Flammable areas

No obvious hard ignition sources, such as fired heaters, are present in the area shown. It may be assumed that ignition is possible anywhere within the flammable area. 

Climate and natural litizards should be evaluated. Lightning arrestors should be installed to prevent lighuiing from directly striking flammable areas. For outdoor operations, temperatures must be considered. 

Figure 40.1. Flammability areas for NH3/02/inert and -hexane/02/inert mixtures. Experimental feed composition used for catalytic tests.

A peculiarity of the processes described in the patents is that all of them use isobutane-rich conditions, with isobutane-to-dioxygen molar ratios between 2 (for processes that include a relatively low concentration of inert components) and 0.8, and so closer to the stoichiometric value 0.5 (for those processes where a large amount of inert components is present). This is shown in Figure 14.1, which reports in a triangular diagram the feed composition claimed by the various companies, with reference to the flammability area at room temperature. Low isobutane conversions are achieved in all cases, and recirculation of unconverted isobutane becomes a compulsory choice. For this reason, Sumitomo claimed the oxidation of CO to CO2 (contained in the effluents from the oxidation reactor) in... 

Figure 14.1 Triangular scheme of composition isobutane/oxygen/inert, showing the flammability area for mixtures at room temperature, and the feed composition claimed by several industrial companies.

Wall penetrations for cables and conduits should be sealed with an approved fire retardant sealant. If conduit is used that subsequently passes through flammable areas, appropriate conduit seals must be used at the MCC terminus. 

Antistatic agents are added to the PVC formulation, to prevent the build-up of static electrical charges, which could lead to an electric shock or a spark causing a fire in a dusty or flammable area. Dust build-up is also reduced. 

Climate and natural hazards. Lightning arrestors should be installed to reduce/eliminate ignition sources in flammable areas. Storm drainage systems should be maintained. 

The Hot Work Permit [29 CFR 1910.119 (k)] element addresses a permit-to-work system for hot work in flammable areas and energy isolation for work on covered equipment. This element supports existing regulations, specifically 29 CFR 1910.252, on hot work. Hot work permits are important for any work that increases the risk of contact between a flammable... 

Gas phase chlorination processes are mostly continuous processes operating in the flammable area. Gas phase explosion hazard is related to burner malfunctions. 

Where chlorination is made by chlorine injection in the liquid phase, gas phase explosion hazard is related to chlorine evolution in the vapour phase, giving a flammable mixture with the solvent or reaction mixture vapour. Here hazard assessment is achieved by comparing the gas phase composition with the flammable area of the gaseous mixtures. Auto-ignition is also considered because the autoignition temperature of gaseous mixtures containing chlorine is close to the ambient temperature. 

Near the self-ignition temperature, the flammable area is enlarged to a wide range of equivalence ratios. 

Review the explosive or flammable areas where the tool is not allowed to be used. 

The hazard from transfer of liquids can be minimized 1 attaching earthing clips at each end of a conductor to the discharge and receival containers, if they are made of conducting metal. Rubber-tyred vehicles and shoes require special treatment in some flammable areas. Anti-static clothing is required. 

It is essential that, with all pump sampling, the flow rate is accnrately calibrated with a detachable inline flow meter. The in-pump flow meter, where present, can be checked at the same time and then used for mid-sample check and re-adjustment. Flow rate must be checked just before completing sampling, and if the flow rate has dropped more than 10%, the sample should be ignored. Some pumps automatically keep flow steady. Remember intrinsically safe pumps (look for a recognized compliance plate on the pump) are needed in flammable areas such as oil refineries and coal mines. 

Flammables area Area in which large amounts of flammables are processed or stored. 

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