In general, spares in the control system (PLC or DCS) are defined as consumable spares, commissioning spares, installed spares, 2 years operational spares, and mandatory spares.
Consumable spares and commissioning spares are normally recommended by the system vendor supplier.
These spares are meant to be consumed before the system is fully operational and these are required to avoid using any of the recommended operational spares. These spares are ordered along with main items.
For instance, Fuses, terminals, relays, printer cartridges, A3/A4 papers, and so on.
Installed spares as the name indicate, are installed within the control system. These spares are utilized when there is the failure of a component within the system so by using installed spare; the system is operational without any downtime.
The requirement of installed spare shall be defined as part of the project scope. Assume if one channel from 16 channel I/O card is not working then it is reconfigured with an installed spare within that I/O module.
Wired spares (as part of installed spare) are a ready-to-operate condition when field cable is connected to spare assigned terminals. Installed spares serve the purpose of replacement and/or future expansion/modification of the system.
Therefore, it has a significant role in overall control system design and its capacity.
2 Years operational spares are essential for the continual operation of the control system. This set of spare includes small items (fuses, relays) to large items (Controllers, servers). The scope of supply of these spares depends upon the project scope.
However, a list of recommendations can be provided by the control system vendor. These spare parts are in form of loose supply and not installed into the system.
On contrary, few spares take longer delivery time, hence, it is beneficial to have them in the warehouse to ensure the continual operation of the plant.
Once in a while, the mandatory spares are described as a part of the project scope. These are also loose spares like 2 Years operational spares and can be used in a lieu of 2 years operational spares.
These spares are used for the substitution of failed components or can also be used for future expansion.
Predominantly, spare space is also considered within the control system to ensure future capacity expansion.
It is paramount to understand the spare requirement defined in projects.
Additional examples of installed spares are as follows
Sometimes, it is pivotal to have a clear mutual understanding of spare parts and spare space when there are ambiguous requirements specified.
It is more appropriate to ask in case of unclear requirements as it will have an impact on overall control system design and related deliverables such as
Author: Jatin Katrodiya
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View Comments
For PLC or DCS System 2 Years Spare Part, is that mandatory to make a spare part stocks beside DI/DO/AI/AO module, like Communication Module, Bus Adapter, Interface Module, or even CPU Module?
Thanks for your answer
Yes, You need the spares including CPU and other parts as per your installed quantity.