Human Machine Interface

It really depends on the specific application and the environmental conditions. For instance, If you want a wall-mounted display, consider the conditions inside the wall. This is especially true if the display is flush-mounted (recessed into the wall).

In a coal-fired power plant where I have done a lot of work, one wall of the control room consists of steel control panels. If the CPU and display are installed into the wall, I use an industrial computer and display, because the steel enclosure is not climate controlled. The environment is very similar to field conditions. Over time, fly-ash and coal dust will accumulate and destroy a standard computer. Also, the temperature in the cabinet can reach 50 C, well beyond the design specs for commercial-grade computers/displays.

If the interface will be in a clean, air-conditioned area (most control rooms are maintained at a slightly greater pressure to prevent infiltration of dust), I usually go with off the shelf electronics. They are much cheaper to upgrade or replace on failure.

On a side note, when I use commercial computers, I also limit access by the operators to the operating system (usually Windows or Linux). More than once I found the control windows minimized while a game, video or other nonsense covers two screens. I set the boot sequence to start the control application, with no way to close it. I also make all removable media devices (floppy, CD, USB flash drives, etc.) password protected, so they can't boot from a CD or install garbage from outside.

Very nice an useful your commentaries.

Yes, the idea is to have a control room environment. Temperature and humidity controlled. Also pressurized.

It seams that will be too expensive to use dedicate displays inside such enviroment.

We are trying to develop the idea and so the philosophy for the system.

Some people think that is not good to use commercial PC for that issue.

They are affraid about using it. ¿?

Have you bad experience about using that harware in a good environment?

Also, what you told about limiting access to operator, must be done.

It really depends on what the cost or consequences of a system failure is in your installation. PCs have a notorious reputation for both hardware and software failures. If you need fault tolerant systems, then the PC isn't the best choice in any environment.

I have not had any bad experience using good quality PC's in a controlled environment. At one point I was told to use an off-brand, and it lasted for 6 months. All of my other installations are either still in operation, or were upgraded because the operating system became obsolete. When you specify the computers, don't skimp. Use an oversized power supply, oversized CPU cooling fan, and the best quality hard drive (not necessarily biggest or fastest) that you can get. Look at technical reviews or manufacturer's documentation for the hard drive to find the mean time between failures (MTBF). A higher number is better.

I have used 2 Gateway 486 standard PC's to control a Hydroelectric Plant for 10 years before I finally upgraded to a Dell Pentium D. I am currently using Dell Pentium 4's to control ash handling, SO2 scrubber, and emissions monitoring equipment with no down time. On all of these I use WonderWare for the interface. It's flexible, user-friendly, and works with most PLC's.

The standard commercial-grade PC's are cheap enough that you can install 2 of them for less than the cost of 1 industrial display. Mill downtime is so expensive that it makes it cost effective to have a hot standby for the operators. In most systems you can run them side by side, so that if 1 fails, the other is already on-line. In my systems, the second unit doubles as an engineering/programming workstation, so the maintenance & engineering staff can work without distracting the operators.

You will need to designate one PC as the primary data historian (server), and make sure it is backed up. I designate the unit not normally used by the operators, so it gets less wear on the keyboard & mouse. I do a full backup once a week, and an incremental backup every 12 hours in between. Right now my backups are all on DAT tapes, but I'm exploring the possibility of connecting an external hard drive and running a mirror image every hour.

All what you say shows that you know very well about what you are talking about!

Mi experience is the same that yours.

In every place where I had been working we had use commercial PC.

The structure we develop was the same that you are telling, also bigger, eight operators interface and two for engineering.

But the question is that in those places the system was a DCS.

Now here we have to use some existing PLC that are working to integrate them in a "control system"

One problem is that there are four brands Schneider/Siemens/Omron/Allen Bradley.

And as I told before, they are afraid about using commercial PC as HMI.

I told them that the "real" control is still running and laying in the PLCs.

And of course it will be better to have two HMI (PC) and no only one dedicate HMI.

Also, as you say, will be cheaper and useful.

Er, is this about the hardware itself, or is it about configuring them?

No I'm talking about what kind of hardware is normal to use in an control room enviroment. Temperature and humidity controlled. Also pressurized

Most of it would be determined by the type of equipment being used for the central control system and the supplier's range.

For example, can a Siemens S7 HMI be coupled to an Allen Bradley SLC 5/04 processor (rhetorical question)? If the equipment is coming from one supplier's range then the supplier's sales office(s) should be consulted with full information about the environmental conditions. In a pressurised control room with temperature and humidity control, it is likely that equipment from the standard ranges will be adequate though it is best to check with the supplier with this information, so as to benefit from the supplier's warranty structure; most HMIs are rugged enough to survive most control room situations.

It depends on who wrote the software....

A lot of stuff in both categories is 'user hostile'.

I'd say find something you like and go with that...

Get some thin clients. They are getting very small now, the size of an external hard drive, and use them for remotes. They are totally sealed and perfect for dirty enviroments. Use them to access the PC or server that is in the controlled enviroment.

Hi:

I understand that you are talking to use external hard drive. Why in you opinion is that useful?.

The idea is to have all the PC hardaware in a controlled environment (rack room).

Of course, as someone said in this forum and I agrre with him, the most important and weak issue in this system will be the hard disc.

As the hard disc is a mechanical "thing" the normal failur will be from that side...

Do you know another kind of storage unit as "big" memory sticks?

We used to use industrial displays in our control rooms but eventually switched over to computer-based displays (Dell PCs). The major reason for the changes was that the industrial displays were much more expensive than the PCs. There were other advantages too:

• The PC based displays were easier to change. When we needed a new display, it was faster and easier to do it on a Windows based platform.
• The PC based displays were easier to "tweek" to get maximum performance out of them.
• The PCs were lighter as well as the monitors so were easier to replace (we just placed them underneath the table).

We do not use a DCS. Ours is a PLC-based system (Allen-Bradley). We bought cards that enabled our PCs to communicate with the PLCs. The newer Control Logix had ethernet cards which simplified our communications even more.

Personally, I've been thinking of combining the two technologies in the control room. I had proposed that we use a PC to project the whole process using LCD projectors. The newer PCs and XP OS allows multiple video monitors so I proposed that we use two to three projectors and butt them together to make one huge display on the wall.

The operators would have touch screen displays but these would be smaller and be used only for control (switching motors on/off, opening/closing valves, inputting data, etc.).

Obviously, the inspiration for this idea came from an old ship of mine...U.S.S. Enterprise, NCC-1701.

Hi:

All what you say about the advantages of PC over industrial Displays is right and I agree with you.

About what you say using industrial displays for operation...why?.

In other mills I had use commercial PC with a SCADA Software and PLC. The operators start/stop pumps, open/close valves, modify set-points and "move" remote valve using the screen and a mouse.

Also in other Power Plant (1,6 GVA) using a DCS (Foxboro I/A)the HMI were commercial PC (Dell PC's).

Also in that places were two "video wall screen" also for operate the plant. It was really amazing

About what you say using industrial displays for operation...why?.

What I meant was that since the process is already visible on the video wall screen, there would be no need to have the same display in front of the operator.

Then, to avoid disturbing the display on the wall, the operator would have a touch screen monitor where he can control the process. His monitor would only have the controls for the motors, valves, controllers, mode selectors, etc.

OK, seams to be fine what you say to use an industrial and dedicated display to operate an the other display (PC or video wall) to show all the other things.

But, what's your opinion about using commercial PC to interface with control? Have you any bad experience or doubt about? It's a great amount of money of difference between using commercial PC or Industrial display.

But, what's your opinion about using commercial PC to interface with control?

They're fine as long as you remember that PCs are not exactly built to survive in an industrial environment.

Inside a control room that's sealed from the outside, with positive pressure to keep out the dust and vapors, with care taken to minimize or eliminate vibration and heat, they're fine. It's also better to use the better branded ones than a no-name unit.

We once had a camera monitoring system that a supplier installed using a no-name brand. About every two months or so, it would malfunction and we'd be with no camera displays for about a day until they come around to fix it.

The only downside I find with commercial PCs is security.

Back when we were using industrial displays, there was no way for the operators to play with them. When we converted to PCs, we deleted the games but computer-savvy operators found ways to bring them back. A few even installed their own games and would play with other operators on the network. A few suspensions brought that down somewhat but others still persisted. Unlike some factories, our supervisors do not stay in one control room but go around the plant managing multiple operations. It was difficult to catch the culprits, I tell you.

I tried fighting back by disabling USB ports, floppy drives, removing CD drives and configuring the computers with passwords and other security stuff. The problem with installing myself as an administrator, technicians as power-users and operators as users, only made things a little worse for me. As administrator, when a PC went bad and needed re-installation of software, I had to be the one to do it. That meant being called in even at night.

Then, there were the viruses. In a factory, a virus can be a dangerous thing. My superiors eventually took pity on me, I guess, and called in the experts.

Today, it's much better. The computers are managed by the IT department and the PCs are better configured. User tracking is being done so illegal stuff is either impossible to install or we can at least track whodunit.

This sounds like commercial PCs are more hassle than industrial displays. They are but the advantages outweigh the disadvantages, in my opinion. Dealing with miscreants is a different matter. They will always be there, but a commercial PC HMI system, if properly configured and managed is much, much better than industrial displays.

Besides, the newer industrial displays are simply PCs in an industrially hardened chassis. From my standpoint, they're the same as an office PC.

OK very nice your analyze.

Some (or perhaps all) stuffs that you had tell were part of my fight and history...

As you said commercial PCs can survive only in a control room. And also must be a recognized brand. Usually I had use DELL and HP one time IBM as a server.

The most dangerous issue, as you said, are virus, and in second way, problems with games and other similar issues.

That was solved in two ways. First asking IT people to help us configuring the machines. And other issue was installing the PCs not at the operators hand. The operator couldn't´t reach in any way the CPU cabinet. At his hand were only the display, mouse/trackball, and keyboard.

About cost, in some way will be better to have two or three PCs instead of one Industrial Display. I hope we shall not be so unlucky to have a problem in al the PCs at the same time!

Horacio,

I agree with everything Vulcan has said. There's really no difference anymore between industrial displays and commercial PC's. Even for your Foxboro I/A (I have an I/A system also), the original interface boxes were Sun workstations running a proprietary version of Unix. The motherboard was wired differently, but they were not hardened electonics. And now Foxboro has stopped selling new Sun boxes. Everything for their systems will be commercial PC's running Windows.

I have found a couple work-arounds for security. The first thing I do is unplug the phone line from the diagnostic modem. The vendor has to call in on a voice line first and identify the reason for access, then one of my techs will plug in the modem.

Another weak spot is your network. If you use ethernet to connect to your PLC's, make sure your hubs and ethernet jacks are also locked up. I had one enterprising operator bring in a laptop and hub of his own, then connect directly to the peer-to-peer network!

I also limit the operators to user accounts, with no administrator privileges. Each of my techs has a separate Administrator account on each PC. Any installs are identified as to who was logged in when the install occurred. This makes it really simply to track any changes.

Your idea about isolating the CPU is also very good. Mine are locked in a ventilated, window-front rack cabinet.

The one other caution I would give is to make sure you use the professional version of the operating system, and not the "Home" version. The administrative functions are much more robust and flexible in the Pro version, plus more networking options are available.

OK it's really an amazing issue that three different people in so different countries have the same experience with more or less the same thing under discussion!

You, pwr2thepeople from USA, Vulcan from Philippines and me, horacio_tabacal from Argentina have the same idea about.

The issue is not the hardware. It must be not a "clone" it must be a good brand.

The issue is not the SCADA software. It will be easy or not to configure or use.

But the real issue will be to block any access to the system to everyone that is not the right one to have such access.

Now I have a hard job. Is to make the other people to agree that is not a problem using commercial PC in our mill. And the issue is to take care about environment for the hardware, and closing any back door for software...And is cheaper than using "industrial" displays.

The good thing here is that everything is to be done...and the bad thing here is that everything must be done.

Okay, maybe a little off topic but not too much (I won't be selecting the "off-topic" box).

I would like the PC manufacturers to come up with a way of allowing a ROM card that has the necessary software burned into it. What I mean is that the Windows OS, the HMI software, drivers, and what-else, are burned into the ROM so that it would be impervious to viruses or crashes. If an infection does get in, all you'd have to do is to reboot in, say, "clear memory" mode and you'd get your system back wiped clean. Then you just reinstall your HMI application program.

I'm not talking about built-in re-installation software. The OS and the application program is a part of the memory, not stored in the hard disk.

This has been done before but the one I saw had DOS built-in. Even if a virus got in somehow, it was easy to get everything back together.

You may ask, "what about updates?" What about them? When we were using industrial displays, their software was burned in also. We didn't need any updates. From experience, updates caused more problems because the updates made the application program or some features unworkable.