We have an application which requires 5 PLC to be interfaced with oil/water probes in a groundwater recovery system. The wells probes need to be intrinsically safe. Is there a more cost effective method than using an individual intrinsic safety barrier for each probe position. Two probes per well, each with three positions (bottom, top, not in either). Thanks in advance

Stu

 

Hi,
Wenn you use Profibus DP with only one barrier then you can put several ET200iS Exi Modules directly behind this barrier. Every ET200iS system can built up with digital in-/output modules and Analog in-/output moduls, even HART Analog modules are present. When you can use Profibus DP (you need one or more Masters) then you can build it with one barrier.

This system is on the market and all components are there.
See "www4.ad.siemens.de/support/index.asp?lang=en":http://www4.ad.siemens.de/support/index.asp?lang=en {type everything together}, choose for "Product Support" "Contents" and wenn you choose this type by search "ET200iS" and you will find all information.

The handbook is also to find under ID 9416153, wenn you go to "Product Support" "Search for Manuals" and type in ET200iS or 9416153 then you can download the handbook to find all the details.

I hope that you have enough information to do something with it.

Best regards,
Lowiek

 

Hello Stu;
Another way to hook up your probes (if they generate digital outputs) could be AS-i Safety At Work protocol. On a standard AS-i master (many types of PLC now offer this interface, see: "www.as-interface.com":http://www.as-interface.com )

you set-up a standard slave network. On this network you can install a safety monitor (specialized slave module) and safety slaves hooked up to your probes; you then program the safety monitor to check signal levels from tthe probes and to react within 5ms to shutdown a motor, cut a relay, generate an alarm signal...
Do have a look at the AS-i web page.

Hope this helps,
Daniel Chartier

 

Depending on the plc you use, some, such as the modicon quantum offer i/o modules that are rated intrinsically safe. This is often less expensive than individual barriers, and reduces wiring costs signifigantly as well.

 

Thanks Daniel,

The hardware is in place already. It's AB 1794 flex i/o. We were wondering if there was a canned interface between the 24 VDC input card (ib-16) and the non explosion proof probes? Any help is appreciated.

Thanks

Stu

 

The Schneider Electric Quantum PLC range has a complete family of Factory Mutal / UL / CSA / SIRA approved Intrinsically Safe I/O modules which can interface to your field devices. These are:
RTD & TC Input 140 AII 330 00
Digital Input 140 DII 330 00
Digital Output 140 DIO 330 00
Analog 4-20 Input 140 AII 330 00
Analog Output 140 AIO 330 10

These can be placed in standard Quantum Racks and combined with any of the Quantum CPUs & communications options.

Regards
Michael

 

It's a good idea to look / contact pepperl and Fuchs (( "http://www.pepperl-fuchs.com/index_e.html":http://www.pepperl-fuchs.com/index_e.html )) They may be of Help to yourself.

Good Luck.

 

Thanks for the replies. The problem is the protocol is locked into DH+ and the hardware is AB remote I/O. Any ideas on an econmical intrinsic safety barrier or any other methods?

Thanks,

Stu

 

I didn't mentioned that this system can directly placed in Zone 1 with 1 barrier and a lot of intrinsik safe I/O.

Lowiek

 

IS barriers are pretty cheap. I don't see any obvious way to make it less costly. You might be able to get a barrier with more than one point on it, but this is really only saving on the amount of packaging, so is not likely to save you any substantial amount. I'd guess that IS barriers are probably priced more by insurance rates than anything else.

Bob Peterson

 

You can use I/S remote I/O systems. These have only one barrier, at the power input.

Check MTL, or Pepperel & Fuchs,

S. Landau
SPEC

 

I believe that this is the wrong kind of "safety". ASI-Safe is for "control reliable" safety, while the original message concerned "intrinsic safety".

The former is for preventing hazardous machine motion, while the latter is for preventing explosions or fires.

************************
Michael Griffin
London, Ont. Canada
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We have available a dual channel intrinsic safe barrier that we use for our deep well probes. Small size - din rail - most certifications. Call or email for more information.
Not on line yet - but basic deep well probe is at: "http://www.almegcontrols.com/Deep_Well_Probe.htm":http://www.almegcontrols.com/Deep_Well_Probe.htm

Thanks Bob Hogg

 

Depending on how exactly the probe works, either IS remote I/O or a simple multiplexer might be the solution to your problem. However not all
systems can cater for non standard inputs like conductivity probes so you might still end up using barriers. I suggest you contact your nearest
MTL rep for help ( "www.mtl-inst.com":http://www.mtl-inst.com )in finding an economic solution that works and that is safe.

Steve Yates