GB2244074A - Remote control apparatus - Google Patents

Abstract

A source 5 of pressure gas at a control location feeds through a conduit 123 to a hydraulic arrangement 101, 102 at a remote location (e.g. a subsea wellhead) to generate hydraulic pressures greater than the gas pressure for the operation of hydraulic equipment 162 through controls. The hydraulic arrangement comprises hydraulic units 101, 102 controlled to be acted upon by the gas pressure and exhausted alternately for continuous delivery of pressurised hydraulic fluid. The hydraulic arrangements 101, 102 include a hydraulic reservoir 138 adapted to recharge the hydraulic units. The arrangement may comprise several sets of units for the generation of several levels of pressure. Conveniently communication means for control means at the remote location are located within the gas passage of the conduit. <IMAGE>

Description

CONTROL APPARATUS TECHNICAL FIELD OF THE INVENTION This invention relates to control apparatus for controlling hydraulic fluid actuated means at a remote location from a control location, in particular it is concerned with the transmission and generation of power required at a remote location, and its control.

For example, hydraulic power at both 3,000 psi and 5,000 psi are typical requirements at a sub-sea well-head for the actuation of well-head controls, and greater pressures are becoming necessary. In fact, pressures up to 10,000 psi. are now needed for the operation of some control actuators at new wells under development.

Current methods generate the standard pressures at the control location (platform) and transmit the hydraulic fluid through small bores in an umbilical connecting platform to well-bead (remote location).

To withstand the pressure the bores have to be small, about 3/8" diameter, which on double-wire-braided hose, for example, is the maximum size for a working pressure of 5,000 psi.

But only a small amount of hydraulic fluid power can be transmitted over such distances through such a small diameter bore due to high pressure losses caused by frictional (viscous) flow of the hydraulic fluid. For example, a well-head may be 20 miles from its controlling platform and even at a flow rate as small as 1 gallon per minute (which could require 20 minutes or more for a large control valve to move from closed to open), the pressure drop could be over 3,000 psi, so that although there is a pressure of 5,000 psi at the platform, the operating pressure at the well-head would be only 2,000 psi, or less during a valve movement. This can be an unacceptable situation when more than one control is being operated at a time.

The present invention overcomes these difficulties, and caters for the provision of very high hydraulic pressures, by providing fluid power from the platform in the form of compressed gas, which has relatively low frictional loss in transmission through the bore of the umbilical.

At the sub-sea installation, (remote location), the compressed gas is used to operate a hydraulic arrangement generating hydraulic pressure supplies at the higher pressures required.

Further, gas moving at relatively low velocity in the fluid power transmission tube provides a safe environment for communication links (as fibre optics) between the control position and the remote location.

The present invention includes for the use of the gas passage as a location for the communication link/s.

The current practice of hydraulic fluid being supplied from a platform through 20 miles or so of hose to a sub-sea installation cannot ensure that the fluid is of the high standard of cleanliness required on arrival. Further, unless a return line for the fluid to the platform is provided, the preferred grades of hydraulic oil cannot be used, as such grades cannot be wasted into the sea. In consequence, inferior grades of hydraulic fluid, glycol-based, water-mixed, are used at present.

A further disadvantage of the use of these inferior hydraulic fluids being wasted into the sea is that they are biocides, causing damage to the marine environment. The present invention enables high quality hydraulic oils to be used with the hydraulic equipment sub-sea, contained in a closed circuit system constantly filtered to high standards of cleanliness, so ensuring reliability in operation of the hydraulic equipment supplied.

BACKGROUND In the control of undersea remote locations such as an subsea wellhead or a remote operated sub-sea vehicle (ROV), the remote location often includes hydraulic pressure fluid actuated equipment controlled from a control location as an offshore platform or attendant vessel. Connections between the control location and the remote location are currently made by an umbilical having bores for the passage of hydraulic pressure fluid to the hydraulic fluid actuated equipment. The umbilical may also contain electrical (eg. multiplex) cables, which may be utilized for the transmission of information and command signals, and also power cables for powering electrical apparatus and instrumentation at the remote location. Such cables are run separately through the length of the umbilical, well removed from the bore for the hydraulic fluid.

Conventional umbilicals are very expensive to manufacture and to maintain because of the very high pressures of the hydraulic fluids transmitted through them, and because of the failure of electrical cables and connections.

The present invention seeks to provide control apparatus which does not require high pressure hydraulic fluid ducts in the umbilical for the transmission of fluid power, ensures cleanliness of the hydraulic fluid supplied to hydraulic equipment, affords a more rapid response of apparatus at the remote location than is possible with the conventional arrangement, and simplifies and improves the reliability of control means.

SUMMARY OF THE INVENTION The present invention proposes control apparatus, comprising a control location including a source of pressure gas, conduit means connecting the source of pressure gas to a remote location, the remote location including hydraulic fluid supply means which is arranged to be acted upon by the pressure gas to attain hydraulic pressures greater than the pressure of the gas, means actuated by the hydraulic pressure, and control means to control the supply of hydraulic pressure fluid to the fluid actuated means.

The hydraulic fluid supply means comprises at least two hydraulic units, at least one of which is arranged to deliver hydraulic fluid at pressure greater than that of the gas whilst the other/s is/are arranged to be recharged with hydraulic fluid.

The hydraulic fluid supply means includes a hydraulic reservoir adapted to receive return hydraulic flows and to recharge the hydraulic units with hydraulic fluid.

The remote location includes changeover means for changing the roles of the hydraulic units such that the one, or those, which was/were previously delivering hydraulic fluid is recharged with hydraulic fluid and the one/s which previously was/were recharged with hydraulic fluid deliver/s hydraulic fluid.

The hydraulic units preferably comprise pistons.

The changeover means preferably comprises detection means which cause the role of each unit to be changed simultaneously.

The hydraulic fluid supply means may comprise a series of sets of units, the units of a subsequent set being pressurised by hydraulic output from a previous set, to achieve yet higher hydraulic output pressures.

Conveniently, the gas supply conduit is used for conveying signals between the control station and the remote location.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is exemplified in the accompanying drawings, in which: Figures 1 and 2 are schematic diagrams of control apparatus according to the invention.

Fig 1 illustrates a single-stage example of the apparatus in which hydraulic pressure outputs are greater than that of the gas pressure.

Fig 2 illustrates the arrangements adapted to attain even higher hydraulic pressures by multi-stage means.

DETAILED DESCRIPTION OF THE DRAWINGS In the drawings, the conventions of BS 2917, 1957 are used in regard to directional control valves showing internal flow paths in envelope form. The flow path envelope is adjacent to the end to which pilot control pressure is applied.

Referring to Fig. 1, at the control location, which may be an offshore platform, there is a source of pressurised gas S which connects by the umbilical 123 to the remote location, which may be a sub-sea wellhead.

At the remote location the hydraulic fluid supply means comprises two piston and cylinder devices 101 and 102.

Device 101 includes a first cylinder 103 and a second cylinder 104 of smaller diameter but axially aligned with cylinder 103. A piston head 105 is slidably disposed in the cylinder 103 and is fixed with a secondary piston 106 extending into the cylinder 104. A piston rod 107 extends from the piston head 105 through the end wall 103a of the cylinder 103 which is remote from cylinder 104. This piston rod 107 rigidly carries an arm 108 which, when piston head 105 is adjacent to cylinder 104, is arranged to move the actuating plunger 109 of a stroke limiting valve 110.

Device 102 is similar to device 101, and includes a first cylinder 111 and a second cylinder 113 of smaller diameter but axially aligned with cylinder 111. A piston head 112 is slidably disposed in the chamber 111 and is fixed with a secondary piston 114 extending into the cylinder 113. A piston rod 115 extends from the piston head 112 through the end wall llla of cylinder 111 which is remote from cylinder 113. This piston rod 115 rigidly carries an arm 116 which, when piston head 112 is adjacent to cylinder 113, is arranged to move the actuating plunger 117 of a stroke limiting valve 118.

The stroke limiting valves 110 and 118 are conveniently supported by brackets 119, 121 attached to the respective cylinders 103, 111, and the plungers 109, 117 are spring loaded to a projecting position by respective compression springs 120, 122. Valves 110 and 118 receive pressure gas from a pressure gas sources S at the control location via an umbilical conduit 123 and branches 124 and 125. When the plungers 109 and 117 of the two valves 110 and 118 are extended the valves block the flow of pressure gas, as shown for valve 118, and connect conduits 126 and 129 respectively to exhausts 135a and 135b respectively.

However, when the respective plunger 109, 117 is depressed the valve permits pilot pressure gas to flow via a respective conduit 126, 129 to a respective pilot pressure chamber 127, 130 of a changeover valve 128. Once this valve 128 has moved to one position it is detent held until it receives control pressure from the other stroke limiting valve 110 or 118.

A conduit 131 conducts pressure gas from branch 125 to valve 128 from which, in the valve position shown, pressure gas flows via conduit 132 to the upper chamber of cylinder 111 remote from cylinder 113.

Valve 128 also connects conduit 133, which leads from the corresponding chamber of device 101, to exhaust 134. When valve 128 is changed over, conduit 132 is connected to exhaust and conduit 133 receives pressure gas.

When plungers 109 and 117 of the valves 110 and 112 are extended the conduits 126 and 129 are connected to exhausts 135a and 135b respectively.

Pressure gas from branch conduit 124 also passes via conduit 136, through a pressure reducing valve 137 and conduit 139 to maintain a pre-set lower pressure in the upper region of a low pressure hydraulic fluid reservoir 138. The pressure reducing valve 137 maintains the desired pressure in the reservoir 138 by allowing flow into or flow out of the reservoir to maintain the desired pressure. Accordingly the valve 137 has an exhaust connection to the exhaust arrangement 177.

Reservoir 138 supplies hydraulic fluid via conduit 141 and branch conduits 142 and 143 to the lower end (as shown) of respective cylinders 103 and 111, through the ports 178 and 179 respectively.

The ports 180 and 181 of the chambers 104 and 113 respectively connect with the conduits 153 and 154 respectively. The branch 153 connects with the conduit 151 through the non-return valve 182 which permits flow only in the direction from the conduit 151 to the conduit 153.

The conduit 151 connects with the conduit 154 through the non-return valve 183 which permits flow only in the direction from the conduit 151 to the conduit 154.

The conduit 153 connects with the conduit 184 through the non-return valve 185 which permits flow only in the direction from the conduit 153 to the conduit 184. The conduit 154 connects with the conduit 184 through the non-return valve 186 which allows flow only in the direction from the conduit 154 to the conduit 184.

The conduit 150 connects hydraulic fluid from the reservoir 138 to the conduit 151.

Thus the conduit 184 is the recipient of delivery output from cylinders 104 or 113, and the conduit 151 supplies charging fluid to the cylinders 104 or 113 when the piston 106, 114, of either commences return stroke.

Conduit 184 branches to the conduit 158 which connects to a port of the control valve 160 the operation of which is described below.

Conduit 159 connecting with another port on the control valve 160 connects to the hydraulic fluid reservoir 138.

The solenoid operated control valve 160 is actuated by control signals from the control location through the communicating link 166, as described later. In its illustrated position valve 160 connects conduit 158 with a conduit 161 opening to one end of an hydraulic actuator cylinder 162, whilst conduit 159 is in communication with a conduit 163 opening to the opposite end of cylinder 162. A piston 164 is slidably disposed in cylinder 162 and is rigidly connected to a piston rod 165 which extends from the cylinder 162, to operate an oilwell control valve (not shown). In the other operative position of valve 160 conduit 158 (the pressure conduit) is connected to conduit 163 and conduit (the return conduit) 159 is connected to conduit 161, reversing the movement of the piston-rod 165.

The operation of the apparatus of Fig. 1 will now be described, commencing at the position illustrated, in which piston rod 107 is in a fully retracted position so that arm 108 is depressing plunger 109, piston rod 115 is extended, and change-over valve 128 is admitting pressure gas to the upper chamber (as shown) of cylinder 111 as pressure gas from source S is admitted via conduits 123, 125, 131, valve 128, and conduit 132 urging piston 112 downwardly to pressurize hydraulic fluid in cylinder 113. The upper chamber of cylinder 103 is connected via conduit 133 and valve 128 to exhaust 134.

Thus hydraulic pressure fluid from cylinder 113 passes into the conduit 154, through the non-return valve 186, to the conduit 184, and so to the branch 158, feeding pressure supply to the control valve 160 which in the position shown passes pressure fluid to the conduit 161 and so to the piston head end of the cylinder 162.

Return fluid from the piston rod end of the cylinder 162 passes through the conduit 163, the valve 160 and the conduit 159 to return fluid to the reservoir 138.

As the upper chamber of the cylinder 103 is at this stage connected to exhaust, as described above, low pressure fluid from the reservoir 138 (through conduits 141, and 142, and port 178) acting on the underside of the piston 105 urges the piston upwards causing hydraulic fluid from the reservoir 138 through the conduit 150 and conduit 151 to pass through the non-return valve 182 to enter the bore 104 below the piston 106 to fully recharge the bore 104 in preparation for the unit's next delivery stroke.

Upward movement of the piston 105 lifts the piston rod 107, removing the arm 108 from contact with the plunger 109, so allowing the spring 120 to change the position of the valve 110, to put the conduit 126, and the chamber 127 of the valve 128 to exhaust. The valve 128, being detent held, remains in its current position so that delivery stroke of the unit 102 continues.

It is noted that this positive charging process of the bore 104 by pressure of fluid from the reservoir 138 ensures that the unit 103 is fully charged before the delivery stroke of unit 111 is completed.

Change-over of the actuator 162 is initiated from the control position (platform), when required, by transmission of an electrical, pneumatic, hydraulic, accoustic or other control signal through the communicating link 166 (see below) from the control location to change the position of valve 160 to reverse the fluid flows to the actuator.

As the piston 112 travels down the cylinder 111 hydraulic fluid below the piston head is returned to the low pressure reservoir 138 from the port 179 via conduit 143. (The hydraulic reservoir 138 is, of course, at a lower pressure than the pressure gas supply acting on piston 112 due to pressure reducing valve 137.) As explained above, low pressure hydraulic fluid has also travelled through the conduit 142 and the port 178 from the reservoir 138 to the lower chamber of cylinder 103 to raise the piston head 105 and piston 106 to recharge unit 103 from the reservoir 138 through the conduits 149 and 151.

When arm 116 eventually engages plunger 117, valve 118 admits pressure gas to the operating chambers 130 of valve 128. Valve 128 thus changes over to remove the supply of pressure gas from the upper chamber of cylinder 111, which is admitted to exhaust, and to supply pressure gas to the upper chamber of cylinder 103. With the upper chamber of cylinder 111 connected to exhaust, pressure fluid from the reservoir 138, acting through the conduit 143 and the port 179, urges the piston 112 upwards (as shown) to recharge the chamber 113, which fills with supply from the reservoir 138 through the conduits 150, the non-return valve 183, and the conduit 154. Fluid pressure (now from cylinder 104) is now delivered through conduit 153, non-return valve 185, conduit 184, and branch 158 to control valve 160 and conduit 161 to cylinder 162.

Return flow from cylinder 162 is through conduit 163, valve 160 and conduit 159 to reservoir 138.

It will thus be seen that the devices 101 and 102 operate alternately to supply the control valve 160, and through it the actuator 162, that each piston 106, 114 completes its stroke before changeover occurs, and that the cylinders 104 and 113, below those pistons, are fully recharged with fluid prior to the delivery stroke. Further, since the piston heads 105 and 112 have a larger area exposed to the pressure gas than the area of pistons 104 and 114 exposed to the hydraulic fluid, the gas pressure required to achieve a desired hydraulic pressure can be many times less than the said hydraulic fluid pressure.

Mathematically, the maximum pressure outputs (P) from the cylinders 104 and 113 of the hydraulic units 101 and 102 are expressed as follows: gas pressure X annulus area above piston 105(112) P = less reservoir pressure X annulus area below piston 105(112) area of chamber 106(113) As the reservoir pressure is low and the annulus area above the piston 105 (112) is great in comparison with the area of the bore 104(113), the hydraulic output pressures of the units 103 and 111 are several times that of the gas pressure. Precise maximum hydraulic fluid output pressures are determined by the pressure of the gas supply.

In one arrangement, when the gas pressure at the exhausts 134, 135a, 135b, 174, 176, and 177, is greater than the pressure of the surrounding environment these exhausts release the exhaust gases into the surrounding environment. However, when it is desirable to reduce the exhaust pressures, as when operating in a deep water location, the exhaust can be connected to an exhaust conduit extending to sea level, conveniently at the control location.

The communications link 166 between platform and sub-sea well-head which may be an electrical wire, fibre optic, accoustic, or other form of communication, runs from platform to sub-sea well-head laid within the conduit 123 where it is protected by the conduit and by the gas in the conduit. At the sub-sea destination this communications link enters the control box 167 which codes and decodes signals transmitted from, and received at, the sub-sea well-head.

For example, a signal sent through the communications link 166 is received in the control box 167, and decoded, giving electrical outputs to the lines 168 and 169 for the desired operation of the solenoids of the directional control valve 160.

It is thus noted: (a) The hydraulic output pressure is greater than that of the pressure of the gas supplied.

(b) That the changeover arrangements effect substantially continuous delivery of hydraulic output.

(c) That other means of effecting changeover switching may be used for example pressure, electrical, or nucleonic.

(d) That arrangements may be made for change-over under control from the control position in emergency.

(e) That a full charge of the hydraulic units before the next delivery stroke is ensured by provision of pressurised charging fluid from the low pressure reservoir.

(f) That although the hydraulic output from the low pressure reservoir has been shown as pressurized by low pressure gas, other means of providing the necessary liquid head may be used, as for example, by the use of weights or by elevating the reservoir in relation to the rest of the hydraulic arrangements.

(g) That return hydraulic flows from the hydraulic equipment return to the reservoir.

(h) That the communication link between the control position (platform) and the remote location (sub-sea wellhead) may be located within the conduit conveying the pressure gas.

(i) That several actuators could be connected in parallel, each controlled from the control location by a control valve (as 160).

(j) That whilst in the foregoing examples the control apparatus has been illustrated as including two hydraulic units in a set in which hydraulic fluid is pressurized it will be appreciated that one or more additional pressurizing hydraulic units may be provided in a set at to increase the volume of hydraulic pressure fluid available and/or to smooth the supply of hydraulic fluid.

(k) That the hydraulic arrangement may comprise several sets of units operating in series or in parallel to output at a variety of pressures, and that the hydraulic outputs may be used for purposes other than the driving of actuators. These features are described below with reference to Fig. 2: Fig. 2 illustrates a two-stage embodiment of the invention in which the first stage, shown to the left, is identical to that described with reference to Fig. 1 and uses the same numerical identifications.

Shown to the right is a similar hydraulic arrangement comprising a second stage set of hydraulic units powered by hydraulic fluid output from the first stage hydraulic output to achieve even higher fluid pressures.

Referring to Fig. 2, the hydraulic units and the changeover controls are identical with those of Fig. 1 and are given identical numerical identifications, except that the numerals are in the 200 series in place of the 100 series - ie. 159 becomes 259.

Differences are outlined as follows: The valve 228 is supplied with first-stage hydraulic fluid output from the conduit 184 through the conduit 231, in place of the compressed gas supply of stage 1.

Instead of exhaust to environment, or back to the surface, as featured in stage 1, exhaust from the valve 228 is taken to the reservoir 138 through the conduit 234.

Thus the pistons 205 and 212 are subjected to the higher (hydraulic fluid) pressures, (instead of the lower gas pressures of stage 1) resulting in even higher hydraulic pressures at output from the cylinders 204 and 213.

The chambers below the pistons 205 and 212 are pressure loaded as before, but now from the reservoir 238, through conduit 241 and branches 242 and 243 respectively for the purpose of lifting the pistons 205 and 202 when required for recharging in preparation for delivery, as described with reference to Fig. 1.

The charge of fluid is supplied by the reservoir 238 through the conduit 250, the conduit 251 and the non-return valve 282 or 283 as appropriate according to the cylinder being charged.

The reservoir 238 requires to be pressurized to a pressure above that of reservoir 138 which may be achieved by gas supply through a pressure reducing valve set to a higher pressure than that of valve 137, or, as shown, by pressure supply from umbilical 123 through conduit 225 and the branch 239.

This higher reservoir pressure is acceptable to the operation of the devices 201 and 202 as the operating (hydraulic) fluid pressure is substantially above gas pressure.

The solenoid operated directional control valve 260 is operated through the lines 268 and 269 from the control box 167, as described in regard to the control valve 160.

Pilot hydraulic pressure for control of pilot operated valves controlling flows of the second stage level of pressure conveniently use first level hydraulic pressure with exhaust to reservoir 138.

In the same way, a device using first level hydraulic pressure, for example a generator driven by a hydraulic motor, will exhaust to the reservoir 138.

A device operating on second level pressure however would exhaust to reservoir 238.

Claims (21)

1. Control apparatus comprising a control location including a source of pressure gas, conduit means connecting the source of pressure gas to a remote location, the remote location including hydraulic fluid supply means which is arranged to be acted upon by the pressure gas to attain hydraulic pressures greater than the pressure of the pressure gas, means actuated by the hydraulic pressure, and control means operable from the control location to control the supply of hydraulic fluid to the actuated means.

2. Control apparatus according to Claim 1 in which the hydraulic fluid supply means comprises at least two hydraulic units at least one of which is arranged to deliver hydraulic fluid whilst an other, or others, is/are arranged to be recharged with hydraulic fluid.

3. Control apparatus according to Claim 2 in which the hydraulic unit/s which deliver/s hydraulic fluid is/are connected to the conduit means, whilst the other hydraulic unit/s is/are connected to gas exhaust means.

4. Control apparatus in according to Claim 2 in which the hydraulic unit/s which deliver/s hydraulic fluid is connected to a supply of hydraulic fluid pressurised by pressurised gas from the conduit.

5. Control apparatus in accordance with Claim 2 in which the hydraulic unit/s which deliver/s hydraulic fluid is/are connected to supply of hydraulic fluid from an earlier stage hydraulic unit.

6. Control apparatus in accordance with the foregoing Claims in which the remote location includes changeover means for changing the roles of the hydraulic units such that the one (those) which was (were) previously delivering hydraulic fluid is/are charged with hydraulic fluid, and the one (those) which was (were) previously charged with hydraulic fluid deliver/s hydraulic fluid.

7. Control apparatus in which in accordance with Claims 1-5 in which the control position includes changeover means for changing the roles of the hydraulic units such that the one (those) which was (were) previously supplying hydraulic fluid is/are charged with hydraulic fluid, and the one (those) which was (were) previously charged with hydraulic fluid supplies (supply) hydraulic fluid.

8. Control apparatus in accordance with Claims 6 and 7 in which changeover means is operable in response to fluid pressures.

9. Control apparatus in accordance with Claims 6 and 7 in which changeover means is operable in response to fluid levels.

10. Control apparatus in accordance with Claims 1 and 2 in which the hydraulic units include pistons acted upon by the pressure gas.

11. Control apparatus in accordance with Claims 6, 7, and 10 in which the changeover means is operated by limit detection means responsive to piston positions.

12. Control apparatus according to Claim 1 in which the hydraulic fluid supply means includes a fluid reservoir.

13. Control apparatus according to Claim 12 in which fluid from the fluid reservoir is used for charging the hydraulic units with hydraulic fluid.

14. Control apparatus according to Claims 1,12, and 13, in which fluid pressure from the fluid reservoir is above the pressure of the gas exhaust from the hydraulic fluid supply means and below the pressure of the pressurizing gas

15. Control apparatus according to Claim 14 in which the reservoir is pressurized from the pressurized gas supply.

16. Control apparatus according to Claims 1 and 12 in which the reservoir is adapted to receive return flows from the hydraulic equipment supplied.

17. Control apparatus in accordance with Claim 1, in which the conduit provides passage for control communication means.

18. Control apparatus in accordance with Claims 1, 4, and 5, in which the hydraulic arrangement comprises more than one stage of hydraulic pressure generation.

19. Control apparatus in accordance with Claim 18, in which different hydraulic pressure outputs are generated at each stage of generation.

20. Control apparatus in accordance with Claim 19, in which the lower hydraulic pressure output is used for pilot operation of control valves.

21. Control apparatus substantially as described.with reference to the drawings.