Some large diameter equipment, such as hydraulic swivels and passive rotating control devices (RCDs), has limited available torque to initiate rotation. When limited available torque is combined with higher pressure sealing requirements, rotary seal breakout torque can exceed available torque. Kalsi Engineering has developed and tested two technologies that significantly reduce the breakout torque of Kalsi Seals while providing high differential pressure capacity. The lowest breakout torque can be achieved using a plastic lined Kalsi Seal. The -307 material provides the lowest breakout torque while the -303 material combines low breakout torque with the highest available differential pressure capacity of any Kalsi Seal. For applications where a plastic lined seal is unsuitable, elastomeric Kalsi Seals can be provided with a low friction treatment.
We completed a series of tests comparing the room temperature breakout torque of standard width Kalsi Seals made with -307 (HNBR with an integral plastic liner), -106 (dual modulus), and -106 LF (dual durometer with low friction treatment) construction. The test setup consisted of a pair of Kalsi Seals retaining Aeroshell 560 lubricant (28 cSt viscosity at 40°C) at 1,000 psi. The dwell time under pressure was 7 days. The table below shows the breakout load, FBO. The -307 seals have 32% of the breakout torque of -106 seals and 57% of the breakout torque of -106 LF seals. The -106 LF seals have 55% of the breakout load of -106 seals.
We also have preliminary tests comparing the room temperature breakout torque of Extra Wide Kalsi Seals made of -307 and -303 plastic lined construction. These tests consist of a pair of Extra Wide Kalsi Seals retaining Aeroshell 560 lubricant at 1,000 psi. The dwell time under pressure was 7 days. The -307 seals have 86% of the breakout torque of the -303 seals.
Breakout load results from standard width Kalsi Seals using Aeroshell 560 lubricant at room temperature;
To estimate seal breakout torque for a shaft of diameter, D, multiply FBO by D^2.
Of all the Kalsi Seals constructed entirely of elastomer that have been tested to date, the -106 LF construction provides the lowest breakout torque. Seals made with the -307 plastic lined construction have significantly less breakout torque than seals made with the -106 LF construction, and roughly the same high pressure extrusion resistance. Seals made with the -303 construction have significantly better high pressure extrusion resistance, compared to seals made with the -307 construction, and only slightly higher breakout torque. The -303 and -307 composite materials are excellent choices for rotary shaft seals used in torque sensitive applications, such as hydraulic swivels and passive RCDs. For available sizes of plastic lined seals, see our shaft seal catalog. For additional information, contact our staff.