GB2230101A

GB2230101A - Weight monitoring apparatus

Info

Publication number: GB2230101A
Application number: GB9006001A
Authority: GB
Inventors: Ron Straine; Robert G Thubron
Original assignee: KARON SALES AND SERVICES LIMIT
Current assignee: KARON SALES AND SERVICES LIMIT
Priority date: 1989-03-16
Filing date: 1990-03-16
Publication date: 1990-10-10
Anticipated expiration: 2010-03-16
Also published as: GB2230101B; GB9006001D0; GB8906074D0

Abstract

Weight monitoring apparatus for offshore drilling operations comprises a support frame 1 suspended from a load arm assembly 2 and supporting a rotatable double sided trough 3. The load arm assembly 2 is attached at one side to a bracket 5 by a (hydraulic) load cell 6. The trough is provided with a pneumatic rotary actuator 10 and appropriate hydraulic circuitry is provided for control of the various components. The trough fills with waste solids discharged from a shaker device in use and on reaching a predetermined load operates the load cell which triggers a control system to initiate the actuator 10. This actuation device 10 inverts the trough to empty the material collected and an associated pneumatic counter increments each time the trough inverts. <IMAGE>

Description

"Weight Monitoring Apparatus" This invention relates to weight monitoring apparatus especially but not exclusively for use in monitoring waste solids in offshore drilling operations.

During drilling operations fluid or mud is pumped down a drill string and exits adjacent the bit where it has the dual purpose of providing lubrication and providing a medium to carry away the waste solids resulting from the drilling operation. The fluid solid mix passes back to the surface for disposal. In many instances an oil based drill fluid is used. This fluid is both expensive and potentially extremely hazardous to the environment. Consequently means are generally provided for separating the fluid from the solids content of the material brought to the surface. This is done first by using a shaker device, in essence a large automated sieve in the form of a conveyer, to separate large solid particles from the mixture and then a centrifuge device on the recovered fluid to separate remaining solids.The solids left from this operation are disposed of usually overboard in the case of an offshore drilling rig. There is a need to monitor the amount of this solid material recovered both to provide an intlication of the drilling progress being made and also to monitor the amount of potentially hazardous material being disposed of. This has previously been done in a crude manner by recording the time taken to fill a bucket from the shaker output, weighing the contents and thus calculating a very approximate rate of solids recovery. Such a method of solids monitoring is both inconvenient and somewhat inaccurate.

It is an object of the present invention to obviate or mitigate these disadvantages.

According to the present invention there is provided weight monitoring apparatus comprising a support frame, material collection means mounted on the support frame, load sensing means for sensing the presence of a predetermined load in said collection means and operating means operable on detection of a predetermined load by the load sensing means to empty the material out of said collection means.

Preferably the apparatus includes a counter device for recording the number of predetermined loads emptied and thus the aggregate quantity of material emptied from the collection means in operation.

Most preferably the counter device comprises a pneumatically operated counter.

Preferably also the load sensing means comprises a hydraulic load cell and an associated pressure switch operable to activate the operating means.

Alternatively the load sensing means may comprise a counterbalanced support mechanism and an associated pneumatic valve operable to activate the operating means.

Preferably also the material collection means comprises a trough mounted in the support frame for rotation about a longitudinal axis from a collecting position to an emptying position on operation of the operating means to empty the material.

Most preferably the trough has two directionally opposed material collection areas the arrangement being such that when one area is in the collecting position the other area is in the emptying position the trough rotating on each operation of the operating means to empty material from each collection area in turn.

Preferably also means are provided for cleaning the emptied collecting means after emptying.

Most preferably the means for cleaning the collection means are water jets.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings in which; Fig 1 is front view of part of weight monitoring apparatus in accordance with a first embodiment of the present invention; Fig 2 is front view of a control panel of weight monitoring apparatus in accordance with the first embodiment of the present invention; Fig 3 is front view illustrating the interior of the control panel of Fig 2; Fig 4 is a schematic diagram of the pneumatic circuitry of the apparatus of the first embodiment of the present invention; Fig 5 is a side view of part of weight monitoring apparatus in accordance with a second embodiment of the present invention;; Fig 6 is a front view of the apparatus of Fig. 5t and Fig 7 is a schematic diagram of the pneumatic circuitry of the apparatus of the second embodiment of the present invention.

Referring to Figs 1 to 4 of the drawings a first embodiment of weight monitoring apparatus in accordance with the present invention comprises a support frame assembly 1 suspended from a load arm assembly 2 and supporting a rotatable double sided trough 3.

The load arm assembly 2 is supported at one side directly in a bracket 4 and at the other side to a corresponding bracket 5 via a hydraulic load cell 6.

The trough 3 is mounted on the frame assembly 1 in bearings mounted in end plates 7 and 8. At one side this is a plain bearing provided with a cover 9 and at the other side a rotary actuator device 10 is provided.

The control system for the apparatus is illustrated in Figs 2 and 3 with a schematic view of the associated hydraulic circuitry being shown in Fig 4. The load cell 6 is connected by hydraulic circuitry to a pressure switch 11 which operates to activate an air supply arrangement 12 which supplies the rotary actuator 10 for the trough 3. In addition a control timer device 14 is provided for activating water jets for trough cleaning. The air supply arrangement 12 comprises a main air shut off valve 15, a filter 16, a regulator 17, an air line lubricator 18 and a direction control valve 19.

The control panel 20 includes a pneumatic counter 21, an air pressure gauge 22, an air supply indicator 23, an on/off control 24 a load cell pressure gauge 25, a manual control 26 for the water jets, a selector switch 27 for manual selection of the direction of trough operation and a manual/automatic operation selector switch 28.

In operation the apparatus is positioned next to the discharge end of a shaker device on a drilling platform so that the trough 3 collects the solid material being discharged from the shaker device.

As the trough 3 fills up with solid material its weight increases and the pressure in the hydraulic load cell 6 increases. This pressure is transmitted to the pressure switch 11 and when it reaches a pre-set level the pressure switch 11 opens to activate the pneumatic circuitry 12. This activates the rotary actuator 10 causing the trough 3 to rotate through 1800 depositing the solid slurry in a discharge ditch. Simultaneously the timer device 14 operates a water valve to give two jets of water into the lower face of the trough 3 to wash it clean. The pneumatic counter 21 operates once each time the trough 3 is inverted. The other side of the trough 3 is now facing upwards and it fills with solids from the shaker until the pressure switch 11 is once again activated as the preset weight is reached.

The trough then reverses its rotation to present a clean face upwards once again for filling.

The process then continues automatically for as long as the solid slurry is coming off the shaker. The simple product of the counter 21 reading and the calibrated weight at which the load cell 6 operates gives the total solids loss from the shaker. In addition the counter can be connected to other monitoring equipment to give read-outs at remote locations if required.

The system has the facility to be operated manually if required by virtue of the manual controls 26, 27 and 28.

In this mode the trough may be rotated in both directions from the control panel and the water wash can be manually activated from the panel mounted control 26.

As the system weighs the shaker discharge continuously it provides more accurate information on overboard discharges than has previously been available. The system is operated entirely on hydraulics and pneumatics and hence poses no problems in potentially explosive environments.

Various modifications and improvements may be made without departing from the scope of the invention.

For example, referring to Figs 5 to 7 of the drawings a second embodiment of weight monitoring apparatus in accordance with the present invention is illustrated.

It has been found that in the working environment motion imparted to the apparatus by sea movement can affect the operation of the apparatus.

The second embodiment illustrated has been developed with the aim of minimising these effects and essentially involves the replacement of the load cell and pressure switch with a pneumatic roller operated valve 30 in conjunction with a counterbalanced support mechanism 31. The counterbalanced support mechanism 31 comprises a load arm 32 pivotally mounted on a support bracket 33 and provided with a counterbalance assembly 34.

The load arm 32 pivots on the support bracket 33 to operate the valve 30 which initiates the pneumatic circuitry in a similar manner to that described in relation to the first embodiment and accordingly like parts have been accorded like reference numerals.

Solid material is transported to the apparatus by a shaker device 35 and gradually fills up the trough which results in the movement of the load arm 32.

The basic two sided trough 3 can be replaced with a single sided trough in installations when space restrictions prevent a standard installation from being used. Fig 7 illustrates schematically a modified hydraulic circuitry layout which is suitable for a system incorporating both the modifications described.

Claims

1. Weight monitoring apparatus comprising a support frame, material collection means mounted on the support frame, load sensing means for sensing the presence of a predetermined load in said collection means and operating means operable on detection of a predetermined load by the load sensing means to empty the material out of said collection means.

2. Weight monitoring apparatus as claimed in Claim 1, including a counter device for recording the number of predetermined loads emptied and thus the aggregate quantity of material emptied from the collection means in operation.

3. Weight monitoring apparatus as claimed in Claim 2, wherein the counter device comprises a pneumatically operated counter.

4. Weight monitoring apparatus as claimed in any one of the preceding Claims, wherein the operating means includes pneumatic actuator means to effect emptying of the collection means.

5. Weight monitoring apparatus as claimed in any one of the preceding Claims, wherein the load sensing means comprises a hydraulic load cell and an associated pressure switch operable to activate the operating means.

6. Weight monitoring apparatus as claimed in any one of Claims 1 to 4 wherein the load sensing means comprises a counterbalanced support mechanism and an associated pneumatic valve operable to activate the operating means.

7. Weight monitoring apparatus as claimed in any one of the preceding Claims, wherein the material collection means comprises a trough mounted in the support frame for rotation about a longitudinal axis from a collecting position to an emptying position on operation of the operating means to empty the material.

8. Weight monitoring apparatus as claimed in Claim 7, wherein the trough has two directionally opposed material collection areas the arrangement being such that when one area is in the collecting position the other area is in the emptying position the trough rotating on each operation of the operating means to empty material from each collection area in turn.

9. Weight monitoring apparatus as claimed in any one of the preceding Claims wherein means are provided for cleaning the emptied collecting means after emptying.

10. Weight monitoring apparatus as claimed in Claim 9 wherein the means for cleaning the collection means are water jets.

11. Weight monitoring apparatus substantially as hereinbefore described with reference to and as shown in the accompanying drawings.