ANTI-KEYSTONE® Packing Technology Design History
When it was incorporated in 1979, New England Braiding Co., Inc. manufactured conventional square-shaped compression packings. Many people in our industry know what mechanical compression packing is and why it’s needed. Not everyone knows that the standard square packing shape is part of the cause of many issues with sealing mechanical compression packing effectively.
When standard square shaped packing is installed around a shaft or sleeve, the square shape deforms and becomes trapezoidal in nature (like an upside-down keystone) as the outer diameter of the packing ring is larger than the inner diameter. This causes the tops of the packing ring to pinch inward while the bottom of the ring (along the shaft) is spread out laterally.
When multiple rings are installed into the stuffing box the shape of the packing looks like this:
SQUARE PACKING KEYSTONING/CHANGING SHAPE PRE-COMPRESSION
“When adjacent rings are compressed in this manner, it creates hardened pressure points due to the difference in packing density. These pressure points are one of the main causes of equipment wear. The packing at those points rubs excessively against the shaft creating friction which can cause excess heat, increased flush water use and scoring of the shaft or sleeve”. This scoring creates a leak path increasing the drip rate of the equipment, when this happens a gland adjustment must be made to control the leakage. A common mistake is to over-compress the packing to stop the leak.”
After this process happens multiple times the packing can get pushed along the shaft and the lantern ring can change position over time which can block the flush port causing the pump to overheat leading to further equipment damage. Eventually the gland follower cannot be adjusted any further and the pump will have to be serviced and repaired before repacking the stuffing box.
SQUARE (KEYSTONE) PACKING SHAPE AFTER OVER-COMPRESSION
In pursuit of a product with superior performance our co-founder and mechanical engineer, Mr. George Champlin, solved the keystone/packing density issue. He invented a method of braiding the packing in a trapezoid shape when flat (straight). This revolutionary design eliminated the hardened pressure points that contribute to the majority of sealing problems by becoming square upon installation.
When multiple rings are installed into the stuffing box the shape of the packing looks like this:
ANTI-KEYSTONE® PACKING PRE-COMPRESSION
As a result of this new design, equipment wear was reduced, electric use and flush water demand all decreased allowing the pump to run more efficiently while further reducing normal leakage rates.
New England Braiding Co.’s ANTI-KEYSTONE® design was the original trapezoidal shaped packing: symbolized by NEBCO’s™ original logo for the ANTI-KEYSTONE® packing design, for which several US and Canadian patents were issued from 1985 through 1989.
After many installations and much further testing, a dramatic improvement was achieved with the invention of the six-sided ANTI-KEYSTONE® Ⅱ Packing Technology (AKⅡ®). Essentially a “Rectangle over a Trapezoid”, this packing design retains its shape when wrapped around a shaft.
This design change resulted in additional benefits beyond those of the original design. These benefits included, increased side to side contact between adjacent rings leading to better “seating” upon compression. Proper seating and compression minimizes the probability the newly installed packing rings “pick up” and spin with the shaft, which can generate excessive heat causing the packing to glaze (or harden) and ruining the packed seal.
The additional material also creates a miniature void in between adjacent packing rings which performs similar to a labyrinth seal. The ANTI-KEYSTONE® Ⅱ (or AKⅡ®) packing still retains all the operational benefits of the original design. As a result, general pump maintenance is reduced, the packing rings are replaced less often while operational costs are further reduced by using less energy and water.
When multiple rings are installed into the stuffing box the shape of the packing looks like this:
ANTI-KEYSTONE® Ⅱ PACKING PRE-COMPRESSION
US and worldwide patents were issued for this new packing design between 1995 and 1998. Symbolized by our ANTI-KEYSTONE® Ⅱ and AKⅡ® logos.
With this evolution in packing technology the “keystone effect” is eliminated allowing the packing to create a better seal and improving the efficiency and service life of the equipment.
Left Picture: Six months service in paper stock using a conventionally braided square aramid-reinforced PTFE/Graphite packing.
Right Picture: Thirteen months service in paper stock using our unique ANTI-KEYSTONE® Ⅱ aramid-reinforced PTFE/Graphite packing.