This is the final part in the five part series on how to write an effective User Requirement Specification (URS). The topic of this final post is ‘Hardware’.
As before, I am really interested in seeing your comments on this. I think understanding other people’s views is really important to people who may be reading this.
My other posts in this series are:
These are my tips to consider when writing about the hardware in your URS:
- Include floor plans of the proposed equipment locations and use this to explain what should be in each room. Explain what power and earthing facilities are available in each room.
- If there are groupings of signals around equipment locations. Consider indicating quantities against the equipment locations on your floor plans. For field based enclosures this will help determine the optimum locations to reduce cabling.
- Do the equipment rooms have easy access for a cabinet? Are there stairs to be navigated? Do we need to include lifting kits? It is important to understand the restrictions as they may impact cabinet build.
- Are there any size or weight restrictions? Any need for earthquake stabilisers? If the answer to any of these questions is yes then explain what the limitations are. Sometimes on projects, space constraints are a major factor. This is often the case on brownfield projects and can impact the designs.
- Describe how the plant interface will be arranged. For example how the I/O will be segregated and the quantities and types at each location.
- Include details of signals which are coming across the serial links. What types are they? What are the protocols? This may be important for the specification of gateways.
- What is the atmosphere like at the final enclosure location? Does it get really hot in the summer months or really damp in the winter? These may affect the heat dissipation and therefore the design.
- Are you bothered about the physical cabinet design? Companies often offer off the shelf cabinets which can be cheaper to purchase and the lead-time is less.
- How many operators will reside in the control room? Do they sit at the consoles or treat the operator station as an additional operator? If so then you may need klaxons.
- Do the operators get disturbed often by field technicians wishing to look at their screens? If so, consider a dedicated screen and meeting area (away from the operator) where they can see the plant status and discuss it.
- How many workstations and servers do you require? Virtual systems are available now. By providing this information your supplier may be able to calculate if it is worth you going virtual based on hardware cost.
- Do the operators need to access multiple systems on a regular basis? If so, can they coexist on the same monitors and can they be controlled using the same peripherals?
- Does the same operator work on the control system and in the field? If so, consider the use of wireless tablets or laptops.
- What level of physical redundancy do you require in your hardware?
- Do you have existing marshalling which needs to be interfaced to? Do you have existing barriers? This may affect the reliability of your system and could be a factor for risk mitigation studies
- Are all the field I/O points in the existing cabinets connected to equipment which is still used? By understanding what is required in the field and what is not can lead to a reduction in the footprint of your system and price.
- What type of cutover strategy is required? Sometimes the hardware specified can be tailored to the needs of the cutover strategy.
- Can existing cabinets be reused by inserting a new backplane? This can be a cleaner solution on some projects.
- Do you need new doors for your cabinets? Older cabinets can have missing doors. These may be replaced during your project to improve the security of your system.
- How accurate is your information on the hardware? Some hardware solutions are more flexible than others. These is often beneficial to Greenfield projects where I/O can be specified before all the packages have been specified.
I hope you have enjoyed reading this five part series and that you have found it useful. Please feel to add your own experience to this.
From Jim: We appreciate any insights and comments you have and you can connect and interact with other automation project experts in the Plan & Design group in the Emerson Exchange 365 community.