Days of change
With the resurgence of manufacturing comes the reality that process systems installed may be outdated. The desire to change out a working, but old system is often thwarted by the realization that replacing I/O and interface devices to match up with the new system can be four or five times as expensive as the system itself, not including commissioning and down-time cost.
If it were possible to replace the processor with a “State of the Art” device, while maintaining the existing I/O and peripherals – it would be possible to realize new functionality (Speed, OPC, interfacing) without the huge cost of commissioning an entirely new system and training the Maintenance personnel to use it.Such a scenario existed at a Steel Mill in BrazilAfter receiving an inquiry regarding the desire to swap out an Allen Bradley Pyramid Integrator PLC (5/250) for a Control Logix system. Spending a considerable amount of time researching the options; We discovered that the only existing method of transferring the logic would be to re-code it in RsLogix and re-define the I/O.
A conversion tool existed for the PLC-5 tool but due to the lack of ASCII output capability from the 5/250 programming tools – automatic conversion was not possible.Because of the size of the project, we decided to write the conversion program.The translation tool assumed that the existing RIO chains and devices would remain intact, no addressing changes or re-configuration would be necessary in the translated program.Paramount - The translated program would be as easy as possible to commission.
Result:
Using the graphic program listing files output by 6200, these files are analyzed by the program and translated exactly (rung for rung) by the tool. The program writes these results to an .L5K file that can be read directly by RsLogix.Other Data, such as I/O configuration, Data Initialization, Symbols are also read from the documentation output by 6200. The result is an “almost perfect” translation.
Test Application:
The process, a Continuous Casting Machine in Brazil, was controlled by three Pyramid Integrators (5 LP’s). Maintenance issues had caused the company to look for cost effective methods of upgrading the now “Silver series” processors. Most proposals received required more than two weeks of “Downtime” to replace the system.Using the translation tool – which had been previously tested on the same code for several weeks. The Control Logix system was assembled and the DH/RIO interfaces connected on Friday evening.
Following two days of testing – the full function test was performed on the following Monday morning with no problems. Production resumed ahead of schedule following the completion of other Maintenance tasks. All within a regularly scheduled Maintenance outage.All Data Highway and Remote I/O connections were kept intact, ie: replaced 1 for 1 with DH/RIO ports. The Level II system, following an “Interchange” upgrade to the current version was not changed.
Supporting PLC-5’s required minor changes to addressing in the Message Blocks communicating with the Pyramid Integrator.As the programs remained the same (Rung for Rung) – Maintenance personnel only required familiarization time with RsLogix – functionality of the programs were not changed.
Method:
The translation tool analyzes the Data Map to assign arrays and variable space in Control Logix, Most symbols are mapped at this time. The Data values are then read in so that the new data arrays will hold the same values as the Pyramid Integrator when the program was saved. This is vital for the 1771 interfaces if they have Block Transfer cards installed as the configuration usually requires downloading at startup. Also – any look up or interpolation tables are correctly loaded in the Control Logix version.Next the Logic listing file is “interpreted”, the ladder logic is read, analyzed and converted to symbolic code for the L5K file – The addresses are converted to Control Logix format and any Symbols are substituted at this time.
All Ladder File comments are directly deposited into the Control Logix Program.Message instructions are then coded so that minimum work is necessary (if any) to fix up BTW/BTR instructions – everything is translated.Serial Port instructions are translated next.The I/O Chain is built under 1 DH/RIO in the produced configuration.
Final placement of the I/O chains and addition of more DH/RIO cards can easily be accomplished, either following the load into Control Logix by dragging and dropping or by editing the .L5K file before loading it.I/O addresses are converted correctly, even with ¼ and ½ racks – the rack names are intuitive and maintain their Octal Rack number (in Decimal Magnitude). That is, Rack 27 (Octal) will be named “Rack_27a” in the Control Logix configuration. If Rack 27 was a ½ rack, and the other half rack was defined, this would be named “Rack_27b”.
The Octal bit magnitudes are all converted to decimal for Control Logix.All descriptions are brought across as well as Symbol information.The result is a near perfect program translation. All conversions to date have yielded minimum errors on load. Typically less than 2% of the program.
Bearing in mind that there are some aspects of PLC-5 programming that do not translate directly to Control Logix.· Bit Indexed Address (ie: 2N14:4{5..8})· File Indexed Address (ie: 2N[1N14]:4)· Loop Instructions, FOR, WIL, GSB require attention as looping within a program file is not permitted in Control Logix.
Follow Up
Due to the method of conversion (Listing file interpretation), this program has since been modified to use AI series programming tool output and has successfully converted PLC-3 and PLC-5 programs. Even though a free PLC-5 conversion tool is available from Rockwell, this program performs a more complete conversion requiring less effort to commission.In progress is an AutoMax/AutoMate front end to this application to complete a conversion from Reliance to Rockwell PLC’s. Other conversions are certainly possible.To Date, we have converted over 20 Pyramid Integrator programs, many PLC-5 and 2 PLC-3 programs, all with successful results.
Offer:
If you have a program that you would like to see converted. Send the source files (they will be treated in the strictest confidence – and promptly destroyed following the test if you so wish)We can usually E-Mail you pdf (Adobe) files, or Screen prints (MS Paint) of select portions of your translation (anything you would like to see) within about an hour of receiving your code (depending on availability). If you would like to schedule a demonstration – please call.We can offer the whole range of services, from simple program translation (via E-Mail) to full turnkey solutions.
Process:
Following the submission of you’re your program for conversion and agreement of terms, we will translate the program and fix any errors, resulting in a loadable Control Logix program. We will send a report with the conversion noting any areas of concern. This process will usually take less than two weeks (large programs) and will usually take less than one week (Normal sized programs). A straight conversion service (Same day) is also available.For further details or to discuss a particular PLC conversion with our engineering staff please contact Bob Chappel at : Advanced Integration Group, Inc.
www.advancedintegrationgroup.net Advanced Technical Staffing PO Box 12537 Pittsburgh, PA 15241 Tel. (724) 746-3707 ext. 222 Fax ( 724) 746-3708
