrical, automation and instrumentation installations, in both cases, need to use equipment with appropriate "Ex" protection types (in classified areas) or associated equipment (in non-classified areas), in addition to performing the applicable installation, inspection and maintenance "Ex" service procedures, according to IEC 60079-14 and IEC 60079-17. 👍
Thus, it is suggested to use the term "UNCLASSIFIED AREA" or "NON HAZARDOUS AREA" instead of "SAFE AREA".
Absolute brilliance! Teaching this to new apprentices and time and time again I find exactly what I am teaching right here at RealPars - Thank you
You're very welcome!
Thank you Realpars. You are doing great!
Glad you like them!
For your example division two actually refers to the presence of a hazardous atmosphere under abnormal operating conditions such as maintenance
Did they flip flop Div 1 and 2 (normal vs abnormal) in this video?
I can’t remember where I read it but it said that Div.2 is presence of a hazardous atmosphere less that 6 hours per year which means emergencies only and Div.1 is over 6 hours per year.
I agree; I also think that they got it switched with Division 1.
4:29 Division 2 means particles present during ABNORMAL operations.
Very useful as usual from RealPars
Glad it was helpful!
another interesting video thanks real pars
Glad you enjoyed it! Happy learning
High quality content ❤️
Thank you, Nikolas!
Thank you!
You're welcome!
Highly recommended videos 🔥
Thank you, Amino!
Hello, the video was really helpful in understanding intrinsic safety in a context of plc control system. But, I have something to clarify. It was said in the video that Div 1 is for environment where combustible dust is present during abnormal conditions. I think abnormal is for Div 2. Would like if you can give clarification on this. Thank you
Correct. Div 1 conditions exist where the hazard is normally present. Div 2 is when the hazard exists under abnormal conditions.
Another interesting video on safety. Is Siemens ET 200iSP better to use in the field as DP compared with the inc. safety barriers?
The ET200iSP I/O cards have IS barriers built into the I/O card. It is a matter of convenience and cost to use the ET200iSP system versus a standard PLC I/O card with external IS barriers. Remember, that all systems placed into or interfacing with Zone 1, Zone 21, or Class 1 Div 2 or Class 2 Div 2 areas, must be designed for the appropriate level of protection from the field instrument through to the PLC or DCS. Just installing ah IS barrier or ET200iSP system is not alone sufficient to ensure safe operation.
Very Nice!
Thank you!
i always isolate the inputs and outputs between the panel and the field
Thanks
You're welcome!
You mentioned at the start, that the video would show how to DESIGN a circuit which is intrinsically safe? Is this video demonstrating the LOOP concept (follow the manufacturer certification exactly) and ignores the ENTITY circuit calculations?
What about the requirements for the circuit calculation, the entity parameters, cable capacitance and inductance? The number of times I’ve had near misses from sub contractors, mistakenly thinking, that when they pick a barrier which will power a device in the field also means it’s safe for the hazardous area is beyond frustrating (at times has lead to follow up action with their employer when competency is an issue). Also, would it not have been easier just to say the barrier must be installed in a safe area rather than give a specific example of a purged panel which achieves this?
@fitz83 Our short videos 9n TH-cam are meant to introduce viewers to concepts used in the automation industry. Entity circuit calculations are quite a bit more involved than what our short videos can cover. And yes, in hindsight, placing the panel in a GP area would have simplified the discussion.
Whats the difference between Ex d and Ex i? What are the applications?
Also all barriers will need a photo eye?
A simplified answer is that Ex-ia sensors are classified as Category 1G/1D equipment, for installation in Zone 0, 1, or 2 and 20, 21, and 22 areas. Ex-d sensors are classified as Category 2G equipment, for installation in Zone 1 or 2 and 21 or 22 areas. Ex-ia sensors (such as a tuning fork level switch) can be installed in a tank with hazardous material , whereas an Ex-d sensor cannot be installed in that location.
so for 4-20 mA we can use a zenner barier and for discrete signals we can use isolated barier? Thank you!
Hello GameLover!
Thank you for your question! Unfortunately, I can’t fully assist as it is not in the contents of our video, as we discuss in Intrinsic safe example 1. But it is a valid question. To help you with your question, here is a head start. Here are 2 links to manufacturers that might be able to help you with these devices you are asking about.
0-10v, 4-20ma intrinsic safety barrier Zener barrier explosion-proof safety
www.alibaba.com/product-detail/0-10v-4-20ma-intrinsic-safety_62468731323.html
www.pepperl-fuchs.com/usa/en/classid_14.htm
Signal Converters - Intrinsic Safety Barriers
Happy learning from RealPars!
What about intrinsic safety for wireless loops? Does the receiver has to comply with IS regulations too?
The short answer to your question is YES. Every part of the "circuit" must be analyzed to insure that the maximum radiated energy does not exceed the threshold for IS installations. A good summary can be found at: www.controlglobal.com/articles/2019/how-to-ensure-intrinsic-safety-for-wireless-systems/. Most wireless installations do not exceed the 2W limitation for the most stringent Group IIC environments, and when installed properly (in Ex d enclosures, for example), can be used in hazardous areas without modification.
Realpars, please what's the difference between this video vis-a-vis IS vs Non-IS cables?
Intrinsically safe cables are designed to be UV and weather-resistant and conform to certain ISI standards. Cables that are installed in IS service should have blue jacketing/insulating covering to distinguish the cables from those installed in non-IS circuits. In many cases, the type of connection made in the hazardous area is restricted to eliminate the possibility of arcing (as with quick-disconnect cables).
@@realpars Thank you RealPars.
Definitely for Electrical control engineering and technicians
Thank you!
On minutes 5:00 when photo-eye ON it will turn on a diode. Where is the power from? Is there any battery inside photo-eye?
The power (usually 12VDC or 24VDC) comes from the PLC card it is attached to, or in some cases, an external power supply. Photo eyes do need a power source.
@@realpars But on the video 05:00 the circuit only connected with light diode to PLC. Is there any other wire to photoe eye to carry 24VDC?
👍
Sir please make videos on mitsubishi plc
Thanks for your topic suggestion, Nikhil!
🔥🔥🔥
Hello
What beautiful animations!
What software do you use to make these animations?
Thank you @RealPars
Thank you! I am actually not sure, as the animations are created by our graphic and animation department.
What happens if the field instrument is not ATEX certified?
If an instrument is not ATEX certified, then there is no guarantee that the construction of the instrument and its circuitry will provide the level of protection against flammable hazards that may be required.
@@realpars even if it’s a simple device
I wish the video in Arabic would be much easier
Hi Jeremy,
Thanks for your comment! We currently only provide our course videos in English, you are always able to turn on the English subtitles as that might make it a bit easier for you.