Platform Independent Functional Specifications • ControlDraw Ltd • Topics: • Real Batch Projects, and what can go wrong. • A Brief History of Specifications and System Life Cycles • Benefits of System Independence • ControlDraw Software
Real Batch Software Projects • The Plant is nearing completion, the IO Cabinets are being cabled in and back at the software supplier's works someone suddenly realises that the project is late. • As testing begins, or a short time before, it becomes clear that there is no way they are going to finish on time. There are thousands of errors and things missing. The project goes into panic mode. • At the suppliers People are working endless hours. They are battling against time, trying to obtain detailed information, testing software and finding faults, working their way through a huge list of comments and deviations. Eventually the software gets delivered, typically with some functionality removed, in to order accelerate completion.
What is the problem? • It is not the Control Systems • Modern Control Systems are wonderful , DCS or PLC/SCADA, they can all do everything that a Control engineer could hope, • If they are programmed right. • It need not take long to program them • If you know what needs programming
Ask the Programmers • Why are there so many errors? • they only programmed what the spec said • the spec was wrong. • most ‘faults’ were ‘improvements’ or ‘changes’ • Why it is taking so long? • they spend most of their time looking for missing information • Things got added • Time is spent changing what they had already programmed
A Brief Instrument Engineers History • We did not used to have ‘Life Cycles’ - We Wrote Specifications and drew schematics • Panel Instruments • Back of Panel Instruments • Panels • Logic Diagrams • Loop diagrams • Our Objects were Physical
We wrote Product Independent Specs • Vendors sold 6*3 panel mounted instruments - all made similar functions • PID, Indicate, Ratio etc • We specified them , Got Quotes, Chose a Vendor • We drew Loop diagrams • Finally we put the model numbers on the Specs • Along came DCS’s and PLCs. • Technology ran ahead of our ability to specify, most especially in Batch.
Life Cycle Concepts • Introduced to cater for complexity • Borrowed from the IT industry • In General, • URS became high level without detail, produced by the ‘User’ • FDS became the container for the Detail • FDS became a supplier document and Product Specific - why?
Rarely includes the detail GAMP Life Cycle Not a strong dependency Not a strong dependency Does this includes Phase Logic, Loops, Basic Control?
Requirement or Functional ? • Examples • “The Reactor uses Cascaded temperature control” • Is a Requirement - and does not depend on system! • “On Step 3 open valve XV1245” • As above
Functional Requirements Specification • Term used by the FDA, Microsoft et al • Includes full detail of all required functions • Can still be system independent • but might presume certain capabilities • Need to be highly detailed • Develop over the life of a project
Graphics System Database Procedures Phase Logic Control Modules Functional Requirements Content • Database • Control Modules • Graphics • Phase Logic • Recipe Procedures • Underpinned by Standards
Detailed Functional Requirements Graphics System Database Procedures Phase Logic Control Modules Where does FRS fit in the Life Cycle? Outline Function Requirements
Requirements Analysis Piping & Instrument Diagrams Identify Process Cells Define Process Cells Identify Units Define Units Identify Equipment Modules Define Equipt. Modules Identify Control Modules Identify Resources Define Resources Identify Control Modules Define Control Modules Implement Order Here? Control & Operability Philosophy Or Here? Process Description + Recipe Data Identify Main Procedures Define Procedures Identify Operations Define Operations Identify Phases Define Phases Health & Safety Requirements Identify essential H&S Requirements Design appropriate Safety Systems Independent Safety Systems Equipment Protection Requirements Design Equipment Interlocks
Graphics Vendor Independent Graphics • Look at a Graphic • Delta-V, Wonderware, Fix - Can you tell? • MS Windows prevails!
System Database Control Modules Vendor Independent Control Loops • Look at Control Loops • Same functionality in any system • Have hardly changed in decades • Used to be SAMA, now IEC1131 Function charts
Control Modules Vendor Independent Interlock Logic • ISA Logic , IEC1131 Ladder Diagram etc • Same functionality
Procedures Phase Logic Vendor Independent Batch Procedures • Different styles, same meaning • Thanks to S88.01 • SP88-02 is coming Fill with 1000 kg Water Manually add 50 kg Salt Heat with steam to 50 C Manually add 30 kg sugar
Advantages of Product Independence • Competitiveness • Can keep vendors competing longer • Can get a more fixed price • Avoids a scope battle with vendor • Can get the Functional Details approved much earlier • Can order the actual system later • The Programmers like it too
Tools for Specifiers • Standards - S88, S5.1, IEC61131 • MS Office for Words, Spreadsheets, Databases • Visio or alike for Diagrams • Maybe CASE Tools - EasyCase, Prosa etc • Demo versions of HMI’s for Graphics • Let’s Look at ControlDraw • www.controldraw.co.uk