Instrumentation/control systems issues

Safety issues in batch reaction systems relating to instrument/control systems are presented in Table 5. The table is meant to be illustrative but not comprehensive. 

Moisture Instrumentation , Buyers Guide Issue, Instruments Control Systems (1973)... 

The papers on NDT issues are also published by the Defectoscopiya , Instruments and Control Systems, Oil and gas, Shipbuilding and other journals... 

The fact that batch processes are not carried out at steady state conditions imposes broad demands on the control system. The instrumentation and control system have to be selected to provide adequate control for a wide variety of operating conditions and a wide variety of processes. In addition, basic process control and shutdown systems have to deal with sequencing issues. This chapter presents issues and concerns related to safety of instrumentation and control in batch reaction systems, and provides potential solutions. 

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). 

Under normal operating conditions, the National Instruments controller monitors for process faults and takes corrective action upon identification. The system will override operator commands issued at the HMI during a safety interlock. The unsafe conditions that result in a process interlock are ... 

An important issue to be considered at an early stage is whether there are any common oause failures between redundant parts within each layer (for example, between 2 pressure relief valves on the same vessel), between safety layers or between safety layers and the BPCS. An example of this could be where failure of a basic process control system measurement could oause a demand on the safety instrumented system and a device with the same characteristics is used within the safety instrumented system. In such cases it will be necessary to establish if there are oredible failure modes that could cause failure of both devices at the same time. Where a common cause of failure is identified then the following actions can be taken. 

Generic Safety Issue (GSI) 064 in NUREG-0933 (Reference 1), addresses the establishment of guidance for the identification of the mechanical sensing lines which interface with safety-related instrumentation and controls systems. 

Seattle Starpath Publications, 2009. Written to assist the practicing weather forecaster, with chapters on weather forecasting on land and sea. Contains an excellent history of the held as well as methods for instrument calibration and maintenance. GDlum, Donald R. Industrial Pressure, Level, and Density Measurement. 2d ed. Research Triangle Park, N.C. International Society for Automation, 2009. Teaching and learning resource on the issues and methods of pressure measurement, especially related to industrial control systems. Contains assessment questions at the end of each section. 

When discussions are to be developed for safety instrumentation functions, associated controls (logic solver) cannot be kept aside. Now, for discussions on control systems, special attention is necessary for batch process and controls. Plant processes and productions can be categorized as discrete process, continuous process, and batch process. Out of these three types, batch process is more complex in the sense that the problems are logisticaUy more challenging. In order to meet this challenge, complex issues are divided into simpler steps, then solving them, and all the solutions are integrated suitably to arrive at a solution for the complex issue. In this way, batch controls follow a special pattern and established standards. Definitions of various processes, with examples, are discussed as follows ... 

The basic characteristics of alarm systems have already been covered at length in Chapter IX. Since an alarm is one of the most fundamental issues in a control system, it will be discussed here again in this context. In this clause, focus will be on independent alarm systems that can be applied to critical applications independently of a programmable logic controller/distributed control system (PLC/DCS). In spite of so much technological developments and modem instrumentation and... 

Digital instrumentation and control systems in nuclear power plants, safety and reliability issues, prepared by National Research Council. 

There are two basic designs of drag flow rheometers controlled strain with stress measurement and controlled stress with strain measurement. Below we Hrst discuss strain control and torque measurement (Section 8.2.2) followed by instrument alignment problems (Section 8.2.3) and normal stress measurement (Section 8.2.4). Then we treat special design issues for stress control. Both designs use the same type of environmental control system, as discussed in Section 8.2.6. 

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