Supervisory system

Plants are particularly vulnerable to human error during shutdowns for repair and maintenance. Tfiis is partly due to the higher level of direct human involvement with the plant, when errors are likely if procedures and supervisory systems are poor. Errors also occur during high stress situations such as emergency shutdowns. Workers need to be trained in how to handle these situations so that less stress is experienced (see Chapter 3). 

The plant components selected should be of proven design supported by strong reference installations. Modem trends are moving towards reduction in manning levels, and the use of central computer control and supervisory systems also ensures maximum efficiency of plant operation. 

Rodriguez-Roda 1, Comas J, Colprim J, Poch M, Sanchez-Marre M, Cortes U, Baeza J, Lafuente J (2002) A hybrid supervisory system to support wastewater treatment plant operation implementation and validation. Water Sci Technol 45(4—5) 289-297... 

All electrical systems, including detection, alarms, supervisory systems, and manual activation systems, should be function tested to ensure proper operation. 

Fire protection system impairment occurs when a fire alarm or supervisory system is shut-off, damaged, fails, or is otherwise taken out-of-service completely or in part. These out-of-service conditions are called impairments. While process monitoring, control, safety, and security-entry systems also provide protective functions, this element of the fire prevention program is only concerned with impairments to fire protection systems and equipment. An essential element of the fire prevention program is a procedure for fire protection impairment handling. 

A set-point control is mainly used to control process variables such as temperature and pH. For example, temperature is controlled by heating and cooling by cooling water, and pH is maintained by the addition of acid and alkali. The modification of a set-point will be done manually or by the DCS, which works as a supervisory system. 

Modelling and Analysis of Hybrid Supervisory Systems Emilia Villani, Paulo E. Miyagi and Robert Valette... 

Because of the batchwise nature of electronic materials processing and the long process sequences, a supervisory system is essential. This system collects information on the state of the system gives status of work in progress schedules work based on process priorities, product requirement, equipment readiness, and materials availability and controls product and raw material inventories. Materials handling concerns the physical movement of wafers through the fabrication line via various mechanical means [32] and is therefore primarily a mechanical engineering problem. The control of the individual unit operations and the incorporation of local control functions in... 

FIG. 21 -51 a Inspection system for an integrated-packaging line packing tablets into glass bottles. Machine vision, bar code technology, and sensor technology are linked together by a supervisory system. Courtesy of AGR International, Inc., Butler, PA 16003.)... 

Hot Oil System. The hot oil system is a self-contained unit consisting of a 7.2 million British thermal units per hour (Btu/hr) gas-fired burner, flame supervisory system, oil reservoir, hot oil pump and associated controls. 

The routing of AGVs is basically performed by a supervisory system. Changes of transport sequences can therefore be implemented immediately as needs arise. The AGV system is therefore highly flexible, limited only by the limitations in the navigation system. 

Additions and improvements to the control system, including partial transfer of the back-up panel to a computer-based supervisory system. 

With the ever increasing complexity of modern engineering systems comes the demand for the ability of a system to autonomously monitor its performance, to detect, isolate and identily faults in critical components. This does not only mean to develop fault diagnosis and supervisory systems for existing systems and processes... 

The alternative to separate control of the header pressures is to control one pressure directly and the other through a differential pressure controller referred to the first. With this alternative, the more frequent choice is to control the chlorine pressure and the hydrogen/chlorine differential pressure. This takes advantage of better control dynamics. An argument for this approach is that it is the quality of the differential pressure control that may determine the life of the membranes, and there is only one control loop variance to deal with. In a poorly designed system, however, responses to the two control signals can be out of phase and introduce fluctuations in the pressures. In order to have a consistent approach in this presentation, we assume that the two header pressures are controlled separately and directly. Differential pressure is measured directly or computed from the outputs of the two pressure transmitters. Monitoring, alarm, and supervisory systems can be appropriate to individual applications. 

Fig. 9.10 P ID system with supervisory control Table 9.6 Rules for supervisory system... 

The supervisory system can achieve a better response in terms of speed and stability. As an example, if the temperature is acceptable but the flow rate is very low, the supervisory system simultaneously increases the flow of hot and cold water, achieving a greater flow but without changing the temperature. Another example is where the temperature is too high and the total flow too low. In that case, the system will maintain the hot water flow and increase the cold water flow this would result in a lower temperature and a higher flow, favoring both goals at once. 

Implicit in the development or implementation of a data-driven system is a description of the data model and the data requirements. The data model, in common with other system components, should be developed to the same integrity as the overall system. Unfortunately, experience and anecdotal evidence suggests that this is not commonly the case. Development of the data model is complicated by the fact that many systems interface with peer, subordinate and supervisory systems [Faulkner 2002, Storey 2003]. 

The level of automation depends largely on site preference and a high level of automation is normally only justifiable when several products at different capacities are manufactured on a single plant. In this case it is important to ensure correct routing of feedstock to reactor and product to storage. Routing of this type can be incorporated into logic checks within the supervisory system. Even in this case, valve automation may not be justified and manual valves fitted with proximity switches can be used to inform the system that the operator has actuated the correct valves. 

FSSS Eumace safeguard and supervisory system (boiler)... 

Node-oriented PTU In computer architecture nodes normally operate independently for their associated application. In a node-oriented FTU, there is replication of the node(s). In case of failure of the primary node, the designated replicas of the primary nodes will take over with a necessary mechanism to allow just one replicated unit to take over to avoid collisions or contention [9]. There are a number of hoiler controls in a power plant, namely, a closed loop control such as a superheater temperature control, furnace safeguard and supervisory system, high pressure bypass, etc., each with different apparently independent applications. In node-based architecture, there may be FTUs for each of these control systems acting as one node. In a particular node, when one of the main units fails any one of the standby controllers takes over irrespective of the application. Here the major concern is the size and capacity, and also the changeover mechanism. 

As described above, in order to be able to approach flaws in their supervisory approach, it is critical that organizations fully understand their current supervisory arrangements and the flaws associated with it. Weaknesses associated with different forms of supervision include a lack of team member interaction with the supervisor, lack of team member autonomy, overloading of supervisor, lack of team member development, lack of clarity over roles and responsibilities, and a lack of leadership (Ward et al., 2004). It is also critical for organizations to identify when their supervisory system is not functioning effectively. 

Continually monitor and assess the supervisory system to ensure that it is working efficiently and to highlight any problems associated with it. Countermeasures should be taken immediately to address any problems identified (see Table 8.3, Table 8.4, and Table 8.5 for examples). 

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