If your control system is at the end of its lifecycle, but you’re unable to afford the time or expense of an upgrade to the whole system, there are some things you can do in the interim to increase the longevity of your aging system. Whether this is a new installation or a legacy system, many of these tips are useful independent of your control systems age.
In most cases, your control system consists of much more than a few PLCs. You have controllers, I/O cards, a network infrastructure with various components, computers for the servers and client stations, gateways or interface devices to allow data to flow between systems, and HMI software applications or proprietary consoles and components.
In an effort to maximize the lifecycle of your system you have to have good preventative maintenance plans but you also need a plan for managing the dependence on aging components and software, which are essential to operation.
Control System Maintenance Tips
As a whole, keeping up with control system releases and properly maintaining it over the entire lifecycle is essential to ensuring the reliability and continuous operation of a system. This is an exercise to thwart the rigorous demands of time, manufacturing, and production schedules. Below are some basic tips to maintaining the existing equipment to maximize the lifecycle of your control system.
Control System Power
Good, reliable, and clean power is a must. This is essential to maintain longevity. Nothing stresses power supplies more than brownouts which lead to premature failure of components. Power surges are another big power supply killer. It’s always a recommendation to install an Uninterruptible Power System (UPS) and run the critical components from it.
This means factoring in temperature, humidity, and dust. Controlling the temperature and humidity around the components in the control system is critical. The warmer the cabinet, the shorter the life of the components inside (above a threshold temperature). This applies to computers as well. Most computers are designed to operate at an ambient temperature of no more than 80 degrees F. As you go above that temperature, there is not enough physical cooling capacity to keep the components below the design temperature, which will lead to failures.
The same issues can occur with dust accumulation, as dust can act as an insulator, keeping the cooling air from properly removing heat.
- Ensure enough space for adequate airflow for PCs.
- Ensure that the server cabinets have enough air flow and are in environmentally controlled rooms. Humidity should also be controlled (this may require external cooling such as fans or an air conditioner).
- Proper control cabinet design with recommended spacing for components (this includes duct spacing around components) and heat dissipation (this may require external cooling such as fans or an air conditioner).
- Keep components free of dust and dirt – the use of good filters and a preventative maintenance schedule to replace filters is a must.
The backbone of your control system is your network. This is often the most crucial and most often overlooked portion of the system. The data has to make it from the processors to the server/HMI so it can be controlled. More and more systems are adopting Ethernet as the go-to choice for control of distributed components. VFD’s, valve banks, remote I/O, etc., are all reliant on a solid network. In most cases, it makes sense to make this as robust as possible. You should explore layout topologies, distributing loads, and fault tolerance using multiple links and switches.
Keeping up with the Joneses
Every control system has a life span, and computers should typically be replaced every 5-6 years and controllers/hardware should be replaced as needed (while still available). For the most part, keeping up to date involves upgrading your computers and the control software. If you follow the latest and greatest version of software supplied by your vendor, you will probably be upgrading PC’s more often due to enhancements and functions offered on the newer operating systems which usually don’t support the older hardware.
Replacing computers seems like a trivial process, but with each passing year, a new operating system pops up and an old one is no longer supported. Additionally, since older operating systems may not support the new hardware, this means you’re forced to go to the newer operating system and upgrade your control software for your DCS or PLC systems. Depending on how many versions of the software you are behind, this could be a really big deal.
It’s not all doom and gloom, but there are some tools you can utilize to get by until you’re ready to make the big switch.
In most cases, it’s possible to virtualize the old system, which would allow you to limp by until a final solution is in place. This works well if you have good control hardware and need an immediate solution to your HMI PC replacement problems. An example would be if you’re still running Process Suite on an old Windows 2000 machine or maybe RSView32 on Windows XP.
This often consists of updating the HMI software to a package that works with your existing and new hardware, such as using PCS7 APACS OS where you still have your old ACM’s but need a new HMI to replace Process Suite. Another example would be upgrading RSView32 to FactoryTalk View SE while continuing to run your SLC’s. Now you can replace hardware as part of a phased approach, running the new and old systems side-by-side on the new HMI software until the upgrade is complete and you have all new hardware. This removes the vulnerability of the old outdated computer hardware running legacy operating systems.
The Value of Planning Ahead
One indication that you are in jeopardy is if you’re buying hardware off of E-Bay. All control system vendors have a product life-cycle model which defines a phased approach for support of their hardware/software. If you don’t know what the lifecycle is of your current systems or if you don’t know where you’re at in the lifecycle, then you are already behind the curve.
Several years prior to when a control system is set to be discontinued, you should begin the process of planning your next steps to ensure you minimize the potential for production outages. Most vendors offer migration paths for nearly every system. Some migrate effortlessly while others are much more involved, requiring a re-write of the code for the new controller. It often depends on where you are in your lifecycle and tools that are offered by the vendor as to how difficult the upgrade process will be.
Looking into the future, it’s hard to predict what will happen with computers, operating systems, hardware, and networking components. Virtualization is a great way to maximize the life of your overall system, opening up the door for added flexibility. You are able to move your virtualized machines from one piece of hardware to the next with reduced effort or downtime.
Using thin-clients is also a great way to help minimize the impact of hardware replaced because these are operating system independent. A very efficient approach to lifecycle management is to couple virtualization of the operating system along with thin-client technology for operator workstations. First, this is a popular choice that decouples the control system from computer operating system so you are not chasing software compatibility like the IT departments. Second, the thin-clients allow for easy replacement with small costs compared to replacement of actual computers and time needed to reinstall the software.
Extending the lifecycle of your control system and squeezing the investment out of production system assets requires proper maintenance but, just as important, it requires lifecycle management practices. This means knowing where you are in your hardware/software lifecycle and having a plan to minimize production outages to allow the assets to continue to meet production schedules.
Both of these elements help reduce the risk of potentially having an unplanned outage, which could be detrimental to your business or at the very least costly. Taking advantage of good maintenance practices and proven technology like virtualization can extend the life of your system, decrease disaster recovery time, lower the overall total cost of ownership, and ultimately reduce the risk of unexpected downtime.