By Matt Migliore
|This integrated assembly from Trelleborg Sealing Solutions includes three spring-energized Turcon PTFE seals, two bearings, and an o-ring. Trelleborg expects integrated assemblies to grow more popular going forward.|
As end-user expectations continue to rise — primarily due to environmental concerns and a more competitive global marketplace — sealing solutions providers are responding with new technologies and methodologies for minimizing the threat of leaks in a range of manufacturing environments. Whereas a leak was once viewed as a visible puddle under a piece of equipment, users today are measuring leaks with highly sensitive equipment capable of reading in the parts per million (ppm) range. “This means that the sealing products must be able to seal at extremely tight levels, even when equipment is in less than perfect condition,” says Dave Burgess, application engineer for the Industrial Gasketing Division of Garlock Sealing Technologies (www.garlock.com).
Ultimately, operating efficiency is driving the rise in end-user expectations on the sealing front. No longer can leaks be tolerated in the manufacturing process, as China, India, and other nascent industrialized nations are forcing manufacturers to look for process improvements around every corner. Likewise, the cost of regulatory action due to environmental noncompliance is pushing the requirement for leak-free operations.
As such, new sealing technologies coming to market today provide more chemically and thermally resistant materials, higher pressure capability, tighter leak specifications, better manufacturing control and consistency, and predictive design tools, among other features — all of which are aimed at improving operating efficiency in one way or another. According to Burgess, these product evolutions have resulted in seals that seal much better than they did 25 years ago.
Keys to Application Success
While most seal manufacturers acknowledge that a 100 percent leak-free environment with low friction and a low price point is an unachievable aim, today’s sealing technologies can be pretty darn reliable when combined with certain application best practices.
Colin Macqueen, director of technology for Trelleborg Sealing Solutions (www.tss.trelleborg.com), says the first step toward sealing success is taking the time to really understand the application environment. “Don’t base your seal specification on what you want, or believe, your temperature and pressure to be,” says Macqueen. “Base your specification on the actual temperature and pressure of the environment you’re operating in.”
Too often, Macqueen says sealing users will assume they know what the operating condition of their process environment is, without actually doing the legwork to identify the actual operating conditions. This, he says, may result in the user specifying a sealing solution that is not rated for the appropriate temperature and/or pressure of the application, increasing the likelihood of premature failure.
Other issues Macqueen recommends users consider prior to specification include: dimensional variations; degree of contamination in the process fluids; and the capability of bearings. In the end, he says users have to prioritize their sealing goals to determine what factors are most important. Since zero leakage and low friction at a low price point is not a realistic set of goals, Macqueen says the user must figure out which characteristics they can be flexible on. In doing so, Macqueen advises users to consider the total cost of ownership of the seals rather than just the purchase price. In order to be successful, Macqueen says users must factor in the cost of failure along with the purchase price of the seal. If the cost of failure is significant, Macqueen says users should consider a higher-end solution that may cost more up front, but will save the user large sums of money over the lifetime of the seal.
Burgess says Garlock Sealing Technologies uses the acronym TAMPS (Temperature, Application, Media, Pressure, and Size) when advising its customers on key considerations. “Of these, the application information is often the most overlooked,” says Burgess. He says the details of the equipment used in the application must be fully understood to ensure the ultimate success of the sealing solution.
Sizing & Material Selection
Regarding sizing and material selection specifically, here the user must dig down deeper into the application to identify the appropriate solution.
Burgess says the mechanical details are critical when it comes to sizing. For example, he says compression-packing applications cannot be sealed tightly without knowing the equipment details (rotary, static, or reciprocating motion), as well as the shaft diameter, diameter of the stuffing box, depth of the box, and sometimes the available bolt load. In many cases, Burgess says users can benefit tremendously by engaging the sealing solution provider’s application support team to help with the sizing of seals. Macqueen says it is also important to plan for seals early in the design phase, as users will often wait until the end of a design to consider the seals, only to find that they have left insufficient room for the optimum seal glands.
When selecting material, Macqueen says it is important for the user to be forthright and specific about the fluids used in the application under consideration, including additive packages, aftermarket substitutions, and known alternatives that may be applied. For example, he says seals in the automotive industry commonly encounter more than 25 different fuel combinations, so it’s important to know what these combinations are up front so the sealing solution can be configured to operate reliably in all possible scenarios. He says, “[Users should] think about the extreme conditions and the exotic materials [they] might need to use to support those conditions.”
According to Burgess, beyond the process media itself, it is equally important to consider the temperature and pressure of the application when specifying materials. High pressures and extremely high (or low) temperatures will require higher-end seals.
Going forward, sealing solution providers will continue to develop technologies that are capable of supporting higher pressures and extreme temperatures. New materials and combinations of existing materials will also emerge on the market, as sealing manufacturers look to offer end-users better performance for unique applications.
Macqueen says he sees future growth in the area of integrated products, such as cassette seals and seal-and-bearing systems, and Smart seals, where embedded sensors provide users failure detection and prediction capability.
However, the continued evolution of sealing technology is very much reliant on the input of the end-user. “How can the technology get better?” Burgess asks himself. After some thoughtful consideration, he answers, “End-users and manufacturers need to continue to communicate needs versus capabilities. New engineered products must remain a priority.”
Matt Migliore is the editor of Flow Control magazine. He can be reached at firstname.lastname@example.org.