Tank active protection systems

Active Protection Systems Table 7-10 Protection for Open-Top Floating Roof Tanks 215... 

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. 

Consider a process that consists of a reactor used for the processing of a highly unstable chemical that is sensitive to small increases in temperature. The reactor is equipped with a quench tank to protect the system against a runaway reaction and is monitored by two temperature sensors (see Fig. 17) T, and T2. Sensor T, automatically activates the quench tank outlet valve when it detects a temperature rise above the specified upper limit. Sensor T2 sounds an alarm in the control room to alert the operator to the process upset. When the alarm sounds, the operator closes the reactor inlet valve. The operator also pushes a quench tank valve button in the control room in case the quench valve fails to open. Note that A is the reactant B, the product and C, the quench. 

In case of failure to actuate the electromechanical protection system, reactor shutdown is accomplished by the emergency boron injection system (Fig 7.2.2.). Activation of the system is possible by opening valves in the pipelines connecting the system to the reactor or by rupture of a membrane with simultaneous opening of check valves in the drain line by direct action of the pressure in the reactor. The boron solution is supplied by gravity due to the location of the system tanks above the reactor. 

I - Reactor 2 - Control rod actuators 3 - Primary circuit pump 4 - Metal-and-water shielding tank 5 - Protective shell 6 - SG 7 - Recirculation channels of ECCS 8 - Active channels of ECCS 9 - Barbotage sub-system for emergency pressure suppression in the protective shell 10 - Soluble poison injection system ... 

On this tank, the LAFIFI includes a trip function to terminate the transfer. For a well-designed and maintained safety instrumented protective system, a response time of two minutes between activation and complete cessation of flow into the tank is claimed. This includes the time needed to take urgent action in case the trip action is not successful - in this case to immediately close another remotely operated valve, readily accessible in the control room (the system having been designed for this emergency closure). 

In nuclear plants, construction cost is strongly dependent on the technology selected, on the seismic characteristics of the site and on the local rules and regulations affecting the type and cost of active safeguard systems and passive protection systems. For these reasons, every attempt at cost evaluation when not aimed at a specific design solution is rather approximate. As a result of this effort, the number of main components (pumps, valves, tanks, etc.) in the MARS plant is reduced to about 50%, with respect to traditional PWRs of the same rated power. 

The Brio refining site is approximately 58 acres in size and is the location of a former chemical production, recovery, refinery, and regeneration facility. The site includes closed impoundments into which hazardous substances were disposed in bulk, storage tanks, and approximately 1,750 drums of hazardous substances. Remediation activities included the excavation and incineration of contaminated soil, installation of protective liners around selected pits, and the installation of a groundwater extraction system adjacent to a gully. 

For means of protection, the use of water based suppression systems may be a hazard due to the disposal of firewater water, which will freeze quite readily in exposed locations. This may also be the case with exposed hydrocarbon fluid lines that, if isolated, say for an ESD activation, may freeze up due to lack of circulation. This will hamper restart operations for the facility. Typical use in the past has been the reliance on gases fire suppression agents for enclosed area, particularly Halon. Other methods include fire water storage tanks that are kept warm, together with fire mains deeply buried and continually circulated. 

If trained to do so and confident that you are capable, activate any fire monitors and/or fixed fire water systems in the immediate area and attempt to cool the tank and surrounding equipment. If the tank is receiving material or product, close a valve on the inlet line at a safe location. Stand by to direct the Emergency Response Team (ERT) to scene Use appropriate Personal Protective Equipment (PPE) First Responder... 

Retraction systems automatically withdraw the furnace camera several feet back from the firebox if the systems sense loss of either water, air coolant, or high lens tube temperature. This gives the lens additional protection from the heated air that would blow against the lens if fans stopped and negative pressure changed to positive pressure. The retraction system is often air-operated, using an air-reserve tank as a purely pneumatic system component. This makes it totally independent of electricity. On loss of air pressure, water coolant, or high lens tube temperature, a solenoid valve opens and activates a rodless cylinder to withdraw the lens from harms way. The system will not return the camera to its inserted position until the problem is corrected. 

Mr. Wigner reported to the Committee on the problems of the radiation protection. The Committee agrees with his opinion that the shielding against radiation is essentially adequate. The circulating helium, however, should be prevented from depositing active materials on the parts of the system that should be accessible after shut down of the operation and in particular on the walls of the upper section of the pressure tank above the chamber, so as to prevent helium from the pile diffusing into the upper section. 

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