Pushing the envelope of mud seal design

Kalsi Engineering just finished the inaugural testing of a radical new partitioning seal that was designed for mud-oil separation (mud seal service) in oilfield power swivels and other lubricant overpressure-type rotating equipment. In such equipment, the pressure of the seal lubricant is maintained at a value that is slightly higher than the pressure of the abrasive drilling mud environment to orient the mud seal.

The 2.75” mud seal (prototype PN 300-133-11, production PN 739-1-11) uses Kalsi type F Enhanced Lubrication™ waves, and has a wider dynamic lip than we have ever tested before. At the narrowest part of the wave, the dynamic surface is twice as wide as that of our Extra Wide Enhanced Lubrication Seal™ product line. The purpose of the extra lip width is to provide extra sacrificial material to accommodate third body abrasive wear. Through careful seal design, the impact on groove width has been minimized, and the new seal fits in a groove that is only 0.460” wide.

Two tests of the new mud seal have been performed at speeds bracketing the operating speeds of typical power swivels. Both tests were performed with a drilling mud environment, an ISO 68 viscosity grade synthetic hydrocarbon seal lubricant, and a radial extrusion gap clearance of 0.020”. Mud was replaced daily.

The first test was performed at 200 rpm, and the bulk lubricant temperature was limited to 162°F by undersleeve coolant circulation. The test was dismantled after 305 hours of operation to inspect the mud seal. The seal was exposed to drilling mud for 284.27 hours of the test, and was still in excellent condition at the conclusion of the test (see photo below). This test included periods of 15, 62, and 200 psi lubricant overpressure. The hydrodynamic pumping related leakage per seal was 1.99 ml/hr at 15 psi, 4.02 ml/hr at 62 psi, and 6.02 to 9.73 ml/hr at 200 psi. Additional testing will be performed at 200 rpm and 200 psi lubricant overpressure to collect more leakage data.

The second test was performed at 80 rpm with 100 psi lubricant overpressure, and the bulk lubricant temperature typically did not exceed 112°F. The test was terminated at 211.68 hours to inspect the mud seal, which was still in excellent condition (see photo below). Hydrodynamic pumping related leakage ranged from 2.25 to 2.65 ml/hr per seal at an average temperature of 102°F.

For available sizes of these Super-Wide mud seals, see our shaft seal catalog. Contact Kalsi Engineering for additional information.


This is the used mud seal from the first test after 284.27 hours of 200 rpm operation while exposed to oilfield drilling mud, and 305 hours of total rotation.


This is the used mud seal from the second test after 211.68 hours of 80 rpm operation while exposed to oilfield drilling mud.