Passive protection systems materials

Industrial fire protection and safety engineers attempt to eliminate hazards at their source or to reduce their intensity with protective systems. Hazard elimination may typically require the use of alternative and less toxic materials, changes in the process, spacing or guarding, improved ventilation or, spill control or inventory reduction measures, fire and explosion protective measures - both active and passive mechanisms, protective clothing, etc. The level or protection is dependent on the risk prevalent at the facility versus the cost to implement safety measures. 

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. 

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. 

Although the knowledge required to assess the potential for the prevention or dissipation of hazards is often held by different abstractions of the overall representation, the semantic relationships of the modeling languages afford efficient access to this information. The effect of protective processes, equipment restraints, sensors and control systems, emergency procedures, etc., are captured as constraints. Constraints may be embedded in the underlying representation as equations, or be associated directly to it via a constraint list, i.e., a collection of explicit process restraints. These restraints may be passive, such as materials of construction, or... 

Platinised titanium anodes (titanium carrying a thin surface film of platinum, of the order of 0-0025 mm thick) have proved successful in cathodic-protection systems employing impressed-current techniques, as electrodes for electrodialysis of brackish water, and in many applications where established anode materials suffer significant corrosion. Platinum-coated titanium anodes can operate without breakdown at very high current densities, of the order of 5 0(X)A/m, in sea water, as although the very thin platinum coating may be porous the underlying titanium exposed at the pores will become anodically passivated... 

Zinc used as a sacrificial material should be characterized by high purity (99.99% Zn, less than 0.003% Fe). The presence of impurities such as iron, copper, and lead very negatively affects the work of a sacrificial anode. They cause passivation of the surface of zinc as a result of which the polarization current decreases in the protection system and the current output is decreased. In order to improve the sacrificial properties of zinc, small amounts of alloy additives are introduced. The following have an advantageous effect aluminum (0.1-0.5% Al) and cadmium (0.02-0.15% Cd), and aluminum (0.5% Al) and silicon (0.1% Si). 

Anticorrosion paints containing polyaniline. As the first actively passivating anticorrosion system, a newly developed PAni primer could perform the important environmental protection function of conserving energy-intensive and raw-material-intensive assets (Section VII.B). 

A.211. This section should describe the design requirements for fire protection inside the facility. It should include passive features, such as isolation, separation, selection of materials, the building layout and zoning, the location of Are barriers, and the safety system layout and protection (including separation of safety related redundant systems). Tne fire protection system is described in para. A. 1008. 

Figure 9.5 Acid cooler, courtesy Chemetics. Cool water flows through 1610 internal 2-cm diameter tubes, while warm acid flows cotmter currently (and turbulently) around the tubes. The tubes are 316-L stainless steel. They are resistant to water-side corrosion. They are electrochemically passivated against acid-side corrosion by an anodic protection system which continuously applies an electrical potential between the tubes and several electrically isolated metal rods ( anodic protection ). Details shell diameter 1.65 m shell material 304-L stainless steel acid flow 2000 m /h water flow 2900 m /h acid temperature drop 40 °C (green pipes=water metallic pipes = acid). Figure 24.7 gives an internal view.

These three passive systems are important in the technique of anodic protection (see Chapter 21). The kinetics of the cathodic partial reaction and therefore curves of type I, II or III depend on the material and the particular medium. Case III can be achieved by alloying additions of cathodically acting elements such as Pt, Pd, Ag, and Cu. In principle, this is a case of galvanic anodic protection by cathodic constituents of the microstructure [50]. 

Passive In this system the aim is to provide protection to the stmctural material for a specified period of time, and will be considered in this section. 

High-permeability passive perimeter gas control systems entail the installation of highly permeable (relative to the surrounding soil) trenches or wells between the hazardous waste site and the area to be protected (Figure 16.6). The permeable material offers conditions more conductive to gas flow than the surrounding soil, and provides paths of flow to the points of release. High-permeability systems usually take the form of trenches or wells excavated outside the site, then backfilled with a highly permeable medium such as coarse crushed stone. 

Absorption Across the Skin. An aqueous carrier may be used for a variety of dermal products. In fact, carriers can be designed to limit the transportation of the penetration of the active ingredient (such as an insect repellent), if the desired effect is to keep the activity on the surface of the skin. Once again, however, only those materials that are dissolved will be available for penetration across the skin to gain access to the systemic circulation. For almost all chemicals in or about to enter commerce, dermal penetration is a passive process. The relative thickness of the skin makes absorption (into the systemic circulation) slower than the absorption across the GI or pulmonary barriers. This is compounded by the fact that the stratum comeum ftmction is to be impervious to the environment. One of the skin s major functions is protection from infection. Once a chemical penetrates into the dermis, it may partition into the subcutaneous fat. Essentially, absorption across the skin is a two-step process with the first being penetration and deposition into the skin and the second being release from the skin into the systemic circulation. The pattern of blood levels obtained via dermal penetration is generally one with a delayed... 

It is important to understand the factors that retard dissolution. The same question is especially relevant in technical systems, and in the corrosion of metals and building materials. Passivity is imparted to many metals by overlying oxides the inhibition of the dissolution of these "passive" layers protects the underlying material. 

Steel, aluminum, concrete, and other materials that form part of a process or building frame are subject to structural failure when exposed to fire. Bare metal elements are particularly susceptible to damage. A structural member undergoes any combination of three basic types of stress compression, tension, and shear. The time to failure of the structural member will depend on the amount and type of heat flux (i.e., radiation, convection, or conduction), and the nature of the exposure (one-sided flame impingement, flame immersion, etc.). Cooling effects from suppression systems and effects of passive fire protection will reduce the impact. 

Fireproofing is a fire resistant material or system that is applied to a surface to delay heat transfer to that surface. Fireproofing, a form of passive fire protection, protects against intense and prolonged heat exposure that can cause the weakening of steel and eventual collapse of unprotected equipment, vessels, and supports and lead to the spread of burning liquids and substantial loss of property. The primary purpose is to improve the capability of equipment/struc-... 

Combination water spray with fire-resistive insulating material 1 to 1V2-hour rated fireproofing plus water spray (as above) 1 to 1V2-hour rated fireproofing plus water spray (as above) Active protection but the passive fireproofing allows some time of protection in event water system fails. 

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