Kalsi Engineering manufactures extremely capable high pressure shaft seals. The ultimate pressure capacity depends on various factors, such as the type of seal carrier and extrusion gap clearance that are used, the seal material, the rotary speed, the ambient temperature, the degree of available heat transfer, and the required seal life.
Using the best seal carrier design practices, we have tested 2.75" (69.85mm) plastic lined Kalsi Seals at 7,500 to 7,800 psi (51.71 to 53.78 MPa) against a hollow rotating washpipe for 1,000 hours. This is the highest pressure we have tested to date, and the rotary seals were still in excellent condition at the end of the test. The surface speed of the washpipe was 252 feet per minute (1.28 m/s). The ISO 150 viscosity grade lubricant was maintained at 130°F (54.44°C) by a small amount of fluid circulation within the rotating washpipe. We are unaware of any other polymeric rotary seal with equal high pressure capacity. Even higher pressures can be achieved by pressure staging.
What is the difference between partitioning seals and pressure-retaining seals?
Kalsi-brand shaft seals hydroplane on a lubricant film, which is one of the keys to their exceptional high pressure capacity. In order to exploit this advantage, one side of a Kalsi Seal must be exposed to a lubricating oil. When Kalsi Seals are used to retain a pressurized media, two shaft seals are required: One seal partitions the pressurized media from the seal lubricant, and the other seal retains the lubricant and partitions the lubricant from the ambient lower pressure fluid environment (such as atmosphere).
In traditional Kalsi Seal implementations, the seal lubricant is pressurized to a value that is equal to or slightly greater than that of the pressurized media. In such cases, the seal facing the pressurized media is referred to as the “partitioning seal” because it partitions the pressurized media from the lubricant. The seal facing the ambient fluid environment is referred to as the “pressure-retaining seal” because it is exposed to the pressure difference between the pressurized seal lubricant and the ambient environment.
The traditional seal implementation described above uses rotary seals that are designed to be exposed to differential pressure acting from the lubricant side. This requires a pressurized lubricant supply, which is not always practical or economical. To address the need for a simpler implementation, Kalsi Engineering has developed special hydrodynamic seals that can operate with a lubricant pressure that is up to 500 psi less than that of the pressurized media. These seals permit the use of simple gravity fed lubricant reservoirs. Although two shaft seals are still required to retain the lubricant, the outboard seal can be a simple radial lip seal. Most rotating equipment uses bearings that are protected by seals, so the need for an outboard lip seal is not an onerous requirement.
Kalsi Engineering continues to innovate in this area. We believe we will eventually be able to introduce products with increased high pressure seal performance that are capable of operating with a lubricant pressure that is up to 1,000 psi less than that of the pressurized media.
What materials allow Kalsi shaft seals to operate with high differential pressure?
Kalsi Seals are available in a variety of materials and high pressure shaft seal designs. Our proprietary -303 plastic lined seal construction is used with our enhanced lubrication seal geometry to provide the highest pressure capacity of all our rotary seals. Seals with -307 and -308 plastic lined construction have a pressure capacity in about the same range of our best all elastomer seals, but with much less breakout torque.
We offer several all-elastomer material combinations for high differential pressure service. The most capable of these are dual durometer seals that have a dynamic lip constructed of our -18 material (95 Shore A HNBR). The next material, in order of extrusion resistance, is our -15 material (90 Shore A HNBR). For a complete list of all our seal material options, visit our materials web page. Our rotary seal handbook describes the various seal materials and geometries we offer, and describes how to implement the seals in rotating machinery.