plumbline logic llc
Understand and validate legacy PLC code
before you change it.
Vendor-neutral analysis and validation
for Rockwell, Siemens,
and IEC 61131-3 control code.
Engineering accelerator without buying a runtime or a one-way migration.
the problem
Your plant runs on PLC code written years ago by engineers who have retired or moved on. Undocumented routines, fragile migrations, and no safe way to test before you change a line.
the solution
Comprehend inherited logic.
Call graphs, tag maps, and plain-language summaries for routines nobody remembers writing.Test before you change.
Coverage and regression checks against exported program logic, so migrations and refactors don't ship blind.Stay vendor-neutral.
Current Assessment Scopes
| Rockwell L5X/L5K exports | Full Support |
| IEC 61131-3 Structured Text | Full Support |
| Siemens S7/TIA | On Design Partner Request |
How We Do It
Comprehend
Review exported PLC project files
and map routines, tags, dependencies, and undocumented logic paths.Assess
Identify migration risk, missing documentation, fragile logic, and areas where regression coverage is needed before changes.Validate
Deliver a practical assessment package: findings, risk areas, test recommendations, and next steps for controls engineer review.
Vendor Neutrality
Vendor migration tools convert toward their own platform. The auto-converted code may run, but can be hard to understand, maintain, validate,
and locks you back in.Plumbline Logic is the neutral party. We assess your code without pushing you toward any vendor's next product.
Your optionality stays yours.
Why Trust Us?
Founder
Built by Joseph Fahnestock,
a distributed systems architect with extensive experience in regulated software.Location
Based in West Michigan, close to the plants and integrators this is built for.Data Privacy
Customer code is anonymized before analysis. No shared-model training on your code. Built for on-prem and air-gap-friendly workflows where customer code cannot leave the environment.
faq
Do you generate
or modify PLC code?
Not yet. v1 is comprehension and test coverage only. Code generation is gated to a future private beta with human-in-the-loop review.
What formats
do you support today?
Rockwell L5X/L5K exports and IEC 61131-3 Structured Text. Siemens S7/TIA import is on the roadmap and will be design-partner driven.
How do you
handle our code and IP?
Code is anonymized before any analysis. Built for on-prem and air-gap-friendly workflows. We do not train shared models on customer code without explicit, written, per-dataset consent.
Is this safety-certified?
No. Plumbline Logic is an engineering aid, not a certified runtime. All output requires controls-engineer review and plant commissioning workflows before deployment.
Have a stack of PLC code no one fully understands?
Start with a paid assessment.
Two-week engagement, fixed scope, NDA first.