What Are the Risks and Benefits of Using a PLC?
Answered September 25 2020
Programmable logic controller (PLC) systems are an up-and-coming selection of software that offers many benefits to large-scale companies, particularly in the manufacturing industry. These industrial, digital computers range from small modular devices all the way to webs of networked devices that span an entire corporation. While smaller PLC systems have been around for a fairly significant time, larger and networked systems do have some significant risks that must be considered before implementing them on a large scale.
Here is an in-depth look at the risks and advantages of typical programmable logic controllers and how companies can leverage them to their fullest potential.
What Are the Risks of Using a PLC?
The top risks of using a PLC system include:
- Affected input/output (I/O) devices
- Defective grounding
- Power issues
- Heat fluctuations
- Highly expensive downtime
Many of these issues lead one into the other. They can also compound over time, leading to systemic issues. Here is an overview of each issue, a basic explanation of what usually causes it, and how to prevent it happening in your system.
Affected I/O Devices
The vast majority of PLC outages can be directly linked to affected I/O devices and power outages. Since over 80% of the system are these devices, every time a device goes down, the system is at some level of risk.
What does a typical affected I/O device look like? Most of the time, a defect will cause a sudden, system-wide stop. In most PLC systems, this is because the system is waiting for a signal to continue through its program sequence. Typically, an engineer must figure out where the sequence has stopped by examining the online devices and tracking the disturbance back to the affected device and I/O point.
If large numbers of devices and points are constantly or regularly going out, the system may be suffering from an internal error, a power fluctuation, or power outage. Depending on your overall maintenance program and the system’s general hardware status, a wide-scale replacement may be needed. Some initial fixes include:
- Checking all devices on a regular basis
- Updating your routine maintenance as a preventive measure
- Implementing a condition-based maintenance program specifically targeted to I/O devices
- Evaluating your system thoroughly
The second major risk factor that affects PLC systems are the inevitable power outages. While this is a risk that every lean company and organization faces on some level, the reliability of all PLC systems depends on a steady power source.
Unfortunately, given the nature of power outages and issues, the causes of power fluctuations can range from frayed extension cords all the way to a temporary blackout. Many companies have specific backup power systems designed for power outages, but these are susceptible to wear and tear as well as the main system is.
The best prevention is regular and proactive maintenance.
Proper grounding is paramount to facility and staff safety. It’s also a good electrical white noise barrier, which prevents distractions when faults occur. Defective grounding can play a large part in sporadic power issues as well.
One easy way to check your grounding on a regular basis is to simply add it to the planned maintenance checklist the facility should already have in place.
Disruptive outside interference in a PLC system is particularly common in heavy electrical environments. The two major kinds of interference that pose a risk are radio interference and electromagnetic interference. The causes are wide, but can include:
- Handheld radio systems
- Nearby radio antenna
- Large motors activating
- Lightning strikes
- Other sources of outside interference
There are many different ways to reduce outside interference, depending on the situation in question. The best course of action if interference is, or may become, a potential risk is to consult with a service engineer and take steps accordingly.
Electrical components are sensitive to heat. When a PLC unit is surrounded by heat-generating devices, is in a location without temperature control, or if no thought has been put into temperature control around PLC units, heat fluctuations pose a significant risk to the I/O devices and the system as a whole.
Highly Expensive Downtime
All of the above issues run into the biggest risk of using a PLC system: highly expensive downtime. Because these systems are so integral to the facility at large, any time that the system is offline has a cost that is hard to quantify. Product lines stop, devices go offline, and work is left incomplete.
Since PLC systems are built to withstand a rugged environment, the answer is not simply to obtain a better system. Rather, a simple checklist of best practices and a robust maintenance system will go a long way to reducing expensive downtime in both the short and long-term.
Now that we’ve covered the major disadvantages of using a PLC system, let’s look at the advantages and where they shine brightest.
What Are the Advantages of Using a PLC?
At a glance, some of the best advantages of PLC systems are:
- Easy integration
- Greater productivity
- Reduced system space requirements
- Flexibility across projects
- Greater ease of troubleshooting
- Increased safety and security
Similar to our analysis of the disadvantages, here’s a breakdown of each advantage and what it offers a typical facility that runs on a large-scale, networked system.
PLC systems are by their very nature networked devices. This makes changes very easy to integrate with the entire system. After the required change is input into one I/O module, the system takes that information and communicates to the others both the change and how it is to be implemented. This enables precious time to be spent elsewhere instead of reprogramming a facility-wide system to accept relatively minor changes.
Leading on from the last point, PLC systems enable greater productivity across facilities for multiple different reasons. These can include, but are not limited to:
- Shorter project times
- Less overall downtime
- Fewer systems to maintain
- Less waste and more economy of time
- Easier storage archiving/maintaining
Because facilities and companies are different, it’s hard to spell out specifically what the greatest productivity advantages will be in any given PLC system.
Reduced System Space Requirements
It may not seem that a PLC system saves so much space when multiple modules are being set up; however, the entire system is contained in these modules. Unlike other facility-wide systems, there is no need for a server room, multiple levels of software, or large amounts of various different kinds of hardware.
All information is held within the system and can be accessed at specific points, reducing the sum total of chaos, locations, and space needed for the entire system.
Flexibility Across Projects
Many of the PLC system advantages come from the fact that all the information is stored in a set of devices as opposed to a scattered system across multiple smaller systems. This creates a large amount of flexibility for specific projects since all the information can be accessed at any given module device.
Greater Ease of Troubleshooting
Troubleshooting is never easy in a large system. However, a few things consistently cut this time down. A PLC system is easily checked and troubleshooted at its core, which is the I/O modules. If it’s not a problem with the modules, it’s an outside problem.
This considerably decreases the amount of systems that need to be checked and the variety of things that can go wrong. While it is important to get a PLC system back on track as quickly as possible, troubleshooting is made easier as a whole.
Increased Safety and Security
Finally, a PLC system offers increased safety and security for the facility and the company as a whole. Traditional systems come with backdoors and other ways of accessing the information that can be problematic. PLC systems typically come with upgraded security and tighter control over the information contained within the system.
Depending on the facility in question, this can be a necessary component, particularly when working with valuable and/or high-risk items. On a less dramatic note, increased security enables companies to monitor, track, and observe their facilities with far greater levels of security than are normally possible on more traditional systems.
A Final Analysis
All the risks of using PLCs may seem frightening at the first of the month; all major facility systems suffer from similar drawbacks. However, PLC system advantages outweigh the risks in many situations, given enough preventive and proactive maintenance as needed.
This is particularly true in facilities and companies that need increased security and flexible infrastructure. Depending on the industry in question, other benefits come and go. However, in the last analysis, the overall lower costs, networking ability, and functionality outweigh many other compatible systems.
If you are in need of a facility-wide system on par with a PLC system, it’s probably a wise decision to look into obtaining one for your needs.
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