GB2124917A

GB2124917A - Tank assembly for storing and/or transporting suspensions

Info

Publication number: GB2124917A
Application number: GB08314636A
Authority: GB
Inventors: Magnus Aase; Bjornar Sundem
Original assignee: GANN MEK VERK
Current assignee: GANN MEK VERK
Priority date: 1982-07-06
Filing date: 1983-05-26
Publication date: 1984-02-29
Also published as: GB2124917B; GB8314636D0; NO822358L; NO154124B

Abstract

The tank assembly which is of particular use in the transportation of drilling mud on board a seagoing vessel comprises in the interior space (1) of the tank, a rotary stirrer (8, 10) which is driven by a motor (3) (e.g. a hydraulic motor) which is also disposed within the tank. The motor (3) may be provided with an extra stuffing box to prevent ingress of the mud into the motor bearings, the stuffing box consisting of a sleeve (21) coupled to the stirrer shaft (8) and driven by the motor shaft (6). A second, stationary sleeve (17) secured to the motor casing (15) coaxially surrounds the sleeve (21) with an annular gap (22) therebetween. At least two annular lip gaskets (23, 24) are provided within the gap (22), the sealing lips thereof facing away from the motor, and an inlet (28) a lubricant under pressure is provided in the stationary sleeve (17) between the two gaskets (23, 24). <IMAGE>

Description

SPECIFICATION Tank assembly for storing and/or transporting suspensions The present invention relates to a tank assernbly for storing and/or transporting suspensions, which has particular relevance to tanks on board a seagoing vessel for transporting drilling fluid, or mud.

Oil and gas drilling requires large quantities of drilling mud, which is introduced into the borehole to balance the gas or oil pressure if the drill bit strikes a well. For different formations, different types of drilling mud of different densities are used.

The density of the drilling mud also depends on the drilling depth at any given time. Another function of the drilling mud is to entrain and carry off the cuttings, i.e. the material ground loose from the formation during drilling. After the drilling mud has been in use for some time, it must be replaced and the used mud sent to special stations for cleaning and rehabilitation.

The transportation, storage and handling of drilling mud in the sizeable quantities required is especially a problem in offshore exploration for oil and gas. The space on board the drilling platform is limited, and it is therefore necessary to supply drilling mud by means of supply boats. These boats must often lie off the drilling platform on stand-by for some time before the drilling mud can be delivered. The materials for the drilling mud can either by delivered to the platform and the mud mixed on the platform, or ready-mixed drilling mud can be transported in special tanks mounted on the deck of the supply boats. These ships are relatively small and deck space is limited. If tanks are mounted on deck, there is so little space remaining that the boat cannot be used for other purposes such as transporting pipes or drill strings.

Transport tanks for drilling mud have also been placed below deck on supply boats. However, the drilling mud requires continuous stirring to prevent the heavier components from precipitating to the bottom of the tank. The sediment from drilling mud can become so hard and solid after some time that it is very difficult to make the suspended solids become part of the suspension again. Propeller stirrers have been provided in the tanks for stirring the suspension, driven by motors on deck above the tanks. Since the tank volume on a supply boat must be divided into many small units, a relatively large number of motors - say, 10 to 12 - must be mounted on deck. It is obvious that so many motors spread out over the free deck space also make it impossible for the boat to be used for transporting other material.

One aim of the present invention is to provide a tank assembly for transporting and storing suspensions, especially tanks on board a ship for transporting drilling mud, whereby drilling mud and other suspensions can be transported and stored without precipitation occurring at the bottom of the tanks even after an extended period, and whereby, in the case of a vessel supporting the tank, the deck space remains free, no deck mounting of motors for stirring the suspension being required.

According to one aspect of the invention there is provided a tank assembly for storing and/or transporting suspensions which comprises, a tank, support means for the tank, a stirrer means of propeller type located in the interior space of the tank, and a motor drivably connected to the stirrer means and also located inside the tank.

Desirably the motor is an hydraulic motor which is provided with an extra stuffing box to prevent the suspension in the tank from penetrating into the bearings of the motor, the stuffing box consisting of a sleeve coupling fastened to a shaft of the stirrer means and driven by a shaft journal of the hydraulic motor, and a stationary sleeve coaxially surrounding the sleeve coupling with an annular gap therebetween, at least two annular gaskets being provided within the gap, and an inlet for lubricant under pressure being provided in the stationary sleeve between the two gaskets.

The provision of an extra stuffing box on the motor, ensures that drilling mud, for example, does not penetrate into the motor bearings. Suitably each gasket has an annular lip providing the seal, the lip on each gasket being on the side thereof remote from the motor.

The extra stuffing box prevents wear particles in the suspension from penetrating into the motor bearings, since lubricant, for example grease, is constantly forced under pressure into the space between the two above-mentioned gaskets and displaces any wear particles which may have penetrated into this extra stuffing box. The external sleeve of the extra stuffing box can be fastened in any convenient manner so that it seals around the original stuffing box of the motor.

According to a further aspect of the invention there is provided a drilling mud transportation vessel comprising a plurality of mud tanks below a deck of the vessel and mud stirrer propeller means rotatably disposed in each tank, characterised in that each stirrer means comprises a motor also mounted within the tank and drivably connected to the propeller means.

With such a vessel, the drilling mud can be transported by sea to a much greater extent and in an entirely different manner than previously. For example, a purification plant for used drilling mud may be mounted on board the vessel and the used mud can then be taken on board the ship for cleaning and renovation. In addition, by mixing different types of materials the drilling mud can be given whatever density is desired, for example a density as required by the same platform from which the used drilling mud originally came, or another density for use on another drilling platform. If the supply vessels do not have a purification plant on board, the used drilling mud can be transported by the vessel to a land-based plant and the vessel can take on a load of new drilling mud for transportation to the drilling platform.

The invention will be explained in greater detail in the following with reference to the accompanying drawings, which show an exemplary embodiment of the invention.

Figure 1 is a schematic illustration of a stirrer means inside a tank, and Figure 2 shows a preferred embodiment of an extra stuffing box used in an embodiment of tank assembly in accordance with the invention.

Within a tank interior 1, supported on two beams 2, a hydraulic motor 3 with an inlet port 4 and outlet port 5 is arranged. On the output shaft 6 of the motor 3, fastened by means of a flange coupling 7, there is a tubular drive shaft 8 for two propeller stirrers 9 and 10. At the bottom of the tank 11, a bearing 12 for the end of the stirrer shaft 8 is provided.

The motor 3 is secured to a mounting plate 13 disposed between the beams 2. There is a recess 14 in the plate for a circular guide 15 at the lower end of the motor. Above the guide are fastening flanges 16 for securing the motor to the plate 13. A watertight sleeve 17 with an annular flange 18is fastened to the guide 15. A gasket 19 is provided in the annular flange to prevent liquid from penetrating into the sleeve. This sleeve thus seals around the original stuffing box 20 of the motor 3. Fastened to the motor shaft journal 6 is a sleeve coupling 21 disposed coaxially within the sleeve 17 with an intermediate annular gap 22 between the two sleeves. Two annular lip gaskets 23 and 24 are provided within this gap. The sleeve coupling 21 has an annular flange 25, which like the flange 18 has an annular gasket 26. The flange 25 is fastened to a flange 27 on the stirrer shaft 8. In the sleeve 17, between the lip gaskets 23 and 24, there is an inlet 28 for introducing lubricant, for example grease, between the two gaskets.

As will be clearly understood from the above description and the drawings, the sleeve 17 with the flange 18, gasket 19 and lip gaskets 23 and 24 from a mud seal which seals completely around the original stuffing box 20 of the motor 3. By pressing grease into the gap between the lip gaskets 23 and 24, any drilling mud or other wearing material is completely prevented from penetrating into the motor's stuffing box and bearings.

Although a hydraulic motor is preferred, a pneumatic motor (possibly acting via a step-down gear box) or even an electric motor can be used within the tank provided it is protected from the environment within the tank.

Claims

1. A tank assembly for storing and/or transporting suspensions which comprises, a tank, support means for the tank, a stirrer means of propeller type located in the interior space of the tank and a motor drivably connected to the stirrer means and also located inside the tank.

2. A tank assembly as claimed in claim 1, in which the support means is a marine vessel.

3. A tank assembly as claimed in claim 1 or claim 2, in which the stirrer means and motor are designed to be able to stir drilling mud within the tank.

4. A tank assembly as claimed in any preceding claim, in which the motor is a hydraulic motor.

5. A tank assembly according to claim 4, in which the motor is provided with an extra stuffing box to prevent the suspension in the tank from penetratjng into the bearings of the motor, the stuffing box consisting of a sleeve coupling fastened to a shaft.of the stirrer means and driven by a shaft journal of the hydraulic motor, and a stationary sleeve coaxially surrounding the sleeve coupling with an annular gap therebetween, at least two annular gaskets being provided within the gap, and an inlet for lubricant under pressure being provided in the stationary sleeve between the two gaskets.

6. A tank assembly according to claim 5, in which each gasket has an annular lip providing the seal, the lip on each gasket being on the side thereof remote from the motor.

7. A drilling mud transportation vessel comprising a plurality of mud tanks below a deck of the vessel and mud stirrer propeller means rotatably disposed in each tank, characterised in that each mud stirrer means comprises a motor also mounted within the tank and drivably connected to the propeller means.

8. A vessel as claimed in claim 7, in which the motor is a fluid-powered motor.

9. A vessel as claimed in claim 8, in which the motor is a hydraulic motor.

10. A vessel as claimed in any of claims 7 to 9, in which a drive shaft of the motor is connected to the propeller means via a mud seal which prevents ingress of mud to the drive shaft.

11. A vessel as claimed in claim 10, in which the mud seal comprises two spaced-apart annular resilient seals and a mass of pressurised lubricant disposed between the seals.

12. A tank assembly for storing and/or transport- ing suspensions substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.