barrier fluid in mechanical seal free sample

Back to back: Two rotating seal rings are arranged facing away from each other. The lubricating film is generated by the barrier fluid. This arrangement is commonly found in the chemical industry. In case of leakage, the barrier liquid penetrates the product.

Face to face:The spring loaded rotary seal faces are arranged face to face and slide from the opposite direction to one or two stationary seal parts. This is a popular choice for the food industry, particularly for products which tend to stick. In case of leakage, the barrier liquid penetrates the product. If the product is considered “hot”, the barrier liquid acts as a cooling agent for the mechanical seal.

Users can choose different material for this double mechanical seal 208, matching for different liquid conditoncarbon, silicon, and tungsten carbide for this mechanical seal as seal face, if for high temerperature, we suggest to choose rubber seal viton for the rubber parts.

Lepu seal make this dual mechanical seal for many years, and offer professional suggestion when client need this grundfos seal, so we are your reliable specialist for grundfos mechanical seal.

Double mechanical seals are commonly used in the following circumstances:If the fluid and its vapors are hazardous to the operator or environment, and MUST be contained

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A mechanical seal is simply a method of containing fluid within a vessel (typically pumps, mixers, etc.) where a rotating shaft passes through a stationary housing or occasionally, where the housing rotates around the shaft.

When sealing a centrifugal pump, the challenge is to allow a rotating shaft to enter the ‘wet’ area of the pump, without allowing large volumes of pressurized fluid to escape.

To address this challenge there needs to be a seal between the shaft and the pump housing that can contain the pressure of the process being pumped and withstand the friction caused by the shaft rotating.

Before examining how mechanical seals function it is important to understand other methods of forming this seal. One such method still widely used is Gland Packing.

Packing needs to press against the shaft in order to reduce leakage – this means that the pump needs more drive power to turn the shaft, wasting energy.

The stationary part of the seal is fitted to the pump housing with a static seal –this may be sealed with an o-ring or gasket clamped between the stationary part and the pump housing.

The rotary portion of the seal is sealed onto the shaft usually with an O ring. This sealing point can also be regarded as static as this part of the seal rotates with the shaft.

One part of the seal, either to static or rotary portion, is always resiliently mounted and spring loaded to accommodate any small shaft deflections, shaft movement due to bearing tolerances and out-of-perpendicular alignment due to manufacturing tolerances.

The primary seal is essentially a spring loaded vertical bearing - consisting of two extremely flat faces, one fixed, one rotating, running against each other.  The seal faces are pushed together using a combination of hydraulic force from the sealed fluid and spring force from the seal design. In this way a seal is formed to prevent process leaking between the rotating (shaft) and stationary areas of the pump.

If the seal faces rotated against each other without some form of lubrication they would wear and quickly fail due to face friction and heat generation. For this reason some form of lubrication is required between the rotary and stationary seal face; this is known as the fluid film

In most mechanical seals the faces are kept lubricated by maintaining a thin film of fluid between the seal faces. This film can either come from the process fluid being pumped or from an external source.

The need for a fluid film between the faces presents a design challenge – allowing sufficient lubricant to flow between the seal faces without the seal leaking an unacceptable amount of process fluid, or allowing contaminants in between the faces that could damage the seal itself.

This is achieved by maintaining a precise gap between the faces that is large enough to allow in a small amounts of clean lubricating liquid but small enough to prevent contaminants from entering the gap between the seal faces.

The gap between the faces on a typical  seal is as little as 1 micron – 75 times narrower than a human hair.  Because the gap is so tiny, particles that would otherwise damage the seal faces are unable to enter, and the amount of liquid that leaks through this space is so small that it appears as vapor – around ½ a teaspoon a day on a typical application.

This micro-gap is maintained using springs and hydraulic force to push the seal faces together, while the pressure of the liquid between the faces (the fluid film) acts to push them apart.

Without the pressure pushing them apart the two seal faces would be in full contact, this is known as dry running and would lead to rapid seal failure.

Without the process pressure (and the force of the springs) pushing the faces together the seal faces would separate too far, and allow fluid to leak out.

Mechanical seal engineering focuses on increasing the longevity of the primary seal faces by ensuring a high quality of lubricating fluid, and by selecting appropriate seal face materials for the process being pumped.

When we talk about leakage we are referring to visible leakage of the seal. This is because as detailed above, a very thin fluid film holds the two seal faces apart from each other. By maintaining a micro-gap a leak path is created making it impossible for a mechanical seal to be totally leak free. What we can say, however, is that unlike gland packing, the amount of leakage on a mechanical seal should be so low as to be visually undetectable.

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Tegra Synthetic Barrier Fluid is designed to meet the needs of a barrier fluid for dual mechanical seals per API Standard 682, Shaft Sealing Systems for Centrifugal and Rotary Pumps. Dual mechanical seals are used to control emissions of volatile air pollutants from industrial equipment. Leading seal manufacturers recommend the use of low viscosity synthetic fluids for extended seal life of API Standard 682 dual mechanical seals.

Tegra Synthetic Barrier Fluid 17 cSt has a low Volatile Organic Compound (VOC) level, so that the barrier fluid itself will not be the source of volatile air pollutants in higher temperature applications.

We have a pump which pumps 23% NAOH (sodium hydroxide solution) It is protected by a double seal and barrier fluid system (seal pot) system. The pump has the double seal to protect for leakage to the environment and acts as a lubricant to the seal. The mechanical seal is changed out on LIFE every 24 months to avoid seal failures. In general, this works very well for us and we seldom have unscheduled failures of these seals. The seal pot fluid used is filtered water which is piped in to the pot and we have have flow and level change detection inside the pot. This provides information and alarms to our control system to detect abnormal usage of the filtered water which would indicate loss of barrier fluid into the process i.e. a seal leak.

Recently, one of our technicians noted a small drip from the drain on the pot. He noted that the residue form the drip on the ground was white in colour. I took a sample of the seal pot water and had it analysed. pH was 9.4. for reference, i pulled a filtered water sample further back on the filtered water header and it was pH 6.8. I shut down the pump and flushed out the seal pot and resampled for pH. It came back at a pH of 8. I put the pump back on line and ran it for 24 hrs and resampled. The pH was 8.4 (slightly up on the previous result) Everything seems normal with the filtered water pressure to the pot so I am wondering how we are getting contamination back into the seal pot water. Anyone out there have any view or experience of contamination getting back into a barrier fluid system? Appreciate any views on this

From the operational point of view of centrifugal pumps, it becomes essential to correctly align the pump and the drive to ensure the mechanical seal functions properly. Attention shall be given to is nozzle loads. During the design as well as during the actual installation, the consideration of the nozzle loads is important. Higher nozzle loads beyond allowable values could lead to deformed casings and may be detrimental to mechanical seals due to rubbing of the shaft at the clearances. The sizing of the shaft in case of end suction pumps (and also the overhang) has to be controlled, which could result in excessive deflection at the mechanical seal faces.

When it comes to reliability of sealing the process liquid, a dual seal arrangement is the preferred choice. There are three arrangements defined in API 682: arrangement 1, 2, and 3. The arrangement 1 is the single seal arrangement. The arrangement 2 is the dual seal arrangement with unpressurized buffer liquid at the outboard seal. Finally, arrangement 3 is the dual seal arrangement with the pressurized barrier liquid at the outboard seals. With the barrier liquid being pressurized in arrangement 3, there is no leakage of process liquid to the atmosphere, and hence it is the most reliable option when it comes to applicability of stringent environmental norms from the point of view of the end user.

However, in order to ensure proper functioning and reliability of dual seals, the operational environment of the pump, piping, seal support system, and monitoring systems play a vital role. There are typically four API piping plans for seal support systems: API Plan 53 A, B, and C, and Plan 54.

All three variations of Plan 53 are similar from the point of view that they circulate the barrier fluid using the pumping screw inside the mechanical seal, but the methods of pressurizing the barrier fluids are different. Plan 53A uses direct pressurized nitrogen to pressurize ¬fluid in the reservoir. This plan is popularly used in most of the cases due to less complexity and also availability of nitrogen pressurizing source at site. However, to ensure reliability, one has to be careful about the absorption of nitrogen gas into the barrier ¬fluid. The amount of gas being absorbed is proportional to the pressure of the barrier system. The barrier ¬fluid with absorbed gas then reaches the seal faces due to circulation and at the ¬fluid film, due to depressurization, the gas may come out and hamper the seal performance. This is a reliability concern, and hence most of the seals with Plan 53A are limited to 10 bar (gauge) pressure. Plan 53B uses a bladder accumulator as a means of pressurization of barrier fluid. This overcomes the limitation of Plan 53A and the absorption of nitrogen into the barrier liquid, which limits the system pressure, which can be used in high pressure applications. The advantage of the Plan 53B is that it can be used in remote locations where the external source of pressurization is not available. The pressure of barrier liquid is maintained due to the expansion of the bladder inside the accumulator, which also enables the supply of make-up barrier liquid to compensate for a small amount of leakage of barrier -fluid. However, the monitoring of the liquid level in the reservoir is not possible, and as such, the sizing of accumulator considering the seal leakage and maintenance interval is critical. As the bladder expands to compensate for seal leakage, it needs to be refilled with barrier liquid. The usual cycle of refill is 25 to 28 days. Considering this as a basis, the size of the accumulator and the pre-charge pressure of nitrogen is estimated.

Plan 53C uses a piston as a means of pressurization of barrier ¬fluid inside the accumulator. The advantage of this design is that it uses the process fluid pressure from the seal chamber directly on the bottom side of the piston, whereas top side is exposed to the barrier liquid. The pressurization is achieved by the difference in the areas. The area exposed to process liquid is larger and is designed with ratios ranging from 1:1.1 to 1:1.25. As the seal chamber pressure is being used as a reference, the system itself takes care of process pressure fluctuations. However, as the piston is in direct contact with the process fluid, the material selection becomes essential. Also, the properties and quality of process ¬ fluid shall be carefully evaluated, it should not hinder the movement of the piston within the accumulator. Another important factor is the dynamic sealing of the process fluid from the barrier fluid. The failure of the piston seal will result in the equilibrium of pressures on both sides of piston, and because of the piston movement, friction and drag come into play. Thus, the plan is not so reliable for low pressure applications and recommended to be used in the applications with pressures greater than 7 bar (gauge).

Although a mechanical seal is a critical piece of equipment, it shall not be treated in isolation and due consideration should be given to the operating environment of the pump, seal support system, and most importantly, the perfect selection for the given application.

Abhijeet Keer is a design engineer who has been working in the fi eld with centrifugal pumps for over seven years. With strengths in mechanical construction and materials, he has gained valuable knowledge working in design with major players in pump industry, such as KSB Limited and Kirloskar Brothers Limited. He completed his Bachelor’s Degree in Mechanical Engineering from University of Mumbai, India. His professional experience covers new product design and developments, material selection and application engineering, and complete mechanical constructions.

Extreme temperatures characterize many refinery processes. Gasoline boiling between 90° and 220° F seems low when compared to kerosene at 315° to 450° F and gas oil at 450° at 800° F. Asset reliability is critical to running these high-temperature processes round the clock. You can reasonably make the case that every major asset and component is critical to an efficient refining process.

But here I want to emphasize the importance of pumps, mechanical seals, and seal support systems. Without pumps, there is no process. Without the proper seal support systems, high temperatures in seal chambers may damage mechanical seals and lead to pump leakage.

While leakage can cause small problems or big ones, you always need to have the risk of sanctions in your mind, especially in high regulation states like California. And with Bay Area refinery budgets as lean as they are currently, it makes sense to choose the right systems from the start to avoid something costly going wrong in the future.

Several factors contribute to high temperatures in the seal chamber, which in turn leads to mechanical seal degradation. A mechanical seal and seal support system may have been perfectly matched to the initial process, working reliably for years. However, a change to a higher-temperature process can exceed the capability of the mechanical seal and capacity of the seal support system.

At higher temperatures, elastomeric components in the mechanical seal may begin to deteriorate. For example, beyond 300° Fahrenheit (150° C) ethylene propylene components eventually degrade and leak. Some hydrocarbons coke at higher temperatures and impede the free movement of mechanical seal components. And process fluids at high temperatures are prone to vaporize, or flash, across the seal faces, causing fugitive emissions.

With increased temperatures of process fluids, the seal support system may no longer be able to maintain the barrier or buffer fluid temperature or flow rate required to maintain the integrity of a dual seal arrangement. When mechanical seals and seal support systems can no longer ensure pump reliability it’s time to select seals, support systems, and components better suited for the job.

If a change to a higher process temperature is causing unanticipated leakage, consult with your preferred mechanical seal vendor. The materials alone can present an overwhelming number of options as seal technology and design continue to evolve. There are now more choices than ever, including:

⇒ Seal faces—carbon, stainless, ceramic, tungsten, and variants incorporating silicon, graphite, or nickel—engineered for resilience and compatibility with process fluids

The benefit of these choices is the ability to match mechanical seals to the specific needs of the process, maximizing seal performance and reliability.

The mechanical seal requirements of high-temperature hydrocarbon processes are best met with dual/ between seal arrangements. A dual seal support system provides fluid between two seals, buffer fluid at a lower pressure than the process fluid, and barrier fluid at a higher pressure than process fluid.

In contrast to a single mechanical seal arrangement where seal degradation or failure results in fugitive emissions or outright leakage, the two seal arrangement provides a more reliable means of preventing high-temperature hydrocarbons from leaking. Here too, rotating equipment and reliability engineers have a number of dual seal design options to choose from, including:

Face-to-face configurations are used in space-constrained areas that cannot accommodate back-to-back or tandem arrangements. Seals share a common stationary component which, if compromised, leads to leakage. You can select from buffer or barrier fluid options.

Gradual or sudden changes in barrier or buffer fluid pressure provide evidence of problems with seals. An experienced mechanical seal vendor can help you navigate the options available to ensure mechanical seals and their components meet each of your specific needs.

Equally important to the reliable functioning of mechanical seals in high-temperature processes is the selection of seal support systems. The mechanical seal you choose will guide the seal support system plan that best meets your needs.

Seal support systems for dual seals are divided into two categories: buffer and barrier. While that seems to simplify the selection, there are a variety of options for each category. To give you an idea of what’s available, I’ve listed a few of the mechanical seal support system options below.

Circulates pressurized barrier fluid from a reservoir to the dual seals. Use plant nitrogen, bladder accumulator, or piston accumulator to supply seal pot pressure. Any leakage across the process side seal is barrier fluid that lubricates seal faces and migrates into process fluid.

Provides clean, dry pressurized barrier gas (typically nitrogen) to the dual seals from an external source. Any leakage past the atmospheric seal is pure nitrogen.

For each of these plans, there are options to fine-tune the seal support system and provide a greater level of reliability for mechanical seals operating in high-temperature environments. Among the many options you may want to include:

An experienced seal support vendor can save you time and money, helping you select and configure the seal support systems with the right components for each of your high-temperature hydrocarbon pumping needs.

Swagelok has been meeting the mechanical seal support system needs of Northern California refineries for more than 50 years. When you work with Swagelok, you have the benefit of a local vendor with facilities in Concord, Fremont, and Santa Clara. Being local translates into on-site support, field verification of your requirements, and rapid delivery of seal support system assemblies, components, and parts.

Following the ISO 9001 Quality Certification standards, our technicians fabricate and thoroughly test your systems prior to delivery. And to give you additional confidence in the quality of our design and fabrication process, Swagelok’s Limited Lifetime Warranty is the industry"s strongest. From the perspective of location, experience, fabrication, and service, you’ll no better partner.

To find out more about howSwagelok Northern California can help you address the challenges of maintaining the proper environment for mechanical seals in high-temperature serviceContact our team today by calling 510-933-6200.

Paul holds a B.S. in Mechanical Engineering from North Dakota State University. Before joining Swagelok Northern California, he was the West Coast Regional Sales Manager for an organization involved in pneumatic and hydraulic applications where he supervised product distribution throughout the western United States, Canada, and Mexico. While in this role, he was able to help provide technical and application-specific expertise to customers and distribution to drive specifications.

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Pumping of low-temperature and cryogenic fluids requires specific and unique engineering technologies for the shaft sealing system. When correctly applied, these technologies provide the containment and reliability to meet pumping equipment operators’ requirements.

Due to their extreme sub-zero temperatures, low-temperature hydrocarbons and liquefied atmospheric gases pose significant challenges to pumping, and particularly to the specification of their shaft sealing systems. To provide long-term reliability while ensuring that these pumped fluids are safely contained, the designs of the shaft seals used in cold-fluids pumps are often highly specialized.

For example, low temperatures have significant implications for the choice of materials used in the seal construction. Metals become increasingly brittle as the temperature is reduced; therefore, thermal constriction and expansion must be factored. The volatility and flammability of low-temperature hydrocarbons pose special challenges for the design of pump shaft seals, as well as for the release of hazardous emissions to the atmosphere. Liquefied oxygen, with temperatures much colder than these hydrocarbons, is a strong oxidizer and can cause certain materials to spontaneously combust.

Low-temperature hydrocarbons are typically pumped at sub-cryogenic temperatures, between –20°C and –140°C (–5°F to –220°F), although lower temperatures are occasionally encountered. They have high vapor pressures at ambient temperatures and are pumped at low temperatures to reduce the pumping pressures. These hydrocarbon fluids include ethylene, LNG, LPG, methane, butane and propylene.

Liquefied atmospheric gases include oxygen, nitrogen, argon and the noble gases. They are typically pumped at cryogenic temperatures ranging from –175°C to –198°C (–285°F to –325°F). Impeller inducers are often used, as they are frequently pumped with a low vapor pressure margin at the pump suction.

Low-temperature hydrocarbons are commonly pumped with API 610 (VS6) vertical multistage double-casing pumps that feature a warming chamber, known as a cofferdam (Fig. 1), which thermally isolates the shaft seal from the cold pumped fluid. Cofferdams enable a greater range of shaft sealing solutions to be used on these pumps, utilizing traditional sealing technology.

A cofferdam is a chamber between the pump discharge and the mechanical seal that is connected to the pump suction, or the vessel from which the pump is drawing suction. Ambient heat surrounding the pump, together with energy from the shaft and bearings, causes the liquid in this chamber to vaporize into a gas, which forms an insulating barrier between the seal and the process fluid. Cofferdams can be incorporated only into vertical pump designs.

Although vertical arrangements are common, various horizontal pumps can also be used. In these types of pumps, the shaft seal is in direct contact with the cold-pumped fluid; therefore, selection of the seal materials for low-temperature operation becomes more critical.

Similar to pumping equipment for low-temperature hydrocarbons, pumps used for liquefied atmospheric gases have a combination of vertical multistage pumps, together with horizontal single-stage pumps. These systems generally do not follow API pump design standards.

However, as the temperatures of liquefied atmospheric gases are much colder than those at which hydrocarbons are pumped, cofferdams cannot be used on these pumps. Although a mixture of vertical and horizontal pumps is commonly used at air liquefaction plants, mobile trailer truck unloading pumps are almost exclusively overhung single-stage pumps, either with direct-drive or speed-increasing gearboxes.

For pump designs where the mechanical seal is immersed in the pumped fluid, the vapor pressure margin in the seal chamber becomes critical. Where the vapor pressure margin is low, the heat energy from the mechanical seal faces can vaporize the fluid around the seal and in the seal interface, resulting in dry running of the seal. In this situation, a dual-pressurized seal is required. A dual-pressurized seal provides a stable barrier fluid to lubricate the seal faces, thereby negating the effect of vaporization of the pumped liquid at the seal faces.

API Plan 53B and 53C barrier systems are commonly selected for dual-pressurized seals to provide a source of warm, clean and stable barrier fluid to the mechanical seal. When an API Plan 53C system is selected, extra care should be taken to ensure that the pressure-amplifying piston and rod seals are insulated from exposure to cold temperatures.

The availability of suitable barrier fluids becomes limited at low temperatures, as the viscosity of many fluids becomes too high at the seal chamber operating temperatures. Mono- and di-ethylene glycol mixtures with water can be used down to temperatures of –29°C (–20°F). Alcohols, such as propanol (propyl alcohol), are suitable for even colder temperatures reaching –70°C (–95°F). Synthetic oils can also be used; however, careful consideration to their pour point is required, and a heating system may be needed to warm the barrier fluid to maintain a suitable viscosity.

When sufficient vapor pressure margin exists within the seal chamber, a dual-unpressurized seal can be selected. Typically, these designs feature a dry-sliding containment seal fitted with API Plan 76, or a combination Plan 72 and 76. These seal arrangements have the advantage of removing the low-temperature limitation of barrier fluid selection.

Pump designs utilizing a cofferdam require a dual-pressurized mechanical seal, as the seal chamber contains no liquid to lubricate the mechanical seal faces.

Icing, due to condensation of atmospheric humidity, can create a problem for sealing systems handling cold hydrocarbons. Since condensing water expands as it freezes, it can interfere with the operation of the mechanical seal if it reaches the seal’s operating mechanism. Extra protection should be applied to equipment exposed to atmospheric elements, such as rain. An API Plan 62 using a dry nitrogen quench can displace atmospheric humidity, thereby protecting the mechanical seal from these effects.

In applications handling liquefied atmospheric gases, pump seal reliability takes precedence when selecting a shaft sealing system. Unlike hydrocarbons, emissions of gases to the environment by liquefied atmospheric gases pose relatively minor hazards and, therefore, are not as critical a factor as seal reliability.

Two commonly employed shaft sealing technologies are used in pumps handling liquefied atmospheric gases: single mechanical seals and segmented bushings.

Single mechanical seals.The most common solution for pumps used in air liquefaction plants and mobile-transportation unloading pumps is the single mechanical seal. The major difference between the two is that the mobile unloading pumps tend to be smaller and often use non-cartridge seals. Cartridge seals are commonly found in larger machinery at air liquefaction plants. Single mechanical seals fall into two sub-categories: contacting wet seals and vaporizing liquid gas seals.

Contacting wet seals utilize a metal bellows to provide elastomer free-axial flexibility. Seal face materials typically include filled tetrafluoroethylene running against a tungsten carbide or hard-coated, stainless steel mating ring.

Vaporizing liquid gas seals (Fig. 2 and Fig. 3), similar in construction to contacting wet seals, feature engineered seal-face topography that allows the controlled vaporization of the pumped atmospheric gas to produce a highly reliable seal that exhibits controlled, low-level leakage rates.

Segmented bushings.A segmented bushings sealing configuration is often found in vertical multi-stage pumps at air liquefaction plants. The design provides a controlled leakage by breaking down the sealed pressure over a series of tightly controlled bushing clearances. Leakage rates are higher than those of mechanical seals; however, these leakage rates are often considered acceptable by this industry.

As mentioned, low temperatures have significant implications for the choice of materials used in the seal construction. This is especially true for elastomers applied in seals for pumps handling low-temperature hydrocarbons. Depending on the material grade used, elastomers have a variety of minimum temperature limits, but none can survive dynamic operation at true cryogenic temperatures.

Engineered polymer seals are an option at temperatures below the limits of elastomers; however, many of these designs will not function with pressure reversals applied to the sealing ring, which may be required in the mechanical seal design when support system failures occur.

Elastomers can survive at significantly lower temperatures below their operational limits when the seals are not in operation (i.e., static); however, they must be warmed up prior to operation. Commissioning of shaft seals containing elastomers must be completed carefully to ensure that equipment is at the correct temperatures before startup. Blowdown—the rapid depressurization of a vessel/pipeline—is one situation that can create excessively low temperatures for mechanical seal elastomers.

Thermal expansion and contraction are also considerations. The cavities in which elastomers or engineered polymer seals are installed will change with decreasing temperatures, as well as the dimensions of sealing elements installed in these cavities. Additionally, clearances between dissimilar materials, such as bushings, will require review. Mechanical seal manufacturers take these factors into consideration during the design of the mechanical seal for these cold services.

Since metals become increasingly brittle as the temperature is reduced, as a general rule of thumb, martensitic and ferritic stainless steels should be avoided in preference to austenitic stainless steels.

Since pumping equipment is often used interchangeably between different atmospheric gases, sealing of liquefied atmospheric gases presents some unique challenges to the selection of materials.

Liquefied oxygen is a strong oxidizer and can cause certain materials to spontaneously combust. Additionally, any organic contaminates on the seal can lead to spontaneous combustion, including metal cutting fluids, fibers from cleaning rags, and even oils from human fingerprints. To meet oxygen service requirements on seals, stringent cleaning specifications must be employed to ensure that the seal is free of any contaminates that may create a fire hazard while in service. Additionally, the materials of construction must include materials that are compatible for use in oxygen service.

Aluminum alloys should be avoided, as they can become hazardous when their protective oxide film is stripped from the material, such as when abrasion occurs. Lubricants used in the assembly and operation of the mechanical seal must be free of hydrocarbons and compatible for use in oxygen service. Packaging of the seal should also be suitable to preserve the cleanliness of the seal prior to installation into the pumping equipment, which must be performed in a suitably clean environment.

Of the many pump mechanical seal applications in use throughout various industries, those that deal with low-temperature and cryogenic processes rank among the more challenging.

It is critical to keep these seals, which handle low-temperature hydrocarbons and liquefied atmospheric gases, in optimal operating condition to ensure that the pumped fluids are safely contained, while providing long-term reliability. HP

Mark Savage is a Product Group Manager at John Crane, responsible for the application, design and development of metal bellows seals for pumps, compressors and rotating machinery. He has worked in the sealing industry for 25 yr and has been involved with the development of best practices for shaft seals and their support systems. Mr. Savage holds a BE degree in mechanical engineering from the University of Sydney, Australia. He is a member of the Fluid Sealing Association and Vice Chair of the Association’s Mechanical Seal Division, Chair of the Mechanical Seal Technical Committee and Vice Chair of the Government Relations Committee. He is also a member of NACE International and the Society of Tribologists and Lubrication Engineers (STLE). Mr. Savage has authored several publications on mechanical seals and support systems and their application to minimize environmental impact.

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Mechanical face seals were first introduced more than 70 years ago for sealing rotating shafts. As the technology of mechanical seals was improved over the years, they were found to offer significant advantages over the existing methods of sealing, for example, with soft packed glands. These benefits included reduced leakage and the elimination of the need for regular maintenance. Today mechanical seals are widely used on centrifugal pumps, compressors, and similar equipment for liquid/gas or gas/gas sealing.