Has anyone encountered PROPRIETARY LADDER LOGIC?


Thread Starter

Hal Popplewell

We have a fabricator to whom we have paid millions of dollars who refuses to turn over any logic diagrams, ladder logic, HMI, etc. claiming it to be proprietary. Is it even safe to start up PLC-controlled equipment without this logic being understood?

I am interested in everyone's views on this subject.
Yes, I've seen companies view their code as proprietary, especially for standard equipment. Was your equipment totally custom, off the shelf for the OEM, or somewhere in between?

I don't have an especially strong opinion about it, I can see the arguments for both sides on this one. It's really something that if one party or the other has a strong viewpoint should be negotiated up front and explicitly set forth in the purchase contract, just like shipping costs, installation, spare parts packages, onsite service, availability for remote troubleshooting, etc.
Read your contract with the supplier or the scope of supply.

Yes, this is quite common. You wouldn't expect to get the source code of Microsoft Office, so if its not in your contract to get source code you should not expect it from an automation supplier either.

The most common reason that PLC or DCS code is given to a customer is that it is the automation code that is the goods being delivered. However, if you just buy a machine, there's no reason to automatically expect the PLC source.

As for the suppliers claims that their logic is proprietary - well that depends on your circumstances. Did you or your company give them the knowledge, algorithms or detailed instructions on how to control the plant? If you did not, then their claim is likely quite valid. In any case, this is a question for a lawyer, not an internet forum.

Is it safe to start the plant? - Well I start my car every morning without knowing how the engine management systems work. Not having enough information to commission the plant is indeed a safety risk, but again whether not having the logic diagrams is "not enough information" is a question I cant answer for you.
A lot depends on your purchase documents. Did you specify the equipment and if so, did you specify the documentation to be provided? Who is responsible for the start up of the equipment? If it is not the fabricator, then they should have to provide whatever support is necessary to safely start the equipment.

A lot may also depend on the local laws - I don't know what country you are in nor am I a lawyer, so the only advise I can offer in that area is to engage an attorney.

Speaking as a (now retired) engineer for a supplier of combined cycle power plant controls equipment, most of control logic and HMI software we supplied was visible to the end user; there were some proprietary parts of the turbine control logic that were locked up, but sufficient descriptive information was provided (you might have had to work to dig it out) to understand the operation.
Discussions of logic code as intellectual property on the PLCS.net forum seem to conclude that the ownership of the intellectual property of the code depends on the whether the code was developed as 'work for hire' with the customer providing logic descriptions, sequences, and I/O specifics, or whether the code was developed by the vendor at his expense, usually code for a machine.

It seems common to spell out who owns the code in a sales contract, so there's no confusion.
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Luca Gallina

well, if someone paid "million of dollars" of equipment without taking care of ownership/accessibility of the related software, I would define him (at least) naive.

One more point: comparison with MS Office sources, which no user owns, cannot apply to our environment: in automation life, plants and machinery naturally undergo casual troubleshooting, evolution and implementations, so there is not (read "there should be not") such a thing like "closed" software. Otherwise, what PLCs have been done for?

Bruce Durdle

If the logic has safety implications, then the site owner/operator probably (depending on legal rulings and requirements) has a duty to ensure the the plant is safe to operate and remains safe to operate throughout its expected life.

In New Zealand, a "designer" is required by law to make available to the end-user all information needed for the safe installation, commissioning, operation and decommissioning of the installation.
At the very least, I would require logic diagrams, flow charts, sequential function charts to allow me to be satisfied that the equipment meets the functional requirements specification. Wiring diagrams are required for maintenance.

If you are happy that the plant will run as required for the expected life, without modification, maintenance or adjustment, then you can **probably** live without documentation. Otherwise you are at the mercy of the fabricator - if he decides to retire on the millions of dollars you have just paid him, then that's your tough luck.

Sounds like the lawyers will get a nice slice of the pie too!

Gerald Beaudoin

My experience has been that generally the equipment we have purchased from North American suppliers have been much more free with machine codes and all the technical details of the equipment. On the other hand, equipment purchased from European suppliers, generally they tend to be much more secretive about whats under the hood. I have seen some machine suppliers scrape off markings from standard components like 741 opamps to be replaced by colored paint dot codes. Most folks who purchase, say packaging equipment, are not in the business of making and cloning packaging equipment. They simply want to PACKAGE whatever it is they make. While some users have the in house expertise to tweak and tinker with internal machine ladder logic, many others simply do not. As previously posted, better make sure it's all spelled out very clearly in the purchase agreement exactly what you are expecting from the supplier. So often these details get overlooked, only to cause havoc later on.
I've seen businesses buying equipment from fabricators taking the information from the fabricator and shopping it to off-shore fabricators. It doesn't say much about the integrity of the businesses doing this to the fabricators they do business with, but it certainly speaks to why more fabricators seem unwilling to release their code in order to prevent it from being used to obtain equipment at a lower price from other vendors.

I'm not suggesting that's what's going on here. I'm only trying to suggest a reason why "fabricators" are more and more unwilling to release ladder logic for even "simple" machines.

But, I'm with the other respondents who've said if the fabricator developed the code with information and assistance from the buyer of the equipment then it's likely not a secret, <b>BUT</b> the ownership of the ladder logic (code) should be (have been) covered in the contract.

Unfortunately, as is usually the case, the only likely "winner" will be the lawyer(s).

Hal Popplewell

Clearly the purchasing contract "should" have specified logic ownership. To clarify, I can offer a few points:

* Part of the process being controlled is proprietary to our company, protected under various patents, and the knowledge of how to control that portion came from us

* One part of the process is, in fact, specified as proprietary to the fabricator and this was know from the beginning

* There are numerous "other" parts of the process which are common process steps and which are the "grey area"

Our interest is NOT in ownership of the "intellectual property but, rather, in sufficient disclosure for the **SAFE** start up and commissioning of the entire process. Wiring diagrams were provided. PLC and HMI logic have NOT been provided.

And, folks, come on, we're not talking about a mass-produced automobile which is subject to countless government statutes and safety rules, here, but, rather, a custom-specified, custom-built set of chemical processing equipment.
> * Part of the process being controlled is proprietary to our company, protected
> under various patents, and the knowledge of how to control that portion came from us

Thanks for givings a few more actual details Hal. The point of my examples was to explain that you should NOT always expect to get PLC source code from a supplier unless it is actually source code that you paid for. There are many examples where source code or PLC logic diagrams etc are not required to safely commission a piece of machinery, and all that is required is suitable installation and commissioning instructions.

Now that you've clarified more about your process (ie its a one off machine controlled by a patented algorithm, which YOU hold the patent for) the machine suppliers claim does indeed seem much weaker. In fact it sounds like a decent lawyer would take the supplier to the cleaners. Especially if you also designed the machine.

If I was in your position, my next email to the supplier would make exactly that threat. But as everyone else has said, (and you already know) you needed a better contract before you handed over proprietary patented information, and you need a lawyer to sort it out if the supplier is being an idiot. Presumably your basic contract with them does at least have a clause about sensitive information?


Steve Richards

In any contract such as this, you need to be sure what you are buying. Which depends on what you are purchasing.

In your original request for tender, you should have had some text in saying "I will become the owner of all software written for this application, I will have delivered to me, software on disks, which will be proven to contain the correct software during factory acceptance testing."

If it is a long development contract, and your supplier requires stage payments, then it is normal for them to upload all of their software, once per week, to a third party (escrow) so that if the supplier goes bust, you can go the the third party and get any software that is up to date at the time of closure.

Having worked on the other side, delivering to the Ministry of Defense in the UK, we would specifically look in the RFQ to see if the customer thought they were buying software that enabled delivered firmware to modified or maintained.

If they did not ask, it would not be offered, after contract award, ongoing negotiations would commence about long term support, you/they pay more.

Your purchasing department needs to get it act together.