Sequence of operation
Step by step, how the system starts, runs, and stops, and what happens between each step.
Functional design
Fix it on paper. Not on the floor.
A functional design spells out how your system will work before anything is built, so the panels, the program, and the quote all match the job.
What it is
A written plan for how the system works
A functional design describes how the system will behave before anything is built. It covers:
Modes
Auto, manual, and maintenance modes, and what each one allows.
I/O & device list
Every sensor, valve, drive, and device, with its signal type and where it lives.
Interlocks
The conditions that must be true before something can move, and what stops it.
Alarms & fault responses
Each alarm, its priority, and what the system does when it happens.
HMI screens
What operators and maintenance see and can do on each screen.
Network & architecture
Controllers, remote I/O, switches, and how they connect.
Interfaces
Data exchanged with WMS, MES, ERP, or SCADA, and with OEM equipment, including who sends what and when.
Safety functions & tests
Safety functions to be confirmed by the risk assessment, and the acceptance tests that prove the system works.
Would you like to know more? FDS, URS, and regulated projects
Also called an FDS
A functional design is often called a functional design specification, or FDS. The name varies; the purpose is the same: one agreed description of how the system works.
In GAMP 5 projects
In regulated work following GAMP 5, the functional design sits alongside the user requirements specification (URS) and functional specification (FS), and later testing traces back to them.
Safety is confirmed separately
The functional design lists the safety functions, but the required levels come from the machine’s risk assessment, not from the document.
The review
Functional design review
A working session to get the design right before build starts.
Walk through it together
We review the document with your operations, maintenance, engineering, and IT/OT teams.
Mark it up
Questions and changes are written on the document, not lost in email.
Agree on changes
Each open item is resolved and the document is updated.
Sign off a revision
A signed revision is the starting point for panel build and programming.
Why it matters
What you get from it
A functional design pays off from the first review through startup and beyond.
Cheaper on paper
A change to a document costs far less than a change to a built panel or a running line.
Everyone agrees
Operations, maintenance, and engineering sign off on the same description of how it works.
Built to the document
Panels and programs are built to an agreed design, not to memory.
The basis for testing
FAT and SAT test scripts come straight from the functional design.
The basis for maintenance docs
Operating and maintenance documentation start from the same description.
Clear change orders
When something changes, there’s a clear baseline to measure it against.
Would you like to know more? How the design carries through the project
From design to test
Each sequence step, interlock, and alarm in the design becomes a test item at FAT and SAT, so testing checks what was agreed.
Fewer surprises at startup
When questions are settled during the review, fewer of them show up during commissioning.
Scope of work
An accurate scope of work
The review also sets the scope, so the quote and the work line up.
What’s in, what’s out
Panels, field wiring, devices, programming, HMI, network, installation, commissioning, training, and documentation, each marked in or out of scope.
Interfaces & owners
Every interface is listed with who owns each side of it.
Assumptions
Written down, so nobody is working from a different picture.
Customer-supplied items
Equipment, information, and site access you provide, listed up front.
Acceptance criteria
What “done” means for each part of the system, agreed in advance.
A quote that matches the job
With the scope clear, the quote reflects the work that will actually be done.
Next step
Start with a functional design review.
Send what you have: drawings, an I/O list, a description of how it should run, or photos of the existing system. We’ll take it from there.