STORAGE AND HANDLING OF HAZARDOUS MATERIALS

SAFETY EQUIPMENT, PROCESS DESIGN, AND OPERATION

STORAGE AND HANDLING OF HAZARDOUS MATERIALS

G^ENERALR^EFERENCES: API-620, Design and Construction of Large, Welded, Low-Pressure Storage Tanks, American Petroleum Institute, Washington. AP-40, Air Pollution Engineering Manual, 2d ed., U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, 1973. AP-42, Compila-tion of Emission Factors for StaCompila-tionary Sources, 5th ed., U.S. Environmental Protection Agency, Office of Transportation and Air Quality, 1995. API Stan-dards, American Petroleum Institute, Washington ASME, Process Piping: The Complete Guide to ASME B31.3, 2d ed., American Society of Mechanical Engi-neers, New York, 2004. ASME, ASME Boiler and Pressure Vessel Code; ASME Code for Pressure Piping; ASME General and Safety Standards; ASME Perfor-mance Test Codes, American Society of Mechanical Engineers, New York.

Chemical Exposure Index, 2d ed., AIChE, New York, 1994. Code of Federal Regulations, Protection of Environment, Title 40, Parts 53 to 80, Office of the Federal Register, Washington. CGA, Handbook of Compressed Gases, 4th ed., Compressed Gas Association, Chantilly, Va., 1999. CCPS, Guidelines for Chem-ical Process Quantitative Risk Analysis, 2d ed., CCPS-AIChE, New York, 2000.

CCPS, Guidelines for Engineering Design for Process Safety. CCPS, Guidelines

for Facility Siting and Layout, CCPS-AIChE, New York, 2003. CCPS, Guide-lines for Process Safety in Batch Reaction Systems, CCPS-AIChE, New York, 1999. CCPS, Guidelines for Safe Storage and Handling of High Toxic Hazard Materials, CCPS-AIChE, New York, 1988. CCPS, Guidelines for Safe Storage and Handling of Reactive Materials, CCPS-AIChE, New York, 1995. CCPS, Guidelines for Mechanical Integrity Systems, Wiley, New York, 2006. Englund,

“Opportunities in the Design of Inherently Safer Chemical Plants,” in J. Wei et al., eds., Advances in Chemical Engineering, vol. 15, Academic Press, 1990.

Englund, “Design and Operate Plants for Inherent Safety,” Chem. Eng. Prog., pts. 1 and 2, March and May 1991. Englund, Mallory, and Grinwis, “Preventing Backflow,” Chem. Eng. Prog., February 1992. Englund and Grinwis, “Redun-dancy in Control Systems,” Chem. Eng. Prog., October 1992. Fisher et al.,

“Emergency Relief System Design Using DIERS Technology: The Design Institute for Emergency Relief Systems (DIERS) Project Manual,” AIChE, New York, 1992. Grossel and Crowl, Handbook of Highly Toxic Materials Han-dling and Management, Marcel Dekker, New York, 1995. Hendershot, “Alter-natives for Reducing the Risks of Hazardous Material Storage Facilities,”

Environ. Prog., 7, August 1988, pp. 180ff. Kletz, An Engineer’s View of Human Error, Institution of Chemical Engineers, VCH Publishers, New York, 1991.

Kletz, “Friendly Plants,” Chem. Eng. Prog., July 1989, pp. 18-26. Kletz, Plant Design for Safety: A User Friendly Approach, Hemisphere Publishing, London, 1991. Kohan, Pressure Vessel Systems: A User’s Guide to Safe Operations and Maintenance, McGraw-Hill, New York, 1987. Mannan, Lees’ Loss Prevention in the Process Industries, 3d ed., Elsevier, Amsterdam, 2005. Prokop, “The Ash-land Tank Collapse,” Hydrocarbon Processing, May 1988. Russell and Hart,

“Underground Storage Tanks, Potential for Economic Disaster,” Chemical Engineering, March 16, 1987, pp. 61-69. Ventsorb for Industrial Air Purification,

Bulletin 23-56c, Calgon Carbon Corporation, Pittsburgh, Pa., 1986. White and Barkley, “The Design of Pressure Swing Adsorption Systems,” Chem. Eng.

Prog., January 1989.

Introduction The inherent nature of most chemicals handled in the chemical process industries is that they each have physical, chem-ical, and toxicological hazards to a greater or lesser degree. This requires that these hazards be contained and controlled throughout the entire life cycle of the facility, to avoid loss, injury, and environ-mental damage. The provisions that will be necessary to contain and control the hazards will vary significantly depending on the chemicals and process conditions required.

Established Practices Codes, standards, regulatory require-ments, industry guidelines, recommended practices, and supplier specifications have all developed over the years to embody the collec-tive experience of industry and its stakeholders in the safe handling of specific materials. These should be the engineer’s first resource in seeking to design a new facility.

The ASME Boiler and Pressure Vessel Code, Section VIII, is the standard resource for the design, fabrication, installation, and testing of storage tanks and process vessels rated as pressure vessels (i.e., above 15-psig design). ASME B31.3 is a basic resource for process piping systems.

Examples of established practices and other resources—some of which pertain to the safe storage and handling of specific hazardous chemicals, classes of chemicals, or facilities—include those listed in Table 23-29 from the publications of two U.S. organizations, the NFPA and the Compressed Gas Association (CGA). Other organiza-tions that may have pertinent standards include the International Standards Organization (ISO), the American National Standards Institute (ANSI), ASTM International (Conshohocken, Pa;

w .astm.org ), and other well-established national standards such as British Standards and Deutsches Institut für Normung e.V. (DIN) standards. Local codes and regulations should be checked for applica-bility, and the latest version should always be used when employing established practices.

Basic Design Strategies The storage and handling of hazardous materials involve risks that can be reduced to very low levels by good planning, design, and management practices. Facilities that handle haz-ardous materials typically represent a variety of risks, ranging from small leaks, which require prompt attention, to large releases, which are extremely rare in well-managed facilities but which have the potential for widespread impact (CCPS, 1988). It is essential that good techniques be developed for identifying significant hazards and mitigating them where necessary. Hazards can be identified and evaluated by using approaches discussed in the section on hazard and risk analysis.

Loss of containment due to mechanical failure or improper opera-tion is a major cause of chemical process incidents. The design of stor-age and piping systems should be based on minimizing the likelihood of loss of containment, with the accompanying release of hazardous materials, and on limiting the amount of the release. An effective emergency response program that can reduce the impacts of a release should be available.

Thus, the basic design strategy for storing and handling hazardous materials can be summarized as follows, with reference to other parts of this section in parentheses:

1. Understand the hazardous properties of the materials to be stored and handled (Flammability, Reactivity, Toxicity, Other Haz-ards), as well as the physical hazards associated with the expected process design.

2. Reduce or eliminate the underlying hazards as much as is fea-sible (Inherently Safer and More User-Friendly Design).

3. Evaluate the potential consequences associated with major and minor loss-of-containment events and other possible emergency situ-ations involving the hazardous materials and energies; and take this information into account in the process of site selection and facility layout and the evaluation of the adequacy of personnel, public, and environmental protection (Source Models, Atmospheric Dispersion, Estimation of Damage Effects).

4. Design and build a robust and well-protected primary contain-ment system following codes, standards, regulations, and other estab-lished practices (Security).

TABLE 23-29 Examples of Established Practices Related to Storage and Handling of Hazardous Materials

Designation Title

National Fire Protection Association (Quincy, Mass.; ww w .nfpa.org ) NFPA 30 Flammable and Combustible Liquids Code

NFPA 30B Code for the Manufacture and Storage of Aerosol Products NFPA 36 Standard for Solvent Extraction Plants

NFPA 45 Standard on Fire Protection for Laboratories Using Chemicals NFPA 53 Recommended Practice on Materials, Equipment and Systems

Used in Oxygen-Enriched Atmospheres

NFPA 55 Standard for the Storage, Use, and Handling of Compressed Gases and Cryogenic Fluids in Portable and Stationary Con-tainers, Cylinders, and Tanks

NFPA 58 Liquefied Petroleum Gas Code

NFPA 59A Standard for the Production, Storage, and Handling of Lique-fied Natural Gas (LNG)

NFPA 68 Guide for Venting of Deflagrations NFPA 69 Standard on Explosion Prevention System

NFPA 318 Standard for the Protection of Semiconductor Fabrication Facilities

NFPA 326 Standard for the Safeguarding of Tanks and Containers for Entry, Cleaning, or Repair

NFPA 329 Recommended Practice for Handling Releases of Flammable and Combustible Liquids and Gases

NFPA 400 Hazardous Chemical Code

NFPA 430 Code for the Storage of Liquid and Solid Oxidizers NFPA 432 Code for the Storage of Organic Peroxide Formulations NFPA 434 Code for the Storage of Pesticides

NFPA 484 Standard for Combustible Metals, Metal Powders, and Metal Dusts

NFPA 490 Code for the Storage of Ammonium Nitrate NFPA 495 Explosive Materials Code

NFPA 497 Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas

NFPA 499 Recommended Practice for the Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas

NFPA 654 Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Com-bustible Particulate Solids

NFPA 655 Standard for Prevention of Sulfur Fires and Explosions NFPA 704 Standard System for the Identification of the Hazards of

Mate-rials for Emergency Response

CGA G-8.1 Standard for Nitrous Oxide Systems at Consumer Sites CGA G-12 Hydrogen Sulfide

CGA G-14 Code of Practice for Nitrogen Trifluoride (EIGA Doc. 92/03) CGA P-1 Safe Handling of Compressed Gases in Containers CGA P-8 Safe Practices Guide for Cryogenic Air Separation Plants CGA P-9 The Inert Gases: Argon, Nitrogen, and Helium CGA P-12 Safe Handling of Cryogenic Liquids

CGA P-16 Recommended Procedures for Nitrogen Purging of Tank Cars CGA P-32 Safe Storage and Handling of Silane and Silane Mixtures CGA P-34 Safe Handling of Ozone-Containing Mixtures Including the

Installation and Operation of Ozone-Generating Equipment CGA S-1.1 Pressure Relief Device Standards—Part 1—Cylinders for

Compressed Gases

CGA S-1.2 Pressure Relief Device Standards—Part 2—Cargo and Portable Tanks for Compressed Gases

CGA S-1.3 Pressure Relief Device Standards—Part 3—Stationary Storage Containers for Compressed Gases

NOTE: Always check the latest edition when using established practices.

5. Design and implement a reliable and fault-tolerant basic process control system to ensure the design limitations of the primary containment system are not exceeded.

6. Include provisions for detecting abnormal process conditions and bringing the process to a safe state before an emergency situation occurs (Safety Instrumented Systems).

7. Design, install, and maintain reliable and effective emergency relief systems, as well as mitigation systems such as secondary con-tainment, deluge, and suppression systems, to reduce the severity of consequences in the event an emergency situation does occur (Pres-sure Relief Systems; Emergency Relief Device Effluent Collection and Handling).

8. Evaluate the risks associated with the process and its safety sys-tems taken as a whole, including consideration of people, property, business, and the environment, that could be affected by loss events;

and determine whether the risks have been adequately reduced (Haz-ard Analysis, Risk Analysis, Source Models, Atmospheric Dispersion, Estimation of Damage Effects).

9. Take human factors into account in the design and implemen-tation of the control system and the facility procedures (Human Error, Key Procedures).

10. Ensure staffing, training, inspections, tests, maintenance, and management of change are all adequate to maintain the integrity of the system throughout the facility lifetime (Key Procedures, Audit Process).

Designers and operating companies will address these items in dif-ferent ways, according to their established procedures. The steps that are addressed elsewhere in this section are not repeated here.

Site Selection, Layout, and Spacing Facility siting decisions that will have critical, far-reaching implications are made very early in a new facility’s life cycle, or in the early planning stages of a site expan- sion project. The degree of public and regulatory involvement in this decision-making process, as well as the extent of prescriptive require- ments and established practices in this area, varies considerably among countries, regions, and companies. Insurance carriers are also generally involved in the process, particularly with regard to fire protection considerations.

From the perspective of process safety, key considerations with respect to site selection, layout, and spacing can be summarized as

• Where on-site personnel (including contractors and visitors), criti-cal equipment, the surrounding public, and sensitive environmen-tal receptors are located with respect to hazardous materials and processes

• Whether the design and construction of control rooms and other occupied structures, as well as detection, warning, and emergency response provisions, will provide adequate protection in the event of a major fire, explosion, or toxic release event

Recommended distances for spacing of buildings and equipment for fire protection were issued as IRI IM.2.5.2, Plant Layout and Spacing for Oil and Chemical Plants (Industrial Risk Insurers, Hart-ford, Conn). These are referenced in “Typical Spacing Tables”

included as Appendix A of the CCPS Guidelines for Facility Siting and Layout (2003). Other resources pertaining to siting and layout include

• Dow’s Fire & Explosion Index Hazard Classification Guide, 7th ed.

(AIChE, New York, 1994), which gives an empirical radius of expo-sure and damage factor based on the quantity and characteristics of the material being stored and handled

• API RP 752, “Management of Hazards Associated With Location of Process Plant Buildings,” 2d ed. (American Petroleum Institute, Washington, 2003), which gives a risk-based approach to evaluating protection afforded by occupied structures

Storage

Storage Facilities Dating back to at least 1974, when a vapor cloud explosion in Flixborough, U.K., claimed 28 lives and destroyed an entire chemical plant (Mannan, 2005), a major emphasis in the safe storage and handling of hazardous materials has been to reduce haz-ardous material inventories. Inventory reduction can be accomplished not only by using fewer and smaller storage tanks and vessels but also by eliminating any nonessential intermediate storage vessels and

batch process weigh tanks and generating hazardous materials on demand when feasible. Note, however, that reduction of inventory may require more frequent and smaller shipments and improved management.

There may be more chances for errors in connecting and recon-necting with small shipments. Quantitative risk analysis of storage facilities has revealed solutions that may run counter to intuition.

[Schaller, Plant/Oper. Prog. 9(1), 1990]. For example, reducing inven-tories in tanks of hazardous materials does little to reduce risk in situ-ations where most of the exposure arises from the number and extent of valves, nozzles, and lines connecting the tank. Removing tanks from service altogether, on the other hand, generally helps. A large pressure vessel may offer greater safety than several small pressure vessels of the same aggregate capacity because there are fewer associated noz-zles and lines. Also, a large pressure vessel is inherently more robust, or it can economically be made more robust by deliberate overdesign than can a number of small vessels of the same design pressure. On the other hand, if the larger vessel has larger connecting lines, the rel-ative risk may be greater if release rates through the larger lines increase the risk more than the inherently greater strength of the ves-sel reduces it. In transporting hazardous materials, maintaining tank car integrity in a derailment is often the most important line of defense in transportation of hazardous materials.

Safer Storage Conditions The hazards associated with storage facilities can often be reduced significantly by changing storage condi-tions. The primary objective is to reduce the driving force available to transport the hazardous material into the atmosphere in case of a leak (Hendershot, 1988). Some methods to accomplish this follow.

Dilution Dilution of a low-boiling hazardous material reduces the hazard in two ways:

1. The vapor pressure is reduced. This has a significant effect on the rate of release of material boiling at less than ambient temperature. It may be possible to store an aqueous solution at atmospheric pressure, such as aqueous ammonium hydroxide instead of anhydrous ammonia.

2. In the event of a spill, the atmospheric concentration of the haz-ardous material will be reduced, resulting in a smaller hazard down-wind of the spill.

Refrigeration Loss of containment of a liquefied gas under pres-sure and at atmospheric temperature causes immediate flashing of a large proportion of the gas. This is followed by slower evaporation of the residue. The hazard from a gas under pressure is normally much less in terms of the amount of material stored, but the physical energy released if a confined explosion occurs at high pressure is large.

Refrigerated storage of hazardous materials that are stored at or below their atmospheric boiling points mitigates the consequences of containment loss in three ways:

1. The rate of release, in the event of loss of containment, will be reduced because of the lower vapor pressure in the event of a leak.

2. Material stored at a reduced temperature has little or no super-heat, and there will be little flash in case of a leak. Vaporization will be mainly determined by liquid evaporation from the surface of the spilled liquid, which depends on weather conditions.

3. The amount of material released to the atmosphere will be fur-ther reduced because liquid entrainment from the two-phase flashing jet resulting from a leak will be reduced or eliminated.

Refrigerated storage is most effective in mitigating storage facility risk if the material is refrigerated when received.

The economics of storage of liquefied gases are such that it is usu-ally attractive to use pressure storage for small quantities, pressure or semirefrigerated storage for medium to large quantities, and fully refrigerated storage for very large quantities. Quantitative guidelines can be found in Mannan (2005).

It is generally considered that there is a greater hazard in storing large quantities of liquefied gas under pressure than at low temper-atures and low pressures. The trend is toward replacing pressure storage by refrigerated low-pressure storage for large inventories.

However, it is necessary to consider the risk of the entire system, including the refrigeration system, and not just the storage vessel.

The consequences of failure of the refrigeration system must be considered. Each case should be carefully evaluated on its own merits.

Preventing Leaks and Spills from Accumulating under Tanks or Equipment Around storage and process equipment, it is a good idea to design dikes that will not allow toxic and flammable materials to accumulate around the bottom of tanks or equipment in case of a spill. If liquid is spilled and ignites inside a dike where there are stor-age tanks or process equipment, the fire may be continuously supplied with fuel and the consequences can be severe. It is usually much bet-ter to direct possible spills and leaks to an area away from the tank or equipment and provide a firewall to shield the equipment from most of the flames if a fire occurs. Figure 23-63 shows a diking design for directing leaks and spills to an area away from tanks and equipment.

The surface area of a spill should be minimized for hazardous mate-rials that have a significant vapor pressure at ambient conditions, such as acrylonitrile or chlorine. This will make it easier and more practical to collect vapor from a spill or to suppress vapor release with foam or by other means. This may require a deeper nondrained dike area than normal or some other design that will minimize surface area, in order to contain the required volume. It is usually not desirable to cover a diked area to restrict loss of vapor if the spill consists of a flammable or combustible material.

Minimal Use of Underground Tanks The U.S. Environmental Protection Agency’s (EPA) Office of Underground Storage Tanks defines underground tanks as those with 10 percent or more of their volume, including piping, underground. An aboveground tank that does not have more than 10 percent of its volume (including piping) underground is excluded from the underground tank regulations.

In document 23 Process Safety (Page 108-113)