Passive protection

Stainless steel develops a passive protective layer (<5-nm thick) of chromium oxide [1118-57-3] which must be maintained or permitted to rebuild after it is removed by product flow or cleaning. The passive layer may be removed by electric current flow across the surface as a result of dissinulat metals being in contact. The creation of an electrolytic cell with subsequent current flow and corrosion has to be avoided in constmction. Corrosion may occur in welds, between dissimilar materials, at points under stress, and in places where the passive layer is removed it may be caused by food material, residues, cleaning solutions, and bmshes on material surfaces (see CORROSION AND CORROSION CONTROL). 

The greatest possible safety against corrosion damage is achieved by passive protection with coatings in combination with cathodic protection. Therefore coating and cathodic protection of pipelines that have strong safety requirements are compulsory in order to protect both people and the environment [2-5]. 

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. 

Passive protective equipment, such as insulation. If 10% of the fire insulation on a vessel is missing, the rest is useless. 

The behaviour of silver in different environments is determined by three principal factors (a) the high nobility of the metal, (b) the formation of passive protective films and (c) the tendency of the metal to form complex ions in solution. 

Humoral antibodies of the IgG elass are able to eross the placenta flxm mother to fetus. These antibodies will provide passive proteetion of the new-born against those diseases which involve humoral immunity and to which the mother is immune. In this fashion, new-born infants in the UK have passive proteetion against tetanus but not against tuberculosis which requires cell-mediated immunity. Seeretory antibodies are also passed to the new-born together with the first deliveries of breast milk (colostrum). Such antibodies provide some passive protection against infections of the gastrointestinal tract. 

Facility Passive Protection Measures (e.g., Containment Dikes, Spacing, etc.) Form 0-2 hours after incident Major... 

Following an explosion incident, local fires develop which it left uncontrolled, result in a conflagration of the entire facility and its destruction. Fire protection measures are provided as required to control these occurrences. The ideal fire protection measure is one that does not require addition action to implement and is always in place. These methods are considered passive protection measures and the most familiar is fireproofing. 

The principle features of passive protection are summarized below ... 

The design basis, especially safety features that are built into the installation, must be documented. Management of change programs must preserve and keep the base record current and protect against degradation or elimination of safety features, including such measures as maximum intended inventories and passive protection systems. 

Passive protection can be used to increase the time to structural failure. For example, intumescent mastic coatings of less than 1 inch thickness have been shown to provide up to 4 hours of fire resistance when applied to steel columns. Cementitious materials have been shown to provide 1-4 hours fire resistance for thicknesses of 2.5-6.3 cm (1-2.5 in). For additional information on passive fire protection, see Chapter 7. 

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. 

Passive protection systems discussed in this section are ... 

The required protection may be obtained by active, passive, or a combination of both protection systems. For example, steel support located in a fire exposed area within process unit battery limits may be protected by either a fixed water spray system or the application of fire resistant insulating material to the steelwork or possibly both. Note Passive protection is generally the preferable method for protecting structural steel. 

Fire resistant insulating material can provide passive protection for both vertical and horizontal structural steel members. The level or rating of fire resistance should be consistent to the expected fire duration. Where only fire resistant insulating material will be used, the material and its installation system should be specified to have a 2- to 3-hour fire rating (UL 1709). In applications using a combination of fixed water spray or sprinkler protection and fire resistant insulation, a 1- to 2-hour fire rating (UL 1709) is frequently specified for the fireproofing. 

Fire-resistive insulating material only 2 to 3-hour rated fireproofing 2- to 3-hour rated fireproofing Passive protection potential for unseen corrosion. 

Fireproofing may also be used as passive protection for pressure vessels. Fireproofing reduces the fire exposure heat input to the protected vessel and the rate of increase of the vessel wall temperature. Outside surfaces of vessels that may be exposed to fire should be covered with a fireproofing material having a fire endurance rating of 2 hours. Refer to Chapter 7 for additional information on fireproofing. 

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