Basic process control

Process control for animal cell fermentation should at least include a set point control of temperature, pH, pO and agitation rate. 

Cell and Tissue Culture Laboratory Procedures in Biotechnology, edited by A. Doyle and J.B. Griffiths. 1998 John Wiley Sons Ltd. 

Alternatively, for vessels up to 101, an electric heating band (barrel heater) may be used, having a power of approximately 30 W of reactor volume. In no case should heating rods or tubes inside the reactor be used, because localized high temperatures, aggravated by the low stirring rate, will cause unfavourable medium alterations and cell damage. 

The control unit of the reactor should be a quick-response sensor inside the reactor (preferably PtlOO with a three-wire connection) and a proportional controller to achieve optimal temperature constancy. In no case should there be a deviation of more than 0.2°C during operation (during initial warming a little more has to be accepted). 

The use of pressurized, sterilizable combined glass electrodes mounted through the reactor vessel wall is widely established. A high degree of accuracy and stabihty is needed to provide a good basis for the control loop. However, a recahbration is necessary both after sterilization and at regular intervals. This is easily done by external measurement after sampling the reactor, because the pH of the sample drifts very slowly. 

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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. 

Basic process control system (BPCS) loops are needed to control operating parameters like reactor temperature and pressure. This involves monitoring and manipulation of process variables. The batch process, however, is discontinuous. This adds a new dimension to batch control because of frequent start-ups and shutdowns. During these transient states, control-tuning parameters such as controller gain may have to be adjusted for optimum dynamic response. 

Same sensor used for basic process control system and safety instrumented system. Failure of sensor leads to loss of control system and safety system functionality. 

Eailure of basic process control system (BPCS) resulting in loss of control. 

Basic Process Control System (BPCS) and Safety Interlock System (SIS)... 

Basic process control terms are summarized below. 

LOPA is a semi-quantitative tool for analyzing and assessing risk. This method includes simplified methods to characterize the consequences and estimate the frequencies. Various layers of protection are added to a process, for example, to lower the frequency of the undesired consequences. The protection layers may include inherently safer concepts the basic process control system safety instrumented functions passive devices, such as dikes or blast walls active devices, such as relief valves and human intervention. This concept of layers of protection is illustrated in Figure 11-16. The combined effects of the protection layers and the consequences are then compared against some risk tolerance criteria. 

Determine the consequence frequency for a cooling water failure if the system is designed with two IPLs. The IPLs are human interaction with 10-min response time and a basic process control system (BPCS). 

Scale-up can also have a significant effect on the basic process control system and safety systems in a reactive process. In particular, a larger process will likely require more temperature sensors at different locations in the process to be able to rapidly detect the onset of out-of-control situations. Consideration should be given to the impact of higher-temperature gradients in plant-scale equipment compared to a laboratory or pilot plant reactor (Hendershot 2002). 

Design and implement a reliable and fault-tolerant basic process control system to ensure the design limitations of the primary containment system are not exceeded. 

Basic process control system (BPCS) System that responds to input signals from the process, its associated equipment, other programmable systems, and/or an operator and generates output signals,... 

Control layer Protection layer that is used to maintain the process within the normal operating limits, such as standard operating procedures, basic process control system, and process alarms. 

Introduction The chemical processing industry relies on many types of instrumented systems, e.g., the basic process control systems (BPCSs) and safety instrumented system (SIS). The BPCS controls the process on a continuous basis to maintain it within prescribed control limits. Operators supervise the process and, when necessary, take action on the process through the BPCS or other independent operator interface. The SIS detects the existence of unacceptable process conditions and takes action on the process to bring it to a safe state. In the past, these systems have also been called emergency shutdown systems, safety interlock systems, and safety critical systems. 

Definition of the Facility - A general description of the facility is identified. Input and outputs to the facility are noted, production, manning, basic process control system (BPCS), ESD, fire protection philosophy, assumptions, hazardous material compositions, etc. 

During the process hazards identification and definition phase of a project design, a basic process control system (BPCS) strategy is normally developed in conjunction with heat and material balances for the process. 

Whatever method is used, there should be a clear design philosophy for the basic process control system (BPCS) employed at a facility that is consistent throughout each process and throughout the facility. Consistency in application will avoid human factor errors by operators. The philosophy should cover measurements, displays, alarms, control loops, protective systems, interlocks, special valves (e.g., PSV,... 

Basic Process Control System (BPCS) - Pneumatic, electronic, hydraulic or programmable instruments and mechanisms that monitor and/or operate a facility or system to achieve a desired function, i.e., flow control, temperature measurement, etc., which are supervised by human observation. 

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). 

You may also find it useful to list the source on each note (basic process control system, interview, etc.)... 

Let s consider a typical basic process control loop (Figure 2.1). A pressure-indicating transmitter (PIT) sends the pressure signal to a proportional integral derivative controller (PID), which sends a signal to the control valve to... 

Similar to 234 Th, downcore profiles of 7Be can also be used to determine seasonal changes in sedimentation and sediment mixing rates in estuaries (Canuel et al., 1990). The basic assumption here, as described earlier, is that the nuclide (e.g., 7Be) traces movements of particles during sediment accumulation and that the delivery and trapping of the nuclide to surface sediments is uniform across habitats within an estuary. The three basic processes controlling the depth distribution are (1) supply rate from sedimentation (2) radioactive decay and (3) postdepositional particle mixing processes. Finally, it should be noted that using 7Be for the aforementioned purposes also requires concurrent measurement of 7Be in atmospheric fallout (Canuel et al., 1990). 

The scope embraces continuous processes with reaction and separation sections. Because our approach in this book is based upon a plantwide perspective, we cover what is relevant to this particular area. We omit much basic process control material that constitutes the framework and provides the tools for dynamic analysis, stability, system identification, and controller tuning. But we refer the interested reader... 

Greg Shinskey (1988), over the course of a long and productive career at Foxboro, has proposed a number of advanced control" structures that permit improvements in dynamic performance. These schemes are not only effective, but they are simple to implement in basic control instrumentation. Liberal use should be made of ratio control, cascade control, override control, and valve-position (optimizing) control. These strategies are covered in most basic process control textbooks. 

In a basic process control action a manipulated variable is adjusted by the controller such as to influence a controlled variable to stay at a given set point. The control action in multistage columns can be a challenge for a number of reasons, some of which are briefly discussed here. 

Consider using statistical process control, reexamine the types and locations of sensors, and use the four basic levels of control (1) basic process control system, (2) alarm system,... 

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