The cost of the gasket is not the question. When it comes to making intelligent choices about replacement gaskets, the key question is: Do you want this problem to go away?
As the manufacturing and process industries struggle to trim costs, there is an ever-shrinking margin for inefficient or stopgap for maintenance techniques. Successful managers are raising their maintenance standards in order to extend uptime and avoid maintenance crises that choke production.
Gaskets are a good example of a relatively low-cost item where improved standards can prevent repetitive maintenance problems. Chronic leaks and blowouts of heat exchanger gaskets, for example, can bring an entire process down. A definite need for improved gasket protection becomes apparent when downtime per failure is considered. This can be particularly true of applications where gaskets are viewed as industry-standard, no-brainers - yet where leaks, unsatisfactory service life and time-consuming labor are endured as acceptable evils that are inherent to "difficult" sealing applications.
With a profusion of process-critical applications throughout industry - heat exchangers, pumps, boilers and innumerable pipe flanges - gaskets are often viewed as commodity items that are unfortunately problematic, requiring frequent servicing and replacement. Today it is becoming intolerable that conventional gaskets are often the cause of process interruptions, maintenance labor, expensive gaskets inventory requirements, and safety and environmental issues.
"Gaskets have been failing prematurely forever," says Gary McCoy, Business Development Manager, A.W. Chesterton Global Marketing Department. "In many applications they are subjected to high pressures, thermal cycling, vibration and other stressful conditions. With often hundreds of gasket installations throughout a plant, many premature failures cause expensive process disruptions or other problems. Yet, in too many cases, the failed gaskets are simply replaced with the same model."
McCoy is a proponent of a new generation of gasket technology, a high-tech, flexible graphite-encapsulated stainless steel design that solves many problems that are inherent to gasket applications on stationary equipment.
"One of the major advantages of a graphite-stainless steel gasket is its ability to go through temperature cycles," McCoy explains. "This is a very thin (approx. 1/32 in.), convoluted stainless steel gasket with a graphite sealing medium on both sides that you compress to the thickness of the gasket metal. We now use this technology in many applications where spiral wound gaskets were traditionally used."
Chesterton, a renowned worldwide supplier of mechanical seals and packing products to the petrochemical, pulp & paper, shipping and other industries, frequently recommends the graphite-encapsulated stainless steel gasket marketed under the SteelTrap(tm) brand. These gaskets are manufactured by Sealing Corporation ("Selco"), North Hollywood, CA.
"For years and years we used the standard gaskets on our main steam drums and our lower water wall headers," says Stuart Bussman at Trans Alta Power, Centralia, WA. "After six cycles, we had to replace them. There are 20 gaskets on each unit, so it was an expensive and time-consuming proposition. Plus, they want them done fast." After successfully testing a graphite-stainless manway gasket in a boiler, Bussman says he decided to try SteelTrap gaskets for the main drums. "We're very pleased with the performance of these gaskets. We've had no cycling problems and the overall cost savings has been very substantial."
Cost is often the issue when gaskets are specified. When compared with spiral wound gaskets, the graphite-stainless technology is similar in cost, but offers substantial savings in other ways. For example, if you live load a SteelTrap gasket, Chesterton and Sealing Corporation will guarantee it for three years of leak-free service. "Whether it's a static application or a temperature cycling application, if it's live loaded, it will be covered by the warranty. No one else in the industry will do that," says McCoy.
At a Texas refinery Chesterton installed graphite-stainless gaskets on over 300 valves. Over a three-year period approximately 20 of those valves required servicing. So, the user not only got at least years of worry-free service life, but any incidental problems were serviced by the supplier.
"The cost of the gasket is not the question," says Vance St. Jean, Sales Manager for Chesterton in Houston, TX. "Your costs aren't really dependent on the sealing device. Your costs are associated with changing it out - the labor, the downtime the process disruptions and the other problems. Once I explain that to one of our refinery customers, they agree with me. Doing it right might be worth thousands of dollars, or it might be worth millions of dollars. It depends on the situation."
"The graphite-stainless gasket is also much more forgiving in terms of poor bolting procedures and imperfect conditions of flange plate surfaces," McCoy adds. "Unlike other gaskets that creep or cold-flow under load, and you lose gasket volume, the SteelTrap eliminates that problem - takes it to zero. Because of the convolutions of the metal, the sealing material is trapped on all sides by metal. That's where the gasket got its name."
McCoy adds that many gaskets can be attacked by the sealing medium. Flexible graphic is a very durable sealing medium, but some chemicals that will attack it. In those applications the graphite is replaced with PTFE, as long as the application is within PTFE's temperature limitations. "If you have a chemical application that requires PTFE, then you have always lived with creep relaxation, or cold-flow, and consequential sealing loss" says McCoy. "But with the SteelTrap there is no more concern for cold-flow or creep relaxation."
Spiral wound gaskets are designed for use within specified pressure ranges. Since most users have different pressure ranges throughout their plants (e.g.150, 300 900, 1200, 1500 PSI) that means you need different gasket for each size of gasket you need within each of those pressure ranges. That's a lot of inventory. Because the equivalent graphite-stainless gasket is self-locating and applicable to pressures ranging from 150 to 2,500 PSI, the inventory requirement is much lower. "A tremendous cost savings to the customer," says McCoy.