Flammable liquids, control

The best way to deal with a hazard in a flowsheet is to remove it completely. The provision of safety systems to control the hazard is much less satisfactory. One of the principal approaches to making a process inherently safe is to limit the inventory of hazardous material, called intensification of hazardous material. The inventories we wish to avoid most of all are flashing flammable liquids or flashing toxic liquids. 

Flammable liquids are considered particularly static-prone if their elec trical conductivity is within the range of 0.1 to 10 pS/m. If no particulates or immiscible liquid are present, these prodlic ts are considered safe when their conductivity has been raised to 50 pS/m or higher. Blending operations or other two-phase mixing may cause such a high rate of charging that a conductivity of at least 1000 pS/m is needed for safe charge dissipation (British Standard 5958, part 1, Control of Undesirable Static Electricity, para. 8, 1991). 

Liquid spills. Possibil- Provide spill control through adequate ity of accumulation of drainage and curbs or dikes flammable liquids. adequate ventilation resulting in fire or explosion hazard. down systems Minimize possibility of ignition Minimize possibility of spills API RP 750 CCPS G-22 CCPS G-24 CCPS G-30 Lees 1996 NFPA 69 NFPA-15... 

Eor health care facilities see NEPA 99. Clean rooms require superior static control measures where flammable liquids are handled. Smoke may be... 

The system is a storage tank designed to hold a flammable liquid under a low positive nitrogen pressure (see Figure 5.1). This pressure is controlled by PICA-1. A relief valve is fitted which operates if overpressurization occurs. Liquid is fed to the tank from a tank truck, and is subsequently supplied to the process by the pump P-1. 

FIG. 23-63 Methods of diking for flammable liquids (a) traditional diking method allows leaks to accumulate around the tank. In case of fire, the tank will be exposed to flames that can be supplied by fuel from the tank and will be hard to control, (b) In the more desirable method, leaks are directed away from the tank. In case of fire, the tank will be shielded from most flames and fire will be easier to fight. (From Englund, in Advances in Chemical Engineering, vol. 15, Academic Press, San Diego, 1990, pp. 73-135, by permission.)... 

To permit the location of life saving appliances, flammable liquid stores, radioactive and emergency control points in safe areas where practical. 

Most heat transfer systems are of a closed loop design that circulates a heat transfer medium between heaters and heat exchangers. Circulation pumps provide flow and regulating valves are used for process control. The heat transfer medium is usually steam, a high flash point oil, or in process plants flammable liquids and gases. Inherently steam is a safer medium to use and is preferred over other mediums. When steam supplies are unavailable high flash point oils (organic or synthetics) are sometimes used. 

Red a. Stop buttons or electrical switches used for emergency stopping of machines. b. Emergency stop handles or bars on machines. c. Hazardous operation indicating lights on control, alarm panels, or in the installation. d. Fire protection equipment and systems (e g., fire hydrants, monitors, reels, alarms, etc.). e. Portable flammable liquid containers. f. Stop condition. g. Identification of ESD isolation valves and actuators. 

Foam-water deluge systems are especially applicable to the extinguishment, prevention and control of most flammable liquid hazards. They may be used for any, or a combination, of the following purposes. 

As in the case of flammable liquid fires and explosions, the control of dust explosions is based upon prevention of ignition and secondarily limitation of damage in the event ignition does occur... 

Most combustible liquids do not present a vapor problem if accidentally released into the atmosphere. The probability of a fire, therefore, is considerably less than it would be if the spill was of a flammable material. If, however, the combustible liquid is at a temperature higher than its flashpoint, then it can be expected to behave in the identical manner a flammable liquid. One major difference between the two in a fire situation is that the potential exists for cooling the combustible liquid below its flash point by the proper application of water (generally applied in the form of water spray). In the event the liquid is burning, and if the fire forces are successful in achieving the required reduction in liquid temperature, then vapor production will cease and the fire will be extinguished because of a lack of vapor fuel. Unless this reduction in liquid temperature can be brought about, the fire will necessitate the same control considerations a low-flash liquid fire would. 

Acaricide The name of a chemical pesticide used to control spiders, ticks, mites miticide. Accelerant A chemical substance used to initiate or promote fire. Flammable liquids may be referred to as accelerants. 

Generally, it is more economical to prevent explosive atmospheres in rooms than to try to provide explosion-proof electrical equipment. Personnel should never be allowed to work in a hazardous atmosphere. Where such an atmosphere cannot be avoided through control of flammable liquids, gases, and dusts, access to the area involved should be limited and the area segregated by hoods or special ventilation. Electrical equipment on open, outdoor structures more than 8 m above-ground usually is considered free from exposure to more than temporary, local explosive mixtures near leaks (86). 

In the case of solutions of flammable liquids having a boiling point below 100 °C, the stainless steel electrically-heated water bath or steam bath provided with a constant-level device must be used. The individual circular type is provided with a series of concentric rings in order to accommodate flasks and beakers of various sizes. A rectangular type, suitable for use in student classes, has several holes each fitted with a series of concentric rings. In both cases the water bath is fitted with an immersion heating element controlled by a suitable regulator. 

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