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How to Avoid Gas Line Ruptures
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How to Avoid Gas Line RupturesAuthor : Matthew Paradiso
Plant Maintenance Resource Center Home Maintenance Articles Ignorance of workplace safety standards is no excuse for noncompliance. For companies that work with compressed gas and other gas handling equipment, dangers related to the use of complicated technology and other safety hazards are a continual risk. Gas line ruptures have the potential to cause lasting damage to people, equipment, and the environment. Your company has a duty to protect its employees from occupational hazards. To ensure workplace safety is upheld, the United States government established regulations that turn this moral obligation into a legal one. Under the Occupational Safety and Health Administration (OSHA) guidelines, employers must “maintain a safe workplace” by planning for any situation for which published standards exist. Proper employee training is vital in avoiding gas line failures. The workers who handle a company’s gas equipment should be familiar with the most common causes of ruptures, such as over-pressurization, regulator failure, mechanical stress, or corrosion. Common Causes of Gas Line Rupture: Over-Pressurization Over-pressurization of a compressed gas cylinder can result in ruptures. The contents of the container may erupt at high speeds or send debris hurtling through the air, posing a great safety risk to bystanders. The escaped gas can pose a threat if it is toxic or otherwise corrosive in nature, and flammable gas may ignite once released from its container and comes into contact with an ignition source, such as sparks, electrical circuits, flames, hot surfaces or incompatible materials. Several safety attachments are available to protect against over-pressurization. Rupture discs are designed so that, as canister pressure rises, the seal will burst and the cylinder’s contents will slowly be released. In situations where temperature could pose a threat, fusible plugs are designed to melt and release the gas long before critical pressure levels are reached. Common Causes of Gas Line Rupture: Regulator Failure Automatic pressure regulators are often used to lower gas pressure in a cylinder to safe levels for a particular job. Two-stage regulators are recommended over single-stage because they deliver a more constant pressure under more precise conditions. But while a safety measure in itself, these regulators can also fail and cause a damaging gas line rupture. Regulator failure often occurs when a compressed gas cylinder is connected to equipment that is not meant for use with that particular type of cylinder. Attaching a flammable gas canister to the connection for an oxidizing gas would be like trying to fit a square peg in a round hole – but with much worse consequences. To help prevent such missteps, different classes of gas may be assigned their own valve outlet designs. Common Causes of Gas Line Rupture: Mechanical Stress Mechanical stress can take a toll on the reliability of your equipment. Gas handling equipment should be kept clean, well maintained, and be made of materials that are compatible with the gas used. Routinely check hoses and attachments for leaks due to wear and make sure the equipment stays clean. Loose hoses are a common cause of accidents because the force of pressurized gas can free them of their connection point. Specialized caps can be installed to protect regulator valves during handling and to keep valve outlets dust-free. Common Causes of Gas Line Rupture: Corrosion Corrosion can weaken compressed gas cylinders and other devices over time, which is why it is particularly important that a gas is not used with equipment that is not meant for it. For example, ammonia gas can mix with mercury to create an explosive reaction. If ammonia is run through a system with mercury pressure gauges, the result could be catastrophic. Corrosive gases often wear metal down, so valve stems can become difficult to open. Workers can minimize the effect by rotating the stem at least once a day and by properly flushing the regulator after use. Regular inspection helps workers to screen for equipment that may have been weakened by corrosion, leakage, pitting, dents or gouges. Gas Line Rupture Hazards and How to Avoid Them Ruptured gas lines pose a major health threat to workers. Gas users and distributors must be aware of the dangers associated with compressed gases. The high pressure under which the gases are stored makes them potentially explosive if mishandled. Asphyxiation can occur if the compressed gases leak in an environment that lacks proper ventilation. Flammable gases should be kept away from sparks or sources of high heat to prevent fires from occurring. Toxic and corrosive gases require special handling as outlined in Material Safety Data Sheets (MSDSs). All leaks should be reported and, if called for in the MSDS, personnel should be evacuated from the hazardous release area. The malfunction of gas handling equipment can result in far-reaching damages. Even a small rupture may lead to expensive lawsuits, hefty government fines, employee injuries or deaths, and property damage. In 2003, Texas-based Brigham Exploration Co. faced $147,800 in OSHA fines in connection with the death of a single worker after a pressurized gas line ruptured. Long term consequences for companies include possible declines in worker productivity and significant harm to a facility’s reputation due to bad publicity. Protective gear, or personal protective equipment (PPE), is good measure against workplace accidents. By donning gloves, eye guards, aprons, respirators and other wear, the risk of exposure to dangerous gases is reduced. MSDSs should be consulted for guidance as to what gear is sufficient protection based on what materials are being handled. Accidents can also be easily contained or avoided when companies properly implement safety equipment. The two most common oversights that violate OSHA regulations are the improper storage of pressurized gas canisters and the failure to install and properly use valve caps. Storage concerns creep up often because environmental changes and simple lapses of judgment can lead to major problems. The damage caused by storage mistakes can range from the deterioration of a canister’s sensitive contents to the explosive effect of propelling a pressurized gas canister though the air with enough force to crush concrete. Compressed gas may be highly reactive to changes in temperature or to corruption of its canister’s seal. For the proper handling of compressed gas cylinders, OSHA requires that they be “stored in a well-protected, well-ventilated, dry location at least 20 (6.1 m) feet from highly combustible materials such as oil or excelsior. Cylinders should be stored in definitely assigned places away from elevators, stairs, or gangways. Assigned storage spaces shall be located where cylinders will not be knocked over or damaged by passing or falling objects, or subject to tampering by unauthorized persons. Cylinders shall not be kept in unventilated enclosures such as lockers and cupboards.” OSHA currently requires compressed gas cylinders to have pressure relief valves or caps installed and maintained in accordance with the organization’s Compressed Gas Association Pamphlets. These small devices are designed to automatically shut off the delivery of gas if the flow exceeds the preset limit. Scott Specialty Gases, a leading producer and supplier of specialty gas products and equipment, developed the Model 1 Series excess flow shut-off valve. This piece of gas handling equipment senses flow as a pressure drop across the preset internal orifice. When the preset differential limit is reached, the valve closes with a “snap action” for a tight seal. The Model 1 Series is a two position valve that is set by an easy-to-use manual knob. In position one, “Open (Reset)”, the valve provides a direct passage from inlet to outlet. In the second position, “Auto Shut Off”, the valve senses the flow and shuts off the passage if the preset flow limit is surpassed. The valve stays shut until it is reset to pass a flow within the limit value. Six flow ranges are available. The actual flow shutoff for each range is dependent on the operating pressure. It is suggested that the range selected provide shutoff at six to ten times the anticipated actual process flow rate to allow for short term flow surges not connected with catastrophic line failure. Implementation of safety measures that take these common oversights into consideration can minimize work delays, equipment damage, noncompliance costs, and human injuries. It’s a wise business move for a company to invest in preventative measures during the use of gas handling equipment. Gambling with workplace safety is a risk that never pays. This article is provided by Scott Specialty Gases. Scott Specialty Gases, a leading global manufacturer of specialty gases located in Plumsteadville, PA. More information on the company can be found at http://www.scottgas.com. This article is copyrighted by Scott Gases. It may not be reproduced in whole or in part and may not be posted on other websites, without the express written permission of the author who may be contacted via email at scottgas@digitalbrandexpressions.com. About the Author Matthew holds a Mechanical Engineering degree from New Jersey Institute of Technology. Matthew joined Scott Specialty Gases in September 1997 as the technical representative for equipment. He is currently the product manager for the Scott equipment line, which includes regulators, flowmeters, valves, etc. Matthew has experience in the environmental field, semiconductor industry and the manufacturing of gas handling equipment.
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