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AS&P - Special Seals

ASP-1 & lB Single Spring Seals

Characteristics: Single coil spring, can have stamped/machined parts. Rubber bellows drive with drive band, rotating face may be various materials.

lB Single Spring Seals


ASP-21 Single Spring Seals

Characteristics: Single coil spring, stamped metal parts, rubber bellows drive with drive band, carbon rotating face, short operating height, low cost industrial seal usually a throwaway, limited repairs, unbalanced.


ASP-6 Single Spring Seals

Characteristics: Single coil spring Seal, stamped metal parts, external rubber bellows and square rubber drive ring. Molded plastic rotating face (carbon available), low cost, produced in high volume, throwaway seal not repairable and is unbalanced.

ASP-2 & 2B Single Spring Seals

Characteristics: Single coil spring, can have stamped/machined metal parts. Rubber bellows drive with drive band and carbon rotating face.

2B Single Spring Seals

Mechanical Seal History

Mechanical seal types range from the simple to the complicated. Of course the most common mechanical seal is a single spring seal. Single spring seals were invented in the 1900s by George Cook far before John Crane, Burgmann, Chesterton, Borg Warner, Durametallic, Flowserve, Pac seal, U.S. Seal Mfg. existed. Today's list of mechanical seal manufactures continues to grow and includes: AS&P, AST, Delta, Sepco, Utex Industries, Flexaseal, Robco, and Anchor Industrial. International sources include: Pillar, Eagle, Burgmann, Vazel, Latty, Vulcan , Roten, Scenic, James Walker, and AES (among others). The seals have also become far more sophisticated.

The question George had to ponder was how to better seal a shaft that was rotating. At that time only braided packing was used. Back then, all packing had to drip to function so there was no way to properly seal a shaft from leakage. The packing's of the day included: jute, hemp (which encouraged smoking a pump) and flax (all plant-based products with limited capability).

George's mechanical seal was it a giant leap forward for engineering. Mechanical seals began by utilizing a single coil spring. Single spring seals are now the most common type available. Due to space restrictions with a large coil spring, however, multi-spring seals and wave spring seals were developed.

As materials evolved so did the mechanical seal. Seal face materials, metallurgies, and secondary elastomer seals all increased mechanical seal capabilities. New designs evolved that capitalized on the new materials. Metal bellows were formed by very tight welding technologies that also had evolved. Because a metal bellows seal will have a static seal on the shaft, a new material called flexible graphite expanded the temperature range of mechanical seals.

Two applications are very difficult for a single spring seal, multi-spring seal or a wave spring seal to function. Heat is the most significant of the two. Spring seals are not only effected by heat, but because the secondary seals are required to be dynamic seals, flexible graphite cannot be used in them. Metal Bellows seals can utilize a flexible graphite wedge to seal the shaft. The flexible graphite is compressed forcing a seal on the shaft by use of set screws at the base of the seal. In previous designs o- rings or a rubber boot were utilized. Flexible graphite is good for a maximum of 850 degrees Fahrenheit ( with oxygen present) and a maximum of 5400 degrees Fahrenheit (with no oxygen present) so, it can be utilized and a far broader range of applications then any elastomer.

A surprising fact about mechanical seals is 50% of failures are caused during installation. The usual reason for this is that seal faces are generally compressed approximately 1/8 of an inch. If the mechanical seal is not positioned correctly on the shaft during installation in the pump the mechanical seal can be over compressed causing premature wear. If the seal is under compressed it will take minimal internal pump pressure to overcome the spring and cause leakage or not seal at all at startup.

The easiest way to overcome installation failures is to utilize a cartridge seal. Cartridge seals consists of a stationary a rotary a sleeve a gland and the connecting fittings to secure them.

Because cartridge seals are pre-assembled, the compression on the seal faces is pre-set. The cartridge seal faces cannot be over or under compressed (energized).

Because cartridge seals are pre-assembled, the compression on the seal faces is pre-set. The cartridge seal faces cannot be over or under compressed (energized).

Cartridge seals can be built utilizing any of the previous evolution styles of mechanical seals including single spring, multiple spring, wave spring, metal bellows or elastomer energized designs.

One of the more sophisticated styles of cartridge seals gaining popularity due to recent state and federal VOC (volatile organic compound) leakage limitations is the double cartridge seal. Because a fluid is maintained between the two pairs of seal faces minimal leakage is possible, and the fluid is contained.

Double cartridge seal rotary faces are mounted in one of three ways: back to back, tandem, or face to face. Which design is best depends on the application and who you talk to. The same can be said about which manufacture makes the best seal. In most cases successful sealing means applying the right design of mechanical seal to the right application. As seals are used and the carbon faces rub against the stationary faces they wear similar to tires, eventually failing. Seals fail like tires, usually the failure is catastrophic. Having a second set of seal faces allows the user to identify that the primary seals have failed while the secondary pair of seal faces contain the leakage. The internal failure of the primary seal faces is easily identifiable by the rising fluid level in the seal pot (the leakage has to go somewhere). Consulting experienced seal experts such as American Seal & Packing is recommended.

When you get more in depth into mechanical seals you begin to consider subjects such as friction ratios (PV), circulation, flushing, quenching, buffer systems and accessories, and various buffer mediums for various applications. It can get complicated.

Selecting the right seal face for your application will define how long your seal lasts. Carbon or even a phenolic face running against a ceramic stationary is most common and does fine in non-abrasive clean fluids such as oil and water. If your running into abrasives your going to want hard faces such as tungsten carbide or silicon carbide or both (running against each other). Chemical applications may require running carbon against a glass filled PTFE (since both have a 0-14 ph range). Knowing what is going to minimize your energy consumption requires considering the PV ratio (friction coefficient). Understanding your priorities and seal applications will help engineering provide a seal face recommendation.

Knowing the difference between flushing a mechanical seal and quenching a mechanical seal is important. Flushing is most common. You flush a mechanical seal to lower the temperature or prevent abrasive deposits from getting near the seal faces. When using a "seal pot" to contain the flush fluid (or buffer fluid) you must consider the purpose of the seal pot. Do you need to compensate for leakage, circulate the buffer fluid, cool the buffer fluid and how much do you need to cool the seal down by using the seal pot. Seal pots can be equipped with internal coils to cool or heat the buffer fluid. They can also be pressurized to overcome system pressure.

A quench on the other hand is used in mechanical seals when an application has a high melting point or vapor and prevents solidification of materials near the seal faces. Allowing a material to get near a seal face and harden will destroy seal faces quickly as the seal turns. Heavy hydrocarbon applications such as tar and asphalt are common quench scenarios. Quenching is also used to improve the flow of high viscosity products such as honey. Preventing crystallization prevents seal face damage. A gas quench is used for icing protection in applications where the temperature reach below 32 degrees Fahrenheit. Nitrogen or dry air is injected into the seal housing, to prevent ice from forming in the first place.

The newest developments in mechanical seals generally has to do with seal face design. Surface features on the seal face, or face topography, are utilized to create supportive forces to counteract the forces trying to crush the faces closed. Engineered patterns and grooves create a pressure profile. Contact loads are reduced using those patterns, grooves and topography on the seal face. Dry running seals or gas seals are designed this way.

In addition to the grooved and wavy seal faces, there are many varieties of micro-surface features that have been introduced into he market. The purpose is to optimize reliability and performance for particular problems. Seal designs will continue to evolve as the market and governmental demands for tighter seals continues to increase.