Chilworth Technology Inc.

NJ, United States

Chilworth Technology Inc.

NJ, United States
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Prugh R.W.,Chilworth Technology Inc.
Global Congress on Process Safety 2017 - Topical Conference at the 2017 AIChE Spring Meeting and 13th Global Congress on Process Safety | Year: 2017

Limiting the accumulation of combustible dusts in the workplace is critically important in the prevention of primary and secondary dust explosions. Guidance on accumulation limits began in 1997 by the NFPA in the form of a layer-thickness criterion. As stated in NFPA 654, "the hazard area shall include areas where dust accumulations exceed 1/32 inch (0.8 mm)." Since that date, there have been several modifications of dust-layer guidance, and the relationship of dust accumulations to electrical classification was introduced in 2008. The 2013 issue of NFPA 654 introduced four additional criteria, for maximum weights of dust accumulations. These criteria can be expressed in terms of grams per square foot, and the results of calculations lead to very low "allowable" values. Two of these "mass" methods require an assumption of the extent of entrainment of dust from accumulations, as caused by a primary explosion; the available data indicate that the suggested entrainment fraction is not "conservative". This paper compiles the current methods for determining the amounts of dust that would be hazardous as fuel for flash fire or secondary explosion. Also presented is guidance for housekeeping to minimize these hazards while providing an environment where general-purpose electrical equipment could be used, in an "unclassified" area. Further, guidance is given for the personal protective equipment that should be worn by persons who perform housekeeping, particularly where large spills are involved.


Zhao G.,Chilworth Technology Inc.
Journal of Loss Prevention in the Process Industries | Year: 2015

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.


Umbrajkar S.,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 | Year: 2015

In order to safely scale up a process from the laboratory to plant scale, adiabatic tests are often performed to simulate worst case scenarios and provide critical data on the consequences of potential adverse events. Smaller scale adiabatic tests will sometimes have a higher phi-factor or thermal inertia compared to a plant-scale reactor. To compensate for the high phi-factor, the data obtained from small scale adiabatic calorimeters is corrected to the phi factor of unity. This phi correction is well understood and routinely used. However, this well-known method to correct bench-scale experimental data for thermal inertia - the Phi factor - does not consider the effect of vaporization on thermo-kinetic data. The volumetric fill ratio of a calorimeter is an important parameter and is directly related to the vaporization-effect. The rate of temperature rise is sensitive to the fill ratio as well. A high fill ratio is desirable, to get more-accurate temperature rise data for a tempered exothermic reaction. A low fill ratio requires a significant Phi correction and could also give a misleading thermokinetic interpretation of a plant-scale reactor. This paper examines the effect of fill ratio on the thermo-kinetic data. Small scale calorimetry techniques like Differential Scanning Calorimetry (DSC) and Accelerating Rate Calorimetry (ARC) are used to study the effect of fill ratio on styrene polymerization.


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 | Year: 2015

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].


Zhao G.,Chilworth Technology Inc.
Design Institute for Emergency Relief Systems (DIERS) 2015 - Topical Conference at the 2015 AIChE Spring Meeting and 11th Global Congress on Process Safety | Year: 2015

Design of pressure relief systems to accommodate runaway reactions often requires using bench-scale adiabatic calorimeters to obtain the kinetic data for a full-scale reactor. The method to correct dT/dt from bench-scale experimental data to a full-scale reactor, phi correction, has been well established. This study developed a similar method to correct exothermic gas generation rates from bench-scale data with a high phi factor to full-scale reactors with phi factor of unity, which is routinely required for the pressure relief system design. The technique was applied to a study of a real case of pressure relief system design for a gassy reaction system.


Prugh R.W.,Chilworth Technology Inc.
Process Safety Progress | Year: 2011

For many novel or unusual chemicals, there may be only one pressure/temperature point that is available for estimating flammability and/or toxicity hazards. This may be the atmospheric-pressure boiling point, the vapor pressure at room temperature, or the vapor-pressure/temperature point that corresponds to both the flash point and the lower flammable limit (LFL). It is shown here how an equation for the vapor-pressure/temperature relationship above and below that point can be developed through use of a second "infinite point." Thus, the liquid temperature that corresponds to a given toxic concentration can be estimated, and the flash point and LFL can also be estimated with only one set of T and P. An infinite point for hydrocarbons was first noted in 1923, and this concept was "rediscovered" and extended to a wide variety of other chemicals in 1949. This article summarizes the previous work and provides a rearrangement of the Antoine equation so that an infinite point can be easily used to estimate vapor pressure (and thereby concentration) at any given temperature. The primary purpose of this article is to provide guidance concerning the use of an infinite point to aid in establishing hazardous concentrations of flammable and/or toxic vapors, particularly in poorly ventilated enclosures, where a range of vapor-pressure data is not readily available. © 2011 American Institute of Chemical Engineers (AIChE).


Prugh R.W.,Chilworth Technology Inc.
Process Safety Progress | Year: 2016

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.


Zhao G.,Chilworth Technology Inc.
29th Center for Chemical Process Safety International Conference 2014, CCPS 2014 - Topical Conference at the 2014 AIChE Spring Meeting and 10th Global Congress on Process Safety | Year: 2014

Design of emergency relief systems to accommodate runaway reactions requires using bench- scale adiabatic calorimeters to evaluate thermo-kinetic data of a full-scale reactor. However, the well-known method to correct bench-scale experimental data for "thermal inertia" - the Phi factor - does not consider the effect of vaporization on thermo-kinetic data. Calorimeter volumetric fill ratio is an important parameter directly relating to the vaporization effect and is discussed in this paper. For a 60% fill ratio, a case study of an aqueous reaction system shows that the measured reaction heat would be 7% less than the actual value for a reaction with a heat release of 800 JIg, 5% less than the actual value with a heat release of 600 J/g, and 2% less than the actual value with a heat release of 300 J/g. The self-heating rate is even more sensitive to the fill ratio. A high fill ratio is desirable, to get more-accurate self-heating data for a tempered exothermic reaction. A low fill ratio requires a significant Phi correction and could also give a misleading thermo-kinetic interpretation of a plant-scale reactor. Applying the same fill ratio of a plant-scale reactor to tests in an adiabatic calorimeter - to get thermo-kinetic data for emergency relief sizing - is recommended. Copyright © (2014) by AIChE. All right reserved.


Ebadat V.,Chilworth Technology Inc.
Journal of Loss Prevention in the Process Industries | Year: 2010

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.


Design of emergency relief systems to accommodate runaway reactions often requires using bench-scale adiabatic calorimeters to evaluate thermokinetic data of a full-scale reactor. However, the well-known method to correct bench-scale experimental data for "thermal inertia"-the Phi factor-does not consider the effect of vaporization on thermokinetic data. Calorimeter volumetric fill ratio is an important parameter directly relating to the vaporization effect and is discussed in this article. For a 60% fill ratio, a case study of an aqueous reaction system shows that the measured reaction heat would be 7% less than the actual value for a reaction with a heat release of 800 J/g, 5% less than the actual value with a heat release of 600 J/g, and 2% less than the actual value with a heat release of 300 J/g. The temperature rise rate is even more sensitive to the fill ratio. A high fill ratio is desirable, to get more-accurate temperature rise data for a tempered exothermic reaction. A low fill ratio requires a significant Phi correction and could also give a misleading thermokinetic interpretation of a plant-scale reactor. Applying the same fill ratio of a plant-scale reactor to tests in an adiabatic calorimeter-to get thermokinetic data for emergency relief sizing-is recommended. © 2014 American Institute of Chemical Engineers.

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