GB2091325A

GB2091325A - Underwater grouting apparatus

Info

Publication number: GB2091325A
Application number: GB8118516A
Authority: GB
Original assignee: Sir McAlpine Robert and Sons Ltd
Current assignee: Sir McAlpine Robert and Sons Ltd
Priority date: 1980-06-17
Filing date: 1981-06-16
Publication date: 1982-07-28
Also published as: GB2091325B

Abstract

Underwater grouting apparatus comprises a submersible vessel 12 for containing cementitious grout out of contact with the external water, a pump 3 for pumping grout from the vessel to and through a control valve 4 which has a discharge port connected to a discharge conduit 38 and a recycle port connected to a recycle conduit 34 and which is adjustable selectively between recycle and discharge settings, an air cylinders 40 and valves for maintaining within the vessel during lowering, emptying and raising controlled excess pressure over external pressure, and means (e.g. lever 11) to switch the control valve between its recycle and discharge settings. Cylinder 40 is preferably in communication with vessel 12 via an automatic pressure regulating valve 41, a demand valve 43, and an inverted U-tube 45 having one end opening into the top of the vessel and the other open below the vessel base. <IMAGE>

Description

SPECIFICATION Underwater grouting apparatus This invention relates to the underwater repair of concrete structures, e.g. concrete gravity platforms for offshore oil production. Damage, e.g.

cavities and fractures, in exposed underwater concrete of such structures requires repair to prevent deterioration (especially if steel reinforcement is exposed) and/or to restore strength. Heretofore repair has been effected by filling and sealing with resin compositions, the latter being expensive, difficult to apply and of restricted use; or, using for example grout, manually or by injection from above the water surface. Repair with cementitious grout would be preferable but the systems available are not satisfactory.

The present invention provides apparatus for use in the underwater repair of concrete with cementitious grout, the apparatus comprising a submersible vessel for containing cementitious grout out of contact with the external water, a pump for pumping grout from the vessel to and through a control valve which has a discharge port connected to a discharge conduit and a recycle port communicating with the vessel and which is adjustable selectively between recycle and discharge settings, means for maintaining within the vessel during lowering, emptying and raising controlled excess pressure over external pressure, and means operable to switch the control valve between its recycle and discharge settings.

The control valve may be operable manually and/or automatically.

For example in one type of embodiment, means are provided for detecting a predetermined minimum level of grout in the chamber and automatically switching the control valve from its discharge to its recycle setting on achievement of this level during discharge of grout from the vessel.

Detection of the predetermined minimum level of grout being reached may be effected by means of a float which falls with the decreasing grout level until on reaching the predetermined minimum level it triggers switching of the control valve from its discharge to its recycle setting.

Instead of or in addition to automatic operation as described above, the means for switching the control valve between its discharge and recycle settings may have an external lever moveable (e.g.

by an attendant diver or by the manipulators of a submersible rig) between discharge and recycle positions. For example the above mentioned float may be attached to such a lever so that it normally urges the lever to its discharge position but on falling to the predetermined minimum lever moves the lever to its recycle position; before discharge of the grout, the lever would be latched in its recycle position. In a preferred embodiment, movement of the lever operates a hydraulic directional valve which in turn operates an actuator to effect the required switching of the control valve between its recycle and discharge settings.

One means for maintaining controlled internal excess pressure (suitable for use, for example, with automatic discharge/recycle control) comprises a pressurised gas container mounted externally of the vessel and communicating with its interior via a pressure control valve for admitting gas to the vessel to a first predetermined excess pressure over the external pressure, and a pressure relief valve for releasing gas from the vessel at a second predetermined excess internal pressure greater than the first. As a precaution, the vessel is preferably provided with a safety blowout member. e.g. a plug or bursting disc, which operates at an excess internal pressure greater than the second.For example, during lowering of the vessel and discharge of grout, the pressure control valve, which is preferably adjustable, may admit gas into the vessel to maintain about 5 psi excess internal pressure; on subsequent raising of the vessel, the excess internal pressure will increase, and the pressure relief valve may operate when it reaches about 20 psi. In the event of failure of the pressure control, a safety bursting disc may rupture or a safety plug blowout at an excess internal pressure of about 50 psi.

In another means for maintaining controlled internal pressure, e.g. when a manually operated control valve is used, a pressurised gas container mounted externally of the vessel communicates with its interior via an automatic pressure regulating valve, a demand valve and a tube one end of which opens into the top of the vessel and the other end of which is open below the vessel base. This provides an automatic gas admission/exhaust system to maintain a small constant excess of internal vessel pressure over external water pressure.

In all embodiments the vessel is preferably provided internally with agitating means, e.g. with rotating mixing paddles or blades, conveniently operated by the same drive source as the pump, e.g. by a hydraulic motor mounted on the vessel.

The grout can then be mixed from its separate components in the vessel, and maintained under stirring or agitation during recycle and discharge.

Currently preferred embodiments of apparatus according to the invention will now be described, by way of example only, with reference to the accompanying drawings, in which like reference numerals denote like parts, and in which: Figure 1 is an elevation view of one apparatus according to the invention in section along lines 1-1 of Fig. 3, Figure 2 is a partial sectional view along lines 2-2 of Fig. 1; Figure 3 is a plan view of the Fig. 1 apparatus; and Figure 4 is a perspective view of another apparatus according to the invention.

The Figs. 1 to 3 grouting unit comprises a vessel 1 2 having a cylindrical body 14 fitted with bolted top and bottom covers 1 6. A hydraulic motor 1 8 is mounted on the top cover and drives a shaft 20 which extends axially through the vessel and connects to the rotor of a Mono pump 3 bolted externally to the bottom cover. Paddles 24 are attached to the shaft and blades (not shown) are fixed to the inside of the vessel so that, when the shaft rotates, the vessel acts as a grout mixer and agitator.

A flow control valve 2 is fitted in the hydraulic circuit so that the speed of the hydraulic motor can be accurately controlled.

A float chamber 5 is located alongside the vessel and is connected to it by means of two pipes 26, the uppermost of which is situated approximately halfway up the float chamber; air is trapped in the chamber 5 above the level of the upper pipe to provide a region free of grout in which a mechanical linkage is located.

A float 28 is located in the float chamber and is connected to a spindle 30 which passes through the bolted top cover of the chamber. The spindle is connected to a manually operable lever 1 (Fig. 2) which, in turn, is connected to a hydraulic directional control valve 32.

The discharge of the Mono pump is connected to a hydraulically actuated multiport control valve 4, from which a recycle pipe 34 leads to the float chamber-and a discharge pipe 38 is led away for connecting to the repair in hand. Control valve 4 is operated, to switch selectively between recycle of grout through pipe 34 and its discharge through pipe 38, by an actuator 8 operated by lever 1 via hydraulic valve 32.

A compressed air cylinder 40, charged for example to 3000 psi, is fixed to the side of the vessel 12 and is connected to the vessel via an automatic pressure regulating valve 7 which is so designed and adjusted as to maintain the pressure inside the vessel at a predetermined pressure, e.g.

5 psi, above the atmospheric or water pressure outside the vessel.

The vessel is also provided with a pressure relief valve 9, a safety bursting disc 10, and a manual pressure release valve 11.

The vessel has a filler port 42 closable by cap 6, and is carried on a tubular steel support frame 44.

The unit can be designed to work at a depth of 500 ft, and with the exception of an external hydraulic power source (not shown), is completely self-contained.

In use, the hydraulic motor 1 8 is connected by hydraulic hoses to a hydraulic power source on an attendant support vessel. With the control lever 1 held in its lower recycle position A by means of a safety catch (not shown), the hydraulic supply is turned on and the agitator paddle speed is adjusted by means of the flow control valve 2.

With the agitator paddles rotating, the vessel is charged with the necessary materials to produce the required grout mix, the grout thus formed being circulated by pump 3 through control valve 4 and back into the vessel via recycle pipe 34 and float chamber 5. When charging is complete, the filler cap 6 is closed, and the air supply from cylinder 40 switched on, regulator valve 7 being adjusted to provide about 5 psi excess internal pressure within the vessel. With paddles 22 rotating, the unit is lowered to the sea bed, valve 7 automatically controlling the internal pressure to about 5 psi above the external water pressure.

With the apparatus positioned on the sea bed, the discharge pipe 38 from control valve 4 is connected by an attendant diver to-a shutter previously fixed to the structure to be repaired.

The safety catch on lever 1 is then released and the buoyancy of float 28 attached to the lever by spindle 30 shifts the lever to its upper discharge position B; this operates hydraulic valve 32 to drive actuator 8 to switch control valve 4 from its recycle to its discharge setting so that pump 3 pumps grout through discharge pipe 38 to the shutter. As the grout level in the vessel falls, the air pressure above the grout is automatically maintained at the predetermined excess value by regulating valve 7.

The diver can stop the flow of grout to the shutter at any time by operating control lever 1 to cause reversion to recycling of the grout.

If and when the level of the grout in the vessel falls to a predetermined level, e.g. about 2 inches, the float 28 pulls lever 1 to its lower recycle position so that control valve 4 is switched to its recycle setting and the discharge of grout is automatically stopped. If the discharge of grout is stopped before the grout reaches the predetermined minimum level, the control lever 1 needs to be fastened in its lower recycle position against the bias of float 28.

When grouting has been completed, the air supply from cylinder 40 is turned off and the apparatus is raised to the surface, the pressure within the vessel being controlledly reduced during this operation via pressure relief valve 9 which is set for example at about 20 psi. In the event of failure of valve 9, the vessel is protected by bursting disc 10 which ruptures at an excess pressure of, for example, about 50 psi.

At the surface, before opening filler cap 6, air pressure in the vessel is released by opening release valve 11.

The second embodiment illustrated in Fig. 4 is similar to that of Figs. 1 to 3 except that it employs a different pressure control system, and that the control valve 4 is operated purely manually by movement of lever 11, the automatic recycling system involving chamber 5, float 28 and valves 8 and 32 etc. being omitted. The pressure control system employed in Fig. 4 consists of a pressurised gas container 40 which is like that of Figs. 1 to 3, but which is connected to the interior of vessel 12 via an automatic pressure regulating valve 41, a demand valve 43, and an inverted U-tube 45 which has one end 46 passing through top cover 1 6 and opening into the top of vessel 12 and its other end 48 open and located just below the base of vessel 12. The pressure within vessel 12 is thus automatically maintained a little above the external water pressure, with gas being admitted or expelled as necessary to maintain this differential. The control lever 11 is moved es required (e.g. by a diver or by the manipulators of a submersible) to switch valve 4 between its recycle setting in which grout pumped by Mono pump 3 is returned via 34 to the vessel and its discharge setting in which the grout is discharged through 38. Various relevant parts not shown in Fig. 4 (e.g. flow control valve 2, shaft 20, paddles 24 etc.), are substantially as in the embodiment of Figs. 1 to 3.Except for the need for an external hydraulic power source for motor 18, the unit is completely self-contained and, due to the simplicity of the gas admission/exhaust system, the vessel is not a pressure vessel and hence is not subject to operational depth restrictions.

For use, the Fig. 4 apparatus is charged with grout as described with reference to Figs. 1 to 3 with control lever 11 in the recycle position, and the vessel is then sealed and the gas supply from cylinder 40 turned on. With the paddles still rotating, the apparatus is lowered to the sea bed, the regulating and demand valves automatically controlling the internal.vessel pressure to maintain it a little above external water pressure. With the apparatus on the sea bed, an attendant diver can connect discharge hose 38 to a shutter previously fixed to the structure to be repaired and then move control lever 11 to the discharge positions; as the grout level in the vessel falls, the demand valve automatically maintains the gas pressure above the grout. Grout discharge can be stopped at any time by the diver shifting lever 11 back to the recycle position. When grouting is complete, gas supply from cylinder 40 is turned off and the apparatus is raised, the expanding gas in the vessel escaping through tube 45 to maintain the small internal excess pressure. Such a repair operation will usually be conducted from a support vessel providing the necessary hydraulic power, motor 1 8 being kept running throughout.

Claims

1. Apparatus for use in the underwater repair of concrete with cementitious grout, the apparatus comprising a submersible vessel for containing cementitious grout out of contact with the external water, a pump for pumping grout from the vessel to and through a control valve which has a discharge port connected to a discharge conduit and a recycle port communicating with the vessel and which is adjustable selectively between recycle and discharge settings, means for maintaining within the vessel during lowering, emptying and raising controlled excess pressure over external pressure, and means operable to switch the control valve between its recycle and discharge settings.

2. Apparatus according to claim 1 wherein the control valve is operable manually.

3. Apparatus according to claim 1 or 2 wherein the control valve is operable automatically.

4. Apparatus according to claim 1,2 or 3 including means for detecting a predetermined minimum level of grout in the chamber and automatically switching the control valve from its discharge to its recycle setting on achievement of this level during discharge of grout from the vessel.

5. Apparatus according to claim 5 including a float which falls with the decreasing grout level until on reaching the predetermined minimum level it triggers switching of the control valve from its discharge to its recycle setting.

6. Apparatus according to any of claims 1 to 5 wherein the means for switching the control valve between its settings comprises an external lever movable between discharge and recycle positions.

7. Apparatus according to claims 5 and 6 wherein the float is attached to the lever so that its buoyancy normally urges the lever to its discharge position, the float on falling to the predetermined minimum level moving the lever to its recycle position.

8. Apparatus according to any preceding claim, wherein the means for maintaining controlled internal excess pressure comprises a pressurised gas container communicating with the interior of the vessel via a pressure control valve for admitting gas to the vessel to a first predetermined excess pressure over the external pressure, and a pressure relief valve for releasing gas from the vessel at a second predetermined excess internal pressure greater than the first.

9. Apparatus according to any of claims 1 to 6 wherein the means for maintaining controlled internal excess pressure comprises a pressurised gas container communicating with the interior of the vessel via an automatic pressure regulating valve, a demand valve and a tube one end of which opens into the top of the vessel and the other end of which is open below the vessel base.

1 0. Apparatus according to any preceding claims wherein the vessel is provided internally with agitating means.

11. Apparatus for use in the underwater repair of concrete with cementitious grout, the apparatus being substantially as hereinbefore described with reference to Figs. 1 to 3 of the accompanying drawings.

1 2. Apparatus for use in the underwater repair of concrete with cementitious grout, the apparatus being substantially as hereinbefore described with reference to Fig. 4 of the accompanying drawings.