Industrial Safety and Health for Goods and Materials Services - Chapter 10 doc

10 Compressed Gases There are two types of hazards associated with the use, stor age, and handling of compressed gas cylinders: the chemi cal hazard associa ted with the c ylinder conten ts (corrosive , toxi c, flammable, etc.) and the p hysical hazards repres ented by the presence of a high-press ure vessel in the wor kplace or laboratory . Figure 10.1 outlines some of the physical attribut es of compr essed gas c ylinders and describes some of the dangers that may resul t from imp roper use. Wheth er we like it or not, there are a lways safet y rules to follow . But when it comes to safet y procedu res for co mpressed gas, these rules are doub ly imp ortant. They shoul d be practiced daily because the safe way is the only way. W hen dealing with compressed gases, there are several items that one needs to be aware of at all times so that handli ng, trans porting, stor age, and use of compressed g as cylinders can be accom plished ef ficient ly and safely. Mishandl ed cylinders may cause a viol ent ruptu re, relea sing the hazardo us con- tents or the cyli nder itself, whi ch can become a dange rous proje ctile. If the neck of a pressurized cylinder breaks accidentally, the energy released would be sufficient to propel the cylinder to over three-quart ers of a mile in height (F igure 10.2). A standard 250 cu ft cylinder pressurized to 2500 psig can become a rocket attaining a speed of over 30 miles=h in a fraction of a second after venting from the broken cylinder connection. Compressed gases have a variety of uses and require special handling procedures. ß 2008 by Taylor & Francis Group, LLC. 10.1 CORROSIVE AND TOXIC GASES Many gases used throughout industry have additional hazards other than those of fire, asphyxiation, or oxygen enrichment. Exposure to some gases may present serious health hazards to unprotected personnel. Before using a corrosive, toxic, or highly toxic gas, read the label and material safety data sheet (MSDS) for the particular gas. Personnel working in the immediate vicinity where exposure to these gases is possible should be informed of their hazards. Exposure to these gases must be kept as low as possible, but in no case should concentrations exceed Occupational Safety and Health Administration (OSHA) permissible exposure limits (PELs) or the current ACGIH threshold limit values (TLVs) set by the American Removable metal cap I stand 57 in. tall. I am 9 in. in diameter. I weigh in at 155 lb when filled. I am pressurized at 2200 psi. I have a wall thickness of about ¼ in. I wear a label to identify the gas I am holding. My color is not the answer. I transform miscellaneous stacks of material into glistening plants and many other things, when properly used. I may transform glistening plants and many other things into miscellaneous stacks of material, when allowed to unleash my fury unchecked. I can be ruthless and deadly in the hands of the careless or uninformed. I am proud of my capabilities, here are a few of them: • I have on rare occasions been known to jetaway, faster than any dragster. • I might smash my way through brick walls. • I might even fly through the air. You can be my master only under the following terms: Treat me with respect—I am a sleepin g g iant. • I may spin, ricochet, crash, and slash through anything in my path. • Full or empty—see to it that my cap is on, straight, and snug. • Never, repeat, never leave me standing alone. Secure me so that I cannot fall. I am frequently left standing alone on my small base without other visible means of support—my cap removed and lost by an unthinking worker. I am ready to be toppled over—where my naked valve can be damaged or even snapped off—and all my power unleased through an opening no larger than a lead pencil. Oxygen capacity of cylinder 244 cu ft at 2200 psi pressure at 70ЊF Bronze valve Safety device Pressed steel neck ring 8½ in.–I.D. 9 in.–O.D. 51Љ FIGURE 10.1 Sleeping giant. (Courtesy of North Carolina Department of Labor, Mine and Quarry Division.) ß 2008 by Taylor & Francis Group, LLC. Conference of Governmental Industrial Hygienists (ACGIH). Contact an industrial hygienist for information on these exposure limits. 10.1.1 POISONOUS GASES Poisonous compressed gases represent a significant hazard. Special precautions not otherwise necessary become prudent when using poisonous gases. Common poisonous or highly toxic gases include the following: . Arsine (AsH 3 ) . Ethylene oxide (EtO) . Hydrogen cyanide (HCN) . Nitric oxide (NO) . Phosphine (PH 3 ) Certain poisonous gases (e.g., ethylene oxide) can only be used if specific OSHA regulations (1910.1047) and safe practices are followed: . Emergency procedures should be made clear to all involved, including personnel from adjacent work areas and managers who might be affected. . Poisonous gas used after normal working hours should require the approval of the chemical hygiene officer for your operation. FIGURE 10.2 Compressed gas cylinder can become a missile, which can penetrate a block wall. ß 2008 by Taylor & Francis Group, LLC. . Fume hoods and other ventilation need to be tested before use and checked frequently during the project that involves poisonous gas. . Notify the environmental health, safety, and risk department before your first use of the poisonous gas. . Police should also be informed about the locations and types of poisonous gas in use. . Document the procedures in your work area according to the chemical hygiene plan. As with all chemicals, obtain and review the MSDS for the poisonous gas. Maintain an extra copy of the MSDS in your workplace’s chemical hygiene plan. Disposal of poisonous gas cylinders can often cause problems. If the cylinder cannot be returned to the manufacturer, disposal cost may be as large as $1000 per cylinder, or more. Even cylinders that can be returned must be shipped on a vehicle that does not simultaneously carry any other hazardous materials or foodstuffs. The energy potential of compressed gas cylinders whether chemical or mechan- ical can be mitigated by following safe work procedures. These safe procedures include use, handling, storage, transportation, and movement of compressed gas cylinders, and those using them should not fail to follow these procedures. 10.2 PREVENTING COMPRESSED GAS CYLINDER ACCIDENTS All systems in manne d areas have unmodified, DOT-approved, compressed gas cylinders and the appropriate regulators may not require engineering controls if general safety rules are followed. Compressed gas cylinders are the most common source of gas for many operations. As a precaution, these cylinders must be adequately secured when in use or storage. The DOE, ASME, DOT, and OSHA agencies all refer to the Compressed Gas Association (CGA) pamphlet (CGA P-l, 1991) for instructions on how to safely handle compressed gas cylinders. Many factors must be addressed to assure safety in the handling and use of compressed gas cylinders. The great amount of energy stored in the cylinders makes preventing accidents paramount in preventing injury, illnesses, and deaths. 10.2.1 CYLINDER USE Follow these recommendations for safe use of cylinders: . Make sure all connections are tight. Use soap water to locate leaks. . Keep cylinder valves, regulators, coupli ngs, hose, and apparatus clean and free of oil and grease. . Keep cylinders away from open flames and sources of heat. . Safety devices and valves should not be tampered with, nor repairs attempted. . Use flashback arrestors and reverse-flow check valves to prevent flashback when using oxy-fuel systems. ß 2008 by Taylor & Francis Group, LLC. . Regulators should be removed when moving cylinders, when work is complete, and when cylinders are empty. . Cylinders are to be used and stored in the upright position. . Cylinder valve should always be opened slowly. Always stand away from the face and back of the gauge when opening the cylinder valve (Figure 10.3). . When a special wrench is required to open a cylinder or manifold valve, the wrench shall be left in place on the valve stem when in use; this precaution is taken so the gas supply can be shut off quickly in case of an emergency, and that nothing should be placed on top of a cyli nder that may damage the safety device or interfere with the quick closing of the valve. . Fire extinguishing equipment should be readily available when combustible materials have a possibility of getting exposed to welding or cutting operations using compressed cylinder gases. 10.2.2 HANDLING Even though the cylinders are constructed of steel, they must be handled with extreme care to avoid damage. Physical abuse, such as dropping, or violently striking cylinders together, can cause damage to the cylinder, valve, or fuse plug, and in turn present a potential hazard. There are several methods of unloading cylinders from a truck to ground level that help prevent damage. These include the following: . V-shaped trough—it allows cylinders to be lowered carefully down onto a shock-absorbing mat on the ground. . Angle-iron cradle—these are used to upend the cylinders and low er them to the ground. Inproper cracking FIGURE 10.3 Care must be taken when opening cylinder valves. (Courtesy of Department of Energy.) ß 2008 by Taylor & Francis Group, LLC. . Elevator tailgate—this is one of the easiest and safest means of unloading cylinders, and is to be used when ever it is available on the transport truck. But remember, the important thing is to be sure the cylinders are not dropped. . Use a four-wheel cylinder cart for moving Standard No. 1 and larger gas cylinders. These cylinders are difficult to move manually because of their shape, smooth surface, and weight (Figure 10.4). . Make sure that the protective valve cover is in place when a cylinder is not connected to a regulator or manifold (Figure 10.5). . Measure the pressure of contents of half-empty cylinders and mark them. Special carriers FIGURE 10.4 Carts for safe and secure movement of cylinders. (Courtesy of Department of Energy.) Valve cap FIGURE 10.5 Cylinders should have valve caps in place when regulators are removed. (Courtesy of Department of Energy.) ß 2008 by Taylor & Francis Group, LLC. . Always assume a cylinder is pressurized; handle it carefully and avoid bumping or dropping. . Never drop cylinders from trucks or any raised surface to the ground. . Lifting a standard cylinder, or any cylinder weighing more than 50 lb, requires two people. Never lift a cylinder by the cylinder cap (Figure 10.6). . Do not handle oxygen cylinders with greasy, oily hands or gloves . The reaction between oxygen and hydrocarbons can be violent, even when small quantities are involved. . Secure cyli nders in suitable cradles or skid boxes before raising them with cranes, fork trucks, or hoists. Do not use ropes or chain slings alone for this purpose. . Never use a gas cylinder as a roller for moving materials or for supporting other items. 10.2.3 STORAGE Cylinders are sometimes shipped tied horizontally on wooden pallets, individually contained by saddle blocks, and double-banded to prevent rolling and sliding. These are not recommended methods for cylinder storage. Instead, the work practices prescribed in this section should be followed (from pamphlet CGA P-l-1991): . Store adequately secured cylinders upright on solid, dry, level footings, preferably outside of occupied buildings and away from traffic lanes. . Shade cylinders stored in the sun during the summer, whenever possible. . Store cylinders away from sources of intense heat (furn aces, steam lines, and radiators). Improper hoisting FIGURE 10.6 Unsafe hoisting practices for gas cylinders. (Courtesy of Department of Energy.) ß 2008 by Taylor & Francis Group, LLC. . Cylinders should be stored in compatible groups. . Flammables from oxidizers . Corrosives from flammables . Full cylinders from empties . Empty cylinders should be clearly marked and stored as ca refully as full cylinders are because of the presence of residual gas. . All cylinders should be protected from corrosive vapors. . Store cylinders in an upright position. . Keep oxygen cylinders a minimum of 20 ft from flammable gas cylinders or combustible materials. If this cannot be done, separation by a noncombus- tible barrier at least 5 ft high having a fire-rating of at least 1.5 h is required (Figure 10.7). . Compressed gas cylinders should be secured firmly at all times. A clamp and belt or chain, securing the cylinder between cylinder waist and shoulder to a wall, are generally suitable for this purpose. . Cylinders should be individually secured; using a single restraint strap around a number of cylinders is often not effective. 20 ft minimum Fuel gas Oxygen Minimum: 5 ft high 1/2 h fire rating Flammable Keep away from fire FIGURE 10.7 Maintain required distances for flammable compressed gases. (Courtesy of the Occupational Health and Safety Administration.) ß 2008 by Taylor & Francis Group, LLC. . Keep valve protective caps in place when the cylinder is not in use. Always store cylinders with the protective caps in place. . Mark empty cylinders EMPTY or MT. . Keep valves closed on empty cylinders. . Keep cylinders away from magnetized equipment. . Cylinders must be kept away from electrica l wiring as the cylinder could become part of the circuit. . Store cylinders in well-ventilated areas designated and marked only for cylinders. . Do not stockpile gas, especially flammables, poisons, or corrosives, beyond the amount required for immediate use. Con sider direct delivery from the distributor when gases are needed. . Limit the use and storage of poisons and corrosives to less than 1 year to prevent stockpiling. Documentation should be required for these materials. The environmental safety and health (ES&H) department’s industrial hygienist should establish and document the maximum quantities of such materials in use and storage to ensure reasonable turnover. The emergency preparedness group should track the materials as an element of its emer- gency response planning program. Extended use or storage of hazardous materials shoul d occur after discussion by the user, the industrial hygien ist, and the emergency preparedness group. The agreed upon storage process should be documented. . Ensure that containers stored or used in public areas are protected against tampering and damage. Furthermore, containers stored inside or outside shall not obstruct exit routes or other areas that are normally used or intended for the safe exit of people. . Use a storage basket for smaller cylinders (<5 L). These b askets are available commercially. 10.2.3.1 Outside Storage Store cylinders outside whenever it is possible. Care must be taken to protect them from bad weather and direct sunlight. Remember, the heat from direct sunlight will cause gas to expand, which creates higher pressure within the cylinder. 10.2.3.2 Inside Storage It is best not to store cylinders inside, but if you must, here are a few things to remember. Do not place cylinders . In passageways . Near elevators . Near loading platforms . By entrances or exits where they might be accidentally hit . Near sources of electricity . Near sources of excessive heat, such as the sparks resulting from welding or cutting ß 2008 by Taylor & Francis Group, LLC. . Where they may become hotter than 1308F . Closer than 20 ft from combustibles such as grease, gasoline, paint, oil, and dirty rags In addition, if a cylinder is frozen to the ground, use warm, not hot, water to free it. If the valve is frozen, again, use warm water, not hot, to thaw it or take the cylinder inside and let it thaw at room temperature. 10.2.4 MOVING CYLINDERS Here are some pointers that should be remembered when moving compressed gas cylinders: . Use of a hand truck simplifies moving cylinders from one location to another. . Cylinders are to be chained or secured in some manner, in an upright position. . Avoid moving in a horizontal position whenever possible, especially cylin- ders containing acetylene. . Protect valves from being damaged or accidentally broken off by the use of properly placed cylinder caps. . Never drag a cylinder, tilt it sideways, and roll it along on its bottom rim or edge. This gets the job done in an easier and much safer way. . Use a cylinder cart and secure cylinders with a chain. . Do not use the protective valve caps for moving or lifting cylinders. . Do not drop a cylinder or permit them to strike each other violently or be handled roughly. . Unless cylinders are secured on a cart, regulators are to be removed, valves closed, and protective caps in place before cylinders are moved. 10.2.5 TRANSPORTATION OF CYLINDERS Cylinders containing compressed gases are primarily shipping containers and should not be subjected to rough handling or abuse. Such misuse can seriously weaken the cylinder and render it unfit for further use or transform it into a rocket having sufficient thrust to drive it through masonry walls: . To protect the valve during transportation, the cover cap should be screwed on hand tight and remain on until the cylinder is in place and ready to use. . Cylinders should never be rolled or dragged. . When moving large cylinders, they should be strapped to a properly design- wheeled cart or cradle to insure stability. . Only one cylinder should be handled (moved) at a time. 10.2.6 EMPTY CYLINDERS Leave some positive pressure (a minim um of 20 psig) in empty cylinders to prevent suck-back and contamination. Close the valves on empty cylinders to prevent ß 2008 by Taylor & Francis Group, LLC. [...]... noncombustible foundations 10. 8.4 NITROUS OXIDE (29 CFR 1 910. 105) Nitrous oxide piping systems for the in-plant transfer and distribution of nitrous oxide are to be designed, installed, maintained, and operated in accordance with the guidelines laid out in the CGA pamphlet G-8. 1-1 964 10. 8.5 OXYGEN (29 CFR 1 910. 253) Oxygen cylinders in storage must be separated from fuel-gas cylinders or combustible materials (especially... a fire-resistance rating of 1=2 h 10. 8.6 COMPRESSED AIR (29 CFR 1 910. 242 AND 29 CFR 1926.302) Pressure of compressed air used for cleaning purposes should be reduced to less than 30 psi (207 kPa) and then used only with effective chip guarding and PPE 10. 9 COMPRESSED GAS AND CYLINDER CHECKLIST To assure the safe use and handling of compressed gases and their cylinders, a checklist can be used for following... can make materials burn that are usually noncombustible (Figure 10. 10) FIGURE 10. 10 A liquid oxygen container in a secured enclosure ß 2008 by Taylor & Francis Group, LLC 10. 6 PREVENTING CRYOGENIC ACCIDENTS 10. 6.1 DOS The following are some of the proper procedures and practices that should be followed when dealing with cryogenic materials: Do wear goggles, cryogen gloves, and loose-fitting clothing... excess of 15 psi (103 kPa gauge pressure) or 30 psi (206 kPa absolute) The use of liquid acetylene is prohibited The in-plant transfer, handling, and storage of acetylene in cylinders are to be in accordance with the guidelines laid out in the CGA pamphlet C-1. 3-1 959 10. 8.3 HYDROGEN (29 CFR 1 910. 103) Hydrogen containers must comply with one of the following: (1) designed, constructed, and tested in accordance... high FIGURE 10. 8 Markings on compressed gas cylinders (Courtesy of the Occupational Health and Safety Administration.) ß 2008 by Taylor & Francis Group, LLC appropriate Placards, container labels, and markings provide information on the products involved The MSDS for the products or other recognized emergency response guides should be consulted for specific hazards, safety precautions, and related... associated with pressurized systems Special storage, use, and handling precautions are necessary to control these hazards There are specific safety requirements for many of the compressed gases such as acetylene, hydrogen, nitrous oxide, and oxygen 10. 8.2 ACETYLENE (29 CFR 1 910. 253) Acetylene cylinders are to be stored and used in a vertical, valve-end-up position only Under no conditions should acetylene... GASES IN THE SERVICE INDUSTRY The use and distribution of compressed gases for welding, health care, storage, and distribution are standard practices in the service industry We would expect these gases to be stored and sold by the warehousing, wholesale, and retail sectors and moved extensively by transportation, but also have wide use in other service sectors and utilities These are possibly less... extensively used in the health sector in the form of oxygen and as cryogenics Also, they are used in routine maintenance activities and as a fuel for forklifts This is also true for the administrative, leisure, and hospitality sectors that employee maintenance personnel who would be using some of these types of gases Each particular sector would need to address the safe use of flammable and combustible liquids... enable the use of these materials in a safe and efficient way Remember, the safe way is the only way 10. 3.4 SAFE HANDLING AND USAGE GUIDELINES Plan carefully when setting up an experiment that involves gaseous materials and gas cylinders The following should be done: Ask questions about the suppliers when purchasing gaseous materials, especially with regard to waste disposal and their cylinder return... all corrective standards? Compressed gas cylinder (CGC) safety checklist 10. 10.1 BASIC SAFETY Some of the basic safety, health rules, and procedures that should be followed when using compressed gas cylinders of any type are as follows: Select the least hazardous gas Purchase only the necessary quantities Select gases with returnable containers When receiving gas cylinders: Check for leaks Visually . needed. . Limit the use and storage of poisons and corrosives to less than 1 year to prevent stockpiling. Documentation should be required for these materials. The environmental safety and health (ES&H). num- bers represent the date of manufacture, and retest date (month and year). A(þ) sign indicates the cylinder may be 10% overcharged, and a star indicates a 10 year test interval (Figure 10. 8). The. cryogens. The Dewars used for this purpose must be nonmagnetic. 10. 5.6.7 Liquid Oxygen Liquid oxygen can make materials burn that are usually noncombustible (Figure 10. 10). FIGURE 10. 10 A liquid oxygen