Last March, the National Fire Protection Association (NFPA) released some startling statistics for the 3-year period ending in 2005. According to NFPA, 1,400 fires occurred annually in which flammable or combustible liquids first were ignited. Direct property damage was approximately $76 million each year.
Occupancies in which these fires occurred were described as institutional, educational, utility, defense or laboratory, manufacturing or processing, mercantile or business and storage. It is evident that chemicals and fuels still have widespread usage in industry for a multitude of important needs, but because of their hazardous nature, special care and handling is paramount. The proper use and storage of flammable liquids must be understood, and it clearly is a critically important subject for employee training.
Handling flammable liquids in the workplace presents numerous hazards. Prior to receiving any hazardous materials, consult the appropriate MSDS and follow the instructions. A drum of flammable solvent arriving at the receiving dock potentially is a powerful explosive that careless handling or storage can detonate. It has been said that 1 gallon of vaporized gasoline can explode with the same force as 20 sticks of dynamite. Because flammable liquids obviously are so hazardous, plant procedures must include the safety factors necessary to keep flammables protected, if not isolated, from exposure to fire.
Designing a safety program to reduce the risk of fires from hazardous materials may seem scary but could be straightforward. It simply requires an understanding of what needs to be done and a focus on education. This two-part series of articles discusses the safe control of flammable liquids in the plant, from storage to transfer and use, to disposal. This first article defines flammable liquids and reviews safe storage practices and the equipment available to maximize safety. The next article will outline the procedures to follow and the equipment to use for transferring, using and disposing of flammables.
DEFINITION AND CLASSIFICATION
What is a flammable liquid? A flammable liquid is defined by OSHA and by the National Fire Protection Association (NFPA) 30, “Flammable and Combustible Liquids Code,” as any liquid with a flashpoint below 100° F. (37.8° C) and a vapor pressure not exceeding 40 psia 100° F. Flammable liquids are called Class 1 liquids and are divided into three groups — Class 1A, 1B and 1C — according to the degree of the hazard. Liquids with flashpoints above 100° F are called combustible. The classification system is outlined in Chart 1.
Flashpoint is the lowest temperature at which a liquid gives off sufficient vapor to form an ignitable mixture with air. In a flammable liquids fire, it's the vapors from the liquid that ignite, not the liquid.
A fire requires fuel, oxygen and heat. The safety equipment and methods used to handle flammable liquids must control one or more of these essentials from the time flammable liquids arrive until they are spent or disposed of as waste and removed from the plant. The safe storage of flammables can be discussed by following a drum of flammable liquid from arrival at the plant through dispensing and use.
Before the drum is moved from the receiving dock, a drum vent should be installed. The 2-inch bung cap simply is removed and the vent is screwed in. A vent should be installed, even if the drum will be stored temporarily, before a pump or a faucet for dispensing the contents is put in place.
The safety drum vent is designed to automatically prevent pressure from building up inside the drum if it is exposed to heat. It also prevents a vacuum from forming if the drum is subjected to sudden cooling. Increased pressure in a drum is a major cause of the explosion of flammable liquids. Both pressure and vacuum can cause a drum to fail or leak.
After an approved drum vent is installed, the drum can be moved safely to a drum storage room or secured in a safety storage cabinet.
OSHA has issued numerous safety requirements to which drum rooms must conform — from the type of construction, lighting, switches and ventilation to the protection systems that are installed. Approved methods of equipping a drum and dispensing liquids from it must be followed. Aisle widths, stacking heights and maximum storage capacities also are indicated. The OSHA regulations — Subpart H, section 1910.106 — should be consulted for specific measures.
NFPA 30, 2008 Edition, “Flammable and Combustible Liquids Code,” especially Chapter 9, also is an excellent guide to proper drum room construction and should be studied before a storage room is built.
Once the drum of flammable liquid is in place in an adequately constructed storage room, it should be connected by a grounding wire to the room's grounding system. Grounding allows static electricity charges to drain off before they can build up to a spark-producing potential. Any earth ground that permits good metal-to-metal contact to the grounding-wire clamping mechanism is acceptable. Cold water pipes commonly are used; however, care must be taken to assure that plastic piping does not interrupt conductivity between the points at which the earth ground is established, and the drums are grounded.
Each drum also must be prepared for dispensing using one of two approved methods, depending on storage position. Horizontally stored drums are faucet drained and depend on gravity flow for dispensing. In addition to being equipped with a safety vent and grounding wire, drums stored in this way must be outfitted with a safety faucet, drip can and bonding wire. The bonding wire connects a container being filled to the drum.
Safety vents provide vacuum relief while the drum is being drained, and pressure relief under normal and emergency operating conditions. Safety faucets are equipped with flame arresters in the spout to prevent flash fires from reaching the drum contents. These self-closing faucets also have a no-drip valve mechanism and can be equipped with flexible metal hoses to ease positioning and filling.
Drums stored vertically are fitted with pumps instead of faucets for dispensing. Use of a pump is generally considered safer and more accurate. Some local codes require pumps for all drums containing flammable liquids.
POINT OF USE CONTAINMENT
A fast-growing approach to flammable liquids storage is to keep as much liquid as possible close to the point of use. It's efficient and saves time. Workers can minimize their exposure to potential ignition sources if they replentish their solvent supply from a drum near their workstations, rather than from the solvent room a quarter-mile away. OSHA permits up to 60 gallons of Class I or Class II liquids and up to 120 gallons of Class III liquids to be stored in safety cabinets close to workstations.
Design and construction requirements for safety cabinets are spelled out in NFPA Code 30 and by OSHA. Cabinets must be made of double-walled, 18-gauge steel with 1 1/2 inches of insulating airspace between the walls, top, bottom and in the doors. Leak-proof, 2-inch sills to contain spills must be provided. Also required are three-point locking doors and a conspicuously placed warning label that reads “Flammable — Keep Fire Away.” Some cabinets come with reflective warning labels for an added measure of safety and visibility in a fire situation.
Venting of cabinets is governed by local code. Some regulations require forced air ventilation from the top to bottom through the flammable liquid cabinets and are ducted outdoors. Conversely, a few codes prohibit venting. All cabinets should have capped vents with integral flame arrestors.
Cabinets come in a wide selection of sizes, shapes and door arrangements. Sizes range from 4- to 120-gallon capacity. Some large units will house drums, either horizontally or vertically, while others are made to hold cans and other smaller safety containers. Smaller models can be mounted on walls or fit under or on benches. Options include self-closing or manually operated doors, adjustable shelves for flexible storage, padlockable handles for user convenience and visible security and foot levelers to assure a solid base.
The next article in this series will discuss safe transfer and use of flammables, along with the cleanup and disposal of flammable waste.
Gary Marcus is vice president of Justrite Manufacturing Co. LLC, headquartered in Des Plaines, Ill. He is a veteran of successful industrial and consumer products companies with over 25 years of experience. Justrite has been in the safety products business for over 100 years and is a leading provider of safety cabinets, cans and other flammable and hazardous liquid storage and dispensing products that keep companies in compliance with regulatory requirements. For a free copy of Justrite's Redbook, a guide to handling flammables safely, visit http://www.justritemfg.com.