GB2243763A

GB2243763A - Tank wall washing

Info

Publication number: GB2243763A
Application number: GB9010544A
Authority: GB
Inventors: Alistair John Hepworth; Eric John Smith; Norman Michael Trowsdale
Original assignee: Conoco Inc
Current assignee: ConocoPhillips Co
Priority date: 1990-05-10
Filing date: 1990-05-10
Publication date: 1991-11-13
Also published as: WO1991017001A1; AU7981191A; GB9010544D0

Abstract

A method and apparatus for collecting samples from wall surfaces within tanks such as industrial storage tanks, ships, cargo tanks and road tankers, for the purpose of testing any contaminent to assess suitability for filling. The method comprises directing a pressurized jet or spray of liquid washing medium on to a selected region of a surface of a wall within the tank, allowing the liquid to wash down the surface under gravity, and collecting a sample of the washing by a collecting means engaged with the surface below the region where the jet or spray impinges on the surface. The apparatus comprises a tank containing liquid washing medium, means for directing a pressurized jet or spray of the liquid on to the surface which is to be washed, and collecting means adapted for engagement with the surface for collecting a sample of the washings.

Description

Tank Wall Washing Method and Apparatus This invention relates to a method of "wall washing" tanks and to apparatus therefor. More particularly, the invention relates to a method and apparatus for collecting samples from wall surfaces within tanks such as industrial storage tanks, ships cargo tanks, road tankers and the like, for the purpose of validating the tanks i.e. testing for any contaminant to assess suitability for filling.

Known wall wash techniques are crude. In one commonly used method a solvent or other liquid is simply poured from a hand held bottle down a surface by a person working within the tank. As the "washing" medium runs down the surface samples of any impurities or contaminants are washed from the surface and dissolved in the liquid. A second person uses a hand held funnel to collect sample "washings" so that their composition can be later analysed.

In another common method a sample for analysis is collected using a hand held swab, such as a cotton wadding dipped in solvent or other liquid washing medium and wiped manually across part of the tank surface.

In both of these known techniques, it is unavoidable that, whilst collecting a sample, the operator personnel have to remain in very close proximity to the tank surface i.e. no more than an arms length away, during the entire washing operation. Since the liquid which is applied to the surface is often a highly toxic chemical, such as carbon-tetra-chloride, the operators are at risk of being exposed to dangerously high levels of vapour and to physical contact with the liquid e.g. through splashes. The period for which an operator can safely be exposed to such vapour is limited, and the effect on long term health of even brief exposure to such substances is not yet fully known. There is also a risk due to the close proximity of the operators to the surface that contaminants, e.g. from their clothing, will be introduced into the sample.

A further disadvantage with such known techniques is that the wall surfaces can only easily be tested if they are within the normal reach of an operator's hand.

It may be difficult, hazardous, time consuming or impossible to obtain samples from some inaccessible regions of a tank and misleading results may be obtained if some surfaces cannot be tested.

With one of the above known wall wash techniques two operators are required, which is inefficient and costly. The methods themselves are also inherently laborious and time consuming to perform, particularly if there is a need to climb ladders to reach otherwise inaccessible surfaces.

Viewed from one aspect the present invention provides a method of wall washing a tank comprising directing a pressurised jet or spray of liquid washing medium on to a selected region of a surface of a wall within the tank, allowing the liquid to wash down the surface under gravity, and collecting a sample of the washings by a collecting means engaged with the surface below the region where the jet or spray impinges on the surface.

The present invention represents a completely new departure from the prior art in that the washing medium is supplied to the surface under pressure in the form of a controlled jet or spray whilst being collected by a collecting device which is engaged with the surface in such a way that the operator can stand remote from i.e.

at a safer distance away from the surface during washing or may even actuate or direct the spray or jet from a position outside the tank in some cases. As discussed in more detail below, the spray or jet may be directed via an elongate hand held lance whose shape may vary depending on whether the spraying operation is performed from inside or outside the tank.

The method may be performed by a single operator if desired. Since the operator may position himself a greater distance from the surface to which the solvent or other liquid is applied, there is at least a reduced level of vapour and a reduced danger from inhalation or physical contact with even a highly toxic washing medium as compared with the known techniques. The application of the liquid in a pressurised jet or spray is a more controlled process than simply pouring the liquid down the tank wall and in practice less vapour is produced.

There is also a reduced risk of accidental contamination of a sample by an operator working in close proximity to the washed surface. The liquid under pressure may be directed onto surfaces within a tank which would be out of reach and thus inaccessible to conventional wall washing techniques.

Viewed from another aspect the present invention provides apparatus for use in the above method, comprising a tank for containing liquid washing medium, pressurising means for pressurising the washing medium, directing means for directing a pressurised jet or spray of the liquid on to the surface which is to be washed, and collecting means adapted for engagement with the surface for collecting a sample of the washings.

The collecting means may be adapted to be releasably fixable to the surface at a desired location before washing takes place and/or it may be provided with a long handle enabling the operator to hold it engaged with the surface whilst standing a relatively safe distance away from the washing zone and manipulating a spray directing means with his or her other hand.

A collecting means which is fixable to the surface may be adapted to be engaged by hand by an operator who can then withdraw to a relatively safe distance whilst carrying out the washing operation. Once a sample has been collected the operator may then return to the collecting means to retrieve the sample and/or to disengage the collecting means from the wall directly by hand. It may be required to collect samples from a plurality of surfaces within the tank, in which case the collecting means may then be disengaged, moved to a new location and remounted by hand after each wash. The reservoir of the collecting means may be changed if completely independent or seperate samples are required.

The collecting means may be mountable to and/or dismountable from a surface from a distance, e.g. by attachment to a long handle or a flexible line which is controlled from a distance. If the collecting means can be dismounted remotely, the need for an operator closely to approach a surface which has recently been washed with a toxic chemical will be avoided.

In one arrangement an operator can withdraw from a tank completely whilst a washing medium is being applied, provided that there are suitable roof hatches or other access to the tank to permit the liquid washing medium to be directed at the surface from outside the tank and to allow maneuvering of a long handle or line where appropriate. In one preferred arrangement in which the collecting means is remotely mountable to and dismountable from a surface, the entire wall washing operation can be performed without the operator having to enter the tank at any stage.

There may be very significant savings in the time required to complete a wall wash if the entire operation or a substantial part of it can be carried out from outside the tank. The environment within the tank may be unsafe or may become toxic or oxygen deficient after the washing medium is applied. It will be time consuming to have to even partially empty the tank of vapour to allow an operator to enter to retrieve a sample and or move a collecting means to a different surface. It will also be inconvenient if operators have to wear protective clothing and breathing apparatus to enter the tank after the end of the or each run.

Any collecting means which is suitable for collecting a sample of washings can be used, and, for example, in one arrangement the collecting means comprises a receptacle and funnel means for guiding the washings into the receptacle. The lip of a funnel or receptacle will preferably be elongate. In another arrangement the collecting means incorporates a swab or sponge.

The collecting means can be fixed to a surface in any suitable manner. In one arrangement there is provided one or more magnets adapted to mount a collecting means to a magnetic surface. In another arrangement which is suitable for attachment to a wider range of magnetic and non-magnetic surfaces a collecting means is provided with one or more suction devices.

Means of biasing part of the collecting means towards the surface may be provided. For example in collecting means incorporating funnel means and/or a receptacle it may be advantageous to bias the device so that a good seal is formed between the washed surface and a lip of the funnel means or receptacle. The biasing means may comprise a pivot support about which a collecting means can be pivoted or levered to form a seal. This may apply to arrangements in which the collecting means are manually supportable against the wall via a long handle and to arrangements in which the collecting means are self-supportingly fixable to a surface.

A collecting means having a long handle may be manually biased towards the surface by means of manual leverage on the long handle about a pivot support.

In one arrangement a long handled manually supportable collecting means having elongate funnel means provided along one edge with a resilient sealing lip is provided with a pivot support. The collecting means is manually pivotable about the pivot support by means of the long handle to form a seal between the surface and the resilient sealing lip.

Preferably, the pivot support may comprise means for fixing the collecting means to a surface and in a preferred arrangement such pivot support is a suction device.

In one embodiment said biasing means further comprise angular adjustment means provided below a pivot support, adapted to pivot the collecting means against the surface. The angular adjustment means may be arranged to lie substantially perpendicularly to the surface in use and may be extendable or retractable as appropriate to abut the surface and pivot the collecting means about the pivot support to form a seal against the surface.

A suitable pump means capable of operating with the particular washing medium is used to pressurise the liquid. In validating ships tanks it may be convenient to pressurise the washing medium using shipboard compressed air or other suitable pressurised gas. As described above, suitable means for directing, from a safe distance, the liquid washing medium onto the surface to be washed may be an extended lance provided at the end remote from the operator with a nozzle, the lance communicating with a tank of pressurised washing medium. The lance may be shaped as convenient depending on whether it is to be operated from within the tank or from outside the tank through an access port, such that the liquid is easily directable. Means such as a gun may be provided for controlling the flow of washing medium to the lance.

The use of an extended lance in combination with a pressurised liquid washing medium allows the washing medium to be directed on to the surface by an operator remote from the surface and allows otherwise inaccessible regions of the tank which are out of the normal reach of an operator to be easily tested. Such an arrangement can easily be operated in combination with the collecting means by a single operator remote from the surface.

Because the washing medium can be applied in a controlled and well directed manner the quality of the sample obtained is enhanced and waste of large quantities of washing medium is avoided. This has desirable environmental benefits.

Preferably the washing medium is applied as a fine jet or spray as required and under controlled pressure to minimise the amount of vapour produced.

The components of the apparatus may be supplied as a readily portable kit, comprising a pressurisable tank to contain washing medium, a gun and lance, and the collecting means.

Viewed from a further aspect the invention provides a washing medium collecting means for use in the above methods, comprising a funnel member communicating with a collecting bottle, the funnel member having an elongate resilient sealing lip extending along a flat upper edge thereof for sealing engagement in use against a surface with which the collecting means is engaged. The collecting means is preferably arranged for pivotal movement to enhance said engagement in use.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, wherein: Fig. 1 shows a perspective view of a first method and apparatus in accordance with the invention; Fig. 2 (a) shows an enlarged view from one side of a part of the collecting means shown in Fig. 1; Fig. 2 (b) shows the collecting means of Fig. 1 with its handle detached, for use in an alternative method; Fig. 3 shows a second form of collecting means for use in a further method in accordance with the invention; Fig. 4 shows an arrangement in which the collecting means of Fig 3 is attached to a flexible line; and Fig. 5 illustrates the collecting means of Fig. 3 attached to a long handle.

Fig. 1 shows a wall wash sample being collected from a surface of a wall within a tank. The apparatus shown in Fig. 1 includes a storage tank fitted with a manually operable piston and cylinder pump of known type, shown schematically at 2, for pressurising a liquid washing medium 3. Means 4 for directing the washing medium 3 on to wall 1 comprise an extended lance 5 having a nozzle 6 at one end. At the other end, lance 5 is provided with a gun 7 which is operable to start, cut off and control the flow rate of washing medium 3 through the lance.

Also shown in Fig. 1 and in greater detail in Fig.

2 (a) is a collecting means 8 which is manually supportable by means of a detachable long handle 9 against wall 1. The collecting means 8 has an elongate funnel means 10 at its upper end, and an elongate resilient polytetrafluoroethylene strip 11 bolted along one side of the funnel means 10. A hollow tubular stem 12 extends downwardly from funnel means 10 and is detachably engaged at its lower end with a bottle 13. A suction device 14 of known type is engaged against the wall 1, but not necessarily actuated to hold the collecting device in place in the arrangement shown in Fig. 1, since the device is supported manually via the long handle.

In Fig. 1 the pressurised liquid washing medium 3 is being directed as a fine spray on to the surface of wall 1 through directing means 4. The liquid 3 is washing down the surface under gravity and is being collected in bottle 13 via funnel means 10 and stem 12.

Samples of any impurities and contaminants on the washed surface 15 will be present in the collected sample and can be analysed to assess the level of contamination and suitability of the tank for filling with particular substances.

In use the collecting means 8 is pivoted about the point of engagement of suction device 14 on wall 1 by means of leverage on the long handle 9 by the operator, to the position shown dotted in Fig. 2 (a). In this position a good seal is formed between the lip 16 of resilient elongate ptfe strip 11 and the washed surface 15 to ensure efficient collection of the washings.

It will be seen that in Figure 1 the wall wash is being performed by a single operator 17 who is holding the lance 5 in one hand and the long handle 9 of the collecting means 8 in the other hand. The operator 17 is performing the wall wash at a distance from the washed surface 15 and is at a significantly reduced risk from exposure to the washing medium 3 than in conventional techniques. It is believed that the vapour levels in the proximity of the operator are about half the levels which would be expected in conventional techniques, and there is less risk of the medium splashing on to the operator. Because the operator 17 stands away from the washed surface 15 the risk of contamination of the sample is avoided. The washed surface 15 is above the normal reach of the operator and would normally be inaccessible for testing under conventional techniques without the use of ladders.

Fig. 2 (b) shows collecting means 18 used in an alternative method, which are identical to the collecting means 8 shown in Fig. 2 (a) with the long handle 9 detached. The collecting means 18 is selfsupportingly fixed to the wall 1 by actuating the suction device 14 i.e. by tightening a clamping member 14' over the sucker of the device to provide firm engagement between the device and the tank wall. Angular adjustment means 19 below the suction device 14 extends from collecting means 18 substantially perpendicularly to the surface of wall 1. Angular adjustment means 19 is threadedly engaged with stem 12 and can be extended or retracted.The angular adjustment means 19 is shown in its retracted position in Fig 2 (a) and is shown extended in Fig 2 (b) such that it abuts the surface of wall 1 and thereby levers the collecting means 18 about the pivot formed by suction device 14 so that a seal is made between the lip 16 of resilient elongate ptfe strip 11 and the washed surface 15.

The collecting means 18 shown can be used with a lance 5 operated from within a tank as shown in Fig 1, or a washing medium could be directed at the surface above device 18 from outside of the tank through a roof hatch or other access port. In these circumstances the levels of vapour and risk of physical contact with the washing medium will be further reduced as the operator can leave the tank entirely during the washing operation and only enter it again to move or retrieve the collecting means 18. The collecting means 18 illustrated in Fig 2 (b) is engageable with the surface of the wall 1 and disengageable therefrom by hand before and after each washing operation. It may however also be possible to adapt it for use with suction or other means for engaging and disengaging with the wall remotely.

Fig 3 shows an alternative form of collecting means 20 comprising a rigid bar 21, around which a sponge 22 (part only shown) is wrapped and secured. A row of magnets 23 is provided along one side of the rigid bar 21, providing means of mounting the device 20 to a magnetic surface within a tank. The collecting means 20 is provided with an eye 24 for attachment to a flexible line 25 and with a socket 26 for threaded engagement with a long handle or rod 27.

The collecting means 20 of Fig 3 is shown in use in a further method in Fig 4 within a tank 28. In the apparatus illustrated schematically in Fig 4 the collecting means 20 is attached to line 25 and the long handle 27 is detached. The device 20 is attachable to the walls of magnetic tank 28 by means of magnets 23 from outside the tank by swinging it towards the wall of the tank on the end of line 25. Two hatches 29 and 30 in the roof of the tank provide access for the line and for a lance 31 for directing pressurised liquid 32 from pump means 33 towards the wall above collecting means 20. The lance 31 is similar in construction to the lance 5 in liquid directing means 4 shown in Fig 1.

Once a wall wash is finished a sharp tug on line 25 will detach the device 20 from the tank wall and it can be swung to another position or retrieved from the tank for analysis.

Fig 5 illustrates the collecting means 20 of Fig 3 in use in a tank 34, attached to the long handle 27 and with the line 25 detached. The tank 34 contains obstructions and the use of a long handle allows better control of the positioning of the device 20 than the line 25, and avoids the risk of the line fouling on any obstructions. The line is made up of sections so that it is of variable length. In other respects the apparatus illustrated in Fig 5 operates in the same way as the apparatus of Fig 4 and similar parts are given identical reference numerals.

An advantage of the arrangements of Figs 4 and 5 is that after possible initial visual inspection of the 'clean' tank to select the areas for testing, a plurality of samples can be taken without the need for an operator to enter the tank once wall washing commenced.

It is to be appreciated that the above embodiments are illustrated by way of example only and, for example, alternative means of collecting the washings from the washed surface and of mounting and moving or retrieving the collecting means, both from within and outside of a tank are envisaged.

Claims

1. A method of wall washing a tank comprising directing a pressurised jet or spray of liquid washing medium on to a selected region of a surface of a wall within the tank, allowing the liquid to wash down the surface under gravity, and collecting a sample of the washings by collecting means engaged with the surface below the region where the jet or spray impinges on the surface.

2. A method of wall washing a tank as claimed in claim 1 wherein the spray or jet is directed on to the surface via an elongate hand held lance.

3. A method of wall washing a tank as claimed in claim 1 or 2 wherein the supply of washing medium on to the surface is directed or actuated from outside the tank.

4. A method of wall washing a tank as claimed in any preceding claim wherein the washing medium is directed on to the selected region of the surface as a fine spray.

5. A method of wall washing a tank as claimed in any preceding claim wherein the method is performed by a single operator.

6. A method of wall washing a tank as claimed in any preceding claim wherein the collecting means is provided with a long handle.

7. A method of wall washing a tank as claimed in any preceding claim wherein the collecting means is releasably self supportingly held on the surface before washing takes place.

8. A method of wall washing a tank as claimed in claim 7 wherein the releasable fixing of the collecting means to the surface and/or disengaging of the collecting means therefrom is carried out from outside the tank.

9. A method of wall washing a tank as claimed in claim 7 or 8 wherein the collecting means is attached to a flexible line by means of which it is handled for engagement with and/or disengagement from the surface.

10. A method of wall washing a tank as claimed in any of claims 7 to 9 wherein the collecting means is releasably fixed to the surface by magnetic means.

11. A method of wall washing a tank as claimed in any of claims 7 to 10 wherein the collecting means is releasably fixed to the surface by suction means.

12. A method of wall washing a tank as claimed in any preceding claim wherein the collecting means comprises a receptacle and funnel means, the funnel means forming a seal against the surface for guiding the washings into the receptacle.

13. A method of wall washing a tank as claimed in any of claims 1 to 11 wherein the collecting means includes a swab or a sponge.

14. A method of wall washing a tank as claimed in any preceding claim wherein the collection means includes biasing means for biasing a part of the collection means toward the surface, the biasing means being operated to form a seal between a part of the collecting means and the surface.

15. A method of wall washing a tank as claimed in claim 14 wherein said biasing means includes a pivot support.

16. A method of wall washing a tank as claimed in claim 15 wherein means of releasably fixing the collecting means to the surface forms the pivot support.

17. A method of wall washing a tank as claimed in claim 15 or 16 wherein the collecting means is pivoted about the pivot support by means of angular adjustment means abutting the surface below the pivot support.

18. A method of wall washing a tank as claimed in any of claims 1 to 17 further comprising the step of performing a laboratory analysis of said sample of the washings to validate said tank.

19. Wall washing apparatus for use in the method of claim 1 comprising a tank for containing liquid washing medium, pressurising means for pressurising the washing medium, directing means for directing a pressurised jet or spray of the liquid on to the surface which is to be washed, and collecting means adapted for engagement with the surface for collecting a sample of the washings.

20. Wall washing apparatus as claimed in claim 19 wherein the directing means comprises an elongate hand held lance.

21. Wall washing apparatus as claimed in claim 19 or 20 which is adapted to supply the washing medium on to the surface as a fine spray.

22. Wall washing apparatus as claimed in any of claims 19 to 21 wherein the collecting means is provided with a long handle.

23. Wall washing apparatus as claimed in any of claims 19 to 22 wherein the collecting means is releasably fixable to the surface in use.

24. Wall washing apparatus as claimed in claim 23 wherein the collecting means is provided with means for attachment to a flexible line whereby said collecting means can be engaged with and/or disengaged from the surface in use.

25. Wall washing apparatus as claimed in any of claims 19 to 24 wherein the collecting means is provided with one or more magnets for fixing to the surface in use.

26. Wall washing apparatus as claimed in any of claims 19 to 25 wherein the collecting means is provided with suction means for fixing to the surface in use.

27. Wall washing apparatus as claimed in any of claims 19 to 26 wherein the collecting means comprises a funnel member communicating with a collecting bottle, the funnel member having a lip adapted for sealing engagement against the surface in use.

28. Wall washing apparatus as claimed in claim 27 wherein said funnel member has an elongate resilient sealing lip.

29. Wall washing apparatus as claimed in any of claims 19 to 26 wherein the collecting means incorporates a swab or sponge.

30. Wall washing apparatus as claimed in any of claims 19 to 29 wherein the collecting means includes biasing means for biasing a part of the collecting means toward the surface in use to form a seal therewith.

31. Wall washing apparatus as claimed in claim 30 wherein the biasing means includes a pivot support.

32. Wall washing apparatus as claimed in claim 31 wherein means of releasably fixing the collecting means to the surface comprises the pivot support.

33. Wall washing apparatus as claimed in claim 31 or 32 wherein the collecting means includes extensible and retractable angular adjustment means adapted in use to abut the surface below the pivot support whereby to pivot a part of the collecting means about the pivot support.

34. Wall washing apparatus as claimed in any of claims 19 to 33 in the form of a portable kit.

35. A washing medium collecting means for use in the method of claim 1 comprising a funnel member communicating with a collecting bottle, the funnel member having an elongate resilient sealing lip extending along a flat upper edge thereof for sealing engagement in use against a surface with which the collecting means is engaged.

36. A washing meduim collecting means as claimed in claim 35 which is provided with a long handle.

37. A washing medium collecting means as claimed in claim 35 or 36 which is releasably fixable to the surface in use.

38. A washing medium collecting means as claimed in claim 37 which is releasably fixable to the surface in use by suction means.

39. A washing medium collecting means as claimed in any of claims 35 to 38 which is arranged for pivotal movement about a pivot support to enhance said sealing engagement in use.