Process management, instrumentation/control systems

It is important that personnel understand how to achieve safe operation, but not at the exclusion of other important considerations, such as reliability, operability, and maintainability. The chemical industry has also found significant benefit to plant productivity and operability when SIS work processes are used to design and manage other instrumented protective systems (IPS), such as those mitigating potential economic and business losses. The CCPS book (2007) Guidelines for Safe and Reliable Instrumented Protective Systems discusses the activities and quality control measures necessary to achieve safe and reliable operation throughout the IPS lifecycle. 

Suggested control and instrumentation for the management of process components are shown in API RP I4C which is still relatively the standard within the industry. All process control systems are usually reviewed by a Process Hazard Analysis, which will deem if the provided mechanism area is adequate to prevent a catastrophic incident. 

Where loss of control could lead to severe consequences, the integrity of the basic process control system and the protective safeguards must be designed, operated and maintained to a high standard. Industry standards such as ANSI/ISA-S84.01 (1996) and IEC 61508 (2000) address the issues of how to design, operate and maintain safety instrumented systems such as high temperature interlocks to achieve the necessary level of functional safety. The scope of these standards includes hardware, software, human factors and management (HSE 2000). 

Keep the control system as simple as possible. Everyone involved in the process, from the operators up to the plant manager, should be able to understand the system. Use as few pieces of control hardware as possible. Every additional gadget that is included in the system is one more item that can fail or drift. The instrument salesperson will never tell you this, of course. 1 Use feedforward control to compensate for large, frequent, and measurable disturbances. 

Operational and maintenance plans should be prepared for the computer system and its associated measurement and control instrumentation. Operational plan review will focus on system reliability, performance, diagnostic records, instrument and system I/O calibration, and the provision of critical data to support the batch record. Procedures for controlling the system (e.g., system management, security, and process operations) should be reviewed to verify that they are current, in place, and being followed. For each procedure required for the system there should be documented evidence that the relevant operatives have been trained in its use. All procedures must be written and approved according to the site procedures for writing and approving SOPs. 

Control And Data Acquisition (SCADA), Industrial PC systems, and Distributed Control Systems (DCS). Measurement and control systems and process management systems are often integrated together. Process Analytical Technology (PAT) is a special case implementing nonintrusive process instrumentation. 

Because research and development engineers are not able to deal effectively with control system design, it is likely that many potentially profitable chemical processes never see the light of day. Processes which cannot be managed by conventional control instrumentation hardware are just not studied or developed, although a little imagination and an appreciation of what is involved in controlled loop behavior might make the processes commercially feasible. 

Automation of analytical instrumentation, sample preparation, laboratory data management techniques, and process analytical chemistry (M>), has been an important component in the improvement in productivity in the analytical laboratory. The integration of expert systems into the automation process will become increasingly commonplace for laboratories in which large amounts of data must be managed, and complex quality assurance programs maintained (LJi)- When instrument control and data... 

The management system model can also be characterized as a feedback or closed-loop control system. In this version, the management team is the controller (who), the process is the system being controlled (what), and the instrumentation (how) monitors the system states and feeds these back to the controller so that deviations between the actual and the desired states can be nulled. The interfaces between each of the elements also represent the management process. Between the what and the how elements is the measurement-to-data interface. Between the how and who elements is the information portrayal/information perception interface. And between the who and the what elements is the decision-to-action interface. Viewed from the perspective of this model, the management of a function would entail ... 

A dramatic decrease of the time of analysis can be achieved by using narrower columns combined with an adjusted improved electronic pressure control system. As today in most forensic science laboratories the procedures developed with the normal capillary GC instrumentation are part of a quality management system, a major change using the possibilities of Fast GC requires a new validation. This, together with the high level of performance reached during the last 15 years in capillary GC, may to some extent slow down the process of innovation in this area. 

A. Coleman, Safety Instrumented Systems Control Valves as Final Elements, Emerson Process Management Chemical Engineering, January 2011. 

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