This blog was co-authored by Lydea Soh, Mary Goode, and Neil Hunter.
Control rooms are an essential part of ensuring the smooth operations of many sites. Their key role is to provide a means to oversee and respond to changes in the system’s state, but they also serve as a key location for critical communication and handovers.
With it being such a central hub for a well-functioning system, it is important that these rooms are designed and optimised to equip every Control Room Operator (CRO) with the capability and capacity to perform their responsibilities efficiently.
Yet, poor control room design has been a contributory factor in many well-known accidents e.g. Three Mile Island (1979), Chernobyl (1986), Deepwater Horizon (2010). A review of recent HSE improvement notices, and observations at some of our clients’ sites, indicate that this can still be an issue, particularly in relation to the design of alarm management systems.
Examples of poor design included persistently high numbers of standing alarms, inappropriate alarm prioritisation (making important alarms difficult to discriminate from those of less importance) and, alarm rates that are unmanageable for operators in abnormal plant conditions. Other examples include the inappropriate location of control rooms, and inadequate design of doors (e.g. failing to close securely, or lacking seals), with the potential to expose operators to hazardous material in the event of an incident.
In this blog, we cover some of the key principles behind effective control room design, drawing upon guidance such as The Engineering Equipment and Materials Users Association (EEMUA) guidance on Control Room Design (EEMUA 201), as well as EEMUA 191, which addresses the design of Alarm Systems.
What is a good control room design?
If you search online for “What makes a control room design good?”, you’ll be met with plenty of search results with different answers. However, most of these results come back to the same core theme of supporting the control room team through:
- Good ergonomics design, e.g. comfort, lighting, sufficient space
- Quicker decision-making processes, aided by the provision of relevant information
- Effective coordination during critical responses and process upsets
This blog walks through the key elements and considerations to address the points above.
Understanding the tasks
A way to ensure a control room (or any other part of a plant) is designed well from a Human Factors perspective is to have clarity and understanding on the exact activities and tasks that will be carried out in the room so that design of the consoles, room layout, and HMIs are centred on the users.
Sites can conduct a Task Requirements Analysis (TRA) to understand, at a high level,
- how the control room is used, including the tasks being carried out within it
- the equipment and resources which are required to complete these tasks
- important communication links between different users of the control room.
The outputs of the TRA help inform design requirements for both physical layout and HMI design alike.
Any task flagged as safety-critical or complex then benefits from undertaking a Safety Critical Task Analysis (SCTA), which is a more detailed analysis into how the task is performed so that the consoles and HMI can be built around the requirements of the process.
Control room design
As mentioned earlier, control rooms are the central location for many activities. Besides the usual monitoring, this room is also where shift handovers, briefings, on-the-job training, and emergency responses happen. Therefore, it is important to consider the availability of physical space within the control room for everyone to carry out their tasks.
Having sufficient space will impact overall comfort for the CROs to carry out their work. If the control room is small, it might negatively impact the accessibility of certain consoles, especially if there are multiple people present in the room. Generally, a control room with two CROs will require 45m2, with an additional 10m2 for every new CRO to ensure enough working space for everyone (EEMUA 201). The room should also be square or rectangular in shape as it provides flexibility for the optimum console layouts for overall information visibility.
Besides the size and physical layout, the lighting and noise should also be designed to support the CROs with their job and wellbeing. Adequate lighting will help with navigating around the room and for general performance when reading screens and documents, while noise levels must be kept to a level where it minimises disruption to the CROs.
The guidance states that lighting levels for the Control Rooms should be around 500 Lux for the main area, which is similar to a well-lit office space and bright enough to sustain any screen and off-screen work. Other areas should be around 200 Lux and bright enough to see and move around safely.
Excessive noise levels are unpleasant for those occupying the room for long periods of time. This hinders conversations and discussions and can also reduce the ability to detect any alarm signals. Meanwhile, very low noise levels could also be a distraction as any changes to noise in the environment would be disruptive. A good balance would be to have some background noise within the range of 40db(A) and 60db(A). Some examples of this would be the soft hum of a fan, and normal conversation noise. Any major fluctuations in background noise, except for alarms, should be avoided.
Human Machine Interface
A large majority of CROs’ work relies on extracting information from various screens and hardware to build their understanding of the plant’s state enabling them to respond accordingly. This means that how this information is displayed and accessed should be designed to support effective decision-making and can be achieved by ensuring that the Human Machine Interface (HMI) is optimised for their requirements.
To support with quick, informed decision-making, HMIs should be
- Intuitive to navigate: CROs need to move quickly between different screens to gather information to build an accurate mental model of the current plant state.
- Purposeful: The information shown on screen should be relevant to the context like showing overall trends in the “Overview” screen, and not detailed information.
- Layered: Screens should follow a hierarchy so not all information is presented at once. This avoids information overload and unnecessary divided attention (e.g. an “Overview” screen shows the big picture which CROs can click on to access exact details for more information)
- Consistent: All measurement units shown should be consistent. If any colours and symbols are used, it is important that they are based on a pre-defined standard and used accordingly (e.g. reds are only used for alarms)
- Standardised in function: For example, turning a dial on the screen from left to right on the screen should always increase the value
- Clear in flagging critical information: Any critical information should be easily seen, even at a glance. (e.g. flagging when a gauge level is reaching the “danger zone”)
- Formatted to show information quickly: Text for identifying items and displaying process data should be easily understood
Alarm management
Alarms are a crucial component of a control room. With so many processes to monitor and oversee, CROs are often dependent on alarms to highlight any abnormalities and process upsets during a shift. Well-designed alarms should act as signals for CROs to respond accordingly.
The alarm configuration should be planned and managed based on how the processes take place on site. It is tempting to configure the system where any process upsets trigger an alarm. However, this could be counterproductive. Too many alarms could lead to alarm overload and, at worst, unnecessary or unhelpful alarms can lead to CROs ignoring the alarms (like the boy who cried wolf).
Alarms should be seen and heard clearly to ensure that they are attended to. However, as mentioned earlier, excessive noise levels could become a source of distraction. A good rule of thumb is that alarms should be around 10db(A) above the overall background noise level and focused to a specific area with directional speakers to minimise distractions to others in the room.
In terms of HMI design, any alarms that appear on the screen should also be immediately obvious and visible. Sensible use of colour to help highlight an alarm, shown at a visible place on the screen, will help the CRO to respond accordingly.
Besides making sure alarms can be seen and heard, alarms should be prioritised so that the most critical issues stand out from less serious ones. Rather than competing for a CRO’s attention, the alarm system helps the CRO understand what needs to be dealt with first. If there are more than one CRO in the room, these alarms need to be clearly segregated so each person can easily identify and respond to them. This avoids any possible confusion that could arise if responsibility is not clearly assigned.
Our colleague Neil Hunter previously wrote a blog on how SHERPA’s Alarm Review Tool (ART) can support the alarm design. Read more here: The Human Factors Psychology Behind Alarm Response
Conclusion
A well-designed control room is built around the principle that it should fit the requirements of the CROs, rather than having the CROs adapt to the design. Whether it’s the physical layout, HMI, or alarm management, each element should be shaped around how CROs actually work, supporting quicker decisions, easing coordination, and giving them the working environment they need to do a demanding job well, shift after shift.
If you’re planning a new control room, or reviewing an existing one, understanding the tasks early is essential to getting the design right from the start. Our other blog Human Factors Engineering in Projects looks at how you can apply the SCTA methodology in more depth.
