Aug. 26, 2024
Agriculture
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Valve seals precisely control the amount of oil entering the valve stem system, making them critical components in maintaining your engine&#;s compression levels. Having a valve stem seal that works correctly within any of your applications can save you time and money by eliminating the need for lengthy engine repairs and replacements. But how do you check for bad valve seals, and what signs should you be aware of?
No one wants to face valve issues because they indicate a severe problem within your machine&#;s engine. Here is where Global Elastomeric Products comes into play. Learn how to find faulty seals and what you can do to avoid these issues.
Table of Contents
Valve stem seals control oil consumption and lubricant in an engine by allowing a specific amount of oil inside the valve stem as it moves. A controlled amount of oil is crucial in maintaining adequate lubrication. Otherwise, too little oil can cause various components to wear as parts rub together. However, excess oil can result in carbon buildup, which can lead to many issues, such as:
Essentially, valve stem seals prevent oil from entering the combustion chamber from the cylinder head. A damaged seal can cause engine oil flooding that will lead to engine failure.
Six ways to assess whether you have a faulty seal on your hands include:
One of the best ways to tell if you have a faulty valve seal is to conduct a cold engine test. After your machine hasn&#;t run for a while &#; even overnight &#; the seal is now cool. Once you start the engine, the seal will contract. Damaged seals will leave a small gap. Leftover oil will then settle at the top of the valve cover head.
When you start the engine, you may also see blue-tinted smoke appear from the exhaust. If this happens, it means the residual oil is passing down through the damaged seal and into the combustion chamber. The bluish smoke, which is burned oil, signifies that the engine needs a new seal, even if it clears after several minutes of running the engine.
Depending on the machines and equipment you use, smoke is often a common form of exhaust. However, when you start seeing it last longer than usual or appear a different color, you know a faulty seal may be the cause. The excessive smoke may also come in more consistent waves as the engine runs for long periods. Be aware of specific machine movements that cause more smoke than usual.
If you notice you&#;re going through more oil than usual, it can be another indication of a bad seal. When oil leaks or burns at higher rates, the seal no longer controls the oil flow. Burning oil increases emissions and can contaminate the catalyst. Unburned fuel in the exhaust skyrockets the converter&#;s operating temperatures, which can cause the converter to overheat and create a blocked exhaust.
Make sure to check the engine&#;s oil level with a dipstick, and refer to your oil log to see if the fluid levels differ. You can make this part of your regular maintenance schedule. While oil leaks are often a clear warning of faulty valve seals, they may not always be visible, so don&#;t rely on this as a guaranteed warning because the oil could be burning off.
Pay attention to your machines if they ever idle. When the engine is at rest, high vacuum levels can cause the oil to build around the heads of the valve system while the valve is closed. If the seal is faulty, you may once again see blue-tinted smoke when the engine begins to run. That means the oil is getting pulled past the seal and into the valve guide. Make sure to shut the engine down and remove it from operation until you can get it repaired.
Depending on the engines you use in the oilfield and agricultural industries, testing the engine&#;s compression can also help determine if your valve stem seals are deteriorating. If the machine has a higher compression level, you have a valve seal issue and you'll need replacements. On the other hand, a lower level may designate a piston ring malfunction.
An engine with broken seals can cause oil to build on the electrodes of the engine&#;s spark plugs. As a result, plug fouling can occur, which is an accumulation of carbon deposits that can cause engine misfires. As carbon buildup increases, so does compression, leading to engine damage from faulty detonation or even issues with pre-ignition.
Knowing these six signs of valve stem seal failure can help you mitigate the issue before problems like oil leaks and high compression levels begin. The sooner you notice different-colored smoke, an increase in oil usage, misfiring engine startups and idle noises, the faster you can make the necessary seal repairs. In return, your operations will remain efficient, productive and safe.
The main causes of a deteriorated seal come from faults within the seal itself and improper installation. Even though valves consist of high-strength rubber, they can break, crack or wear down. Seals could even be missing from a botched installation. Any of these faults in the seal will cause oil to reach the engine&#;s cylinders.
As valve stem seals begin to fail, carbon buildup forms, which also affects other engine components like the valve seat and guide &#; which is why quick repairs are critical.
In some cases, there still may be excellent compression. However, if high oil consumption is present, it will then cause higher operating temperatures that can lead to broken or cracked seals. Seal problems can also form from an improper clearance between the valve and valve guide. When it&#;s loose within the cylinder head, it can move laterally, wearing out the valve.
The best thing you and your crew can do is refer to your preventive maintenance schedule for each piece of equipment in your fleet and complete regular safety checks.
Daily or weekly inspections will help you find leaks and problems before they become more severe.
It&#;s also essential to invest in top-quality valve seal solutions that are free of defaults. Partnering with a company that guarantees seal products with no defaults places you ahead of the competition, giving you a competitive advantage.
Because many factors can indicate a bad valve stem seal, you&#;ll have to investigate and not always rely on the various signs. If you have the appropriate training and qualifications, go ahead and start your inspection. Otherwise, rely on the experts for guidance.
Open the hood to the engine and check the oil level of your machine using a dipstick. Is it significantly lower compared to other times after a similar amount of usage? You can also check to see if there is any excess clearance between the valve stem and guide. Leaks are an obvious sign the valve stem seal has issues &#; but these aren't always present, even when the seal is failing.
Start the engine and observe the exhaust. Is there a lot of smoke coming out of the pipe, and does it have a blue-gray tint? If so, the engine is burning leaked oil &#; which is why you may not see any leaks under the hood.
Listen for odd noises like rattling or tapping as the engine idles. Any unusual sounds can indicate problematic valves.
Check for engine and error lights that can indicate a problem. You can hook the machine up to a diagnostic reader to scan for different error codes. For example, valve seal and valve guide issues will read as specific codes, so reference the owner&#;s manual for assistance.
If worse comes to worst, you will need to disassemble the engine and inspect the valve stem seals and other components. Relying on the professionals for this step may be best to ensure more parts do not get damaged throughout the process. You or the expert should look for dented, cracked, broken or deteriorated valve seals.
Related links:For more information, please visit valve stem seal supplier.
Valve stem seals' replacement costs are affordable in the long run because new seals prevent more catastrophic engine damage.
If oil is leaking from your engine, you&#;ll want to find a temporary, stopgap solution until you identify the issue and make repairs. For example, you can use an oil stop-leak additive in the oil filler, just like you would with regular engine oil. The additive will give the valve seals a quick fix by causing them to expand, creating a rapid extension of life.
You can also add high-mileage oil with seal conditioners that can slow or stop oil leaks. This type of oil keeps the seals pliable to help prevent corrosion.
Once you make a short-term fix, it&#;s crucial to start on repairs or replacements right away. Prolonged valve failure can affect the entire engine and hydraulics system, costing you expensive repairs or replacements in the future.
Failed parts can also affect your workers' safety and well-being. Your machine may begin to operate hazardously with a jolt of power or faster/slower movements than usual.
Once you&#;ve taken the correct preventive measures, replace the leaking seals using the following steps:
Fast valve stem seal replacements are just as essential as choosing a manufacturer that knows the vitality of a well-designed valve stem seal. Look for custom solutions that can fit your specific requirements if your machines are unique to your industry or operations.
You will want to invest in top-tier solutions that are free of defaults. For example, Global Elastomeric Products has an inventory of rubber seals that provide an elastomeric seal for your engines. We focus our valve seal portfolio on durable, temperature- and chemical-resistant solutions. We can also manufacture any customized rubber compound to fit your unique needs.
Our packer elements and valve seals include:
Quality means everything when you&#;re trying to meet your oil or agricultural industry quotas, including valve seals. Your business needs to rely on elastomeric products that produce defect-free replacement parts just as much as you count on efficient employees on your rig. If you neglect quality, you can put your operations and workers at risk of breakdowns and injuries.
Functional valve stem seals are crucial in keeping your operations efficient. Whether you work in the agricultural, oil or another industry, your machines drive daily operations. If you&#;re experiencing seal leaks, deterioration or damage, Global Elastomeric Products has what you need.
We guarantee our standard and custom in-house seal designs will be free of defects. Our experts design, manufacture and distribute our valve seal product lines while keeping your specifications at the forefront of each customization. We can generate product designs and engineer seals for any oil field or agricultural application. Global Elastomeric Products is the solution to your leaking and damaged seals.
Reach out to us online with questions or for more information about our solutions. You can also request a free quote by calling us at 661-831- to help you better understand our valve stem seal products.
Selection of valve stem sealing is a critical component of the valve specification process. When chosen wisely, the design will perform reliably for the long term.
Figure 1. This control valve is subjected to EPA&#;s Method 21 &#;sni&#; &#; test to determine the fugitive emission leak rate after a prescribed number of mechanical and thermal cycles. There are many methods of sealing valve stems on control and isolation valves. When chosen carefully, a valve stem seal provides years of reliable service, reduces environmental emissions, and minimizes product loss. When inappropriately applied, a valve stem seal can leak constantly, increase maintenance costs, create environmental issues, and place operating personnel at risk. The right valve stem seal increases efficiency by minimizing product loss, which in turn reduces energy use, because less product needs to be made to satisfy demand.
Before delving into the details of selecting a valve sealing method, it is best to understand the challenges of sealing a valve stem and explain how this might be done. Control and block valves fall into one of two major categories: sliding stem or rotary.
A sliding stem valve has a rod protruding from the body that rises and falls to open and close the valve. A rotary valve has a shaft extending out the side of the valve that is connected to a plug, disc, or ball. As the shaft turns, the rotary valve opens and closes. In either design, the valve stem must exit the body and be capable of relatively friction-free movement, while containing the process and preventing leaks.
The valve stem sealing assembly makes that possible. Sealing is usually accomplished in one of two ways: conventional packing or bellows seals. Details of how these methods work, along with pros and cons of each method, follows.
Valve stem seals must accomplish two contradictory goals. First, they must seal the valve stem completely and reduce&#;and ideally eliminate&#;any fugitive emissions from the process. Second, they must accomplish this feat while allowing the valve stem to move freely and continue sealing, even as the valve stem cycles thousands of times. Several industrial standards address these requirements, but the required performance and test methods vary significantly.
The three main fugitive emissions standards are TA Luft, FCI 91-1, and ISO . TA Luft is the least comprehensive of the three, offering leak rate standards based on gasket size and process temperature. However, it lacks specific test parameters for the number of test cycles required or the travel distance, so it is hard to compare the leakage results among different valve designs.
FCI 91-1 was created by the Fluid Control Institute and is more closely aligned with the leak detection and repair requirements mandated by the Environmental Protection Agency (EPA). It uses EPA&#;s Method 21 to &#;sniff&#; the valve packing and determine the leak rate (figure 1). This standard provides details on how to test a valve. A valve stem seal design achieves various classification ratings based on the resulting leak rate after a specified number of mechanical and thermal cycles.
By far, the most comprehensive standard is ISO . It has a variety of leakage classification rates for both control and isolation valves based on mechanical cycles, thermal cycles, and stem size. It also allows testing with either helium or methane, and it dictates two different ways to measure stem seal leakage for helium, each of which is much more involved than a simple sniff test. Specifically, the upperworks of the valve are encased in an airtight enclosure and either flushed with a test gas or subjected to a full vacuum, while the inside of the valve is pressurized with helium. The amount of leakage can then be precisely measured.
When evaluating the performance of a valve stem seal arrangement, it is important to determine how the valve was tested and what specific classification it met. It is relatively easy to achieve very low leakage rates if the valve is mechanically cycled a small number of times. It is much more difficult to achieve and maintain very low leakage rates when the valve is mechanically cycled thousands of times, while enduring thermal cycles as well. The thermal cycles affect sealing due to the high expansion rate of PTFE (a synthetic fluoropolymer of tetrafluoroethylene, also known as Teflon) and the poor recovery rate of graphite, making packing design challenging.
The most common method of valve stem sealing employs a series of PTFE or graphite rings that encircle the valve shaft (figure 2 left). The rings are compressed with a combination of a packing follower, packing flange, and bolts to push down and squeeze the packing rings against the shaft. The compressed rings allow the valve stem to move while maintaining a seal against the valve body and shaft to keep process fluids from passing through the stem and escaping. In certain applications, the packing need only protect against gross process leaks, so relatively minor fugitive emissions are not a concern and free stem movement is considered a more important requirement.
To achieve and maintain low emissions, packing must be &#;live loaded&#; to keep constant pressure on the sealing rings (figure 2 right). This is usually accomplished using compressed Belleville-type springs. These springs maintain a constant force on the packing, ensuring it seals over time, even as the rings wear from stem movement. Unfortunately, the increased pressure tends to restrict valve movement, so the sealing materials and valve stem finish must be carefully chosen to minimize fugitive emissions, while allowing valve stem movement. Figure 2. The picture on the left shows a typical rising stem control valve with standard packing. More modern packing designs, shown on the right, employ compressed Belleville-type or other special springs to maintain constant pressure on the packing rings. This ensures the fugitive emissions are limited to 100 ppm or less, even as the rings wear.
An alternative to valve packing is a valve bellows seal. A bellows seal uses a welded or mechanically formed metal barrier around the valve stem that can compress and stretch like an accordion (figure 3). Because the seal is made of metal with a very low rate of deformation in critical areas, bellows seals achieve virtually zero leakage.
Figure 3. Bellows seal designs usually employ a welded leaf design (detail left and middle) or a mechanically formed design (right). A formed design can withstand many more cycles than a welded leaf design, but it is usually about three times longer. Welded leaf bellow seals (figure 3 left and middle) are manufactured by welding together a stack of washer-like plates of thin metal to make a flexible seal with many folds over a given length. A formed bellows (figure 3 right) uses a flat sheet of metal formed and welded into a tube. The tube is then mechanically and hydraulically formed into a bellows.
Both designs can stretch about the same distance per fold, but because the formed bellows has far fewer folds per inch, its overall length is usually three times longer (figure 4). However, the reduced number of welds and corresponding mechanical stress allow formed bellows to last significantly longer in most applications. Figure 4. This valve employs formed bellows to achieve zero valve stem leakage. As an added precaution, the valve also includes integral standard packing above the bellows.
Because bellow seals are constructed of relatively thin metal and subjected to mechanical stress and corrosion, they can crack and fail over time. For this reason, a bellows seal valve usually has a standard packing above it to contain the process should the bellows fail in operation.
Each method of valve stem sealing has pros and cons, so the best choice depends on the application. Perhaps the biggest advantage of standard or environmental packing is its comparatively low cost, along with a wide variety of valve packing materials and designs to suit most applications. Valve packings can also be adjusted and replaced without disassembling the valve.
The biggest advantage of a bellows design is its ability to deliver zero leakage. Such a specification is critical for lethal service applications. The bellow materials can also be chosen to handle higher temperatures and corrosive applications. Because the operational life of a bellows seal is based on the number and length of strokes, the estimated time to failure can be predicted with some accuracy, so replacement can be planned.
Each design has disadvantages as well. The performance and lifetime of packing is based on many variables, which are not always easily predicted. Small leaks usually can be addressed by tightening the packing, but at some point, the packing must be replaced. Also, the surface finish of the valve stem can have a big impact on the life and performance of a packing design. Regardless, all valve packing will leak to some extent, and this may not be acceptable in certain applications.
As mentioned previously, bellows seals will fatigue and eventually fail. When that occurs, the valve must be fully disassembled to replace the bellows seal. For this reason, the total cost of ownership for a bellows seal is typically higher than that of packing.
Figure 5. This 24-inch by 30-inch letdown valve employs a specially designed large stem diameter environmental seal for extremely low leakage rates, as demonstrated here during a test at &#;56°F. When properly selected and applied, both packing and bellows seals can handle challenging applications. In one liquified natural gas application in Australia, a 24-inch by 30-inch letdown valve used a specially designed environmental packing arrangement and had very low valve stem leakage, despite operating at cryogenic temperatures around &#;300°F (figure 5). Any fugitive emission from this valve translated into lost product, lost energy, and environmental damage&#;so it was critical to minimize leaks.
A Chinese chemical plant had a lethal service hydrogen cyanide application requiring virtually zero leakage while in operation, so a bellows seal design was selected. Upon commissioning, the plant reported zero measurable emissions, and after six years, still had no reported leakages. The valves went through 50,000 full cycles and more than 10,000 partial cycles annually.
Proper selection of valve stem sealing is a critical component of the valve specification process. When chosen wisely, the design will perform reliably for the long term, translating into significant reductions in environmental emissions, product losses, and maintenance costs. Losing less product improves efficiency and is a key component of energy management.
The number of design options are extensive, so end users may find it helpful to consult with their valve vendor to determine the best sealing design, materials of construction, and other details for their specific applications.The number of design options are extensive, so end users may find it helpful to consult with their valve vendor to determine the best sealing design, materials of construction, and other details for their specific applications.
All figures courtesy of Emerson
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