Process hazards static electricity

Saletan, D. L., The Theory Behind Static Electricity Hazards in Process Plants, June 1, 1959, p. 99. 

This Concept Series book supports several of the twelve elements of process safety enunciated in Guidelines for the Technical Management of Chemical Process Safety, including process knowledge and documentation, process risk management and enhancement of process safety knowledge. The purpose of the book is to assist designers and operators of chemical facilities to understand and reduce potential hazards associated with static electricity. 

Saletan, D.I., How to calculate and combat static electricity hazards in process plants II, Chemical Engineering, pp. 101-106, June 1959. 

Explosivity Fine dust dispersed in air in sufficient concentrations and in the presence of an ignition source, is a potential dust explosion hazard. Minimum concentration for explosion is 0.25 oz. ft The recommended fire extinguishing media is water spray, dry chemical, alcohol foam, or carbon dioxide. Acetaminophen is capable of generating a static electrical charge. Processes involving dumping of acetaminophen into flammable liquid, inert atmosphere in the vessels, or temperatures of flammable liquid should be maintained below its flashpoint. 

One of the main hazards of air-entrainment sublimation is the risk of fire many substances that are considered to be quite safe in their normal state can produce explosive mixtures with air. All electrical equipment should be flameproof, and all parts of the plant should be earthed (grounded) efficiently to avoid the build-up of static electricity. Vacuum operation after nitrogen purging can provide a much safer processing enviromnent. 

There are many indirect hazards that electrical and electronic equipment create or to which they contribute. For example, failure of electrical power can make building interiors dark and exiting dangerous or impossible. Failures of computer equipment or electronic sensors can add to hazards in processes or control systems in aircraft, industrial plants, or other places. Radio frequencies, field-induced currents or static buildup can interfere with critical... 

The choice for floor covering materials depends on the kind of activities. As an example, in a preparation room where iodine or organic solvents will be processed, the floor should be chemically resistant in the first place. When processing inflammable products the generation of sparks due to static electricity has to be prevented. For aseptic handling chemical resistance of course is much less important. The primary emphasis for a floor in a premise for handling radiopharmaceuticals or other very hazardous substances, is on suitability for thorough and effective decontamination and disinfectirm. 

Loading is one of the most hazardous operations in the process industries. These facilities represent a strategic point in the process that, if lost, may adversely affect the entire operation of the facility. Pipeline transport is the preferred method of material transport but cannot be accommodated in instances where smaller quantities are involved or where trans-ocean shipment is required. The most prevalent hazard with loading facihties is the possibility of overfilling, displacement and release of combustible vapors, buildup of static electricity, and collisions with transferring facilities and carrying vehicle (primarily ships, barges, or trucks). 

Static charge generation causes an ignition hazard only if the accumulated charges create an electric field sufficient to produce an electrical discharge in a flammable atmosphere. In most processes, this means that the electric field intensity at some location must reach the breakdown strength of air (nominally 3 X lO " V/m). The objective of static-control measures is to ensure that electric field intensities cannot reach this value. 

---