Inherently Safer Design

Which of the following describes an inherently safer process design strategy with respect to the the potential for a runaway chemical reaction generating heat and pressure and potentially an explosion reaction vessel?

A chemist develops a chemical reaction process which has a maximum adiabatic reactor temperature less than the boiling point of the reaction mixture and also less than the onset temperature of all decomposition reactions, and no gaseous products are generated by the reactions.

Which process does not describe an application of the inherently safer design strategy "moderate"? -A plant replaces anhydrous ammonia with 20% aq ammonia solution for neutralization of an acidic waste stream - A plant storing anhydrous monomethylamine (b.p. = -6 C) decides to refrigerate the storage tank to reduce the storage pressure to atmospheric -A process development chemist discovers that one of the reactants in a process, sodium hydroxide, reacts in a side reaction with the process solvent ethylene dichloride to form toxic vinyl chloride, and replaces the ethylene dichloride with a non-reactive solvent.

A process development chemist discovers that one of the reactants in a process, sodium hydroxide, reacts in a side reaction with the process solvent ethylene dichloride to form toxic vinyl chloride, and replaces the ethylene dichloride with a non-reactive solvent.

Which of the following describes a procedural strategy to managing the risk of a runaway reaction?

A reaction with a maximum adiabatic reaction pressure of 200 psig is conducted in a reactor with a design pressure of 150 psig. One of the reactants is gradually added at a rate to control the reaction temperature, and the reaction stops if the reactant feed is stopped. The process operator is trained to monitor the reactor temperature and pressure, and stop the reactant feed if either gets too high. A properly sized rupture disk discharging to a properly designed and sized treatment system is provided.

What is not an example of inherently safer design?

Air bags and seat belts are added to automobiles to protect occupants in case of a collision.

Which of the following describe inherently safer design strategies? - Substitute - Minimize - Simplify - Moderate -All of the above

All of the above

Which of the following statements about inherently safer design is NOT true?

An inherently safer process can eliminate all hazards to workers and the public

Which of the following describes an active strategy for managing the hazard of a dust explosion in a combustible solid powder packaging system?

The dryer is fitted with dust explosion relief rupture disks which are properly sized following NFPA standards, and which relieve to a safe place.

A reactor feed tank is filled with a flammable raw material from a much larger storage tank in the tank farm. Overflow of the feed tank would result in a spill which could ignite resulting in a fire. Which of the following process safety management approaches would be described as the most inherent?

The overflow from the feed tank is piped back to the supply tank, so any overflow till flow back to the vessel which the feed comes from.

Which of the following describes a passive strategy for managing the hazard of a dust explosion in a combustible solid powder packaging system?

The packaging system is built with a design pressure of 200 psig (the maximum explosion pressure from a dust explosion of the material being dried is 140 psig).

Which statement best reflects the results of the case study described in the paper, "Implementing Inherently Safer Design in an Existing Plant" (Process Safety Progress Vol. 25, No. 1, March 2006, pp. 52-57), the replacement of the bromine storage tank with cylinder storage of bromine?

The use of bromine in cylinders is inherently safer to the public surrounding the plant, but may be inherently less safe to plant operators because they are required to connect and disconnect bromine cylinders more often than previously with truck deliveries. However, the company is more confident that it can manage the risk to operators because it has more control over implementation of passive, active, and procedural process safety management systems.

(T or F?) A complete process safety management system, considering all of the multiple hazards of a chemical process, will require use of all process safety management strategies - inherent, passive, active, and procedural.

True

(T or F?) Any measure of the inherent safety characteristics of a process will require some judgement of the relative importance of the different hazards associated with chemical processing (fire, explosion, acute toxicity, chronic toxicity, etc.), either explicitly or embedded in the calculations for an overall inherent safety index.

True

Which of the following statements is most accurate?

"Green" chemistry and elimination of toxic materials from a manufacturing process an reduce or eliminate some risks, but may also increase other process risks or introduce new risks

Define the four process safety management strategies - inherent, passive, active, and procedural.

- *********************** THis needs an answer

Which statement DOES NOT describe a process hazard? - Acetylene gas cylinders following European Standards are maroon in color - Gasoline is a flammable liquid - The acid in an automobile battery is corrosive to the skin - The heating jacket of a reactor contains steam at 150 psig pressure - Acrylic acid can polymerize releasing heat and generating pressure in a closed container

- Acetylene in maroon cylinders

Which of the following can be used as a measure of some of the inherent safety characteristics of a process? - The Dow Fire and Explosion Index - The Dow Chemical Exposure Index - Accident consequence modeling, including fire, explosion, atmospheric dispersion modeling, toxic exposure models, physical and environmental damage models - Overall inherent safety indices under development by various research organizations - All of the above

- All of the above

What are the potential benefits resulting from a process design alternative which minimizes the size of equipment containing hazardous material or energy?

- The amount of toxic material in case of a leak is reduced - Other process safety management strategies (passive, active, procedural) may become more effective or feasible for smaller equipment - Smaller equipment is often cheaper, making a plant more economical - Control of process conditions such as temperature, mixing, concentration gradients, etc., is often better in smaller equipment which can improve product quality, reduce side reactions, and improve process yield.

An operator is injured when he is mixing up dilute sodium hydroxide solution by adding solid NaOH to an open tank containing water. He adds the NaOH too fast, and the heat of dilution causes the solution to erupt from the open tank splashing the operator. What is the inherently safest approach to preventing a recurrence of this incident?

Buy sodium hydroxide solution from the supplier at the required concentration and eliminate the mixing operation.

You are going to paint a room in your house. You have some left over solvent based paint which you could use. How can you apply inherently safer design philosophy to reduce the risk of painting?

Contact local community hazardous waste disposal facility, take the left over paint to them, and buy a can of water based paint to use.

(T or F?) A smaller chemical reactor will always be inherently safer with regard to all potential hazards and upset conditions.

False

(T or F?) An inherently safer process is guaranteed to improve plant safety.

False

(T or F?) Because the properties of some materials which make it hazardous are the same as those which make it useful (e.g. gasoline is flammable), consideration of inherently safer design is not useful for facilities which manufacture or use those materials.

False

(T or F?) Inherent safety is a new concept in engineering, invented by Trevor Kletz in the late 1970s.

False

(T or F?) Inherently safer design is only applicable to chemical and process industries.

False

(T or F?) Process dynamics and non-steady state considerations are not relevant to consideration of inherent safety.

False

Which of these statements is most accurate? - Inherently safer design is only applicable at early stages of process invention, development, and technology selection. - Inherently safer design is applicable at all stages of the process life cycle. - Inherently safer design is not a useful process safety management approach for an existing plant. - Inherently safer design is applicable at all stages of a process life cycle, although the potential benefits are greatest at early stages of process invention, development, and technology selection.

Inherently safer design is applicable at all stages of a process life cycle, although the potential benefits are greatest at early stages of process invention, development, and technology selection.

Which of the following statements is true about a plant which is considering replacement of a large storage tank for a very toxic and volatile raw material from approximately 400,000 pounds?

It is not possible to make a general statement about the overall inherent safety of the proposal without knowing details about the location of on site and off site population, transport option and routes for the raw material, and other site specific information.

A continuous process to manufacture methyl isocyanate (the highly toxic material released from a plant in Bhopal, India) with immediate consumption of the methyl isocyanate by downstream processes with a total plant inventory of a few kilograms is an example of which inherently safer design strategy?

Minimize

Which of the following safety and environmental risks are not the primary objectives of inherently safer design? - Pollution caused by emissions from a chemical process operating as designed - Fires - Immediate toxic impact of chemical spills and other releases - explosions

Pollution caused by emissions from a chemical process operating as designed