Active protection systems design

The operational aspects of building protection are important considerations, even though they are less quantifiable than the protection metrics. The need for continuous operation has an important influence on protection system design. If part of the protective response is building evacuation or movement of personnel to an interior shelter, essential operations could be disrupted. Key activities that cannot be disrupted must be accounted for by the protective architecture. Similarly, the tolerance for false alarms could vary from building to building depending on the need for continuous operation. 

Associated with each of these demands that may cause the hazardous event were various protective systems. These were either hardware (e.g., ventilation system, flammable gas detectors) or procedural (e.g., instructions on allowable maintenance activities). For any particular demand to lead to the hazardous event, all the protective systems designed to protect against that demand must have failed to perform. Again, this failure may be a hardware failure (e.g., the gas detector has drifted out of calibration) or a human error issue (e.g., the flammable gas detector alarm warned of a flammable leak but Ihe operator failed to take appropriate action). 

Secondary containment systems are best described as passive protective systems. They do not eliminate or prevent a spill or leak, but they can significantly moderate the impact without the need for any active device. Also, containment systems can be defeated by manual or active design features. For example, a dike may have a drain valve to remove rain water, and the valve could be left open. A door in a containment building could be left open. 

Although the first industrial application of anodic protection was as recent as 1954, it is now widely used, particularly in the USA and USSR. This has been made possible by the recent development of equipment capable of the control of precise potentials at high current outputs. It has been applied to protect mild-steel vessels containing sulphuric acid as large as 49 m in diameter and 15 m high, and commercial equipment is available for use with tanks of capacities from 38 000 to 7 600000 litre . A properly designed anodic-protection system has been shown to be both effective and economically viable, but care must be taken to avoid power failure or the formation of local active-passive cells which lead to the breakdown of passivity and intense corrosion. 

Where process, safety, and environmental considerations permit, vacuum protection may be provided by properly sized ever-open vents. Alternatively, active protective devices and systems are required. Vacuum breaker valves designed to open and admit air at a predetermined vacuum in the vessel are commonly used on storage tanks, but may not be suitable for some applications involving flammable liquids. Inert gas blanketing systems may be used if adequate capacity and reliability can be ensured. Where the source of the vacuum can be deenergized or isolated, suitably reliable safety instrumented systems (e.g, interlocks) can be provided. 

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. 

What are the specific requirements when designing active and passive fire protection systems ... 

An active fire protection system requires some action to occur before it functions per its design intent. This action may be taken by either a person or control system. Examples of active fire protection systems are monitors, water spray systems, foam systems, emergency isolation valves, and ESD systems. 

Measures to reduce the impact of fire include active and passive systems. Active systems include automatic sprinkler, water deluge, water mist, gaseous agent, dry chemical, foam, and standpipe handle systems. Passive protection is provided by fire resistive construction, including spray-applied or cementitious fireproofing of steel, concrete/masonry construction, and water-filled steel columns. Chapter 7 provides details on the design of fire protection systems. 

This chapter provides the fundamentals of design for passive and active fire protection systems. A passive system should be used wherever possible, as this is an inherently safer approach than an active system. 

Fire barriers should be considered when the spacing recommended can not be met and hazards are not easily mitigated with active fire protection systems. Barriers, such as walls, partitions, and floors, provide physical separation of spaces and materials. The effectiveness of a fire barrier is dependant on its fire resistance, materials of construction, and the number of penetrations. Inattention to the integrity of penetrations is one of the primary reasons fire barriers fail to provide proper protection. Factors to consider in the design and placement of fire barriers include ... 

The size of the system should be limited to avoid overtaxing the fire water drainage systems. For locations with multiple systems it is common to activate 3 or 4 systems to ensure adequate protection. Many designers use 2,000 gpm (7,571 Ipm) and 65 psi (207 kPa) as a reasonable limit on size to avoid the issues discussed... 

Chapter 7 provides a basic understanding of fire protection systems (both passive and active), general design information on fire protection commonly used in process industries, and the advantages and disadvantages of different fire protection systems. 

The position of the radionuclide in the molecule of interest is also critical as it will affect the biological behavior of the radiopharmaceutical. Chemical reactions must be designed to be stereospecific in many cases, as the production of a mixture of different stereoisomers complicates the purification of the final radiopharmaceutical. Synthesis procedures must also be easy to automate, as very elevated activities are used for the synthesis of PET radiopharmaceuticals (several curies usually) and appropriate radiation protection systems must be used. 

Many of the formulations for plant protection are designed to help the active substance to penetrate the cuticle of plant leaves or insects. It is therefore not surprising that these formulations sometimes enhance the skin absorption in humans. To account for this in Europe, EC Directive 91/414 for pesticides requires testing of both the active substance and the formulated product (EEC, 1991). The United States Environmental Protection Agency (USEPA) requires that the vehicle system duplicates that used in the field (USEPA, 1998). Since many pesticides are... 

Level of protection 3 (LP-3) is a low-level active protection designed to detect and identify threat agents in time to execute therapeutic responses, but not quickly enough to warn occupants of the threat before exposure occurs. LP-3 requires a broad-spectrum detection and identification system that determines a threat agent within a time period necessary for operational response and treatment. 

A protection system can be designed to use passive or active approaches or both. Although active approaches, detection, and identification technologies are necessary to achieve LP-3 and LP-4, the components of passive protection (LP-1 and LP-2) are integral in these active systems. Sensor systems cannot perform to their best capacity without the high air quality provided by LP-1 and LP-2 systems. Similarly, LP-3 and LP-4 systems are not useful if operational plans are not available and in place to respond to alarms. 

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