Four Major Criteria Implicated In Product Hose Safety, Long Life
Oct 1, 1998 12:00 PM
The essential elements to be considered for product hose use are application, testing, and maintenance. Add the importance of training personnel who will be handling the hose, and the list totals four major criteria for every user, say tank truck industry spokesmen.
To stop short of these considerations compromises safety and carries inherent financial risks. "Cleanup costs from a product spill caused by a hose failure can be as much as $25,000 to $50,000," says Kip Hart, vice-president of Hart Industries Inc, a Middletown, Ohio, distributor. "Lawsuits have brought million-dollar settlements after a catastrophic hose failure. At the very least, the cost of the hose itself is a significant factor."
Hoses in the tank truck industry are used to transfer gases, liquids, and solids. Selecting the right hose for the job is extremely important because even the best hose can fail if it is inappropriately used or poorly maintained. Understanding hose sizes and vulnerability to temperature, pressure, chemicals, and other products are essential elements for making decisions about application, Hart says.
Hoses are composed of a tube, reinforcement, and cover, and are made from many different materials. The tube is always in contact with the material being conveyed and may need to be made of a special material in order to meet specifications.
The reinforcement is the component that supports the tube and permits the use of pressure to convey the product. The reinforcement is commonly called the braid or spiral.
The cover, often the part that takes the worst beating, protects the reinforcement from various types of abuse such as abrasions, cuts, chemicals, and the environment.
"Service life of the hose is unique in each type of setting," says Bill Thompson, regional sales manager for Titan Industries, Southgate, California.
With the many hoses that are on the market, carriers may find it difficult to be familiar with the models and understand the applications, says Norman Biggs, regional tank truck manager in Houston, Texas, for Goodall Rubber Company, Ewing, New Jersey. "Help is available from manufacturers and distributors through marketing professionals who are specialists," he says. "Our role is no longer just sales. Once we qualify a customer by industry, then we can start considering the various applications and requirements."
Hoses may look deceptively similar to one another, says Howard Aspinall, chemical industry specialist, Boston Industrial Products of Dana Corp, Toledo, Ohio. But no one hose is complementary to all products. "This is particularly important if the hose is carrying corrosives," he says.
Dayco Industrial Division, Dayton Ohio, provides an acronym, "STAMPED," as a key for remembering the principles involved for selecting the correct hose, according to Gary
Zweig, Dayco marketing manager. The letters and their meanings are: "S" is for size, which includes inside diameter, length, and in some cases the outside diameter. "T" is for temperature, internal and external; minimum and maximum. "A" is for application, what the hose is supposed to do and in what environment. "M" stands for the material (product) to be conveyed by the hose. "P" is for pressure, normal working pressure and/or vacuum. "E" is for ends, or couplings needed - their type, size and thread. "D" stands for delivery, which defines when and where the hose/hose assembly is needed.
"The materials used to manufacture the tube are selected on the basis of products involved," states the National Tank (NTTC) Truck Carriers Cargo Tank Maintenance Manual. "Putting a hose in the wrong service can quickly destroy the tube, regardless of thickness of composition."
Product transfer hoses should be rated in accordance with manufacturers recommendations for the specific application, says Hart.
Many hose manufacturers and distributors have chemical resistance charts that can be used as guides for selecting suitable chemical product hoses. Some companies, Dana Corp/Boston for example, provide a chart on World Wide Web sites. These charts and other industry resources, such as brochures and manuals, target specific applications and ensure proper hose selections no matter what product is being transported.
Although hose selection must be based on product suitability, hose testing is of equal importance and should be required not only before initial use, but in continuing regular cycles. Any damage to the hose, or excessive bending and crimping, should prompt inspection and possible testing. Manufacturers and distributors agree that any company that provides hoses should have testing facilities that demonstrate the hose's bursting pressure.
Thompson recommends the Rubber Manufacturers Association standards guide as a reference for testing. "Hoses should be tested once or twice a year, depending on their use," he says.
The NTTC Maintenance Manual makes the distinction that inspections serve no purpose unless the hose bursting pressure is known and appropriate for the specific tank application.
Hart points out that federal rules governing hose testing are in a gray area. Hoses that are used with hazardous materials must meet certain testing requirements, but hoses used with other products are not specifically addressed. They are listed under a general category of equipment, he says. However, a propane hose failure that resulted in an incident has garnered the attention of the Occupational Safety and Health Administration, which has begun action to establish new rules for the LPG industry.
"With hose inspection and testing, most problems can be eliminated," says Hart. However, he warns that some companies may be tempted to shortcut inspection and testing to keep up with schedules driven by the current energetic US economy.
The third consideration involving hose use addresses preventive maintenance that results in safety and cost savings. Chip Lynn, president of E H Lynn Industries, Broadview, Illinois, says that maintenance is paramount in ensuring long life for the hose. "Once it is tested, then the hose condition is only that good until it is used again. A hose can be in service and then because of abuse or routine use, it could possibly fail."
By discovering the damage, maintenance employees can then follow the trail to the root cause, which may prevent future mishaps, Lynn says.
Information from Gates Rubber Company, Denver, Colorado, calls for regular inspection and pressure testing as part of a maintenance procedure. Hoses should be inspected at regular intervals for hose stress, soft spots, cuts, and abrasions. After any indication of severe end pulls, and/or flattened, crushed, and kinked areas, the hose should be removed and pressure tested. Couplings should be checked for seepage and slippage.
Andy Harrington, composite hose product manager for Senior Flexonics Inc, Romeoville, Illinois, notes that the life of a composite hose can be extended through simple steps in inspection, testing, and maintenance. A composite hose is manufactured from multiple layers of thermoplastic fabrics and films, which are held in place by internal and external wire helices.
Visual inspection should note dents, displacement of inner and outer wires from normal pitch, displacement of end fittings or signs of end fitting leakage, and breaks or flattening of the outer wire, according to Harrington. Other damage to look for includes chemical attack, deterioration, and physical damage to outer cover and carcass.
When a hose is cleaned, certain procedures should be followed to prevent damage. Edgard van Hove, president of FlexTraco Inc in Houston, Texas, notes that his company's composite hoses should be cleaned after use, the method depending on location and product. Flushing out with clean water, hot water, and detergents and solvents at ambient temperatures is sufficient in most cases, according to the FlexTraco Inc brochure. Low-pressure steam can also be used as long as the temperature does not exceed the maximum working temperature of the hose.
In conjunction with proper maintenance, hoses should be stored on a solid support base or foundation and in dry, cool areas, manufacturers and distributors say. Careful attention should also be paid to whether the hose should be coiled or laid out, which depends on the type of hose and cleaning methods used.
Drivers play an important role by being able to quickly recognize equipment problems and report them. Many companies encourage drivers to communicate with maintenance personnel in order to expedite testing and repairs, notes Tom Alfredson, marketing specialist for Goodyear Tire and Rubber Company. "With formal training, drivers know what to look for," he says.
Hart agrees. "The hose is only as good as the training of the person that uses it," he says. "There are four groups of people who should be trained: management, maintenance personnel, tank wash employees, and drivers."
Personnel training has become an unwritten standard in the tank truck industry, says Alfredson. "Companies have taken it on themselves to do this, and that's great for us from a manufacturer's standpoint because we've been trying to show that a hose is not indestructible. With trained people taking good care of the hose, the expected service life can be obtained."
"The operator should be familiar with the characteristics, properties, hazards, and regulatory factors concerning the chemicals being conveyed," says Aspinall. Although it might seem obvious, one major problem is being overcome by teaching drivers not to run over hoses.
"There are enough characteristics (parts) in a hose that each can be used to train people," says Lynn. "Drivers can learn that fittings should be round. Gaskets should be there and secure in the fitting. No braiding or wire should be sticking out of the cover."
Driver awareness is also being directed to the damage that can result from extreme hose bends. "Excessive bends invite failure," Dayco states. Training should demonstrate methods drivers can use to properly support hose during handling to avoid kinks or tight bends.
"What I've seen personally is that tank truck carriers, most of the majors and many of minors, have instituted in-depth training programs," says Alfredson. "Some companies I've been to have a specific employee, like a human resource person, to make sure that personnel know how to handle hoses. Or, they will send their people to training programs."
Industry spokesmen agree that the time and expense spent in training can offset the costs that result from incidents related to hose failures, including materials costs, repair costs, and missed or delayed deliveries. "At the end of every year, everyone checks their bottom line to see where they can improve," says Thompson.
In addition to the four considerations discussed, changes that affect hoses are occurring in research and development, governmental regulations, and miscellaneous industry market adaptations.
Some companies are supporting a move to have all transfer hoses located only on loading and receiving sites, removing them entirely from the vehicles, says Hart. This discussion has been active for many years. Other issues on the horizon include expansion of governmental regulations driven initially by the propane incident. "We'll see a number of things evolve from this, beginning with propane hoses," he adds.
Research and development have already produced hoses made from a new plastic with ultra high molecular weight (UHMW) for chemical products. Its value stems from the ability to handle a broad range of chemical products. However, Hart points out that it is vulnerable to high temperatures. A more common hose is a modification that blends vulcanized rubber, which can withstand temperatures to 250 F, depending on the chemical being conveyed, he says.
Goodall's Biggs points out that development in hoses has advanced particularly in couplings that are mounted permanently onto the hose and the methods used in attachment that call for specialized equipment. "It really needs to be done correctly. We discourage customers from doing it themselves," he says. "The liability rests on whoever installed the end fittings."
Permanent couplings allow hoses to stand higher pressures and temperatures, Aspinall says. "We seem to be heading to permanent couplings. It began with food, then moved to pharmaceuticals, and then to acids and caustics."
Most couplings are made of carbon-steel or malleable iron. In some applications, special materials are required such as stainless steel or bronze for handling corrosive chemicals or nonsparking metals such as brass or aluminum for highly flammable fluids. "The point where hose and coupling meet is often subject to extra stress," Dayco points out in its information. "It's good practice to inspect this point to detect damage or creep."
Problems often arise when clamps are applied improperly and when manufacturers recommendations are ignored, says Hart. Clamps that are not permanent may be replaced by carrier maintenance personnel, or they may be sent out. In either case, the work must be done properly to prevent leakage or coupling ejection.
Clearly, there are many considerations involved with the use of product hoses in the tank truck industry. Company personnel are likely to reap the rewards when they are knowledgeable of product application, follow strict testing schedules, provide preventive maintenance, and instruct employees in care and handling.
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