FEATURE PLCs, Industrial PCs & HMIs
Long live the PLC! Neil Ballinger, head of EMEA at EU Automation, shares his advice on how to best look after PLCs P
LCs are ruggedised computers that receive information from connected sensors or other input devices, process the received data and generate outputs based on pre-established parameters. They range in size from small devices with a few dozen inputs and outputs (I/O) , to larger machines with thousands of I/Os, and can automate specifi c operations or machine functions, such as automatically starting and stopping a process or control the automation of an entire production line. Unlike personal and desktop computers, PLCs are designed to withstand factories’ harsh conditions in terms of temperature range, vibration, dust and moisture. However, their resilience doesn’t mean they don’t require any maintenance to keep running properly. PLCs are durable and can easily last over 20 years if regularly maintained and updated. They are extremely versatile, fi t in many applications, so ultimately their maintenance strategy will be unique to their model, application and specifi c production line. There are, however, some general guidelines that are valid for all PLCs and that can help manufacturers extend the lifetime of this machine.
Protecting assets The fi rst step to keep a PLC in good condition is to protect it from dust and other airborne debris. Given that PLCs are ruggedised machines, it’s easy to underestimate what dust can do to them, and dust produced during normal factory operations can contain corrosive or conductive contaminants that can seriously damage them. For example, iron dust can stick to surfaces and solidify. The graphite dust produced in a metal foundry is even trickier – it is highly conductive and, if it reaches the PLC’s electronic boards, it could cause a short circuit that would permanently damage the board. Graphite dust is also fl ammable, which exposes electrical equipment to fi re hazards. To keep contaminants at bay, it’s a good idea to regularly blow away dust and debris with canned air. This prevents the formation of dangerous build-up in the system and its components, including I/O modules.
24 February 2021 | Automation
Unlike personal and desktop computers, PLCs are designed to withstand harsh conditions in factories, in terms of temperature range, vibration, dust and moisture, among others
It is also possible to install the PLC in a low-dust enclosure. In this case, it’s important to prevent overheating by changing the ventilation fi lters often, and making sure that air can circulate freely. It’s also essential to check that its power sources are not causing any short circuits or electricity spikes and that power fl ows consistently. Another important step is to check that sockets, plugs and terminal strips are securely connected, especially in high-level vibration areas. Screws and bolts that secure the I/O modules and the PLC system should routinely be checked to prevent any rattling. Finally, electromagnetic or radio
interference can impact the functionality of a PLC. Such interference can be caused, for example, by handheld radio transmitters used by maintenance personnel, or even by routine factory processes such as welding. Shielding PLCs with proper materials or positioning them far from interference sources will help improve their performance.
Upgrades and life extension During the lifetime of a PLC, it might become necessary to upgrade the system, for example by adding or substituting I/O modules or replacing worn parts. For legacy PLCs it’s important to keep a stock of replacement parts on hand, especially for critical components such as those of the main CPU board. To avoid keeping vast parts inventories, it’s a
good idea to talk to a specialised supplier to ensure that if obsolete or end-of-life components wear, they can quickly be replaced before a breakage causes the PLC to stop.
When installing new I/O modules, it’s always good to check their backward compatibility. Modern I/O modules often support wireless and Ethernet connections, diagnostics for predictive maintenance and other features not necessarily found in legacy systems. However, new modules with backward compatibility should provide seamless integration with an older system. Some I/O modules can even be replaced when power is still on, allowing manufacturers to upgrade the system with zero downtime. Ideally, replacing the entire PLC for a new one should never be the consequence of failures and breakages – such an investment should be determined by a specifi c strategy for growth, and should only happen when the machine has objectively reached its limits in terms of how well it will serve the plant in the near future. Prevention, correct maintenance and
regular upgrades of both hardware and software can easily extend the active life of a PLC, regardless its age.
CONTACT:
EU Automation
www.euautomation.com/uk
automationmagazine.co.uk
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46
