Alarm status displays

The alarm systems should have a philosophy that relates to the input data - number, types, degree of alarm, and displays and priorities. The information load on the operator has to be constantly taken into consideration, e.g., the distinction between alarms and status signals versus operator action that needs to be initiated. 

Failure status display (alarm lamp keeps illuminating). 

The visual display units (VDU) based operator-interface integrates a number of systems into one flexible interface technology. This includes the use of large screen displays that enable plant overview and alarm status information to be visible from any likely operator location in the main control room, thus facilitating crew group plant status awareness and decisionmaking. 

Each of these categories represents different activities, behaviors, and competencies. It is therefore not surprising that the display requirements for these categories of activity differ. Guidelines such as EEMUA 201 2002 advocate the use of multiple screens, such that read-only screens display only the current system picture and alarms status. These displays should be supplemented with additional displays for optimization and abnormal situation handling. 

On correct entry of the password the system status display can be accessed. This takes the form of a picture display of the system showing all valves, pump and sensor outputs (Fig. 1-4). Colours are used to display the active flow path and windows are used for numerical display of all sensor outputs. The display is also interactive, allowing the operator to switch valves and pumps by moving the cursor to the appropriate switch on the display and clicking the mouse. Thus this display is all that is required to both monitor and control the system manually. In addition, should an alarm condition occur a separate alarm panel is displayed, indicating which alarm has been triggered. 

Representational layout of control panels. Where the physical location of items is important, for example, area displays in fire control systems, the layout of the displays on a control panel should reflect the geographical layout of the plant. In other cases a functional arrangement of the elements of the process plant will be appropriate, for example, when monitoring the status of the system via an alarm panel. 

In addition to the abbreviated LCD display on the fire alarm panel, an annunciator should be provided to graphically display facility conditions in all areas. Often this annunciator is an additional panel provided with the fire alarm system, which contains a graphic display or representation of the plant or area being monitored as well as illumination capabilities which identify the status of all monitored plant areas. 

Operator interface with system is via a two position operator s console. Each operator has two working color CRTs and a custom keyboard. A fifth single CRT dedicated to alarm displays is shared by both operator positions. Additional equipment includes multi-pen chart recorders, alarm logger and report typer. The operator monitors operations via continuously updated custom graphic displays, status and alarm reports on the CRTs and can call up displays and execute control commands by using special function push buttons in the keyboard. 

The original GC control system took the form of a central room which monitors the flowllne6, oil, water, and utility sections, plus a smaller satellite control room monitoring the gas compression and gas conditioning section of the plant. Closed loop process control, such as separator liquid level, pressure, flow and temperature control were handled by local pneumatic analog controllers. The key process variables are displayed in the control room via electronic instrumentation. All the key process and equipment trouble alarms are annunciated m the control rooms, plus the on/off status of key machinery and open/close status of key valves are displayed. 

Monitors the status of the analyzers and displays alarms and transmits them to peripherals. 

The physical forms of readout and alarms depend on the status of the instrumentation. A handheld device with LCD display and input buttons/pads is adopted by most manufacturers. An audio alarm is also available. An on-screen menu-driven method is used for setting up user features such as display content and styles. A historical glucose graph is also available. 

An operator interface is used to record data gathered by the PLC.1 The operator interface is usually another computer (sometime called the human-machine interface or HMI). The HMI uses process displays with real-time sensor readings so that the operator can quickly assess the status of the system (see Figure 6.17). The operator uses the control panel to adjust alarm settings and to turn on and off process equipment. Once running, however, the PLC controls and runs the system automatically, without further input from the operator. Common HMI status indicators are listed below ... 

Data Logging, Archiving, Trending Display, Alarms, Messages and Status Reporting... 

Data logging, archiving, trending display, alarms, messages and status reporting... 

Safety-related information should be distinguished from non-safety-related information and highlighted. In addition, when safety interlocks are being overridden, their status should be displayed. Similarly, if safety-related alarms are temporarily inhibited, which may be reasonable to allow so that the operator can deal with the problem without being continually interrupted by additional alarms, the inhibit status should be shown on the display. Make warning displays brief and simple. 

Video display capability of abnormal cable tension, rod motion, rod position and various Control System malfunctions is available in the main control room. These displays provide alarm and system status indication to the operator. 

A read-only communications link should exist between the ESD and plant control systems to allow the display of alarm and status irrftnmation to the operator... 

Room 105/106 has been established as the Operations Center for the HCF, and is the normal route for entry and exit from the HCF. This Center serves as the focal point for communications to personnel working in the facility. HCF system status and radiological conditions are monitored and displayed at this Center. Additionally, there are diverse and redundant modes of communication throughout the facility, under both normal and emergency conditions. There are three communication systems used in the HCF (not including radiation, fire, or intrusion alarms) (1) a telephone system, (2) a public address (PA) system, and (3) an intercom system. 

Data links are used to communicate between the control stations and the control and protection system. The alarm system which categorizes, prioritizes, and displays alarms is interfaced to a modem display system that makes it easy for operators to analyze the status of the whole system while sitting in their work stations (sit down see-over operation). The operator can select any function and the relevant displays will appear on the screen. The operator can interrogate that function for any information. The operator could also select any component and alter its current status. 

Human factor engineers should determine (for example by human factor task analysis) the nature of annunciation and the equipment to be used to provide it (for example messages that are alarm window based or visual display unit based). They should also determine how best to provide plant operators and main-tainers with the information they need to fiilly understand the plant status at all times and with the means of making operational adjustments when necessaty. These decisions could necessitate additional hardware interfaces and software functionality. 

Clear unambiguous displays of levels/alarms and plant status. 

The overall purpose of the main eontrol room is to provide a comfortable environment for die operators and supervisors to safely, efficiently, and reliably monitor and control plant process during normal, abnormal, and accident conditions. Displays are provided to enable the operators to determine the plant status, and control facilities are provided to allow the operators to execute control actions. Alarms are provided to draw the operators attention to key indications that may... 

Remote (or mimic) panels are required with gas detection and alarm systems. These are a visual display board that should be situated in a position near the main entrance that is clearly visible from the outside of the building. When the detection/alarm system is activated, the remote panel indicates the affected zone and whether the status is warning or alarm. This allows the emergency services or others to assess the situahon without entering the building. 

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