Protection systems prevention

The reason for choosing cathodic protection is almost always cost effectiveness. The cathodic protection system prevents corrosion across the whole of the protected area of the structure, unlike localized patch repairs. If repeated cycles of patch repairs are too expensive or unacceptable, then... 

Risk sensitivity results are also very useful in identifying key elements in your existing loss prevention program. For example, suppose your fire protection system was assumed to have a very low probability of failure because you test it weekly. Fire protection failures may not show up as an important contributor to your total risk (because failure is so unlikely), but your total risk estimate may be extremely sensitive to any change in the probability of fire protection failures. Flence you should not divert resources away from testing the fire protection system unless the alternate use of funds will decrease risk more than the reduced testing will increase risk. 

Flare systems are subject to potential flashback and internal explosion since flammable vapor/air mixtures may be formed in the stack or inlet piping by the entry of air, and the pilot constitutes a continuous ignition source. Flares are therefore always provided with flashback protection, which prevents a flame front from travelling back to the upstream piping and equipment. Design details are described later. 

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. 

External events are accident initiators that do not fit well into the central PSA structure used for "internal events." Some "external events" such as fire due to ignition of electrical wires, or flood from a ruptured service water pipe occur inside the plant. Others, such as earthquakes and tornados, occur outside of the plant. Either may cause failures in a plant like internal events. External initiators may cause multiple failures of independent equipment thereby preventing action of presumably redundant protection systems. For example, severe offsite flooding may fli 1 the pump room and disable cooling systems. An earthquake may impede evacuation of the nearby populace. These multiple effects must be considered in the analysis of the effects of external events. 

The test took more than an hour. The protective system was therefore out of action for about 5% of the time. There was a chance of 1 in 20 that it would not prevent an explosion because it was being tested. It was, in fact, under test when the oxygen content rose. 

In the past, copper was believed to be toxic to most microbiological species. Although this may be true in a test tube under laboratory conditions, it is not generally true in the real world. In this real world, microbial communities excrete slime layers which tend to sequester the copper ions and prevent their contact with the actual microbial cells, Aus preventing the copper from killing the microbes. Many cases of MIC in copper and copper alloys have been documented, especially of heat-exchange tubes, potable water, and fire protection system piping. 

Overall effectiveness of protective systems and emergency controls. Protective systems, such as alarms, shutdown systems, and emergency controls, are often the keys to incident prevention and timely operator response. Protective systems that are properly designed, tested, and well maintained can reduce the frequency of event occurrence. Conversely, systems that are not tested and maintained may result in a high frequency of event occurrence. 

In general, the safety of a process relies on multiple layers of protection. The first layer of protection is the process design features. Subsequent layers include control systems, interlocks, safety shutdown systems, protective systems, alarms, and emergency response plans. Inherent safety is a part of all layers of protection however, it is especially directed toward process design features. The best approach to prevent accidents is to add process design features to prevent hazardous situations. An inherently safer plant is more tolerant of operator errors and abnormal conditions. 

A water spray protection system around vessels is recommended to prevent this type of failure. These water spray protection systems, commonly called deluge systems, are designed to keep the vessel cool, flush away potentially hazardous spills, and help to knock down gas clouds.13 Deluge systems can also provide enough time to transfer material out of a storage tank into another (safe) area. 

This accident was attributed to the lack of design protection to prevent the backup of ammonia into this storage tank. It also appears that mitigation techniques were not part of the system (deluge systems, dikes, and the like). 

Identified hazards can either be reduced at the root (e.g., reduction of inventory) or by introduction of protective systems (e.g., automatic emergency shutdown). The increased understanding of the chemistry and the process that is obtained from hazard evaluation procedures provides guidance for many other elements of process safety management as well (e.g., procedural instructions, emergency strategies, personnel training, and preventive maintenance). 

Ignition sources at devices, protective systems, and components must be avoided, depending on zones (Table 23-7) i.e., the zone determines the minimum extent of preventive measures against danger of ignition. 

A general application of loss prevention practices is considered prudent both by insurers and petroleum companies, so overall, all facilities are required to achieve the corporate protection standards. In fact the premium of insurance is normally based on the level of risk for the facility after an insurance engineer has "surveyed" the facility. Isolated cases may appear where less fixed protection systems are provided in place of manual fire fighting capabilities, however the general level of overall loss prevention level or risk is maintained. Insurers will also always make recommendations for loss prevention improvements where they feel the protection levels are substandard and the risk high. Where they feel the risk is too high, they may refuse to underwrite certain layers of insurance or charge substantial additional premiums for reinsurance requirements. 

Effect of Safety Measures An evaluation of the mitigation effects of layers of protective systems of different integrities, on the effects or prevention of an incident. 

The O2 molecule is essential to all aerobic forms of life, but many anaerobic organisms (e.g. anaerobic bacteria such as Clostridia spp.) are killed after only brief exposures to molecular O2. However, it is well established that even aerobic organisms, including man and other animals, show signs of oxygen toxicity when exposed to O2 tensions above those normally found in air (i.e. >21% O2). Such toxicity does not normally occur because aerobic cells possess protective enzymes that prevent either the formation or the accumulation of oxygen metabolites. It is only when these protective systems be-... 

A Risk Management System (RMS) is vital for effective loss prevention. Fire protection is an essential part of an RMS. Appropriately designed, installed, and maintained fire protection systems are paramount to mitigating the direct consequences, and preventing the escalation, of fires in processing facilities. 

It is not the intent of this Guideline to deal in depth with facility security issues. However, effective fire prevention in a processing facility depends on people in addition to systems to detect developing fires and other incidents and to detect unauthorized intrusion into the facility. Intruder-caused vandalism, damage, spills, releases, or fires are not common, but are a credible threat. The potential fire prevention and protection requirements to manage the risk of security events from terrorism need to be considered in the overall fire protection system design. 

The company or facility should make use of the services of an engineer knowledgeable and trained in fire protection. Ideally, a registered fire protection engineer should be available to review fire protection designs. Fire safety, loss prevention, or process safety engineers should assist in the analysis of hazards, selection of protection system specifications, approval of the system, and acceptance testing. 

Fire protection systems achieve exposure protection by absorption of heat through application of extinguishing agents to structures or equipment exposed to a fire. The application of some extinguishing agents removes or reduces the heat transferred to the structures or equipment from the exposing fire, as well as limits the surface temperature of exposed structures and equipment to a level that will minimize damage and prevent failure. 

Fire protection systems achieve prevention of fire by operating until flammable vapor, gases, or hazardous materials dissolve, dilute, disperse, or cool. 

The elimination of a fire hazard may be the ideal solution, but it is often not possible. In general, the optimum level of fire protection is achieved by selecting from the other appropriate prevention and mitigation options. The higher the performance availability (or lower the probability of failure-on-demand) of each selected fire protection feature, the more effective the overall fire protection system. The generally preferred approach to improve effectiveness is to select a combination oipassive and active fire protection features. 

Solid floors in multilevel process structures can provide a passive means of containing any spilled liquids or solids and preventing materials from falling onto lower levels. To maximize the effectiveness of solid floors, the floor design should include appropriately located drainage for spills and fire water runoff. Fire protection systems can be designed to effectively manage liquid pool fires. 

Inspections consist of a visual check of the fire protection systems by qualified personnel to ensure the system is available for immediate use. Visual checks should be made using a checklist. The inspection should verify that the fixed and portable equipment is ready to be operated. The associated devices, fittings, piping, and valving are inspected to ensure they have not been tampered with and that there is no obvious deterioration, physical damage, or condition to prevent operation. Documentation of the visual inspections may vary from... 

Fire protection system impairment occurs when a fire alarm or supervisory system is shut-off, damaged, fails, or is otherwise taken out-of-service completely or in part. These out-of-service conditions are called impairments. While process monitoring, control, safety, and security-entry systems also provide protective functions, this element of the fire prevention program is only concerned with impairments to fire protection systems and equipment. An essential element of the fire prevention program is a procedure for fire protection impairment handling. 

Protective system—Systems such as pressure relief valves that function to prevent or mitigate the occurrence of an incident. 

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