GB2224120A - Remotely controlled thermal actuator - Google Patents

Abstract

An arrangement for the remote control of an actuator comprises an energy transmitting conduit (1), a radiant energy source for transmitting radiant energy along the conduit from one end thereof and an actuator, at the other end. The actuator comprises a chamber (8) containing a volatile liquid, which on receipt of energy from the radiant energy source, is caused to vaporize to displace a valve-operating element (7). The energy may be I.R. microwave, heat or from a laser. The conduit is pressurised and when the element (7) is sufficiently displaced the pressure is available via conduit (6) and port (10) as power source. The apparatus is for use in under sea oil installations, chemical and nuclear power industries and for the remote control of vehicles. <IMAGE>

Description

REMOTE CONTROL SYSTEMS Field of the Invention This invention relates to remote control systems for, for example, controlling operation of an underwater valve of an oil or gas pipeline.

Background of the Invention Equipment controlled from a remote source or base is normally connected to the source or base by some form of umbilical cord such as an electric cable, a hydraulic or pneumatic hose or a wire. More sophisticated systems which have been utilised include radio, direct microwave or acoustic control systems but these can be vulnerable to interference. They also often require a good line of sight between the remote source or base and the equipment.

When long distances are involved, for example distances of the order of 10 kilometres, which may be the case in respect of equipment that is mounted underwater, umbilical systems tend to be favoured. The principal reasons for this are reliability and the capability of transmitting sufficient power to the equipment to facilitate direct operation of movable components such as valves. Wire cables are too cumbersome and impractical for operation over such distances and direct pneumatic power suffers from long transmission time lags due to having to overcome the compressi bility of gases and the relatively low rate of travel of a compression signal in a pneumatic power line. Of the remaining transmission media, hydraulic systems are efficient for transmitting power but still suffer from response delays when long distances are involved.

Electrical control systems have a rapid response but tend to be vulnerable to breakdowns associated with water ingress.

Alternatively, electrical systems can be complex and expensive and some are both complex and expensive and vulnerable to breakdown.

It is accordingly an object of the present invention to provide a remote control system which is of more general application than the remote control systems at present in use. It is a further object of the invention to provide a remote control system that has a rapid response but does not involve electrical components or circuitry at the location of the terminal or equipment which is to be controlled.

Summary of the Invention The invention provides a remote control system comprising an energy-transmitting conduit, a radiant energy source for transmitting radiant energy along the conduit from one end thereof and a responder at the other end of the conduit, said responder comprising a chamber containing a volatile liquid which, on receipt of energy from said radiant energy source, is caused to vaporize to effect displacement of a valve-operating element.

The conduit may be in the form of a flexible tube having a reflective inner surface. The tube may, for example, have an inner lining manufactured from a material which is highly reflective, for example polished stainless steel. Alternatively, the tube may be formed from a synthetic plastics material, the inner surface of which is coated with a layer of a reflective material as, for example, by chromium plating. Such a tube may be used, for example, for the transmission of infra-red or microwave radiation.

As an alternative, the conduit may be in the form of an optical fibre or fibres and the radiant energy source may be a laser.

The flexible tube may itself function as a pneumatic power line, the flexible tube containing a gas under pressure, which pressurised gas provides an operating means responsive to operation of the valve-operating element.

Brief Description of the Drawings Figure 1 illustrates schematically a remote control system for the activation of a sub-sea valve from the surface station mounted upon an oil rig or production platform, and Figure 2 is a sectional view of the valve.

Description of the Preferred Embodiment As shown in Figure 1, a remote control system comprises an umbilical 1 in the form of a flexible tube which extends between a sub-sea valve 2 and a control station. The flexible tube 1 may have an inner lining which is manufactured from a material which is highly reflective, for example, polished stainless steel. Alternatively, the flexible tube may have a lining formed from a synthetic plastics material coated with a reflective medium, for example, a layer of chromium plate. The sub-sea valve 2 is shown in more detail in Figure 2 and operation thereof is under the control of a radiator 3 located at the control station.

The radiator 3 may be a heat radiator, for example, a halogen bulb, or it may be a microwave radiator, the radiator being arranged so that it can be switched on or off to effect control of the valve 2. The radiator 3 is coupled efficiently to the upper end of the umbilical or flexible tube 1 to permit propagation of radiant energy along a path which is closely parallel to the longitudinal axis of the tube.

As shown in Figure 2, the flexible tube 1 is connected to the valve body with the end of the tube 1 engaged in a socket within which is located a heat-conducting diaphragm 4. The diaphragm 4 forms part of an actuator chamber 8 which, in turn, is coupled to a valve spool 7. The actuator chamber 8 has a cylindrical wall which is constructed from a flexible metal bellows which is secured, as by welding, to the diaphragm 4 and to the spool 7 to form a gas-tight enclosure.

The valve spool 7 has a through port closed by a plug 9 and a low boiling point liquid is introduced into the chamber 8 via the port which is then closed by means of the plug 9.

The low boiling point liquid can be, for example, a halogenated hydro carbon. For sub-sea applications in, for example, the north sea, the valve body will be retained at a constant standby temperature of the order of 4" centigrade, i.e. that of the surrounding seawater and the halogenated hydro carbon which is chosen may typically have a boiling point between 10 and 20 centigrade.

The flexible tube 1 acts as a wave guide and, in some respects, it is of advantage to have a small-bored tube since the incident angle of any wave radiation reflecting from its inner surface is then optimised to produce minimal energy losses. The flexible tube 2 may contain a low density gas which is maintained under an elevated pressure to provide a power source for operation of a main sub-sea valve. As an alternative, the gas within the tube 1 may be maintained at substantially less than atmospheric pressure to provide a vacuum effect. As a further alternative, a separate hydraulic power source may be provided.

In use, radiant energy from the radiator 3 directed through the umbilical or flexible tube 1 will be received by the diaphram 4 and will cause the liquid in the chamber 8 to vaporize.

This vaporization of the low boiling point liquid in the chamber 8 will create expansion of the bellows and consequent movement of the valve spool 7. In the position shown in figure 2, the valve spool 7 acts to prevent communication between a bypass line 6 and a pilot port 10. When, however, the valve spool 7 moves to the right of the position shown in Figure 2, the gas within the flexible tube 1 is free to pass through the bypass line 6 to the pilot port 10 to operate either a main valve or further pilot valves. When the radiant energy source 2 is switched off, the temperature of the gas within the chamber 8 will fall as a result of the continuous cooling of the valve 2 from the surrounding seawater. As the gas within the chamber 8 condenses, the valve spool 7 will return to its original position thus relieving the valve of its activating pressure.If valve activation speed is of particular importance, a double-acting arrangement may be used with horizontally opposed actuator chambers positioned one at each end of the valve spool 7.

Since the transfer of control energy is essentially by radiation, the operating speed of the valve is substantially directly related to the time taken for the transfer of energy within the valve 2 itself and is not related to the length of the umbilical or flexible tube 2. Appropriate selection of the valve chamber components will permit relatively rapid operating times as compared to hydraulic control lines as at present employed, particularly for long umbilicals typically of the order of 10 kilometres in length. A further advantage of the invention is that it provides limited component vulnerability with no underwater electrical connections, batteries or power generation systems.

If the gas within the transmitting umbilical or flexible tube is maintained at an elevated pressure, this will serve to purge water from the control line. The valve components and interconnections will be produced from materials which are resistant to chemical and galvanic corrosion when exposed to seawater.

Typical materials include titanium, aluminium bronze and the alloy sold under the registered trade mark NInconel".

The remote control system may be used in connection with a remote optical fibre displacement measuring system as described in co-pending application number 86 14222. The optical fibre of the measuring system may be part of the control umbilical or flexible tube 1 and the measuring system may provide a feedback signal which is used to effect proportional control of the valve or other operating element, for example, a positionable hydraulic actuator, should the need arise.

Although a particular application of the remote control system is the control of underwater valves, the invention is not restricted to such applications. The system may be used in, for example, the chemical and nuclear industries where operation within hazardous environments prohibits or limits the use of electrical systems.

Another possible application of the invention is in a remote control system for a vehicle where other criteria, such as weight saving factors ,may be of particular significance.

Claims (5)

CLAIMS:

1. A remote control system comprising an energy-transmitting conduit, a radiant energy source for transmitting radiant energy along the conduit from one end thereof and a responder, at the other end, the responder comprising a chamber containing a volatile liquid, which on receipt of energy from the radiant energy source, is caused to vaporize to displace a valveoperating element.

2. A system according to Claim 1 and in which the conduit is in the form of a flexible tube having a reflective inner surface and with the inner surface comprising either a reflective inner lining of for example polished stainless steel, or being formed from a synthetic plastics material, the inner surface of which is coated with a layer of reflective material for example by chromium plating.

3. A system according to claim 1 and in which the conduit is in the form of one or more optical fibres with the radiant energy source being a laser.

4. A system according to any of the preceding Claims, in which the conduit functions as a pneumatic power line, the conduit containing a gas under pressure, the pressurised gas providing a mode of operation in response to operation of the valve-operating element.

5. A remote control system substantially as described herein with reference to and as illustrated in the accompanying drawings.