Fluid handling – Processes – Involving pressure control
Reexamination Certificate
2003-04-28
2004-10-19
Hepperle, Stephen M. (Department: 3753)
Fluid handling
Processes
Involving pressure control
C137S505000, C137S505420, C137S551000, C137S624140
Reexamination Certificate
active
06805145
ABSTRACT:
The invention relates to a method for maintaining a fluid pressure within a defined volume, and simultaneously registering discharge of fluid from the volume as a result of leakage or consumption.
The invention further relates to a regulating valve for maintaining a fluid pressure within a defined volume, and for simultaneous registering of discharge of fluid from the volume a result of leakage or consumption, which valve comprises a valve housing having a first chamber constituting said volume and communicating with a valve outlet, and a piston arranged in the chamber and being influenced in a first direction by a biasing spring and a reference pressure, and cooperating through an operating rod with a valve body for opening and closing of a passage between a valve inlet and the upstream end of the chamber, the valve body being spring-loaded towards the closed position in the opposite direction to that of the piston, so that the valve is closed when the piston is in equilibrium in the chamber at a first pressure in the chamber, but opens when the pressure in the chamber sinks below the first pressure.
Such a method is of interest in connection with the operation of rotating machines for use in subsea installations for oil and gas production, to keep control of pressure conditions and a possible leakage in mechanical seals in such machines. Typical machines will be multiphase pumps, wet gas compressors, water injection pumps, rotating separators, etc. Such mechanical seals for example are used for sealing between a process liquid and a barrier liquid in case of rotating shafts, and the sealing function often is contingent upon having a hydraulic overpressure from a pure barrier liquid lying for example 10-20 bar above a surrounding pressure which normally will be the process liquid pressure. The mechanical seals normally have a certain leakage of barrier liquid into the process liquid. It is therefore necessary to provide for a continuous supply of barrier liquid. After some time of operation the consumption of barrier liquid in subsea installations may increase because of wear of the mechanical seals, and it may be necessary to carry out an overhaul of the rotating machine. In this connection it is important to have a continuous control of the barrier liquid consumption, so that replacement can be planned and carried out in time.
In the rotating machines which are installed at the seabed today, and which utilise a barrier liquid for lubrication and cooling, the pressure regulation usually takes place from a platform or a production ship. The pressure is controlled by a hydraulic power unit (HPU) on board the platform or the production ship. The pressure is set on a fixed pressure or is changed based on pressure signals from the machine and the process at the seabed. Such a system has a slow response and will only be used in case of relatively short distances between the HPU unit and the subsea installation. Such a system will also have limitations at greater ocean depths because of static head and thereby a minimum pressure below which the system can not regulate.
There are also known other subsea regulating systems in which a pressure regulating function is effected at the seabed. These known solutions are relatively complicated and space demanding, the solutions consisting of a system having a major number of valves, compensator bellows against process pressure, etc.
The object of the invention is to provide a method and a device implying a very simple pressure monitoring and pressure regulation in connection with mechanical seals of the relevant type, and which solve the problems discussed above in that the regulation takes place locally at the rotating machine.
The above-mentioned object is achieved with a method of the introductorily stated type which, according to the invention, is characterised in that the fluid is supplied from a pressure regulating valve provided with a means opening for the supply of fluid to the volume when the pressure therein has sunk bellow a first value, and shutting-off the fluid supply when the pressure in the volume has reached a preset second value which is substantially higher than the first value, a pressure pulse delivered from the regulating valve thereby being registered, and that the frequency of delivered pressure pulses is monitored and utilised as a measure of occurring leakage and/or consumption of the fluid.
The stated object is also achieved with a regulating valve which is of the introductorily stated type, and which is characterised in that the valve is provided with a means causing that movement of the valve body to the closed position of the passage only takes place at a second pressure in the first chamber which is substantially higher than the first pressure, so that a distinct pressure increase occurs at the valve outlet after each opening of the valve. This pressure increase can be registered as a distinct pressure pulse even if the higher second pressure is not achieved immediately.
In the present invention said monitoring is carried out simply by registering the pressure pulses generated each time the regulating valve opens for the supply of fluid, i.e. barrier liquid, to the relevant volume. The pressure pulses suitably are registered with a standard pressure sensor mounted in the barrier oil circuit on the rotating machine. In case of installation of several rotating machines on the same subsea structure, these may use a common umbilical for the supply of barrier oil from the platform or production ship in question. This is connected to the valve inlet and has a constant supply pressure which is higher than the level of the outlet pressure of the valve at the valve outlet. Based on the frequency of the pressure pulses it will be possible to monitor the sealing condition and compensate for the current barrier liquid consumption. The valve device according to the invention only consists of a valve housing and constitutes a much simpler and more compact solution than what is used in the prior art.
REFERENCES:
patent: 2586131 (1952-02-01), Wells
patent: 3621887 (1971-11-01), Johnson
patent: 5234026 (1993-08-01), Patterson
patent: 0 964 235 (1999-12-01), None
patent: 2 099 112 (1982-12-01), None
patent: WO 99/28722 (1999-06-01), None
patent: WO 01/50052 (2001-07-01), None
Framo Engineering AS
Hepperle Stephen M.
Wood Phillips Katz Clark & Mortimer
LandOfFree
Method and device for maintaining a fluid pressure in a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and device for maintaining a fluid pressure in a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and device for maintaining a fluid pressure in a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3316146