Small Scale PROFIBUS PA. Application story of a customer who has switched from Ex HART to IS PROFIBUS PA utilizing a multi-vendor solution - James Powell, Siemens Process, Canada

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Small Scale PA
Presented by: James Powell, P.Eng.

2. 20XX-XX-XX
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Agenda
•What has changed?
•The application
•The HART solution
•The problem with HART/ why PA
•The PA solutions
•How do the economics work out?

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What has changed?
Up until the last few years, the cheapest Profibus master was still
over a thousand £.
Then…
-HMS Ethernet to Profibus gateway (~450 £)
-S7-1200 micro PLC with Profibus interface (~500 £)
-IFAK gateways (~1200 £)
Plus, to link to PA, last year there were two manufacturers, now
there are 4:
-Siemens
-P+F
-Procentec
-IFAK
Profibus is not just for large applications anymore!

4. 20XX-XX-XX
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Application: Small Scale Oil and Gas

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The HART solution
Multi-drop HART
Used a HART to Modbus RTU converter (HCS by Moore
Industries)
3.6 mA
I total = 8*3.6 = 28.8 mA200 ohms
5.76 V
28V
22.24 V
Minimum Voltage for LR250 ~ 18.2 V
Results
90% of sites worked with the odd problem
9% of sites were problematic
1% of sites did not work at all

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Problem with HART
-Sizing the HART resister (having to modify it in cold weather
operation)
-HART waveform
3.6 mA
I total = 8*3.6 = 28.8 mA200 ohms
5.76 V
28V
22.24 V
Minimum Voltage for LR250 ~ 18.2 V

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Why Profibus PA?
Very robust physical layer
Easier to put together than multi-drop HART (no HART resister to size)
New features possible:
- IS wiring possible
- status information
- transparency to the instrument

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Robust Physical Layer - Examples
Jetso-Diesel Orange Sky
Univar Baker Petrolite

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Simple Wiring
Simple Trunk wiring
No fancy junction boxes
Simple terminal strips
No HART resister

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Flame-proof vs. Intrinsically Safe
 Rigid Conduit
 Epoxy Seals
 Expensive fittings
 Longer time to install
 Not very flexible
 More expensive
 Can’t do live service
 Not as safe
 Flexible cable
 Plastic cable glands
 Simple to install
 Safer (less prone to
human error)
 Live servicing
EX Proof
Costs $$
Intrinsically Safe

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Status Information is transmitted each time
BYTE 1 BYTE 2 BYTE 3 BYTE 4 STATUS
IEEE FLOATING POINT VALUE STATUS BYTE

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Transparency* to the Instrument is now possible with new hardware!
*Note: Transparency can be done with HART as well, but not with the hardware they were using

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1st Trial Site!
Picked the site that HART would not work at all
Replaced the LR250 HART heads with LR250 PA heads
Changed the wiring
Used simple terminal strips
It worked right away!
No repeats and a perfect waveform!

14. 20XX-XX-XX
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The current solution!
PROFIBUS Pa (31.25 K bit/s)
CLASS 1 DIV 1
PROFIBUS Pa (31.25 K bit/s)
GSM/GPRS Modem
Ethernet Switch
Micro-PLC (Schneider Electric)
SITRANS LR250
Anybus Gateway (Profibus master on
One side and Modbus TCP/IP server on the
Other side)
Siemens DP/PA Ex Couplers
Pactware with SITRANS DTM
INDUSTRIAL ETHERNET
MODBUS TCP/IP

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The current solution!

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Economics of PA and IS instead of Ex construction
Multi-drop HART (using Ex)
-Used cheaper gateway
-Had no transparency
-Expensive Ex fittings
-Because of Ex fittings, instruments
are hard to remove
- HART comms did not always work
Profibus PA (using IS)
-Used cheaper fittings
-Did not have be careful with conduit
-Had a more expensive gateway
-Required couplers
-Instruments were slightly more expensive
-Had transparency
-Worked!
For their typical application, the Profibus solution was only between 15% and 20% more expensive
then HART multi-drop, but cheaper when you take into account that:
- Profibus worked!
- Transparency could reduce site visits
- if you have to change an instruments, it was now easy!

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Alternate Solution
PROFIBUS Pa (31.25 K bit/s)
CLASS 1 DIV 1
PROFIBUS Pa (31.25 K bit/s)
GSM/GPRS Modem
Micro-PLC
Ethernet Switch
IFAK IsNet Lite with Modbus and PA module
Pactware with SITRANS DTM
LR250
This has a lower capital costs
Profinet

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Contact
James Powell
Business Developer
Process Instruments / Siemens Canada
1954 Technology Dr.
Peterborough, Ontario, Canada, K9J7B1
Phone: +49 (123) 45 67 89
Fax: +49 (123) 45 67 89
Mobile: +49 (123) 45 67 89 0
E-mail:
james.powell@siemens.com
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