1. Field of the Invention
This invention concerns a rotary machine coupled to a drive source by a magnetic coupling. In particular, the invention concerns a sealing arrangement for such a machine which is submerged in liquid, which may be water or a chemical liquid in a tank.
2. Description of the Prior Art
Machines are well known for compressing or expanding a fluid for the chemical industry or for oil and gas processing. The machines have included a rotor mounted on a stator to rotate in a fluid chamber, a rotary shaft on which the rotor is fixed, and which extends outside the stator through a shaft passage thereof Bearings are mounted in the shaft passage for guiding and supporting the shaft. Outside the stator, the rotary shaft is connected to a drive shaft from a drive source such as a motor or a turbine or the like.
U.S. Pat. No. 5,334,004 to Lefevre et al. shows a compressor or turbine where the drive shaft is magnetically coupled to an external drive source but with the internal drive shaft enclosed in a bell filled with a liquid under pressure. A closed enclosure is formed around the shaft passage which receives the shaft which drives the rotor. The Lefevre arrangement prevents leakage of dangerous gas from the inside to the outside of the rotary machine.
A primary object of the invention is to provide a sealing arrangement for a magnetically coupled rotating machine.
Another object of the invention is to provide system reliability for a rotary machine which is installed in a submerged environment such as water or a liquid chemical.
The machine of the invention includes a housing with a rotor mounted on a shaft supported by bearings which are separated, according to a first embodiment, from the fluid being processed by the rotor by means of high pressure, heavy duty mechanical seals. A barrier fluid between the mechanical seals and a rear magnetic housing, or “bell,” is provided under high pressure. According to a second embodiment, the seals of the first embodiment are eliminated such that the rotor pressure is applied directly to the shaft bearings. In both embodiments, a cavity on the outside of the housing surrounds one magnet of the magnetic coupling and is filled with another liquid under pressure that enables the entire arrangement to be submerged in a deep sea environment or in a tank containing liquid chemicals while providing a barrier from seawater or chemicals entry into the housing.
An internal magnet 20 is fixed to an interior end of rotary shaft 14. A first enclosure 22 surrounds the internal magnet 20 and is formed by the bell shaped member 24 and the shaft passage 16. The first enclosure extends to a seal structure 26 which may be a dual or single mechanical seal. A dual seal 26 is illustrated in
As illustrated in
The rotary shaft 14 is driven by magnetic coupling between internal magnet 20, inside bell 24, and external magnet 25 which is rotated via motor shaft 38 by a motor 50 disposed in a motor cavity 40. Pressurized liquid is provided in the motor cavity 40 and a second enclosure 45 which surrounds the external magnet and motor shaft 38. The motor cavity 40 and second enclosure 45 are pressurized to a pressure P4 by a pressure source/compensator 31. The pressure P4 may be slightly higher than the ambient pressure P5 for subsea conditions (or chemical tank conditions) which could typically be from 0 to 300 bar.
The entire machine of
The arrangement described above provides a sealing mechanism for rotating machines such as a pump, cyclone, separator, or turbine for either water, hydrocarbons, chemicals or slurry applications. The arrangement is especially designed for such rotating machines which are submerged in the sea. The arrangement provides sealing of components to achieve system reliability. It also enables separation of the process fluid, which may contain sand particles, from other vital components such as bearings and the magnetic coupling.
As illustrated in
The dual mechanical seals 26A, 26B, one 26A facing the process cavity 34, the other 26B facing the barrier cavity 22, provide added security against failure. If sand particles or the like were to penetrate the seal 26A facing the process cavity 34, a second seal barrier 26B exists to inhibit particle intrusion into the cavity 22 in which the bearings are positioned.
It is preferred to provide seals 26 which are capable of handling “reverse” pressure. Such a condition would exist where pressure P1 in process cavity 34 is larger than pressure P2 or P3 in barrier cavities 21, 22. Seals 26A, 26B are preferably hard surface seals so as to be able to withstand operation with sand particles in the liquid.
Although dual mechanical seals are preferred, a single mechanical seal can be provided, whereby a single pressure is provided rather than the two pressure P2 and P3 as illustrated in
As indicated above,
The arrangements of
As illustrated in
The motor 50 and motor cavity 40 can be pressurized by a liquid, shared with the liquid in the second enclosure 45. The liquid is supplied and pressure compensated by source/compensator 31. The pressure P4 is compensated toward the ambient pressure condition P5 of the subsea environment or chemical liquid in a chemical tank. The pressure P4 of the second enclosure 45 of
This application is a continuation of U.S. Ser. No. 14/218,640, which was filed on Mar. 18, 2014, entitled “Sealed Magnetic Drive for Rotary Machine” and is incorporated by reference herein for all purposes.
Number | Date | Country | |
---|---|---|---|
Parent | 14218640 | Mar 2014 | US |
Child | 14516079 | US |