I am in the process of ordering a Siemens SITRAN MAG 6000 I EX d flow transmitter

The marking is as follows
EEx de [ia] ia [ib] II C T6. This is the exact marking

I understand that this is Flameproof. Now do i have to install a isolation barrier with this or i can directly take the analog input to PLC. There is no requirement to have intrinsic safety.

 

First, you need to read the certification documents and manufacturer's information to find out exactly what circuits are covered by each method of protection. I have had a quick look at the Siemens site and it quotes a certificate no "Sira 11ATEX2124X" - ending in X indicates that special conditions apply. It would appear that the unit you have is a "remote" type, with the transmitter located apart from the flow tube\, so there are circuits between the transmitter and tube, and between the transmitter and receiving device.

In general, the brackets around [ex ia] indicate that the apparatus is capable of supplying energy to the external circuit -as you would expect if it is a two-wire self-powered circuit (the power coming from the Ex de circuitry). If you are connecting the output from the transmitter to another device such as a PLC input module that could also become a source of energy into the wiring in the hazardous area, that end of the loop also needs energy limiting such as a barrier.

If the transmitter is not installed in a hazardous area, and the connecting cables also are not run through a hazardous area, then you don't need energy limiting.

Hope this helps.

Bruce.

 

In this system since the PLC is in the Explosion proof enclosure Exd enclosure chosen is very small. so when the IS cable enters the panel i am finding it impossible to ensure 50mm space segregation between the IS cable and the non IS cable within this enclosure. The cable from the Panel to the point it terminates to the instrument is properly segregated. The problem is inside the panel. The isolator terminal itself are 50mm away from the nearest any power source or cables.

I am thinking that since the length of cable where segregation distance of 50mm is not being maintained is short(in Centimeter)this should not be an issue. Would that be a correct statement. If not is there a work around.

 

The first thing is that you need to find out exactly what specific codes and standards are applicable in your situation - my information is based on IEC60079.11 but other documents or a modified version of this may apply. Also talk to the person who will be inspecting or checking the final installation for compliance - they may have a specific interpretation of wht you have to do.

To get back to first principles - the main objective is to make sure the system is safe - and in this case that means that the energy from the non-IS circuits can't get into the protected IS wiring. While 50 mm segregation between IS and non-IS services is the accepted norm, you can also achieve compliance by maintaining an earthed metal barrier between the two types of circuit. But if you can't meet the 50 mm requirement because of space limitations, you probably can't fit a metal barrier either. As the enclosure is Ex d, you cannot simply add internal partitioning without getting the result re-certified.

My question at this stage would be - what else about the installation is not up to the requirements of the application - specifically the fact that it's in a flammable atmosphere.

If you are the end-user in all this, it is not really your problem - you need to make sure that the equipment provided is fully compliant. While there may be a lot of pressure on you to accept something that is non-compliant, you may well be the nearest target later on if something does go wrong.

 

you can go without barrier, but will need a 250 ohm register across instrument. better to go with barrier for the sake of simplicity.

 

Rashid,

You need to be little bit careful with this instrument. There are various parts of the mag flow sensor and transmitter that has achieved various certification. What I have found from manufacturer's website that the transmitter 6000 has achieved Atex Exd (EN 60079-1), Ex-e (EN60079-7) and Ex-i (EN 60079-11)certification. You need to discuss with manufacturer and review the detailed certificate to understand which part has achieved what certification? From the catalogue the keypad and LCD display are Ex-i certified to able them to operate in hazardous area. The transmitter needs separate power supply. It seems to me the power supply module is in Ex-d enclosure. However, I am not sure about transmitter output module. Most probably that is also in an Exd enclosure and you need not install any barrier in the safe area. But this you have to confirm with the manufacturer.
Another interesting point is this transmitter and 3100-ex sensor have achieved Class 1, Zone-2 certificate only from FM and CSA. According to FM certificate they are considering this as "non-incendive" equipment. Definitely if you are going to use this instrument in USA or Canada, you can't use it in Zone-1 or Div. 1 area.

From my experience of similar type of equipment, I have seen normally from the senor to transmitter - there are various protection technology which are taken care of by the manufacturer. If you put the transmitter as integral unit or remote nearby in the hazardous area, you need not do anything else. From transmitter to control room, normally the power supply and signals both are coming from Exd enclosure and there is no separate barrier is required.

 

Since in the IS loop i am using Active barrier, which means i do not need the dedicated IS Ground. But if the IS cable is shielded I can terminate this to the standard instrument earth. Please confirm this.

Secondly with regards to capacitance and Inductance of the Cable, does a shielded cable increase or decreases the capacitance or inductance of the cable.

regards
Rashid iQbal