University of Kansas Lecture 2 2015

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Plant and Environmental SafetyCPE 624, KJN, Lecture 2, 2015

2Public opinion survey: Would you say chemicals do more good than harm, more harm than good,or about the same amount of each?

(Source: The Detroit News.)

From Chemical Process Safety, Third Edition, By Daniel A. Crowl and Joseph F. Louvar (ISBN: 0131382268)Copyright 2011 Pearson Education, Inc. All rights reserved.

Figure 1-5 Results from a public opinion survey asking the question, Would you say chemicals do more good than harm, more harm than good, or about the same amount of each? (Source: The Detroit News.)

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Figure 1-6 Types of loss for large hydrocarbonchemical plant accidents. (Data from The 100 Largest Losses, 19722001.)

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Figure 1-7 Causes of losses for largest hydrocarbon-chemical plant accidents. (Data from The 100 Largest Losses, 19722001.)

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Figure 1-8 Hardware associated with the largest hydrocarbon-chemical plant accidents. (Data from The 100 Largest Losses, 19722001.)

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The most fundamental lesson of Three Mile Island, onethat must be continually emphasized, is thataccidents can happen.Report by the Energy & Production Congressional Subcommittee,1980

What does this suggest? Whether its driving while texting, producing sugar with inadequate dust control, or not putting in that one extra fire control system, humans tend to underestimate the risks involved in many activities.7

Introduction to Inherently Safer Chemical Processes8

Inherently Safer Plants

Apex, North Carolina10/06/06EQ Industrial Services, Wayne, Michigan owned facility

Hazardous Waste Facility burns.

~16000 evacuated because of chlorine release.

Fire burns to avoid environmental damage.

If you dont have it, it cant leak.9

Thought: What you dont have, cant leak. Trevor Kletz

Question: If you develop, design, operate and control a chemical process such that the consequence isreduced because of different chemistry, chemicals,conditions or simplicity, wouldnt the safety of theplant be improved? Is this better than layers ofprotection?

Inherently Safer Plants10

Inherently Safer ProcessesA chemical manufacturing process is

INHERENTLY SAFER

if it reduces or eliminates the hazards associated withmaterials and operations used in the process, and thisreduction or elimination is permanent andinseparable.

Process Design

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Risk of an Event = Consequence * ProbabilityChemical process plants have an inherent risk. Managers of eachsite must decide what is a tolerable risk. Risk can be reduced byreducing the consequence and/or reducing the probability.

**Risk can never be eliminated and many of the potential hazards are not immediately obvious.

A Hazard is defined as a chemical or physical characteristic that has the potential for causing harm to people, the environment orproperty.

Hazards are characteristic of the materials and chemistry.

Hazards are characteristic of the process variables.Inherently Safer Plants12

Minimizing RiskTo minimize risk while still producing our product, there are two major paths available:Process Risk Management Strategies

Inherent Passive Active ProceduralInherently Safer Design Strategies

Minimize Substitute Moderate SimplifyThese strategies can decrease either the probability of a given event, or the consequence of that event, or both13

Process Risk Management StrategiesInherent: Eliminate the hazard by using materials and process conditions which are non-hazardous

Passive: Minimizing the hazard by process equipment design features, which reduce either the probability or consequence of the hazard without active function

Active: Using controls, safety interlocks, and emergency shutdown systems to detect, and correct or mitigate process deviations (engineering controls)

Procedural: Using operating procedures, administrative checks, emergency response, and other management approaches to prevent accidents, or to minimize the consequences of those accidents (administrative controls)

* Note these are in order of reliability!14

Exercise for 1/22/15

Group with the people sitting next to you and write down a specific strategy for each type of process risk management for the following situation:

We wish to produce a polymer product from monomer. Some reaction pathways are exothermic, and can runaway.

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Strategies for Reducing Risk Solutions Inherent:

Passive:

Active:

Procedural:16

Strategies for Reducing Risk Possible Example Solutions Inherent: Choose an atmospheric pressure reaction pathway with no volatile solvents used on the vapors produced. (No potential for overpressure.)

Passive:Choose a reaction pathway which could generate 150 psig pressure in case of a runaway, but use a vessel designed for 250 psig. (The reactor can contain the accident unless damaged.)

Active:Run the same reaction in a 150 psig reactor, but use an interlock to closes feeds if the operating pressure rises a set amount over nominal operating pressure, and includes a rupture disk to reduce pressure directing contents to effluent treatment.

Procedural:The same reactor without the interlock. The operator isinstructed to monitor the pressure and shut down feed in the case of an overpressure alarm, and direct contents to effluent treatment. (Human error)17

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University of Kansas Lecture 2 2015