Ensuring that your sealing devices work properly and deliver the service life you expect from them begins with where and how you plan to use them.Sealing devices, such as gaskets, O-rings, oil seals, bearing isolators, valve packing, expansion joints and hydraulic components, are all items to consider when it comes to achieving optimal plant performance. Without them, pumps would leak, valves would release chemicals into the air, flanges would spray process fluids and oil would drip from gearboxes, among other things. Unfortunately, sealing devices also have something in common with everyday consumer items like cars and household appliances-their owner/operators seem to care most about them when they fail to function properly.
Where and how you apply a sealing device is crucial to its ability to deliver for you. Following the seven steps outlined here can help you make sure that you are selecting the right solution for a particular application.
Step 1. Identify the problem
Ask yourself several questions.
First, what's your facility's definition of a leak? If you are a chemical or hydrocarbon processor subject to the EPA volatile organic compound (VOC) regulations, the rule of thumb that "if it's not dripping, it's not leaking," is certainly not your world. You think in terms of parts per million, "fugitive emissions." If you work in a distribution center with hundreds of gear motors running materials-handling equipment, visible oil leaks from gearboxes is your standard. If you come from a pulp and paper mill living up to the standards of ISO 14000, you think of leaks in terms of thousands of gallons of un-conserved water poured down the drain after it flushes or drips from a pump seal.
Second, what is the desired area of improvement? The focus for many is "improved efficiency." Specifically, this can mean reducing fugitive emissions, water conservation or reduced downtime. The concept is very simple: optimize resources and raw materials to improve profitability. Perhaps a more specific end is the target of improvement-such as reducing work orders to repair equipment seals, increasing the time between replacements or reducing the amount of time required to replace a seal component.
Third, what do you think the problem is? It's helpful for end-users to be able to express themselves in this regard. A good supplier of sealing solutions will know how to listen, interpret the need, evaluate, define the root of the problem and offer viable/value-tested solutions.
Step 2. Identify cause(s) of the problem application
This step is probably one of the more difficult areas to address. The reason it is that the problem could be as simple as an equipment-related issue-such as a worn shaft in a pump, a scarred stem in a valve, a rotating shaft with high run-out or a warped face on a flange. Conversely, the cause could be external to the equipment, including:
Get to the causes: failure analysis and troubleshooting…
Elementary my Dear Watson! There is a certain element of detective work required when identifying root causes of a sealing device failure.
A used sealing device creates a "fingerprint" of the equipment in which it was used. A trained person can tell how the sealing component was installed and its exposure to thermal, chemical and equipment conditions. For example, by inspecting the thickness of a used gasket, one can determine if it was properly compressed and in what condition the flange was, or if the previous gasket was properly removed. Inspecting the dimensions and wear patterns on the lip of an oil seal will tell if the lip was subjected to harsh chemicals, a rough shaft surface or a shaft with high runout or misalignment.
Once the causes are understood, the necessary characteristics of the sealing solution can be identified. For instance, a seal with the ability to handle temperature cycling in addition to imperfect equipment conditions may be needed. Perhaps there is no seal that will be able to handle the problem and last an acceptable length of time. Equipment overhaul may be necessary.
Step 3. Identify sealing needs and expectations
It would be an understatement to say that there are many needs and requirements to be considered and satisfied when selecting the proper sealing solution. It might be a little surprising to learn that not all of the needs will be completely obvious-and that these can be can be just as important as the more apparent ones.
To select the best sealing solution(s) for an application, the end-user needs to define the expectation of performance. When determining what performance is expected from the sealing device, two categories must be addressed-the Needs and the Implied Needs. The Needs are typically immediate, urgent and factual in nature. The Implied Needs, while not always verbalized in the initial conversation with the seal
supplier, are very important to the end-user. It is vital that you identify both types of "needs" in order to determine the correct solution (see Table I).
Fortunately, the majority of fluid sealing applications can be handled with consideration of just a few of the requirements in Table I. It is helpful to keep many of these in mind when seeking sealing solutions for difficult problems. The list of the critical requirements, though, may change depending on the services, equipment and industry.
Step 4. Identify service conditions: T-A-M-P-S-S
TAMPSS is a simple way to make sure that nothing is missed when gathering information on the application. It stands for: Temperature – Application – Media – Pressure - Size – Speed.
While many of these variables may seem obvious, it is important for users to understand what information is required and why. Refer to Table II for a description of each.
Step 5. Select the correct solution
Once all of the data has been collected, the next step is to select the proper product for the application. For any given application there are usually two or more choices of materials and a greater number of competitive, generically equal products. A bit of advice, though: don't be penny wise and pound foolish when selecting sealing devices and components. Some points to consider before a seal is specified and purchased include:
A common mistake is to try to save dollars up front by going with a lower-grade product that appears to do the same thing as a higher-performance product. Again, remember to take the whole cost of the sealing solution into account. A product that will successfully operate through the standard maintenance cycle without causing unscheduled downtime is the optimum product. The driving question is, "What is the financial impact of taking the process or plant offline to deal with a leak?"
Step 6. Install properly
We've all heard the phrase, "Give a man a fishing pole, teach him to fish, and he will never go hungry again." Likewise, in the sealing industry, we give the end-user the proper tools and installation instructions, then teach him/ her how to perform proper installation so as to optimize plant performance and minimize/eliminate unscheduled downtime.
Sealing solutions require adherence to the manufacturer's installation and handling instructions. The most premium of products will not perform well if they are not installed and handled properly. Therefore, you should expect the sealing solution provider to provide practical instructions that allow you to achieve effective installation. Field support may be necessary, depending on the criticality of the application or resources of the user.
A case in point, the Garlock Applications Engineering Department conducted a study on 100 gaskets returned for analysis. Fig 1 shows the reasons for premature failure that were identified.
Step 7. Engage in regular preventive maintenance
Each of us typically engages in some level of preventive maintenance in our daily lives, whether it's having our car's oil changed every 3,000 miles, or simply brushing our teeth in the morning. We know these activities pay off for us. By the same token, daily or weekly inspection of your fluid-handling systems will pay off by minimizing downtime and allowing you to take corrective actions before irreversible failures occur. Changing sealing devices on a routine basis is part of good operating practice. Working closely with your sealing solutions provider will contribute to optimizing seal use and performance. Correct identification, troubleshooting and gathering of information regarding problematic sealing issues will lead to specification of better sealing solutions for particular applications. Taking the time to familiarize yourself with the simple steps outlined in this article-and following them-will free up your time to address the other important maintenance issues facing your operations.