Foam blankets

Provision of a partial seal on exposed liquid interfaces, e.g. a foam blanket or a layer of floating inert spheres. 

Surface-active agents are often added to the pickle if the inhibitor has no surface-active properties. They assist the penetration of the acid into the scale, reduce drag-out losses, and form a foam blanket on the pickle. This blanket reduces heat losses and cuts down the acid spray caused by the hydrogen evolution. 

The use of aqueous foams to control fume or vapour release from reactive chemicals is discussed. An acid-resistant foam NF2 controlled fume emission from 35% and 65% oleum, and from titanium tetrachloride, but was not effective for sulfur trioxide and chlorosulfuric acid. An alcohol-resistant foam NF1 suppressed ammonia vapour emission by 80%, and Universal fire foam reduced evaporation of ethylene oxide, vinyl chloride and methanethiol, and reduced vapour emission of 1,3-butadiene by 60%. Safety aspects of foam blanketing are discussed [1]. Equipment and application techniques are covered in some detail [2],... 

Foam Smothering Best for Class B Pool Fires (Two-dimensional fires) Not for electrical fires Foam blanket may break-up Not applicable for LPG... 

The air foams generated by AFFF solutions possess a lowviscosity and have fast spreading, leveling and self-sealing properties. Like other foams, AFFF acts as a surface barrier to limit fuel vaporization and exclude air. To ensure extinguishment, the foam blanket should cover the entire surface of the spill or fire. 

Certain wetting agents and some dry chemical powders may be incompatible with some foams. If they are used simultaneously, an instantaneous breakdown of the foam blanket may occur. Precautions must be taken to ensure that such agents are fully compatible with the foams being used. 

Metraxt is an aqueous system developed to clean up metals on solid surfaces. Metraxt can be applied as a foam blanket that allows application to overhead, vertical, and horizontal surfaces. This technology is formulated to extract heavy metals from concrete, asphalt, and metal surfaces by bonding with them. 

Foam - The application of a foam blanket is the only means available to the fire forces for the extinguishment of large petroleum storage tank fires. The foam blanket extinguishes by preventing... 

Where the vapours to be controlled are flammable, many of these foams are quite similar to the protein, fluoroprotein, and aqueous-film-forming foams used in firefighting [590,594,598] (see also Section 12.9). Where longer-term odour and toxicity control are more important many of these foams are polymer-thickened and gelling foams [592-594]. Other applications of foam blankets are discussed in Sections 10.5 and 13. 

Other dust-suppressing applications of foam blankets include ... 

Other applications of foam blankets are discussed in Sections 9.7 and 13.9. 

Table 13.3 provides some examples of agricultural colloids. Beyond foods and the processing of agricultural products into foods, as covered in the previous sections of this chapter, there is a range of crop-protection products. These include pesticides and foam blankets. There are several books and reviews related to agricultural colloids [861-864],... 

Figure 13.8 Illustration of the application of a foam blanket to protect a small tree. A tube (20) is clamped (34) to the trunk and positioned so that foam can be pumped through a nozzle (26) over the top of the tree. From this point the foam provides a blanket covering branches (30) and the spaces between branches (12). Note that the blanket also drapes all the way down to ground level. From Cole and Beattie [874].

Other agricultural applications of foam blankets include prevention of erosion and distribution of soil particulates by wind [589], and reducing ammonia and odour emissions from intensive feed-lot operations, such as in hog-farming operations, by blanketing waste slurries, both in animal houses and spread over fields. Here a cover is needed that will allow passage of fresh wastes, or rain, and that can be easily re-formed, although the foam has to be stable in the presence of ammonia. Applications of foam blankets in areas beyond the agricultural sector are discussed in Sections 9.7 and 10.5. 

A somewhat different application of foam is in blast and fire suppression during attempts to deactivate, or intentionally destroy, suspected terrorist bombs. When such a device, or even a small explosive device used to destroy the suspected item, explodes, severe damage can be caused by the compression wave emanating from the blast or from the fireball that may follow the blast. In Section 9.6 it was mentioned that foam blankets have been developed for blast noise and pressure wave... 

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