https://www.facebook.com/PIprocessinstrumentation/, https://www.linkedin.com/showcase/11107902. Some asset management software can provide warnings when measured leakage exceeds a threshold set by the user. When the container is half filled, a signal from the condition monitoring master control unit alerts an operator that the container should be drained and notes the collection time, typically measured in a span of months. and food Weve been campaigning to have this changed, and we voluntarily submit our mechanical seals to a far stricter test. Seals Operating Principles > Fluid Storing this piece of information along with subsequent leakage measurements in a facilitys asset management software allows maintenance and reliability personnel to review trends and discuss the health of the equipment with OEM representatives. Beyond that solution, there are seal-less pumps such as canned or magnetically driven designs that can also be costly but completely leak free. In practice, this gap is affected by many parameters including face flatness, load, viscosity and speed; it can easily vary from 5 to 50 microinches or more. The Integrity Test has proved to be one of the major benefits of API 682 by virtue of contributing measurably to a decrease in startup problems. The test involves filling the vessel with a liquid, usually water, and pressurizing it to the specified test pressure. . Young is an active participant in the Hydraulic Institute. Therefore, test times for dual seal chambers could potentially be reduced. The API 682 Integrity Test permits a maximum pressure drop of 0.14 bar (2 psig) over a five minute period from a maximum 28 liter (1cu ft) reservoir pressurized to 1.7 barg (25 psig). This method can help keep the long-term success of a plant in mind. These seals are typically less expensive to install and simpler for teams to operate and maintain. Swagelok Northern California is a locally owned sales and service center of Swagelok, a company celebrating 75 years in business. Have sealing surfaces been badly scratched? ASME certified pressure vessel fabricators undergo a rigorous program to ensure compliance with the rules and regulations of the ASME Boiler and Pressure Vessel code. With hundreds to thousands of centrifugal pumps in your refinery, best practices in panel design, tubing geometry, and location of vents and gauges facilitate efficient visual inspection and maintenance. Even though most mechanical seals effectively seal both air and liquids at low pressure, not all do. In accordance with API 682, PumpsShaft Sealing Systems for Centrifugal and Rotary Pumps, seal cartridge assemblies are to be tested using pressurized air prior to shipment to insure that the cartridge has been properly assembled. A loose pump or motor mount, misaligned shaft, damaged impeller, or burned-out bearing induce vibrations that undermine mechanical seal integrity and reliability. Next Month: How do I determine bolt torque for flange connections? Duct Leakage Criteria. Higher adhesion of a liquid to another surface creates a flatter droplet. Mechanical seal leakage can involve either the process fluid itself or some external sealing fluid. Every cartridge that passed one test also passed the other and vice versa. Contact our team today to learn about custom solutions for your plant or refinery. Why is it important to monitor and record liquid leakage from mechanical seals, and what should be kept in mind when doing so? Our expert Field Engineers are available to consult on-site to assess your requirements and recommend solutions tailored to your specific pumping needs. A seal support system properly configured for your mechanical seal and pumping process helps minimize the chance of pump leakage. Find out how the plant is experiencing reliable disinfection of wastewater and meeting all disinfection requirements now. Swageloks petroleum industry experience, highest-quality components, and assembly services enable us to design, fabricate, and test (following ISO 9001 quality standards) mechanical seal support systems to help minimize mechanical seal leaks and meet stringent California environmental standards. We have locations in Fremont, Sunnyvale, and Concord, CA (USA). A seal support system supplier like Swagelok will then design, fabricate, and test the support systems that are specifically tailored to your mechanical seal and pumping conditions. Will it need cleaning away periodically? Cartridge-mounted, end-face seals were primarily introduced for installation on American National Standards Institute centrifugal pumps for making axial shaft adjustments. Mechanical seals depend on a small amount of leakage of process or barrier fluids to function properly. The value of this field will override other options. Availability Quantifying leakage in very small gaps and at the exit of the seal faces. As should be expected, large seals tend to leak more than small seals. All end-face mechanical seals operating effectively on high-speed applications allow a small amount of vapor to pass through the primary seal interface. The pump shaft displaces a liter or so. While in this role, he was able to help provide technical and application-specific expertise to customers and distribution to drive specifications. Common questions among industrial plant professionals are: Under what conditions will a mechanical seal leak? and What is a normal degree of leakage when the equipment is operating? This will provide insights into this sometimes-confusing area of plant maintenance and operation with additional focus on applications involving high-temperature heat transfer fluids. In fact, it has been so beneficial that many OEMs and End Users now do the API 682 Integrity Test on all cartridge seals regardless of whether that cartridge is per API or not. Various face treatments can be applied to the sealing faces such as slots, grooves, waviness or special lapping processes. Seal leakage and its changes that occur over time can provide reliability personnel with significant information about the entire pumping system. One factor stands out as the primary cause of premature seal failure application. industries The Integrity Test of 4th Edition does not differentiate by face technology, size, proportions, arrangement, materials, lapping technology, etc., etc. WHAT IS A MECHANICAL SEAL? They are: Three variables that most affect the design selection of mechanical seals are: equipmentcharacteristics,applicationand operating conditions, and theleak rate objective. . Seals Collecting seal leakage in a closed container keeps fluid from spilling into the workspace, reducing fire risk while also capturing a contaminant that can foul the work area. Hydropad technology lowers face operating temperatures and improves efficiency. A properly configured mechanical seal support system will incorporate the components and function to maximize pump reliability. Non-contacting seals definitely leak more than contacting seals. It was essential, "All political parties must engage with the oil & gas industry to secure the strong pipeline of, Manufacturing optimism reaches 14-month high despite doldrums.'. Effective forces We use cookies to ensure you the best experience on our website. Health, safety and environmental rules may require clearing the baseplate or ground of any uncaptured external leakage as well. The proper seal is important when attempting to meet water quality standards. of terms, Home The leakage rate needs to be sufficient to ensure that there is a lubricating fluid film between the lapped seal faces to minimise friction, heat generation and wear, whilst at the same time being low enough to be acceptable. Merrill received a Bachelor of Science in mechanical engineering from the University of Tulsa and a Master of Science from Western Michigan University. Image 1 shows three simplified and idealized pressure profiles in the sealing gap (h), for when the pump shaft is static (3), as the shaft starts to rotate (4), and finally the hydrodynamic zone (5) when the shaft is rotating and the hydrodynamic pressure rises in the gap. Average leakage will be in the 1-cc-per-day range, which is within acceptable tolerances of most process fluids. Some types of rotating equipment are not equipped with a seal chamber or stuffing box for installing a gland. With multiple factors having to work together to ensure mechanical seal reliability, diagnosing the reason for the leak can be a challenge. Application limits Pipe based reservoirs for API 682 sealing systems must be built entirely of piping components and ASME B31.3, Process Piping, (ISO 15649) is the governing standard. The education is provided in the public interest to enable a balanced assessment of the most effective solutions to pump technology issues on rational Total Life Cycle Cost (LCC) principles. Zach Nepa of SEPCO discusses the basics and maintenance of air seals. Often, seal environmental controls are over looked, resulting in shorter seal life. An average liquid leakage rate of less than 5.6 g/h per pair of seal faces. The Integrity Test is not designed to insure performance; it is the Qualification Test that is designed to demonstrate performance. The wearing process changes the face profiles to compensate for the seal face pressure and thermal distortions and affects the seal face surface finish. In any mechanical seal application provision must be made for leakage. Power consumption Common units of measure for leakage are drops per minute (dpm), milliliters per hour (ml/hr, same as cc/hr) and ounces per hour (oz/hr). Problems solved Should that occur and liquid rapidly fills the container, a high-level signal would alert the operators the situation needs urgent attention to determine the best course of action. They should not be applied where the liquid side of the seal is exposed to lower pressure than its atmospheric side, usually less than 1 atmosphere (14.7 PSIA). Seal faces cannot be permitted to run dry, as the frictional heat buildup of hard contact will very quickly cause them severe damage and lead to extensive leakage. Air seals use a knife of air to seal the process instead of seal faces. In spite of the benefits of the Integrity Test, there are times when a seal cartridge passes the Integrity Test but leaks more than expected in the field. A spiral groove mechanical seal (SGMS) would experience failure due to phase change of fluid film between two end faces. Without proper remediation, external leakage can seep into the ground. (The exact calculated values depend on assumptions and coefficients used.). This means that many test chambers would be required. Rotating equipmentis the primary application in which end-face mechanical seals can be cost effectively considered and applied. HI Pump FAQs is produced by the Hydraulic Institute as a service to pump users, contractors, distributors, reps and OEMs. PodCast-> The Brutal Truth about Sales & Selling PodCast - on all your favorite PodCast Players, Ahmed Sarwat, M.Sc., CRL, VMA, VIB.CAT.II, Characteristics of the liquid to be sealed. | Terms of Use, Mechanical These can be separated into five general categories: 1. At times, the leakage rate itself is unknown, but accumulated leakage is visible. Where and when to use the right pressure technology, Available resources for maintaining water purity throughout the treatment process, The Reliability Journey of a Midwest Manufacturing Facility. In fact, the Integrity Test does not even include the gland plate bolts. in Mechanical Engineering from North Dakota State University. Proper configuration tailors the seal support system to the specific temperature, pressure, and process fluid conditions of the pumping process. Viton o-rings, seals, Simriz seal failure If so, theres a good chance these changes exceed the operating specs of the mechanical seal and seal support system and lead to an unacceptable mechanical seal leak rate. All Rights Reserved. Pump and system parameters having an impact on how much mechanical seal leakage will be incurred could include: Having visibility into a seals regular (and irregular) leakage history is now possible. This can lead to uncontrollable leakage. For example, this occurs when a pool forms around the equipment or a stain appears, but the seal is not actively leaking at the time of inspection. seals In a properly operating mechanical seal, this thin liquid film, out of necessity, leaks to the low-pressure side of the seal, usually outside the pump. How will barrier fluid be replenished? The vast majority of seals that did fail the initial JC test were reported to have had either cut O-rings or scratched faces. The amount of leakage to atmosphere, which is dictated by the plants leak rate objectives and/or regulatory requirements, must be controlled by the seal design chosen. Understanding the basics of mechanical seals and how they may be adapted for different application requirements is critical when choosing the best seal for the application and ensuring optimal overall system reliability. This is because the size of the droplet can also be controlled by the geometry of the dispensing tip, the temperature of the liquid and impurities that are present. John Merrill is a principal engineer with EagleBurgmann and resides in Charlotte, North Carolina. Many of the test rigs looked like a pot. Higher surface-tension liquids appear to leak less than those with a lower surface tension, but this is not the case. One milliliter is equal to 1 cubic centimeter. A liquid-lubricated seal may have no visible leakage. Home Resources Whitepapers Published: 10/01/2014 This follows-on from our previous post, where we demonstrate video evidence of a mechanical seal which was able to pass the API 682 air leakage test, despite leaking 270 to 1300 times the allowable maximum leakage rate specified in section 10.3.1.4.1 of the standard. When testing a single seal, the test volume is essentially that of the pot. This video contains audio description. Properly designed, these pump arrangements need not have shaft seals; flow that would normally cool and lubricate the seal is simply allowed to exit the pump and run directly back to the reservoir. Most of them are within the plant teams control. 1 Introduction Seals are a crucial machine element used to confine a high pressure fluid to some given volume. This inspector also witnesses the ASME hydrostatic test which, apparently, is now 1.3 x MAWP. The actual leakage rate depends on the mechanical seal type and diameter, the properties of fluid being sealed, the shaft speed, the sealed pressure, the operating temperature. Seal failure is defined as excessive leakage. Dumping a liquid down a drain or sewer or placing a crystallized solid in a trash can is unacceptable. The UM fabricator is inspected annually by ASME. A brand new mechanical seal provides a specific level of protection against pump leakage, but by itself, it cant necessarily ensure the level of leak protection you need in your Northern California refinery. Key Normal leak rates range between immeasurably small to steady drips or temporary to even small steams. The risks from exposure to process leakage include both acute and chronic health issues. Due to the interfacial surface roughness most seals exhibit leakage [ 1, 2 ]. That is, suppose a certain vessel has an MAWP of 600 psig; it would be hydrostatically tested at 900 psig. Components are selected to help ensure the optimum operating environment for each mechanical seal. The fabricator undergoes an ASME inspection every three years. Several critical factors have to work together to achieve and maintain the proper leak rate. Many individual internal and external factors, as well as interactions between them, affect the rate of seal leakage. Synthetic oils and glycols are slip hazards for operations personnel. Thats not a comprehensive list of seal support system problems for which to check. See Equation 1 for how the theoretical leakage rate of a liquid-lubricated mechanical seal can be calculated. A high surface tension allows a much larger droplet to form. Abrasives in the sealed fluid can destroy the seal face surface finish in a short time. The hydrostatic test duration is 30 minutes without leaking. Gabriel Young is a senior engineer with EagleBurgmann in Denver, Colorado. forces in a mechanical seal, We are located in the Denver Technological One example can be found in wastewater treatment plants where raw sewage must be moved with high-speedcentrifugal pumps. For more than 50 years Swagelok has been working with refineries in Northern California. About the same time (early 1990s), Roger Jones had a pump and seal air test rig built at the Shell Deer Park Refinery in Texas. Website Map | Privacy Statement Roger then took the volume of the seal test rig and proportioned the results to get an acceptable leakage rate for a 1 cubic foot volume during a five minute test period. All Rights Reserved. Many pumped liquids are sufficiently volatile that the fluid frictional heat gain from traversing the seal face causes the leakage to vaporize. The answers to these questions provide more insight into the performance of the seal. A timely review of leakage rates and accumulation allows users to schedule repairs and avoid equipment damage or catastrophic failures. Figure 1 shows data that the authors recorded over a typical drip temperature range and a dispensing tip similar to small-diameter tubing. process Cartridge seals are simpler to install, but errors still occur. These fugitive emissions can bring sanctions from Cal/OSHA or BAAQMD. Whereas, fluids that contain dissolved solids, slurries, polymers and heavier hydrocarbons will present visible leakage. These and several other factors affect seal performance. Gordon just said something like How about one cubic foot? while envisioning the physical size of a test pot that might be needed to hold a big cartridge.
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