balanced mechanical seal in stock

Excellent axial movementThe seal can move ± 2,0 mm independent of the compression of the springs. The seal follows the movement of the shaft without influencing the compression of the springs. This feature is essential when sealing equipment with flexible bearing units.

Patented protected spring packageThe springs are located outside both the product and the flush. Minimizing the risk for clogging, which is one of the most common causes for seal failure. Patent No: 900912-2

Safe drive of rotating surface at the atmospheric sideThe rotating face on the atmospheric side is driven by three big drive pins machined into the sealing face. The pins are not in contact with the quench liquid, eliminating the risk of them being blocked axially by residues from the quench.

Hygienic applicationsSmooth surfaces without cavities or closed spaces make the seal suitable for food and drug applications. If required, the gasket may be replaced with O-rings according to EHEDG in order to achieve a hygienic designed seal suitable for CIP (Cleaning in Place).

H4 designThe rotating sealing face on the product side has the new “H4-design”. This means that the seal face is O-ring mounted and the outer diameter of the seal face is the same as of the holder. This prevents the forming of turbulent flows, which cause heavy wear in abrasive liquids.

Hygienic solutionsSmooth surfaces without cavities or closed spaces make the seal suitable for food and drug application. If required the gasket may be replaced with O-rings in execution according to EHEDG to achieve a hygienic designed seal suitable for CIP (Cleaning in Place).

H4 designThe rotating sealing face on the product side has the new “H4-design”. This means that the seal is O- ring mounted and the outer diameter of the seal face is the same as of the holder. This prevents the forming of turbulent flows, which cause heavy wear in abrasive liquids.

Optional additional flange for flushingThe seal may be equipped with an extra flange when flushing into the media is needed. The standard design is without flange since the chamber with a small gap given by the flushing flange may encourage material build-up if flush is not connected.

The balance of a seal refers to the distribution of load across the seal faces. If there is too much load on the seal faces, it can lead to a leakage of fluids from within the seal which essentially renders the seal useless. Moreover, the liquid film in between the seal rings runs the risk of vaporising.

This can result in higher wear and tear off the seal, shortening its life span. Seal balancing is therefore necessary to avoid disasters and to also elongate the life of a seal.

A balanced seal has a higher pressure limit. This means that they have a larger capacity for pressure and they also produce less heat. They can handle liquids that have a low lubricity better than unbalanced seals.

On the other hand, unbalanced seals are typically much more stable than their balanced counterparts as far as vibration, cavitation and misalignment are concerned.

The only major drawback that an unbalanced seal presents is a low pressure limit. If they are put under even slightly more pressure than they can take, the liquid film will quickly vaporise and will cause the running seal to run dry and thus fail.

Optimal performance is attained by selecting from three standard seal face balances; the BXQ seal is high balanced for flashing hydrocarbon applications

• Drive mechanisms external to the product;• Seal faces positioned for maximum protection;• A dynamic elastomer moves on a non-metallic surface, eliminating fretting defects;• Hydraulically balanced;• ...

Cartridge seals for critical, toxic and emission control applications, where single seals are notaccepted;• Built-in pumping device improves barrier fl uid cooling;• Springs locations prevents contact ...

... corrosion;• Monolithic rotating unit virtually eliminates clogging in the seal area;• A dynamic elastomer moves on a non-metallic surface, eliminating fretting defects;• Hydraulically balanced;• Cartridge ...

Single mechanical seal, balanced, independent of the direction of rotation with multi-spring configuration. The MTM180 Series represents the mechanical seal ...

Single mechanical seal, balanced, external, independent of the direction of rotation with multi-spring configuration. The MTM190 Series represents the mechanical seal ...

Single echanical seal, balanced, independent of the direction of rotation with multi-spring configuration. The springs are never in contact with the fluid. The MTM190 Series represents the mechanical ...

... dual unpressurized arrangement, without outboard seals also incorporating the same non-pusher technology, the seal can be configured to suit both the operator and pipeline needs.

Flexible seal, suitable for the narrower seal housing and suitingcommon European seal housing standards. STK A1 has a longworking length and is fitted with a seal head ...

Optimal performance is attained by selecting from three standard seal face balances; the BXQ seal is high balanced for flashing hydrocarbon applications

• Drive mechanisms external to the product;• Seal faces positioned for maximum protection;• A dynamic elastomer moves on a non-metallic surface, eliminating fretting defects;• Hydraulically balanced;• ...

Cartridge seals for critical, toxic and emission control applications, where single seals are notaccepted;• Built-in pumping device improves barrier fl uid cooling;• Springs locations prevents contact ...

... corrosion;• Monolithic rotating unit virtually eliminates clogging in the seal area;• A dynamic elastomer moves on a non-metallic surface, eliminating fretting defects;• Hydraulically balanced;• Cartridge ...

Single mechanical seal, balanced, independent of the direction of rotation with multi-spring configuration. The MTM180 Series represents the mechanical seal ...

Single mechanical seal, balanced, external, independent of the direction of rotation with multi-spring configuration. The MTM190 Series represents the mechanical seal ...

Single echanical seal, balanced, independent of the direction of rotation with multi-spring configuration. The springs are never in contact with the fluid. The MTM190 Series represents the mechanical ...

... dual unpressurized arrangement, without outboard seals also incorporating the same non-pusher technology, the seal can be configured to suit both the operator and pipeline needs.

Flexible seal, suitable for the narrower seal housing and suitingcommon European seal housing standards. STK A1 has a longworking length and is fitted with a seal head ...

Since failure of the mechanical seal on the shaft is the number one cause of pump shutting down, it is important to know the standard terms of the world of mechanical seals.

Mechanical seals are comparable to precision instruments. These seals use margins with many decimal places. The mechanical seal life depends on many factors, and it can vary from a few intense minutes to many trouble-free years. In general it can be stated that: the more attention paid to the mechanical seal and related equipment, the longer they will last.

Years ago, packing materials such as stuffing box packing were used for most shaft seals. These types of shaft seals required a fair amount of leakage to keep the packing properly lubricated and cooled. Until 1915 the mechanical seal was invented. This shaft seal managed to keep the fluid in by using two incredibly flat surfaces (one that rotates with the shaft, and one stationary in the housing). Despite the fact that these treads also need a little bit of ‘leakage’ to create a hydrodynamic layer, this is often not noticeable as this liquid evaporates. Most pumps today have mechanical seals. However, because the parts and surfaces are so delicate, it is also the number one cause of pump failure. This requires a better understanding of this type of seal and its application.

A set of (very flat lapped) treads as primary seal: the minimum distance between these treads, which are perpendicular to the shaft, minimizes the leakage. Often two different materials are used as the tread, a harder and a softer material, to prevent the materials from sticking together. One of the treads is often anti-friction corrosion material such as carbon graphite. A relatively hard material such as silicon carbide (SiC) or ceramic alumina is often used for the other tread. However, when processing abrasive substances, two hard surfaces are normally used.A tread is mounted stationary in a house.

Mechanical seals require a fluid to maintain lubrication. The running surfaces are usually lubricated by a very thin layer of liquid (or gas) between the two running surfaces. Lubrication can also come from another fluid other than the product, depending on the seal requirements.

Pusher seals use a secondary seal that moves axially along the shaft or shaft sleeve to maintain pressure on the running surfaces. This allows the seal to compensate for wear and any less accurate shaft alignment. The advantage is that this seal type is the cheapest. The main disadvantage of this configuration is that the secondary seal can gall on the shaft or shaft sleeve, especially when processing abrasive product.

This is the category in which the bellow seals fall. These seals do not use a secondary seal that must be able to move along the shaft or shaft sleeve to maintain contact. The secondary seals do not move with this type of seal under any circumstances, not even during use. The tread wear is compensated for by an elastomer or metal bellows. A disadvantage of this type of seal is the higher cost price of the seal and that a larger seal must be used in a corrosive environment because the material of the bellows is otherwise too thin.

We speak of a balanced seal if the pressure on the running surfaces caused by the pressure in the system is taken into account. It may sound crazy if the goal is to achieve shaft seal, but a mechanical seal must leak! After all, the running surfaces of the primary seal must be lubricated with the pumped product. When the pressure on the product side exceeds approximately 250 psid, the pressure on the treads can increase to such an extent that no liquid film can form between the surfaces. The lack of lubricating film will cause the seals to wear out very quickly.

To overcome this problem, the balanced seal was introduced in 1938. With a balanced mechanical seal, high pressure is taken into account by adjusting the surface of the tread, which distributes the stuffing box pressure over a larger surface. Balanced seals are easy to recognize, there is a step in the shaft sleeve and/or the running surface. Incidentally, this works a bit more complicated with a metal bellow, but the principle remains the same. Mechanical seals can also be designed to balance for overpressure on both sides of the tread assembly.

Cartridge seals consist of a pre-mounted mechanical seal on a shaft sleeve that can be installed as a whole over the shaft or shaft sleeve. Cartridge seals are very easy to install and the chance of short service life due to suboptimal installation is less probable. It should come as no surprise that cartridge seals are a lot more expensive than the previously discussed seals. On the other hand, there are lower maintenance costs. Incidentally, it is not always possible to apply a cartridge seal if, for example, there is no space in the house.

The Safeseal Type SE1 is a customer-fitted (OEM standard) single, balanced component or cartridge seal designed for clean and lubricating fluids such as water, different types of oils, solvents and paper stock. The Type SE1 seal is designed especially for the Sulzer APP and APT pump series and Scan pump. The SE1 seal is easy to install and maintain. In spite of its simple design, SE1 is very advanced in its technical capabilities, including, for example, a patented thermal method for seal face holding and an elastic thrust ring.

A double cartridge mounted face seal which is both stationary and balanced, which can be used in higher pressures and at higher speeds than unbalanced alternatives. it can be used with a pressurized barrier fluid (double seal applications) or unpressurized buffer fluid (tandem applications). The GMP-II seal is available in a wide range of materials to suit the application requirements.Minimum Shaft Diameter: 1.000 in. / 25.4 mm

Many early mechanical seal designs placed the spring inside the process fluid. Most products (process fluids) that are sealed are not very clean. When the spring mechanism of the mechanical seal is immersed in this unclean fluid, dirt collects between the springs. This situation eventually impacts the spring’s ability to respond to movements and vibrations, and the ability to keep the seal faces closed. Over time, clogging of the springs will cause premature seal failure.

The ideal design offers springs on the atmospheric side of the mechanical seals. The springs will be protected from the process fluid and their ability to work will not be impeded.

The pressure from both the seal springs (Ps) and the hydraulic pressure of the liquid in the pump (Pp) provide a compression force that keeps the seal faces closed. Balanced seals reduce the seal ring area (Ah) on which the hydraulic pressure of the liquid in the pump (Pp) acts.

By reducing the area, the net closing force is reduced. This allows for better lubrication that results in lower heat generation, face wear, and power consumption. Balanced seals typically have higher pressure ratings than unbalanced seals.

Mechanical seals can be designed with inserted seal faces or with monolithic seal faces. In both cases, the sacrificial seal face is often made from carbon/graphite. This material offers good running properties but is relatively weaker from a mechanical standpoint than other options. Inserted face designs use a metal rotary holder to transmit the shaft torque to the seal face.

The disadvantage of this inserted face design is that the face and holder material have different coefficients of thermal expansion. This changes the net interference force between both parts when they are exposed to heat from the process fluid or face friction. The seal face deforms, which results in leakage and accelerated wear.

More modern seals are equipped with monolithic seal faces that are made out of only the seal face material itself. The torque transmission is applied directly to the seal face. This is possible if the geometry of the seal face is designed in a particular shape to give it the strength to handle the torque through its geometric design. These monolithic seal face designs have been made possible through the use of Finite Element Analysis (computer modeling).

Monolithic seal faces provide a more stable fluid film between the faces, and they do not deform in operation compared to inserted faces (or to a much lesser degree). Therefore, they are more commonly used nowadays when reliability and low emissions are vital.

All mechanical seal designs have at least one secondary seal that interacts with the dynamic movement of theflexible mounted face. This secondary seal moves with the springs to keep the seal faces closed and is defined as thedynamic secondary seal. During operation of a rotary design, springs will keep the seal faces closed. They adjust with each rotation for any misalignment from installation and parts tolerances. As the springs compensate, the dynamic secondary seal moves back and forth, twice per revolution. This rapid movement prevents the protective chrome oxide layer (the layer that protects the metal) from forming. Erosion of this unprotected area under the dynamic secondary seal will cause a groove to develop. Eventually this groove becomes so deep that O-Ring compression is lost and the seal leaks. In most cases, fretted shafts must be replaced to achieve an effective seal.

With rotary mechanical seals, it is important that the stuffing box face is perpendicular to the shaft for the faces to stay closed. There will always be some resulting misalignment from installation and parts tolerances. The springs must adjust with each rotation to keep the seal faces closed. This adjustment becomes more difficult at higher speeds.

In contrast, a stationary seal is a mechanical seal designed in such a way that the springs do not rotate with the pump shaft; they remain stationary. Because the springs do not rotate, they are unaffected by rotational speed. The springs do not need to correct or adjust with each rotation; they adjust for misalignment only once when installed.

Rotary seals are simple in design which makes them inexpensive. They are suitable for lower speeds only. Stationary seals are more complicated to design but are suitable for all speed ranges. Because of design complexity, stationary seals are more commonly configured as cartridge seals rather than component seals.

Marco Hanzon is Vice President of Global Marketing for A.W. Chesterton Company. He has been an active member and past chairman of the Mechanical Seal Committee of the European Sealing Association. Marco"s experience includes working as an In-Field Support Engineer for mechanical seals.

Reverse balanced mechanical Seal which is called shortly RB seals are assembled outside of the pressurised area. Because of less contact of pumping medium on the face of the seal, the rpm of the shaft should be very less enable to reduce the face friction temperature. Due to these drawbacks, we can use these types of seals only in agitator/mixture/blender machine shafts with low rpm from 1rpm to 800rpm. In some special cases, we can use the same seal at higher rpm with the support of external coolant.