how does a mechanical seal work brands

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.

Mechanical seals are designed to prevent leakage of fluid from centrifugal pumps that support industrial processes. Mechanical seals depend on mechanical seal support systems for reliable operations. I’ve provided information below to help explain mechanical seal support basics. I’m hopeful it’ll help you gain a better understanding of mechanical seals and the various types of mechanical seal support systems, their applications, and optional configurations to help boost reliability in your Northern California Bay Area refinery.

A mechanical seal is used to contain fluid within a centrifugal pump where the impeller shaft passes through a stationary housing. There’s a range of mechanical seal designs to cover every conceivable pumping process. Low to high pressure, low to high fluid temperatures, clean plant water to heavy hydrocarbons. To cover that wide range of pumping processes and conditions there’s an equally wide range of seal support systems and custom configurations to match the need.

At its simplest, a mechanical seal support system is designed to provide the proper seal chamber environment to maintain the integrity of the mechanical seal. The system provides cooling and lubrication to reduce mechanical seal friction and heat and prevent leakage. To accomplish this, mechanical seal support systems deliver process fluid, water, oil, or inert gas to the seal chamber at the required pressure, temperature, and flow.

Maintaining the proper seal chamber environment prevents leakage that could lead to loss of profitable products, degradation of pumps and their supporting infrastructure, or in the worst cases, conditions that pose environmental risk and subject you to Cal/OSHA and BAAQMD sanctions.

Centrifugal pumps and mechanical seal support systems are critical to the petroleum industry. As a result, the American Petroleum Institute has developed a standard to describe the different seal support systems, known as piping plans. See API Standard 682: Pumps—Shaft Sealing Systems for Centrifugal and Rotary Pumps for a listing of the various plans. The complete document is over 250 pages, but below I"ve distilled the document into a greatly simplified overview of mechanical seal support basics.

Mechanical seal support systems can be grouped into three categories—process side, dual or in-between, and atmospheric side. Let me explain the basics of these categories by describing the type of mechanical seal, the typical pumping applications, and the various API plans that provide the required environment for the mechanical seal and pumping conditions.

Process side mechanical seal support systems provide the lubrication and cooling to a single mechanical seal to keep process fluid within the pump volute. Process fluid is used for lubrication and cooling in three ways: it is circulated from the discharge to seal chamber, from the seal chamber to the suction, or from discharge to seal chamber and then to suction. Alternatively, a flush fluid that provides lubrication and cooling can be delivered from a reservoir which is part of the seal support system or an external source, such as plant water.

This single-seal solution is used when the pumped fluid poses no environmental threat in the event that the pumped fluid vaporizes as it crosses the seal faces and dissipates into the atmosphere. The table below summarizes the API Plans in the process side category, indicates the types of fluids used to provide cooling and lubrication, and the components that differentiate the plans and their capabilities.

Process side mechanical seal support systems cover a range of pumping processes, from clean, moderate-temperature, non-polymerizing fluids to high-temperature dirty or contaminated fluids. Cooling and filtering options enable these plans to remove contaminants that would damage seal faces. Pumping applications can include:

Dual or in-between mechanical seal support systems deliver a buffer (unpressurized) or barrier (pressurized) fluid to a seal chamber that contains a double mechanical seal—two seals arranged in series to maintain the buffer/barrier fluid between the two seals. The inboard (primary seal) keeps process fluid within the pump housing. The outboard (secondary seal) prevents the buffer/barrier fluid from leaking to the atmosphere. The buffer/barrier fluids that lubricate the seal faces and dissipate heat can be gas or liquid.

Pressurization of barrier fluid is provided by plant nitrogen, bladder accumulator, piston accumulator for API Plans 53A, 53B, and 53C respectively. Plan 54 is pressurized by the external pump. Plan 72 buffer fluid is plant nitrogen.

Atmospheric side mechanical seal support systems deliver an unpressurized fluid (also known as a “quench”) to the atmospheric side (exposed to air) of a mechanical seal. This method is used when a single mechanical seal cannot operate properly without the aid of the quench. In comparison to the process side and dual seal support systems, there are only two variants:

API Plan 62 - Quench From External Source delivers clean water, low-pressure steam, or nitrogen to cool the seal faces and prevent oxidation or coking of process fluid.

Our brief explanation of mechanical seal support system basics shows you the wide range of capabilities and applications. There’s a solution for every type of pumping process. You don’t need an in-depth understanding to obtain the maximum benefit from a mechanical seal support system if you work with a local vendor in the Northern California Bay Area who has deep industry experience.

In addition to knowing which mechanical seal support system is best for a specific pumping process, a local vendor who conducts an on-site evaluation is able to make specific recommendations regarding system design, instrumentation, and components to boost pump reliability. Fabricated and thoroughly tested in Swagelok’s Fremont, Santa Clara, or Concord facility, you’ll have a mechanical seal support solution custom-configured to the specific requirements of your pumping process.

Swagelok Northern Californiawill be happy to explain mechanical seal support basics and advise you on the specific plans to improve pump reliability. To arrange an on-site consultation by one of our Field Engineerscontact our teamtoday by calling

The mechanical seal is one of the most important components of a pumping system. As the name suggests, the seal is a simple component that forms a barrier between the motor and the volute of a pump, protecting the motor against leakage.

Leakage is death to any mechanical instruments and pumps are no exception. Fluid leakage often results in corrosion of the casings, sleeves and bearings. Corrosion left unattended over a period of time will will degrade the construction material of the pump. Fluid leakage that enters the motor shaft can short circuit the motor.

Naturally, these problems will impede proper pump functioning and eventually could stop the pump from running altogether. Companies often spend a lot in terms of money, wasted manpower and lost operational time to fix leakage.The mechanical seal is designed to prevent that leakage from ever happening. Mechanical seal shaft failure is the number one cause of pump downtime according to WaterWorld magazine.

Submersible wastewater pumps, such as sewage pumps, are particularly susceptible to the dangers of leakage as their operation depends on being surrounded by water that may contain potentially corrosive or clogging waste solids. This water can accumulate in the motor casing and obviously a submersible pump cannot be drained without interrupting operation.

A wide variety of seal types are available for any number of applications. The type of seal most commonly used in sewage pumps is an end face mechanical seal.

In an end-faced seal two ringed “faces” or seal heads rest flat against each other (but are not attached) in the seal chamber, which is located between the volute (the “wet end” of the pump) and the motor. An actuator, such as a spring, presses the faces close to each other.

The rotating motor is inserted through the two ringed faces and attached to the impeller. As the motor shaft rotates, the upper seal (closer to the motor) rotates with the shaft. The bottom seal closer to the volute remains stationary.

This action creates a sealing interface which keeps the water in the volute and prevents leakage. A minimal amount of water might escape the sealing interface but this liquid essentially acts as a lubricant for the seal and will eventually evaporate from heat.

All the components of an end faced mechanical seal work in unison to prevent leakage and are equally important to proper functioning. The main components are:

1. The primary seal faces that rest against each other. The primary seal faces are typically made of durable materials such as silicon carbide, ceramic carbide or tungsten. Certain materials work better for certain applications. For instance, silicon carbide is resistant to acidic liquids, less so to alkaline liquids. Generally, face materials should be of high hardness and should have the ability to slide on each other.

2. Secondary seal surfaces or faces. The secondary faces surround the primary seal faces, but do not rotate. The secondary surfaces hold the primary faces in place and create an additional barrier. Secondary faces can come in a variety of forms – examples include o-rings, elastomers, diaphragms, mating rings, gaskets and wedges. The secondary face also allows for shaft deflection and misalignment.

3. Actuator or a means of pressing the seal faces together and keeping the entire seal properly aligned to the shaft. Often (but not always) a loaded spring. The actuator is mounted above the seal face closer to the motor while the motor shaft passes through the spring.

Mechanical seals are precise, sensitive and temperamental instruments. Even seemingly minor mishandling can negate the seal’s functionality. Therefore Pump Products highly recommends leaving the mounting and installation of mechanical seals to qualified technicians.

Before you actually handle your mechanical seal, be sure to wash your hands thoroughly. Because the faces are meant to be extremely flat, even small particles from the oil of human hands can damage the surface integrity of the faces and render the seal useless. Make sure to wipe the seal itself with an alcohol solution, in case another person touched the seal faces during the packing or shipping process.

The following is a basic guide to replacing a defective mechanical seal. Each seal should come with its own specific instructions, but this is overview covers the most essential parts of the mounting process.

2. Carefully remove the old seal head, taking care not to scratch the motor shaft. Take note of how the seal was mounted; the new seal will be mounted in the same manner.

Mechanical seals are classified by construction type and the construction type is expressed through a letter code. The seal listing code will designate the construction material of each component. For example, here is a construction code guide from U.S. Seal:

The construction materials of the seal will in turn inform what specific seal is suited for your specific pumping application. You can consult a material recommendation chart to best choose the right mechanical seal.

The above chart is a guide to identifying and sizing the appropriate mechanical seal for your pump. Because seals are specifically engineered instruments, making sure that the seal is properly sized for a specific pumping system and application is critical. Manufacturers often make specific recommendations for the type of material to use for an application as well – a recommendation chartis helpful.

The use of the word “seal” is a misnomer; as a mechanical seal is a restrictive flow path,that is either an angular or radial gap.The flow through this gap is generally so low it goes unnoticed if a liquid or inconsequential if a gas.

A mechanical seal works byretaining a liquid or gas inside a rotating piece of equipment. Mechanical seals can be designed to prevent contamination of the process by the environment and prevention of leakage of the process into environment.

The basic components of a mechanical seal are a Rotating Part and a Stationary Part. The primary seal of a mechanical seal consists of a rotating face and a stationary face. The faces are kept lubricated by maintaining a thin film of fluid between each face. There is a very small gap between these 2 components which creates a restrictive flow path.

There are other components namely o-rings or gaskets which are used as secondary seals and hardware which is used to support the seal faces and to attach them to the rotating part (i.e shaft) and stationary part (i.e cover plate).

The primary seal of a mechanical seal is made up of 2 seal faces where these two parts meet is where the seal gap is located. The mating surface of the seal face is machined to a very tight tolerance.

Double Seal (Barrier) => consists of two primary seals in various arrangements. There is a barrier fluid between the two primary seals which is at a higher pressure than the process. There is always some leakage of the barrier fluid in process & out to atmosphere. As long as barrier pressure is maintained there is no leakage of process to atmosphere or contamination of process by environment.

Double Seal (Barrier) – Wet => is a double seal where the barrier is a liquid. It is generally the most robust seal. It has a good pressure, speed and temperature capabilities.

Gas Contacting Seal– the seal faces are in contact, the soft face wear acts as a lubricant. Low pressure, speed and temperature capabilities and possibilities of wear getting into the process.

Gas Non Contacting Seal – the seal faces are NOT in contact. They are kept apart by a flow of gas between the faces. Good temperature, speed and pressure capabilities. If operated correctly their is no wear but care must be taken in order to minimise shaft run out.

Cartridge seal =>is where the rotating and the stationary hardware are pre-assembled before mounting onto the pump/mixer. Cartridge seals are much easier to fit & maintain compared to the component seal.

A lip seal is a specific type of seal, it is a radial seal, where the part that seals against the rotating surface is a narrow cross section, soft material i.e the lip and it is made from an elastomer or non-elastomer material with a backup spring. Most commonly used to seal bearings in Mixers/Agitators. A lip seal rotates too quickly to be used on pumps.

Abarrier fluid is any gas or liquid which is used to pressurise a double mechanical seal. It must be compatible with the process, generally non-toxic and a good lubricant.

Please consult the pump manufacturer/distributor for guidance on these calculations for mixer seals, the barrier pressure is set at a certain value above the maximum vessel pressure.

Packing is a material that is stuffed between a rotating shaft and a stationary part gland to maintain pressure. Packing is a low cost alternative to mechanical seals.

We supply mechanical seals into the pharmaceutical, bio-technology, chemical processing, mineral and ore processing, semi-conductor and general industries.

Depending on your particular application, if you are looking mechanical seals to suit a pump application; Mechanical Seal for Pumps, or if you are trying to source mechanical seals for an agitator or tank mixer; Mechanical Seal for Agitator, or perhaps you have a hygienic application in mind, take a look at our range of Mechanical seal for Hygienic & Aseptic applications.

Our Mechanical Seal specialists can advise you on the appropriate selection of a seal support system which will deliver years of reliable service and operating cost savings in the longer term.

If you have any query around how to install mechanical seals or have some concerns around seal failures, why not contact one of our seal specialists below to discuss it in more detail and find out how we can help solve your issues and get your process running reliably again.

Double mechanical seal - This is where two mechanical seals are used within a pump. The first seal retains the fluid within the pump as per the standard mechanical seal above. The second seal contains a barrier fluid to ensure the faces are kept clean and are lubricated preventing failure. Without such liquid, the mechanical seals would run dry and fail.

Cartridge seal - When a mechanical seal is first inserted within a pump its clearances should be set. By utilising a cartridge clearances do not need to be set as the unit is pre-assembled eliminating the need for time-consuming assembly and spring setting on site.

Packed gland - A packed gland is when a braided material which has an appearance similar to a flat rope is wrapped around a shaft. A packed gland is also known as stuffing as the packed gland is typically wrapped tight around the shaft and inserted within a chamber known as a stuffing box. Packed glands must leak a little to allow cooling from immediate contact with the shaft to prevent burning, and over time do wear shafts. Packed glands were used more historically as they were utilised before mechanical seals were invented. They are still used in some boiler feed pumps where seal failure is common from overheating, cavitation or the presence of high fine solid content is expected as it is a cheap way to seal the pump rather than utilising expensive flushing liquids or double mechanical seals such as in dredging.

Expeller Seal -An Expeller seal is a shaft sealing arrangement where a rotating part called an expeller is mounted where gland packing or a mechanical seal is normally fitted. Its appearance is similar to that of another impeller, with rigid vanes mounted on the rear of a disc, which as it rotates reduces shaft pressure creating a dry seal around the shaft without a gasket or packing.

However once rotation stops, so does the dynamic sealing meaning a seal must be in place to prevent media leaking. This can be done by either external flush, packing, lip seals or an inflatable bellows.

An expeller seal is useful for slurry pumps used within mines at remote locations where a seal flush is required, which consume vast amounts of water. As water is scarce, and expensive in such areas sizeable savings can be made by switching to such a sealing arrangement.

Typically Mechanical seals are usually manufactured in Carbon Ceramic, with a Stainless Steel Spring. Carbon is a good general choice for the majority of applications where a fluid is compatible, not contaminated and fairly clean.

Hard faced mechanical seals are typically used when the fluid handled may be harsh, and contain solids. Such seals are usually made in Silicone Carbide or Tungsten Carbide due to its hard wearing construction it is built to withstand unexpected small solids such as Sand, dirt, stone and is a great choice for heavy duty applications.

Do you require replacement mechanical seals and gaskets? Suffering from frequent seal failure or replacement? We can help diagnose the cause and eliminate recurring failures.

Full containment of fluid without leakage therefore suited to a variety of expensive, and toxic chemicalsExpensiveEconomicalRequires slight leakage to ensure packing is cooled. Over time leakage increases. Leakage causes secondary issues such as slip or trip hazards, extra cleaning and disposal costs.

More Durable & more suited for long term operationEasily DamagedMore forgiving than mechanical seals, accepting particles, and large shaft movements such as in the Paper & Mining Industry. Can continue to be used even when pump has experienced excessive wear.Requires replacement more often adding to wear and tear of pumps as they are assembled and disassembled. More labour intensive

Safer as double seals, or cartridge type can be fitted drastically reducing the possibility of leakageIf packing requires fresh water supply as a flush it can leak to contamination or dilution of the pumped liquid

Mechanical seals, invented in the early 1920s, became the go-to rotating shaft sealing method in the 1950s within the oil and gas industry and continued to gain market share through the 1990s, becoming common in most process industries and applications. Their ability to seal rotating equipment better than the traditional braided packing methods was evident. Over the last 30 years, their usage has become a standard procedure for many application maintenance programs.

Mechanical seals are critical to applications in which the pumped medium is considered toxic, corrosive, or explosive. Compounds classified to be hazardous or fugitive emissions typically use double seal technology.

Modern mechanical seals use ultra-precise, ultra-flat opposing faces, one stationary and one rotating with the shaft.  The opposite faces are so precisely paired that they leave a gap measured in microns. The microscopic gap causes the pumped medium to vaporize as it is moved centripetally to the seal edge. The result is a seal that does not measurably leak. It also creates a low friction environment for rotating shafts; low friction at the stuffing box results in lower energy costs for rotating equipment.

While mechanical seals, when installed and maintained correctly, create effective seals, they can be problematic because of their inherent complexity and the need to keep the opposing faces perfectly mated and cooled. Installing these seals on equipment with shaft runout, a scored sleeve, or worn parts can lead to premature failure and costly downtime.

This type of seal"s complexity and precision-based nature also leads to a high price compared with other sealing methods. Many seals can be in the $10s of thousands of dollars per application. Because of their high cost, mechanical seals should last 3 to 5 years between rebuild cycles to fully realize a return on investment.

In some applications that require a mechanical seal on worn equipment, you can install an o-ring mounted bearing to mitigate shaft movement, which can protect the critical seal faces. (see the SealRyt ORM)

Stuffing box mounted bearings were first introduced in the early 2000s when SealRyt patented the PackRyt® Bearing System. Well known for their high-performance braided packing, SealRyt engineered a load-bearing, close clearance polymer that is machined to custom fit each stuffing box.

Bearings are manufactured from high compressive strength polymers. These polymers are designed to be chemical and high temperature resistant but carry an ultra-low friction coefficient.

Bearings work similar to mechanical seals but without the ultra-precise, micron-level clearances. Bearings stabilize the shaft, reducing runout or wobble, bringing the shaft into concentricity. Bearing systems work in concert with packing or mechanical seals to create a close clearance seal at the bottom of the stuffing box that stabilizes the shaft, then the braided packing is layered into the remaining space and compressed using the gland follower. The combination of shaft stabilization and close clearance fit provided by the bearing allows the packing to seal effectively and longer than packing alone.

Bearings can also incorporate a lantern ring into their design, allowing for a flush channel. The benefit of combining the lantern ring into the bearing is that it prevents movement. In a standard packing/lantern ring/packing (or 2L3) setup, the packing can push the lantern ring past the flush holes resulting in misalignment and overheating. Teflon lantern rings are also easily crushed when doing basic packing maintenance. The joined bearing and lantern ring unit are made from a non-compressible polymer, so once installed, the lantern ring is always aligned.

Additionally, bearings can automatically reduce the amount of flush used in the process. An 85% reduction in flush usage is common. The close clearances throttle the flush down without the need for external flow controls.

Many industries rely on old pump equipment that has outdated stuffing box designs. Many older OEM pumps have placed the flush inlet close to the bottom of the box, which results in dilution and sealing issues. Bearings can be machined with internal channels (patented) to relocate the flush without modification to the stuffing box. By moving your flush location, you can reduce water usage that goes directly into the process.  (see the SealRyt Diverter®)

Bearings are effective and long-lasting seals, but there are some drawbacks. The bearing must fit to work properly, which means the stuffing box needs to be measured accurately (How to Measure). Bearings rely on close clearances to prevent shaft movement, but that also means they are a snug fit and can be difficult to install or remove without the proper knowledge and tools. (Note: Ask our engineers about ExtractPRO™ Technology).

Bushings are almost as old as packing. Early engineers looked to space packing out into different configurations that resulted in improved performance. Bushings, such as lantern rings, allowed the ability to transform the dynamics of the stuffing box.

The difference between bearings and bushings is simple: Bearings are designed to bear the load and contact the rotating shaft. Bushings are designed to be a non-contact spacer and, depending on design, to alter flush flow characteristics. So there are two main differences: clearances and materials. Bushing clearances are much larger to ensure that the part DOES NOT come into contact with rotating shaft. Contact with the shaft leads to damage of the bushing material. Bushing material tends to be low durometer materials such as rubber, polyurethane, and other semi-hard plastics such as carbon-filled Teflon.

The utilization of bushings is related to flush control. Bushings allow flush to circulate more freely inside the stuffing box, but they don"t limit or regulate flush volume independently. The varied designs on the market can alter the fluid dynamics inside the stuffing box environment. Bushings are used in conjunction with packing. In this configuration, the packing does the brunt of the fluid sealing. There are a few designs of bushings to operate with mechanical seals.

Packing has been used for centuries, since the first use of rotating equipment as pumps. Rope packing gets its name from jamming rope around a rotating shaft to be sealed. The term stuffing box is a relic of this early sealing method. It"s the most common rotating shaft sealing method because it"s relatively inexpensive and reasonably effective.

Packing has come a long way from using organic twisted fiber. Today modern braided packing is made from high-tech synthetic fibers woven into complex patterns that create a square-shaped packing compressed into a stuffing box in layers. The packing gland is then tightened enough to create a seal but allows the shaft to rotate. Essentially, packing seals through both friction as well as hydraulic pressure break-down.

Using braided packing to seal requires the correct combination of material characteristics depending on the temperature, rotational speed, and medium being sealed. The packing should be low friction as it contacts the shaft and be durable to withstand the rotational wear. Packing that has heat conductivity is a huge plus as well.

There is a wide variety of packing styles and configurations, and not all packing is the same. Generic packings generally are utilized in various common applications and in bid situations where low price is considered a requirement. They are effective for a while, then wear out/compress and need to be replaced. More advanced packing is designed for specific applications, higher reliability requirements, and a higher predictive quotient. When choosing packing consider these parameters: Temperature, Speed, pH, Media, and Safety. An engineered packing can be more expensive by the pound, but it lasts longer and saves on downtime and maintenance hours.

The spring is used to provide tension between the seal surfaces as they wear. It also provides tension on the seal when no product pressure is present. The two seals are machined using a process called lapping to achieve the necessary degree of surface flatness to achieve a leakproof operation.

As previously mentioned, mechanical seals are available in either single seal or double seal varieties. A single mechanical seal consists of a pair of sealing surfaces, while a double mechanical seal consists of two pairs.

Single mechanical seals are found in pumps used for simple duties such as pumping water, milk, animal fats, and beverages, as well as many other food processing applications.If the fluid to be pumped is more challenging in certain respects, then a double mechanical seal may be warranted to provide extra security. “Challenging” in this context includes fluids that are abrasive, such as crystalline sugar slurries.

Both single and double mechanical seals may also come with a flush. All types of mechanical seals generate heat from friction between the moving surfaces, and a cooling fluid — called a flush — circulates around the seal to remove the heat.

The flush provides constant lubrication when the product flow is not sufficient; the fluid flow is intermittent (e.g., entrained air in a CIP return pump); or the product is abrasive or sticky (sugar, chocolate, etc). This flush fluid may be the same as the fluid being pumped or an entirely different fluid and may be heated, filtered, or otherwise treated to improve its performance.

Double mechanical seals always come with a flush. Single mechanical seals can also be configured with a flush option (via a lip seal) without adding a second seal.

When you have a sugary or sticky liquid, the flush also helps remove particles that may be left behind in pumping certain products and helps to keep the seal wetted and safe from drying out. In the case of a manufacturer like Alfa Laval, a single mechanical seal with flush is available and solves most product sealing issues. Note: mechanical seals are more complex than O-rings, and require some care when installing.

A mechanical seal is a component which helps join mechanisms together by preventing leakage, containing pressure, or excluding contamination. A mechanical seal consists of a stationary element, a rotating element, and a spring to supply force to hold the two elements together. Mechanical seals are utilized predominantly in pump applications, and are available in a number of head and seat configurations.

A mechanical seal contains a primary sealing surfaces, a secondary sealing surface, a means of actuation and a means of drive. Mechanical seals can be divided into either dynamic or stationary categories. Dynamic mechanical seals will employ a secondary dynamic seal (o-ring) which moves axially with the primary seal face. Stationary mechanical seals will employ a static secondary seal (o-ring, packing, or bellows). Mechanical seals come in numerous classifications and materials and are considerably more complex than standard oil seals. Pleasecontact a Bearing Service representative to assist in identifying the right mechanical seal for your application.

Historically, centrifugal pumps have usually been designed with packing seals. Packing seals are packed with a lubricated fibrous material that came into direct contact with the shaft, so flush water is necessary to cool and lubricate the shaft. Flush water has to be directed away from the process to prevent contamination, and care has to be taken to protect the bearing box from flush water that contaminates the oil, as well as to prevent the safety problem of water pooling on the floor.

Mechanical seals may have a higher initial cost, but they often save a great deal of operational cost depending on how much flush water a packing seal pump consumes.

Balanced Seals have a system where forces acting on both faces are balanced, so there is more even lubrication of seal faces. Balanced seals have a higher cost than unbalanced seals, and they tend to last longer. Unbalanced seals show less leakage and are more inexpensive, but they have a lower mean time between failures and are not recommended for high pressure applications.

Pusher seals use one or more springs to maintain sealing forces, while non-pusher seals use elastomeric or metal bellows. Pusher seals can be used at very high pressure applications, but they have an elastomeric seal that can wear. Non-pusher seals are ideal for medium/low pressure and high temperature or dirty applications.

Conventional mechanical seals are installed as components. Cartridge seals have all the seal elements contained within a single assembly, so they are quick to install and reduce the chance of installation errors.

Many industrial processes still use a packing seal for positive displacement pump applications. Packing seals, which are designed to allow some controlled leakage, can be a reliable method of preventing excessive leaks. However, stricter standards in industries like food processing are reducing the amount of acceptable leakage.

​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Chesterton is the world leader in design innovation of split seals. Our innovative split seals have been used to seal thousands of process-critical pieces of rotating equipment with exceptional​​ ​results and many years of leak-free operations.

Chesterton was the first company to offer commercially-viable split seals for plant-wide use, which revolutionized pump sealing across industries. Since that time, we"ve launched a number of innovative split seal designs now used as a standard by companies around the globe.​ We offer shaft diameters ranging from 25-914​ mm (1-36 in.)​

​A split seal has components split into two equal halves which are secured as one unit on the seal shaft. The major advantage of the split seal design is that it allows you to install the seal with no dismantling of the pump (or equipment)—an enormous time-saver! Chesterton"s split seals offer virtually leak-free performance. This leads to improved safety and environmental compliance and nearly eliminates sleeve wear, and flush water usage,  among many benefits.

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At Gaddis Mechanical Seals, our industry-leading seal repair services allow us to repair or upgrade most mechanical seals. In rare cases, though, the damage to a mechanical seal is too severe to repair. Gaddis Mechanical Seals has replacement seals for over 400 brands of OEM pumps, mixers and grinders. We have the ability to provide these replacement seals at a significant cost savings over OEM seals due to the cross referencing ability of our records that go back almost 40 years and our inside engineers ability to identify the type of seals used in your equipment. Over the years, Gaddis Mechanical Seals has formed close relationships with some of the best mechanical seal providers in the world today. By leveraging these relationships, we are able to pass our sizable savings on to our customers in order to offer the best mechanical seals on the market at the lowest prices you will find.

Our engineers will also work with you to fully understand your specific requirements in order to ensure that we provide the perfect mechanical seal for your needs. If you want to guarantee that you purchase a mechanical seal that will function in the application while also ensuring that you receive the best price on the market today, we at Gaddis Mechanical Seals are able to help.

Our NUTECH cartridge mechanical seals are designed to fit all ANSI pumps for ease of installation and are pressure tested at our Texas manufacturing facility prior to shipping. We can custom design any cartridge style seal to fit your most demanding applications. We use premium grade materials of construction throughout. All seals are made in the USA.

LINK-SEAL® is a modular, elastomer sealing system that creates a permanent, hydrostatic seal for nearly any cylindrical object as it passes through a barrier.

LINK-SEAL modular seals are considered to be the premier method for permanently sealing pipes of any size passing through walls, floors and ceilings. In fact, any cylindrical object may be quickly, easily and permanently sealed against the entry of water, soil or backfill material.

For the system approach, metal or non-conductive Century-Line™ sleeves with water stops may be ordered with LINK-SEAL modular seals to ensure correct positioning and a water tight seal of the installation within poured concrete walls.