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Ebadat V.,Chilworth Technology Inc.
Chemical Engineering Progress

The article discusses electrostatic hazards associated with common operations involving liquids and powders. Adequate precautions must be taken to avoid ignition of flammable-vapor, dust-cloud, and/or hybrid atmospheres during processing and handling operations in the plant. Minimum ignition energy (MIE) test is performed according to ASTM E2019 (1). It determines the lowest electric-spark energy that is capable of igniting a flammable atmosphere at its optimum ignitable concentration. Electrostatic chargeability is a measure of a powder's or a liquid's propensity to become charged when flowing through piping or ducts or when otherwise processed. Many chemical operations involve the manual addition of bulk solids and powders, as well as small quantities of liquid additives to vessels containing flammable liquids. Source

Zhao G.,Chilworth Technology Inc.
Journal of Loss Prevention in the Process Industries

Tank discharge gas/vapor flow problems are frequently encountered in both practice and design. To perform this type of design calculation, the first step is to identify whether the flow is choked or not through a trial-and-error solution of an equation for adiabatic flow with friction from a reservoir through a pipe. Developing a direct method without any trial-and-error to identify a choking condition would be helpful for expediting the flow calculations. This paper presents an easy and quick method to identify the choking of gas flow for an emergency relief system consisting of a rupture disk and vent piping. This greatly simplifies the design calculations. The proposed method for validating the venting adequacy of existing ERS circumvents the iteration calculation and the use of Lapple charts. Three case studies for the design of vent piping for rupture disks support the proposed method. © 2015 Elsevier Ltd. Source

Prugh R.W.,Chilworth Technology Inc.
49th Annual Loss Prevention Symposium 2015, LPS 2015 - Topical Conference at the 2015 AIChE Spring Meeting and 11th Global Congress on Process Safety

Recently, OSHA published Assigned Protection Factors for several types of breathing-protection devices. Proper use of such devices would allow a person to enter an environment that is at the Maximum Use Concentration of the toxic gas or vapor of interest. Thus, it is essential that the concentration of the gas or vapor be known prior to protected entry into that environment. For many toxic vapors, the "worst-case" equilibrium concentration above a spill of the liquid at a given temperature can be readily calculated as the ratio of the vapor pressure divided by atmospheric pressure. Then, the type of respirator to protect against that calculated concentration can be determined. Also, the ratio of the maximum equilibrium concentration divided by the OSHA Permissible Exposure Limit could be considered to be a Toxicity-Hazard Index, and this Index would be numerically equal to the required Protection Factor. For many chemicals, the coefficients for a vapor-pressure-versus-temperature equation may be readily available. If not, one set of vapor pressure and temperature values can be used with the "infinite point", at about 1,625°C and 55,500 psia [about 2.9×106 mmHg]. Source

Prugh R.W.,Chilworth Technology Inc.
Process Safety Progress

The safety and health standards of the Occupational Safety and Health Act do not specifically address life safety in chemical plants, other than requiring owners and operators to "provide a safe place to work" and to ensure that "employees may evacuate the workplace safely." NFPA 101 would classify chemical plants as high-hazard industrial occupancies, and a primary concern is to ensure "minimal danger to occupants in case of fire or other emergency before they have time to use exits to escape." NFPA 1 also requires that the design and operation of buildings and facilities "provide an environment for the occupants that is reasonably safe from fire and similar emergencies, for the amount of time needed to evacuate." Thus, most life-safety requirements are concerned with safe exit. There are, however, other life-safety hazards that should be of concern to chemical plant owners and operators. They include many single-exit locations, such as the upper levels on distillation/fractionation columns, scrubbers, and other tall equipment; elevated work platforms as atop multistory buildings and smokestacks; platforms above tank cars, tank trucks, and hopper cars; at the head of bucket elevators; work spaces above false ceilings; and ladder-access roofs over operating areas. Also, chemical-plant life-safety hazards include flash fire (flammable vapors and combustible dusts); releases of toxic gases and vapors; and vessel rupture from runaway reaction or other causes of overpressure. This article presents practical countermeasures for these life-safety hazards. © 2016 American Institute of Chemical Engineers. Source

Ebadat V.,Chilworth Technology Inc.
Journal of Loss Prevention in the Process Industries

The majority of powders that are used in the processing industries are combustible (also referred to as flammable, explosible). An explosion will occur if the concentration of the combustible dust that is suspended in air is sufficient to propagate flame when ignited by a sufficiently energetic ignition source.A systematic approach to identifying dust cloud explosion safety against their consequences generally involves:. -Identification of locations where combustible dust cloud atmospheres could be present. -Understanding of the explosion characteristics of the dust(s). -Identification of potential ignition sources that could be present under normal and abnormal conditions. -Proper process and facility design to eliminate and/or minimize the occurrence of dust explosions and protect people and facilities against their consequences. -Adequate maintenance of facilities to prevent ignition sources and minimize dust release. This presentation will discuss the conditions that are required for dust cloud explosions to occur and presents a well-tried approach to identify, assess, and eliminate/control dust explosion hazards in facilities. © 2010 Elsevier Ltd. Source

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