Equipment control systems

Narrowly focused, the tenets of 21 CFR 11 are indisputable that firms must establish and maintain the integrity of their electronic information. What has been lost is the clear indication of which electronic information the requirements apply to. In my opinion, data generated outside a computerized system, that are manipulated by that system and are ultimately available in hard copy should not be subject to this ruling. Validation of the computerized system should be more than sufficient to establish that the final documentation accurately reflects the input information. In that instance, the computerized system is little more than a tool whose functionality can be readily established, yet firms are endeavoring to assure 21 CFR 11 compliance for numerous systems in which the computer is little more than an adjunct to the cGMP activity and corresponding hard copy. Batch record preparation, SOP and test method archives, and many process equipment control systems are examples of systems in which requirements for 21 CFR 11 compliance appear excessive. A system that processes or communicates data or records and subsequently retains and stores hard copies should not be subject to the 21 CFR 11 requirements. Far too many systems are being unnecessarily held to the very restrictive portions of 21 CFR 11. Electronic record retention as defined in 21 CFR 11 has its place, but not necessarily in every computerized system used within the industry. 

Occasionally the qualitative and intuitive methods of risk assessment fail, and something better is required. For example, a designer may have taken steps to address some hazard, but be unsure whether these are sufficient. There is also the possibility of failure of equipment, control systems or operating procedures which may reduce margins of safety. In these circumstances, quantitative risk assessment may be considered. This is an attempt to put numbers to the risks so that we can judge them objectively. 

A term used to cover a broad range of systems, including automated manufacturing equipment, control systems, automated laboratory systems. Manufacturing Execution Systems (MESs) and computers running laboratory or... 

The rationale behind the definitions of iow demand mode and high demand or continuous mode in lEC 61508 is based on the failure behaviour of a safety-related system due to random hardware faults. Underlying much of the reasoning is the distinction between safety-functions that only operate on demand and those that operate continuously . A safety function that operates on demand has no influence until a demand arises, at which time the safety function acts to transfer the associated equipment into a safe state. A simple example of such a safety function is a high level trip on a liquid storage tank. The level of liquid in the tank is controlled in normal operation by a separate control system, but is monitored by the safety-related system. If a fault develops in the level control system that causes the level to exceed a pre-determined value, then the safety-related system closes the feed valve. With such a safety function, a hazardous event (in this case, overspill) will only occur if the safety function is in a failed state at the time a demand (resulting from a failure of the associated equipment or equipment control system) occurs. A failure of the safety function will not, of itself, lead to a hazardous event. This model is illustrated in Figure 4. 

Human activity Hazards caused by insufficient control or incorrect warning display, life support, probable action error, hazardous location Injury or even death caused by abrasion, cuts, bruises, bums, falls, etc. Sensory impairment or loss. Equipment/control system damage caused by maloperation, handling, or nonuse of protection... 

HAZOP is used to identify the design, operating, and quality problems related to planned process. Operational problems generally come from human error, operating procedural error, or from equipment/control system reliability issues. HAZOP is well suited for such applications. 

Human error, equipment/control system failure, or procedural mistakes should be dealt with properly. 

The need for I C upgrade projects can pose major challenges to plant operators. The nature of I C equipment - control systems, alarm systans, protection systems - is... 

Control systems are safe and chosen taking account of expected failures, faults and constraints in the planned use of the work equipment Control systems do not create increased risk to health or safety and that any fault in or damage to any part of the control system or loss of supply of energy used by the work equipment cannot result in additional or increased risk to health or safety or impede the operation of stop and emergency stop controls... 

Liquid chemical feed systems consist of storage tanks (with containment for hazardous chemicals), chemical piping, and metering pumps (with calibration equipment). Control systems monitor the level of chemical in the tanks, pressure and flow in the piping, and pump settings. A schematic of a typical liquid chemical feed system is shown in Figure 7-1. 

EnvironmexAsia (Asian Int l Environmental Management Technology, Equipment Control Systems Exhibition Conference, with WatermexAsia2003, Asian Int l Water Management Technology, Equipment Control Systems Exhibition Conference)... 

If improvements should be achieved by an automation of the inspection process this requires a control of the process parameters of the whole equipment by an integrated "intelligent" system and not by displays still being controlled by the human inspector. This integrated control-system ensures that the inspection conditions are at the highest reproduction level. 

To operate the MPI or LPI equipment at stable and reprodncable inspection conditions modern units are equipped with a monitoring and control system called "Quality Assurance Package" (termed QAP). The QAP System is ba.sed on an industrial PC with a bus system and field sensors. It ensures that process parameters important for the reproducability of the MPI or LPI are controlled an held between defined limits by a central computer system. It can be adapted to any old system, as well as integrated into new systems. 

Pollutants. The problems posed by ak pollutants are very serious. Within a museum, measures can be taken to remove harmful substances as efficiently as possible by means of the installation of appropriate filter systems in the ventilation equipment. Proposed specification values for museum climate-control systems requke filtering systems having an efficiency for particulate removal in the dioctyl phthalate test of 60—80%. Systems must be able to limit both sulfur dioxide and nitrogen dioxide concentrations <10 /ig/m, and ozone to <2 /ig/m. ... 

Beneficiation faciUties require air and water pollution control systems, including efficient control of dust emissions, treatment of process water, and proper disposal of tailings (see AiRPOLLUTlON CONTROLMETHODS). In handling finished fluorspar, operators must avoid breathing fluorspar dust and contacting fluorspar with acids. Proper disposal of spills and the use of respirators and other personnel protective equipment must be observed. Contact with fluorspar may irritate the skin and eyes. 

The impact of the regulations in Table 4 is to require users and producers of VOC ketones to limit release by either reformulating to new solvent systems, to install environmental control systems which recover and recycle solvents, or reduce emissions with carbon absorption beds or incineration equipment. The use of some individual ketones will decline further, but the overall short-term use of ketones is forecast to remain stable (10). 

Three types of computer control systems are commonly used for pilot-plant instmmentation. The first is a centralized system, usually based on a minicomputer or occasionally a mainframe. These systems have large storage capacities, substantial memories, and much associated equipment. They typically control all the pilot plants in an area or faciUty. Centralized systems are economical if a large number of units are involved but are becoming less common due to their high installation and maintenance costs as well as the limitation that any failure of the central system shuts down all pilot plants involved. 

A central location where instmment leads are short is preferred. In modem faciHties with distributed control systems, all units are controUed from a central control room with few operators. Only a few roving operators are available to spot trouble. It is desirable to deep process equipment a minimum of 8 m away from the control room. Any equipment and hydrocarbon-containing equipment should be separated by at least 15 m if possible. Most control rooms are designed with blastproof constmction and have emergency backup power and air conditioning. The room is pressuri2ed to prevent infusion of outside air that may have hydrocarbon content in the explosive range. 

An industrial fermentor of capacity up to several hundred kiloliters equipped with aeration and stirring devices, as well as other automatic control systems, is used. The cultures must be sterilized and aseptic air must be used owing to the high sensitivity to bacterial contamination of L-glutamic acid fermentation. 

A compressor is typically a specially designed device, and comes with far less surplus capacity than other process components. As a result compressors merit great care in specification of flow, inlet pressure, and discharge pressure. Similarly, the control system and equipment need to be carefully matched to provide turndown with maximum efficiency. 

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