Radiant energy – Invisible radiant energy responsive electric signalling – Flow metering
Patent
1994-07-06
1995-12-26
Fields, Carolyn E.
Radiant energy
Invisible radiant energy responsive electric signalling
Flow metering
G01N 2312, G01F 100
Patent
active
054790204
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a metering device for a fluid.
BACKGROUND OF THE INVENTION
Particularly in the context of oil extraction systems, it is required to measure the proportions of the components in a multi-phase fluid flow, for example, a crude oil flow containing gas and/or water in varying proportions. It has been proposed in WO 90/13859 (FD20) to provide a mixer apparatus for fluids incorporating a choke or venturi, and to associate measuring or metering equipment with the venturi to determine mass flow rates of the fluid phases flowing through it. Such metering equipment can include a densitometer employing a .gamma. or X-ray source located at one side of the fluid flow for transmitting its radiation transversely through the fluid to a radiation sensor or detector located at the other side of the fluid flow.
The use of a .gamma. or X-ray source and detector presents a problem for such metering equipment in that the tubing within which the fluid flow is confined should be highly transparent to the metering radiation whilst being resistant to the fluid flow and having necessary strength and rigidity. The first of these requirements effectively precludes the use of steel tubing and it has been proposed in EP 0 236 623 to employ beryllium as the material of the wall of the tube across which the radiation is transmitted. The toxicity of beryllium however presents manufacturing problems.
SUMMARY OF THE INVENTION
The present invention accordingly relates to a metering device in which radiation from a source is transmitted through a multiphase or other fluid to be entered to a sensor or detector responsive to the radiation from the source. The invention is concerned with the provision of a device of this kind in which tubing guiding a flowing fluid has appropriate mechanical and physical characteristics and does not unduly attenuate the radiation to be transmitted across it.
The invention accordingly provides a metering device of the kind described in which the material of the tubing wall, or other tubing portion through which the radiation is transmitted, is boron carbide (B.sub.4 C). Boron carbide has appropriate absorption (or transparency) characteristics for .gamma. or X-rays and is not adversely affected by exposure to such multiphase fluids as are encountered in oil production systems, namely, oil mixed with variable proportions of gas and/or water.
Boron carbide is not however ideal in respect of its mechanical properties. The invention accordingly also provides a metering device of the kind described in which the tubing comprises an inner tube or sleeve of material having high transparency to the radiation, for example, boron carbide, and a reinforcing or supporting outer layer providing additional mechanical strength. The outer layer should of course be as transparent as possible to the radiation. The outer layer can comprise a thread or fiber or other elongate element wound around the sleeve, preferably embedded in a settable plastics material to force a coating of fiber reinforced plastics material. For example, carbon fiber can be wound externally around the boron carbide sleeve to preload the sleeve against the forces it will experience, and the fiber then embedded in the settable plastics material, for example, an epoxy resin. The coating can be employed to bond the inner tube to an external support tube, for example, of steel, provided with apertures, conveniently in the form of aligned radial bores, which can function to collimate the radiation, for the unobstructed transmission of the radiation through it.
The invention also provides a metering device of the kind described in which tubing guiding the fluid flow comprises a tube of material of appropriate mechanical properties, for example, steel, provided with aligned transverse apertures for the radiation, the apertures being closed by elements of material, for example, boron carbide, of relatively high transparency to the radiation. A steel tube can thus be provided with aligned radial bores closed by plugs
REFERENCES:
patent: 2953681 (1960-09-01), Frazier
patent: 4862490 (1989-08-01), Karnezos et al.
patent: 5025160 (1991-06-01), Watt
Fields Carolyn E.
Framo Developments (UK) Limited
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