[0001] This invention relates to the cleaning of vessels from any solius element or residue
remaining after the discharge of materials of liquid, gaseous or flowable solid form,
or after maintenance operations involving derusting or descaling, which vessels can
be land-based, or sea-based on rigs or platforms for material storage or be the cargo
carrying holds or tanks of ships. The invention is more particularly concerned with
the cleaning of the tanks or holds of ships.
[0002] Escalating manning costs in ships in recent years has, predictably, led to a concerted
move on the part of owners to reduce their crews to the minimum comp- atable with
statutory requirements and the efficient operation of their ships. This in turn has
stimulated research into technical advances capable of eliminating or at least reducing
labour intensive operations on board ships.
[0003] This is particularly true in the design and operation of bulk and combination carriers.
However, in this field the task has been bedevilled by a swiftly changing pattern
of world trade. The steady decline of the liner trade of such ships has given rise
to a demand for highly flexible ships more suited to voyage and time chartering. In
turn, this requirement has highlighted perhaps the most labour intensive operation
of all in this class of ship - hold cleaning. The solids element remaining after the
discharge of cargo which can be say grain at one time or say iron ore or coal the
next time can be of the order of many tons. Not only can the solids element be left
on the hold bottom but also residues can remain on the hold walls which- have to be
washed down to the hold bottom for removal. In dcrusting or descaling operations which
usually involve the use of blasting grit, again many tons of solids have to be cleaned
from the hold before anti-corrosion treatment can be carried out.
[0004] Various arguments have been advanced as to how often holds require cleaning, some
operators maintaining it is only necessary when changing from one type of cargo to
another while others clean their holds on a weekly basis. The truth is, there is no
hard and fast rule on the subject. In some cases the nature of the cargo is such that
if the holds are not washed immediately after discharge the residues can harden to
a point where it is almost impossible to remove them. Again cargo residues harbour
moisture which can aggravate corrosion problems. What is not in doubt, however, is
the cleaning job whatever its nature is time consuming and labour intensive and therefore
costly. The longer the cleaning job takes, the greater the down time,which in bulk
and combination carriers reduces their flexibility and increses their operating costs.
[0005] Faced with the inevitable, the operator of bulk and combination carriers has two
options open to him dependent on the previous cargo and the next one to be carried.
These basically are, simple sweeping of the hold bottom or a combination of washing
down and sweeping. Where washing down is involved there are again various options
- the use of a) ordinary wash hoses, b) a high pressure wash unit inaucing air into
the water flow, c) tank washing machines in either the fixed or portable mode but
either way more usually associated with tank cleaning in oil tankers. The common factor
in each case is that the solids element has to be removed from the hold bottom. Where
washing down is involved this is even more essential if abrasive materials are not
to find their way into the ballast lines and pumps causing potentially expensive damage.
[0006] Again, in the case of oil bulk ore or oil ore tankers,the residue left in-the tanks
after discharge of the oil may take the form of a thick sludge which has to be cleaned
from the tank bottom before they are refilled which is time consuming, labour intensive
and costly.
[0007] Similar problems exist with stationary land or sea-based material holding vessels
such as containers, tanks or hoppers.
[0008] It should be appreciated that the term "bottom" is used herein in relation to "vessel"
in a generic sense to embrace the tank top ceiling of a ship, the base area of a ship's
hold on which cargo is supported and the floor of a storage container such as a hopper
grain silo or tank, or bottom say of a sewage pond.
[0009] The length of time and number of personnel required to carry out the cleaning operation
are directly related to the method which has hitherto been employed to remove the
residue from the bottom of the vessel, and which is basically a "bucket and spade
job". This can either involve the residue or other solids material, such as rust scale
and grit blastabrasives, being spaded into bucket grabs or other suitable containers
for transport out of the vessel for ultimate discharge,or alternatively, spaded into
a portable jet pump which has been lowered into the vessel and is supported on the
vessel bottom with its entrainment jet located above the vessel bottom. Even if the
capacity of a portable jet pump could be increased whilst still keeping its portability,
the cleaning time is still dictated by the ability and number of men to spade the
solids material into the pump, the limit being typically, for a heavy material such
as iron-ore, 2 to 2) tons per man hour. Thus, the time consuming and labour intensive
nature of this operation can be readily appreciated, particularly when one considers
bulk carriers, which may have as many as eight holds, each 90 feet deep and having
a bottom area of 700 square metres, for example.
[0010] In another hold cleaning system known to the applicants vertically arranged eductors
are disposed behind the bulkheads, the eductors being enclosed within fluid lines
which connect them to remotely disposed suction inlets in the hold bottom, and acting
to suck the solids material from the holds. Such eductors are not very efficient,
can block and in the event of wear from abrasive materials, the whole eductor has
to be replaced, which is an expensive and time consuming operation, not the least
because of the disposition of the eductors behind the bulkheads.
[0011] Recent reductions in manning level legislation have resulted in a more urgent need
for a vessel cleaning system, in particular for the holds of ships, in which the aforesaid
disadvantages are avoided or substantially reduced.
[0012] Accordingly, the main object of the present invention is to provide a method of and
installation for cleaning vessels in which the cleaning time and number of personnel
required are substantially reduced, which is much more efficient, in which any worn
parts may be easily and quickly replaced, which can cope withthe larger particle sizes
of solids materials without sacrificing efficiency, which can both be installed in
existing ships or into ships being built, and which in the case of bulk or combination
carriers considerably increases their flexibiility.
[0013] To this end and from one aspect, the present invention consists in a method of cleaning
a vessel from solids material from the bottom of the vessel, in which the solids material
is entrained in at least one pressurized jet of fluid, characterized by providing
at least one aperture in the vessel bottom, generating, said entrainment jet beneath
said vessel bottom and said aperture,with said entrainment jet being projected in
a direction which is substantially parallel with said vessel bottom and being exposed
to the vessel interior through said aperture, providing at least one pressurized jet
of washing fluid to wash the solids material from the vessel bottom, through said
aperture and into entrainment with said entrainment jet, and leading the fluid entrained
solids material out of the vessel.
[0014] From another aspect the present invention consists in an installation for use in
cleaning solids material from the bottom of a vessel, in which the solids material
is entrained in at least one pressurized jet of fluid, characterized by means defining
at least one aperture in the vessel bottom, means for producing a pressurized jet
of fluid for entraining solids material therein, and disposed in at least one location
beneath said vessel bottom and beneath said aperture, said means including nozzle
means for projecting said entrainment jet in a direction which is transversely of
said aperture and generally parallel with said vessel bottom, means for producing
at least one pressurized jet of washing fluid for washing solids material from the
vessel bottom, through said aperture and into said entrainment jet, and at least one
discharge line for the passage of fluid entrained solids material out of the vessel,
whereby in operation said entrainment jet is exposed to the vessel interior through
said aperture, and solids material washed through the aperture by the pressurized
washing fluid passes directly into said entrainment jet to be entrained therein and
the fluid entrained solids material is discharged through said discharge line in the
fluid flow engendered by the entrainment jet.
[0015] The invention also consists in a vessel, or a ship comprising at least one vessel
such as a hold, provided with such an installation.
[0016] Because of the disposition and arrangement of the or each entrainment jet and the
fact that the or each entrainment jet is exposed to the vessel interior through the
aperture it is an extremely simple matter using pressurzied jets of washing fluid
to wash the solids material from the vessel bottom directly into the entrainment jet(s)
which considerably reduces time and the number of operating personnel required. Since
the entrainment jet is exposed to the vessel interior, i.e. is in direct communication
therewith, without the solids material having to pass through a fluid line or through
valves, speed and efficiency of cleaning is considerably increased as compared to
all the systems known to the Applicant. Even if screens such as grilles, gratings
of wire mesh or the like are placed over the aperture, which is preferred in order
to.prevent solids material having a particle size which is beyond the permissible
maximum from entering the entrainment jet, this in no way interferes with the exposure
of the entrainment jet to, or direct communication between the entrainment jet and,
the vessel interior. When used on board ship the method and apparatus have considerable
advantages over the known systems. Spading is eliminated. The number of ship personnel
required to operate the method and installation can be reduced to as little as two.
In the case of a bulk carrier changing over cargoes,
[0017] the cleaning time can be reduced as little to 2 - 5 hours per hold depending on the
materials involved. Thus, the requirement for flexibility with bulk and combination
carriers is not only fully met but is to the applicant's knowledge met to a degree
which is without parallel in any of the known hold cleaning systems. The method and
installation can be operated under bad weather conditions at sea since the hatches
can be left in position on the holds which eliminatesthe possibility of the loss of
opened hatches overboard.
[0018] Furthermore, unlike cleaning systems utilizing partial suction with eductors, the
method and installation according to the invention creates a positive head which allows
vertical lifts well in excess of 30 metres to be achieved, which provides the further
advantage that depths of tanks or holds for shipboard applications pose no problems.
Moreover, with installations constructed in accordance with the invention blocking
is virtually eliminated and the throat size of the jet entrainment arrangement can
readily be made of greater bore size enabling the installation to deal effectively
with larger solids particle sizes. For example particle sizes of 4 inches (95 mm)
and larger can be accommodated. Indeed when tank washing machines are employed, for
cleaning the holds of ships, the whole cleaning operation can be automated, which
further reduces the cleaning time and number of operating personnel.
[0019] The entrainment fluid is selected in dependance upon the nature of the solids material
and may be fresh water, sea water, oil, compressed air, steam, methyl gas or hexyl
alcohol or other suitable liquids, gases or mixtures thereof. With most bulk or combination
carrier cargoes, sea water can be used and is used for obvious reasons.
[0020] The washing fluid may be high pressure water by itself or water in which air is induced
into the water flow.
[0021] In order to facilitate the flow of washing fluid entrained solids material from the
aperture and into the entrainment jet, means such as a hopper or funnel is advantageously
provided for guiding the solids material into entrainment with the jet. Such a hopper
or funnel has its wider open upper end fixed to that part of the vessel bottom which
defines the aperture and its lower narrower end fixed to a housing which defines an
open-topped chamber across which the jet flows, with the open lower end of the hopper
or funnel being in communication with the chamber through its open top. This ensures
that the solids material is quickly and efficiently directed straight from the vessel
bottom into the entrainment jet by means of the high-pressure jets of washing fluid.
[0022] The hopper or funnel conveniently has a rim at its upper end which preferably rests
on a flange which is inset into the aperture, the inset being of sufficient depth
to accommodate the flange, a screen, a sealing gasket and a removable cover such that
the cover is flush with the vessel bottom to avoid damage, the cover being in position
when the vessel carries solidsmaterial and being removed for a cleaning operation.
[0023] In a preferred embodiment of the invention, the nozzle means is detachable, e.g.
by mounting it in a holder by means such as screw-threads,and projects into the chamber
with the nozzle being connected to a source of pressurized fluid via a suitable supply
line. The entrainment jet is directed across the chamber and into a mixer chamber
for the fluid entrained solids material which in turn is connected, preferably via
a diffuser, to the discharge line, which carries the solids material in the flow of
fluid engendered by the jet which in the case of a ship can be overboard or alternatively
to a suitable storage container on deck, or waste reception tank for subsequent discharge.
[0024] The arrangement of the jet nozzle, open-topped and mixer chambers and diffuser, acts
as a jet pump which utilises the venturi principle and, as will be appreciated, has
the considerable advantage of not having any moving parts.
[0025] For any given size of jet entrainmentarrange- ment the particle size to be handled
can be optimized by adjusting the distance between the nozzle and mixer entry to relate
to the mixer diameter, the ratio of the distance between the nozzle to mixer entry
to mixer internal diameter preferably being of the order of 1:1.
[0026] With ships having double bottoms, the jet entrainment arrangement is conveniently
mounted between adjacent vertically extending floors which run longitudinally of the
ship within the double bottom, i.e. between the tank top ceiling and ship bottom and
)to provide a chest or enclosed space for the jet arrangement, the opposite open ends
of the containing space can be closed off by partitions extending between the adjacent
floors.
[0027] Again in the case of ships, in particular those having double bottoms, the aperture
and thus the entrainment jet could conceivably be located anywhere in and beneath
the tank top ceiling (vessel bottom). However, applicants have found that the optimum
position for a hold having one such aperture and entrainment jet is adjacent the bilge
well which is located in the aft/outboard corner of the or each hold, and this constitutes
another preferred feature of the invention. This has the advantage that when the flow
of pressurized fluid to the nozzle means is stopped at the end of a cleaning operation,
when liquids are used as the cleaning and entrainment fluids, the liquids in the supply
and delivery or discharge lines flow back into the hold through the aperture and can
enter the adjacent bilge well for discharge by the bilge pump system. If a second
entrainment jet is required for the or each ship hold, it can advantageously be positioned
in the opposite aft outboard corner of the or each hold.
[0028] In accordance with another preferred feature of the invention, a further facility
can be provided with the removal sealing cover in position over the aperture in the
vessel bottom to clean-out debris. e.g. segiment or rust scale from adjacent double-bottom
tanks, and to suck up water from inside the double bottom. When such tanks are used
to carry ballast water, such ballast water can include a substantial amount of mud
if taken in from the bottom of a river estuary for example. Accordingly, the jet entrainment
arrangement is provided with an inlet or aperture which is preferably in the open-topped
housing and which is additional to the aperture in the bottom of the vessel, for connection
to a fluid line. When the additional inlet is used for cleaning out sediment and scale
from the double-bottom tanks and cleaning remaining debris from the vessel bottom,
the fluid line is conveniently a flexible hose. The flexible hose can be brought into
hold interior through any of the existing normally closed entry apertures for access
to the double-bottom tanks. In the case of sucking up water or other liquid from the
double-bottom tanks, the fluid line is preferably a rigid length of pipe having an
outwardly flared free end. This arrangement is such that a suction is produced enabling
debris from the adjacent double-bottom tanks to be sucked through the hose and entrained
into the entrainment jet for discharge. When a gas such as air or steam is used as
the entrainment fluid a strong vacuum of the order of24 inches of mercury (0.829 kg/cm
2) is produced. The additional inlet is located in the housing wall, advantageously,
opposite the opening in the open-topped chamber in the bottom wall of the housing
or in a side wall of the housing. This is an extremely important optional feature
of the present invention and can eliminate the necessity for bilge pumps since water
in the bilges can also be sucked out by means of the vacuum created by the entrainment
jet.
[0029] The additional inlet or aperture is normally closed, for example by means, of a removable
blanking plate or by a manually, electrically, pneumatically or hydraulically operated
plate valve. When the inlet is in the bottom wall of the housing the blanking plate
or plate of the valve forms in effect the bottom wall, when closed. By providing suitable
connections, e.g. of the bolt and flange type, it is a simple manner to connect the
flexible hose or flared pipe. The free end of the flared pipe is conveniently located
a short distance from the ship bottom inside the double-bottom tank, e.g. about 1
inch (2.54 cm).
[0030] In order to ensure that only those particle sizes of the solids material compatible
with the jet arrangement and bore size of discharge line are accepted into entrainment
jet, a grill or grating may be inset into the aperture around the open funnel or hopper
top so as 'effectively to screen the solids material particle size to the maximum
permissable.
[0031] In a typical installation either one or two jet entrainment arrangements can be fitted
in each ship tank or hold. Where only one jet entrainment arrangement is employed
provision will have to be made to ensure a suitable trim to allow for drainage to
the arrangement.
[0032] All requisite control valves can be at deck level and provision made to break the
fluid supply line to ensure against accidental flooding of the holds or tanks in the
event of failure to close the deck valve.
[0033] Maintenance of the jet entrainment arrangements is minimal and normally involves
no more than exchanging nozzles and mixer chambers when after prolonged use these
become worn - a simple five minute operation. It is another feature of this invention
that replacement of worn mixer chambers and nozzles can be simply and quickly achieved
through the aperture. without having to go to the expense of long downtime and replacement
of the whole jet entrainment arrangement. Moreover, the nozzle replacement facility
enables changing over of nozzles for differing solids material cargoes to optimize
efficiency.
[0034] Typically, to cover all current ship sizes, the jet entrainment arrangements can
be supplied to handle 80, 100, 120 or 240 tons of entrainment water per hour but can
handle more if the circumstances require it. In the range given above, the body of
the arrangement can be of the same dimensions with the different performance requirements
being met simply by varying the jet nozzle and mixer chambers to which end the nozzles
are removably mounted in suitable holders and the mixer chambers detachable, as aforesaid.
[0035] In the case of a ship, the jet entrainment arrangement can be incorporated into an
extension of the conventional bilge well or into a conventional pipe tunnel extending
along the centre line of the ship.
[0036] When installations constructed according to the invention are installed in existing
ships it is a simple matter to cut the necessary aperture in the hold or tank bottom
for accommodating the jet entrainment arrangement.
[0037] Supply and discharge lines can then be easily run down the hold or tank bulk-heads
and beneath the bottom.
[0038] When ships are being built with the installations, the vertical lengths of the supply
and discharge lines can be disposed behind the tank or hold bulk- heads.
[0039] Service access can be simply achieved,when it is desired to change the nozzle and/or
mixer for example, through the aperture to the entrainment jet, and unbolting the
various parts such as the hopper, unscrewing the nozzle and/or unbolting the mixer.
[0040] The invention further consists in a kit of parts for use in the production of any
of the installations defined hereinabove.
[0041] In order that the invention may be more readily understood, reference will now be
made to the accompanying drawings, in which:-
Fig. 1 is a diagrammatic side elevation through a bulk carrier incorporating an installation
constructed in accordance with the present invention,
Fig. 2 is a plan view of the bulk carrier of Fig. 1,
Fig. 3 is a section through Fig. 1 and showing the bottoms of the holds of the bulk
carrier,
Fig. 4 is a cross-section through one of the holds of the bulk carrier of Fig. 1,
Fig. 5 is a diagrammatic perspective view of one of the holds of the bulk carrier
of Fig. 1 with parts broken away,
Fig. 6 is a cross-secion through the double- bottomed tank of the hold of Fig. 5,
showing one form of jet entrainment arrangement,
Fig. 7 is a plan view of the jet entrainment arrangement of Fig. 6,
Fig. 8 is an end-view of the'jet entrainment arrangement of Fig. 6,
Figs. 9 and 10 are cross-sections,through the jet entrainment arrangement of Fig.
6, and taken along the line X- X of Fig. 9, respectively,
Fig. 11 shows an alternative mode of locating different sized mixers in the jet entrainment
arrangement of Figs. 6 to 10 ,
Fig. 12 is a flow diagram illustrating one way of operating the installation,
Fig. 13 is a flow diagram of the installation, and
Fig. 14 is a block diagram of an electrical control circuit for the installation.
[0042] Referring to Figs. 1 to 5 of the drawings, the bulk carrier which is generally indicated
by the reference 1 is of double-hulled construction having double-bottom and side
tanks 2 and 3 respectively and seven cargo carrying holds 4, constituting vessels
for containing solids material, which are closed by respective hatch covers 5. The
bottom or deck of each hold 4 on which the solids material rests, is constituted by
the tank top ceiling 6 of the associated double-bottom tank 2 and the bottom proper
of the bulk carrier is indicated by the reference 7. The bulk carrier is also provided
with wing tanks 8 located in the upper regions of the holds 4.
[0043] Each hold 4 is provided with an installation for use in cleaning the hold from solids
material, such as a cargo of grain, remaining on the tank top ceiling 6 after the
discharge of the cargo and prior to loading with another cargo of solids material,
for example iron ore. Each installation comprises a jet entrainment arrangement which
is hereinafter referred to as a jet pump and which is indicated by the reference 9,
and a means for supplying the pressurized jet(s) of washing fluid including two tank
washing machines 10. Since the installation'is on board a ship, water being readily
available, is almost invariably adopted for use as the washing fluid and as the entrainment
fluid and, therefore, will be used for the purposes of this description. Mounted on
and extending longitudinally of the deck 11 of the bulk carrier 1 are water supply
lines in the form of headers 12 and 13 for the jet pumps 9 and the tank washing machines
10 in all the holds 4. The headers 12 and 13 are connected to a single pump 14 of
suitable capacity or, alternatively, to respective pumps 14, 14a of which the pump
14a is shownin dashed lines in Fig. 2. Branch lines 15 extend to each hold from the
header 12 and are connected to respective water supply lines 16 having on deck horizontal
sections with gate valves 16a from which the lines 16 extend vertically down-through
the holds behind the aft bulkheads 17 and beneath the tank top ceilings 6 to the jet
pumps 9. Alternatively, as shown in Fig. 5, one water supply header 12, 13, may supply
both the jet pumps 9 and the tank washing machines 10.
[0044] The tank washing machines 10 are connected to the water supply header 13 or to -
the common water supply header 12, 13 (Fig. 5) by branch lines 18 having gate valves
18a therein (Fig. 5). As shown in more detail in Fig. 5, each jet pump 9 has a water
entrained solids material discharge line 20 projecting therefrom and horizontally
beneath the respective tank top ceiling 6, vertically upwards behind the aft bulkheads
17, out through the deck 11 where there is a horizontal section 21 which extends to
a gate valve 21a located near one side of the bulk carrier 1. A conveniently flexible
hose 22 is connected to.the outboard side of the gate valve 21 and leads over the
ships side. The discharge line 20 has a diameter which is greater than that of the
associated water supply line 16, both the supply and discharge lines 16 and 20 conveniently
being metal pipes. The bore size of each discharge line 20 is of greater diameter
than that of each supply line 16; for example the discharge lines may have an internal
diameter of 4 inches (95 mm) and the supply lines 16 an internal diameter of 3 inches
(75 mm). In places where the installation is installed in an existing ship, the supply
and discharge lines 16 and 20 conveniently run down the aft bulkhead 17 inside the
hold 4.
[0045] Each tank washing machine 10 includes a casing 23 mounted on the deck 11 and a water
delivery line 24 depending from the casing 23 and extending through the deck and into
the hold 4, the water delivery line 24 terminating in a washing unit 25. The delivery
line 23 andthe washing unit 24 are retractable into the deck mounted casing 23, from
inside the hold 4.
[0046] As shown in Fig. 5, each jet pump 9 is disposed in a fluid-tight chest 26, beneath
an aperture 27 located in the tank top ceiling 6 aft of each hold 4 adjacent one of
the outboard bulkheads 28 and a bilge well 29 in one aft/outboard corner of the hold.
The fluid-tight chest comprises portions of floors 30 which extend longitudinally
of the ship's hull and vertically between the tank top ceiling 6 and the hull bottom
7,a portion of the bulkhead 28 and partitiors 31 and 31a.
[0047] Additional jet pumps 9 (only three shown by the dashed lines in Fig. 3) may also
be located beneath respective apertures in the tank top ceilings 6 in the other aft/outboard
corners of each hold 4.
[0048] Referring more particularly to Figs. 6 to 10, each jet pump 9 is mounted in the chest
26 by means of flanges 32, 33 at its opposite ends which are removably fixed as by
the diagrammatically illustrated bolts 34 to the floors 30. The bolts 34 also extend
through mounting flanges 35 and 36 on the water supply and discharge lines 16 and
20 respectively to secure them to the floors 30 in alignment with apertures therethrough.
Passing from its upstream to its downstream ends, the jet pump 9 comprises a supply
pipe 37 leading from the supply line 16, a nozzle holder 38 projecting through the
upstream end of a housing 39 and carrying a nozzle 40 within the housing, a mixer
41 surrounded by a tubular sleeve 42, the mixer and sleeve projecting into the downstream
end of the housing 39 and a diffuser 43 leading into the discharge line 20. The supply
pipe 37 and diffuser 43 mount the flanges 32 and 33 respectively. The nozzle holder
38 and supply pipe 37 are removably fixed together as by the diagrammatically illustrated
bolts 43 passing through mounting flanges 44 and 45. The nozzle holder 38 passes through
an aperture in the housing 39 and is welded in the aperture around weld lines 46.
[0049] The mixer sleeve 42 has mounting flanges 47 and 48 located inwardly of its upstream
end and at its downstream end respectively through which pass the diagrammatically
illustrated bolts 49, 49a, which removably fix the sleeve 42 to housing 39 and to
a mounting flange 50 which is rigid with the upstream end of the diffuser 43. The
sleeve 42 enables interchanging and the locating of different sized mixers, by access
through the aperture 27,
[0050] in a manner to be described. The mixer 41 is located coaxially within the sleeve
42 and with respect to an aperture in the housing 39 through which the upstream end
of the mixer and sleeve project by means of a screw-on end cap 51 and to the diffuser
42 by the engagement of the downstream end 52 of the mixer in an annular mating recess-
(not visible) in the diffuser flange as in Fig. 9 or in a separate annular mounting
piece 53 which is located in the diffuser flange recess 54 as shown in Fig. 11.
[0051] The nozzle 40 is replacably and adjustably mounted in the nozzle holder 38, for example
by means of an external screw thread (not shown) on the nozzle engaging with an internal
screw thread (not shown) in the bore of the nozzle holder.
[0052] The housing 39 defines an open topped chamber 55 which is in communication through
its open top with a hopper or funnel 56 for guiding solids material entrained in the
washing water from the aperture and into a pressurized jet 57 of the entrainment liquid
generated by the passage of liquid through the nozzle 40. The housing 39 has an access
aperture 58 in one of its walls which is closed by a cover or blanking plate 59.
[0053] The lower smaller open end of the hopper 56 is provided with an inwardly directed
flange 60 which is secured as by the diagrammatically illustrated bolts 61 to an inwardly
directed flange 62 which is integral with the housing 39 and extends around the open
top of the chamber 55. At its upper wider open, the hopper 56 has an - outwardly directed
flange or rim 63 which rests on an inwardly projecting annular lip 64 below the aperture
27 and which is removably fixed to the lip 64, by the diagrammatically illustrated
bolts 65. An annular sealing gasket 66 is positioned on the rim 63 and a screen or
grille 67 for screening solids material particle size to the maximum permissible for
the jet pump 9 extends across the aperture 23 and rests at its periphery on the gasket
66. The position of the lip 64 is such that the hopper rim 63, gasket 66, screen 67
and a removable cover 68 are inset in the aperture 27 and the cover 68 is flush with
the surface of the tank top ceiling 6. The cover 68 is secured to the lip 64 as by
the diagrammatically illustrated bolts 69, with the gasket sealing the cover in the
aperture 26, when the hold carries cargo and is removed by undoing bolts 69 for a
cleaning operation.
[0054] In order to replace the mixer 41 by one of an increased or reduced size, in the embodiment
of Fig. 9, the cover 68 is unbolted and removed together with the screen 67 and gasket
66, the bolts 65 and 61 are undone and the hopper is removed through the aperture
27, The nozzle 40 is unscrewed and removed through the aperture 27, The end cap 51
is unscrewed and removed together with the mixer and sleeve 42 through the aperture
26. Since the annular mating recess for the end 52 of the mixer 41 is matched to that
mixer, the diffuser is unbolted by undoing bolts 34 and 49 and is removed through
the aperture and replaced by a diffuser having an annular recess which matches the
end 52 of the replacement mixer and is then located in the annular recess in the flange
of the replacement diffuser, and a suitable end cap is screwed back on. A nozzle appropriate
to the replacement mixer is screwed into the nozzle holder, the hopper 56 is bolted
back into position and the gasket 66, and screen 67 are replaced. This operation can
be simply and quickly achieved which is a very important factor in view of the location
of the jet pump 9 beneath the tank top ceiling 6.
[0055] An even quicker and easier way of changing the mixer 41 since it does not require
the diffuser also to be changed can be achieved by use of the annular mounting piece
53 illustrated in Fig. 11. The annular recess 54 in the diffuser flange 50 has been
machined out to mate with a tapered external diameter of the mounting piece 53 which
locates in recess 54. The mounting piece or ring 53 has a tapered internal bore 71
constituting an annular recess which mates with a complementary taper on the downstream
end 52 of the replacement mixer 41. All that needs to be provided is a range of mounting
pieces with appropriately shaped bores or recesses 71 for a range of mixers having
complementarily shaped downstream ends 52.
[0056] These features which facilitate interchanging of mixers are very important aspects
of the present invention. The direction of flow of entrainment water through the jet
pump 9 is indicated by the illustrated arrow heads in Fig 9
-
[0057] Optionally, as shown in Figs. 6 and'8, the housing 39 is provided with an inlet aperture
74 additional to, and in the bottom wall of the housing 39 opposite to, the aperture
27. The inlet aperture 74 has a vertical pipe 75 fixed to the housing wall by means
of the diagrammatically illustrated bolts 76 passing through flanges 77. The pipe
75 may be removably connected either to the vertical pipe or elephants foot 78 having
an outwardly flared free end 79 disposed a short distance above the hull bottom 7,
by the diagrammatically illustrated bolts 80 passing through flanges 81 and 82 on
the pipes 75 and 78 respectively or to a flexible vacuum hose (not shown) having a
suitable fixing flange. In Fig. 10 an alternative position for the additional inlet
aperture is that provided by the opening 58 when the cover or blanking plate 59 is
removed.
[0058] In order to open the inlet aperture 74, there is a normally closed plate valve 83
provided with an actuator 84 which biasses the valve into the closed position so that
even if the operating mechanism, or circuit for the actuator fails, the plate valve
remains closed. This is important as the.plate valve 83 should always be closed during
a cleaning operation. With the cover 68 closing aperture 27, the plate valve 83 open,
and-the entrainment jet--57 flowing, the pipe 78 or hose can be used to suck up debris
and water from the double-bottom tank 2 and into entrainment with the jet 57.
[0059] The operation of the installation will now be described with reference to Figs. 12
to 14 and in relation to one hold 4 of the bulk carrier 1. A control room 88 illustrated
diagrammatically in Figure 14 has appropriate switches for operating the or each pump
9 and supply pump 14 and 14a if provided, all the valves and the tank washing machines
10. There are two jet pumps 9 illustrated in Figures 13 and 14 and two tank washing
machines 10 and an isolation valve 89 is preferably provided in the line 16 leading
to one of the jet pumps 9 so that only one jet pump may be used if required. To commence
a hold cleaning operattion to remove solids material, as represented by the white
triangles in Fig. 12, remaining on the tank top ceiling 6 after the discharge of cargo
from the hold 4, the cover 68 over the aperture 27 is removed , a supply valve 90
in header 13 upstream of the pump 14, a suction valve 91 in the sea water suction
intake line 92 downstream of the pump 14 and the gate valvesl8a are opened and the
tank washing machines 10 are switched on from the control room so that the pressurized
washing water passes down lines 18 and lines 24 (Fig. 5) to the washing units 25.
A supply valve 94 located in the header 12 downstream of the pump 14, gate valves
16a and 21a for one jet pump 9 and, if desired, isolation valve 89 as well as gate
valves 16a and 21a for the other jet pump 9 are opened from the control room, so that
water under pressure, as represented by the black triangles in Fig. 12,is supplied
down lines 16 to each of the jet pumps 9 to generate the entrainment jets 57 (Figs.
7 and 9). The solids material is washed by the flow of pressurized washing water from
the washing units 25 of the tank cleaning machines 10 through the aperture 27 and
into entrainment with the pressurized jets 57 and the water entrained solids material,
as represented by the black and white triangles in Fig. 12, is discharged through
the discharge lines 20 and out of the hold, through the horizontal line sections 21
and overboard through flexible hoses 22.
[0060] The deck pressure of the water supplied by the pump 14 to the headers 12 and 13 may,
by way of example, be 125 p.s.i. (8.75 kg/cm
2).
[0061] If it is desired to utilize the vacuum facility of the jet pumps 9 to suck up debris
and/or water from the double-bottom tanks 2, either with a flexible hose or the flared
pipe 78, the cover 68 must be replaced or be left in position, the or each valve 83
is opened by operating the or each actuator 84 by switches in the control room 88,
the pump 14 is operated and the valves 94 and 16a, 21a for one jet pump 9 and if required
the valve 89, and valves 16a and 21a for the other jet pump are opened, whereby the
or each entrainment jet 57 produces a vacuum and the sucked up debris and/or water
from the double-bottom tanks is entrained in the entrainment jet(s) and discharged
through the line(s) 20 and hose(s) 22.
[0062] It will be appreciated that various modifications may be made without departing from
the scope of the invention. For example, other washing apparatus utilizing pressurized
cleaning fluids may be used instead of the tank washing machines 20.
[0063] In the appended claims the term hold means is used generically to embrace the hold
of a ship such as a bulk or combination carrier and the tank of an oil bulk ore or
oil ore tanker.
1. A method of cleaning a vessel from solids material from the bottom of the vessel,
in which the solids material is entrained in at least one pressurized jet of fluid,
characterized by providing at least one aperture (27) in the vessel bottom (6), generating
said entrainment jet (57) beneath said vessel bottom (6) and said aperture (27) with
said entrainment jet (57) being projected in a direction which is substantially parallel
with said vessel bottom (6) and being exposed to the vessel interior through said
aperture (27), providing at least one pressurized jet of washing fluid to wash the
solids material from the vessel bottom (6), through said aperture (27) and into entrainment
with said entrainment jet (57), and leading the fluid entrained solids material out
of the vessel (4).
2. A method as claimed in claim 1, characterized by closing said aperture (27) in
said vessel bottom (6), providing another aperture (74) which is normally closed and
which is communicatable with said entrainment jet (57) and with a space (2) disposed
beneath said vessel bottom (6) and containing at least one of debris and liquid,connecting
a suction line (78) to said aperture (74), leading said suction line (75, 78) into
said space (2) and opening said another aperture (74) therebycommunicating said space
(2) with said entrainment jet (57), whereby at least one of said debris and liquid
is sucked through said suction line (75, 78) and into entrainment with said entrainment
jet (57) for discharge in the fluid flow engendered by the entrainment jet.
3. An installation for use in cleaning solids material from the bottom of a vessel,
in which the solids material is entrained in at least one pressurized jet of fluid,
characterized by means defining at least one aperture (27) in the vessel bottom (6),
means (9) for producing at least one pressurized jet of fluid for entraining solids
material therein, and disposed in at least one location beneath said vessel bottom
(6) and beneath said aperture (27), said means (9) including nozzle means (40) for
projecting said entrainment jet (57) in a direction which is transversely of said
aperture (27) and generally parallel with said vessel bottom (6), means (10) for producing
at least one pressurized jet of washing fluid for washing solids material from the
vessel bottom (6), through said aperture (27) and into said entrainment jet (57),
and at least one fluid line (20) for the discharge of fluid entrained solids material
out of the vessel (4), whereby in operation said entrainment jet (57) is exposed to
the vessel interior through said aperture (27), and solids material washed through
the aperture (27) by the pressurized washing fluid passes directly into said entrainment
jet (57) to be entrained therein and the fluid entrained solids material is discharged
through said discharge line (20) in the fluid flow engendered by the entrainment jet.
4. An installation as claimed in claim 3, characterized in that said nozzle means
(40) is disposed in and extends transversely of an open-topped chamber (55) across
which the said entrainment jet (57) flows and which is defined by a housing (39),
means is provided for guiding the washing fluid entrained solids material passing
through the aperture (27) into the entrainment jet (57), said guide means being a
hopper or funnel (56) having an upper wider open end provided with an outwardly projecting
rim (63) which is inset in the aperture (27), which rests on, and is removably fixed
to an annular supporting lip (64) which is rigid with the vessel bottom (6) and which
projects beneath said aperture, said hopper (56) having a lower narrower end which
is removably fixed to said housing (39) and said hopper being in communication with
said entrainment jet through the open top of the chamber (55).
5. An installation as claimed in claim 4, characterized in that the lip (64) supports
an annular sealing gasket (66), a screen (67) for screening the solids material particle
size to the maximum permissable for the entrainment jet and a cover (68) which closes
said aperture (27) when said vessel is carrying solids material and which is removable
to open the said aperture (27) for a cleaning operation, said sealing gasket (66),
said screen (67) and said cover (68) being inset in said aperture (27) and said cover
(68) having an upper surface which is flush with the vessel bottom (6).
6. An installation as claimed in claim 4 or 5, characterized in that said at least
one entrainment jet (57) is directed by said nozzle (40) into a tubular mixer (41)
for the fluid entrained solids material, said mixer (41) being surrounded co-axially
by a tubular sleeve (42) of larger internal diameter than the exernal diameter of
said mixer, said mixer and said sleeve having upstream ends which project into said
housing (39) opposite said nozzle means (40), said tubular sleeve (42) being removably
fixed towards its upstream end to said housing (39) and at its downstream end to a
diffuser (43) which communicates upstream with said mixer (41) and communicates downstream
with said fluid discharge line (20), and means for removably locating said mixer (41)
in said sleeve (42) and with respect to said diffuser (43) and said nozzle means (40),whereby
said mixer (41) may be removed with said sleeve (42) through said aperture (27) in
said vessel bottom (6) and interchanged with a differently sized mixer.
7. An installation as claimed in claim 6, characterized in that said means for locating
said mixer comprises an end cap (51) which removably engages with the upstream ends
of said mixer (41) and said sleeve (42) and which has a bore therethrough which aligns
with the mixer bore, means (47) defining an annular recess in the upstream end of
the diffuser (43) and a downstream end (52) of said mixer (41) which is of complementary
shape to said annular recess and which engages therein.
8.An installation as claimed in claim 6, characterized in that said means for locating
said mixer comprises an end cap (51) which removably engages with the upstream ends
of said mixer and said sleeve and has a bore therethrough which aligns with the mixer
bore, means defining an annular recess (54) in the upstream end of said diffuser (43),
an annular mounting piece (53) having a mating portion having a shape which is complementary
to that of, and engaging in, the annular recess (54), means defining a recess (71)
in
said mounting piece (53), and
a downstream end (52) of said mixer which is of complementary shape to said mating
recess (71) and which engages therein.
9. An installation as claimed in any one of claims 4 to 8, characterized in that the
nozzle means (40) is adjustably and removably mounted in a holder means (38) which
is fixed to and projects into said housing (39).
10. An installation as claimed in any one of claims 4 to 9, characterized by means
defining a space (2) beneath said vessel bottom (6), means defining another aperture
(74) in said housing (39) which is additional to said aperture (27) in said vessel
bottom (6), which aperture (74) is normally closed and is communicatable with said
chamber (55) and with said space (2), means (76, 77) for connecting a suction line
(75, 78) to said aperture (74) and leading into said space (2) and means (83, 84)
for opening said another aperture (24),whereby in operation of said entrainment jet
(57), when said aperture (27) in said vessel bottom (6) is closed, said another aperture
(74) is open and said suction line is connected thereto, at least one of debris and
liquid in said space (2) may be sucked through said suction line (75, 78) and into
entrainment with said entrainment jet (57) for discharge in the fluid flow engendered
in said entrainment jet.
11. An installation as claimed in claim 10, characterized in that said means for opening
said another aperture comprises a valve (83) which is biassed into a closed position
and actuator means (84) which is operable to open said valve.
12. An installation as claimed in any one of claims 3 to 11, characterized in that
said nozzle means (40) is connected to a source of pressurized fluid through a supply
line (16) and in that said discharge line. (20) has a bore size which is of greater
diameter than that of said supply line and which is capable of accommodating solids
material particle sizes at least of the order of 4 inches (95 mm).
13. A ship incorporating an installation as claimed in any one of claims 3 to 12,
characterized in that the vessel is a hold means (4) of the ship (1).
14. A ship as claimed in claim 13, characterized in that the means (9) for producing
the pressurized entrainment jet is incorporated into an extension of a bilge well
or into a pipe tunnel extending along the centre line of the ship (1).
15. A ship as claimed in claim 13 or 14, characterized in that the supply and discharge
lines (16 and 20) extend from deck level and down at least one bulkhead (17) of the
hold means (4) and beneath the bottom (6) of the hold means (4).
16. A ship as claimed in claim 15, characterized in that vertical lengths of the supply
and discharge lines (16 and 20) are disposed behind the bulkhead (17) of the hold
means (4).
17. A ship as claimed in any one of claims 13 to 16, characterized in that the supply,
washing jet and discharge lines (16, 18 and 20) have control valves, all of which
are located at deck level, with one of the control valves (90 or 94) being operative
to. shut-off fluid flow to the supply line (16) and washing jet line (18) to ensure
against accidental flooding of the hold means (4).
18. A ship as claimed in any one of claims 13 to 17, characterized in that the aperture
(27) in the hold means (4) beneath which the means (9) for producing the pressurized
entrainment jet (57) is disposed is located adjacent means defining a bilge well (29)
in one aft/outboard corner of the hold means (4).
19. A ship as claimed in claim 18, characterized in that the hold means (4) has a
second means (9) for producing a pressurized jet of entrainment fluid and disposed
beneath a second aperture in the bottom of the hold means (4), said second aperture
being located-in the other aft/outboard corner of said hold means (4).
20. A ship incorporating an installation as claimed in claim 3, characterized in that
the ship (1) has a deck (11),a plurality of said vessels constituted by cargo carrying
hold means (4) beneath said deck (11) and characterized by means defining a plurality
of double-bottom tanks (2) including tank top ceilings (6) forming the bottoms of
said hold means (4) and the bottom (7) of the ship's hull, each hold means (4) being
provided with at least one of said means for producing a pressurized jet of entrainment
water constituted by a jet pump (9) and disposed beneath a respective said aperture
(27) in the respective tank top ceiling (6) and located in a position which is aft
of the respective hold means (4), at least one supply pump (14) for supplying a pressurized
flow of water to said jet pumps (9) and to said means (10) for producing at least
one pressurized jet of washing water, said pump (14) being connected to a water suction
inlet line (92) and to header means (12, 13) extending lengthwise of the deck (11),
first branch lines (15) extending from said header means and communicating with water
supply lines (16) extending down in to the respective hold means (4) along bulkheads
(17) of said hold means (4), said water supply lines extending beneath the respective
tank top ceilings (6) and being connected to respective ones of said jet pumps (9),
discharge lines (20) leading from said jet pumps (9) beneath said tank top ceilings
(6), up the bulkheads (17) to the ship's deck (11) and over one of the ship's sides,
second branch lines (18) extending from said header means and communicating with respective
said washing water jet producing means (10) of which there is at least one for each
hold means (4), each said means (10) having delivery lines(24) terminating in washing
units (25),which delivery lines (24) and units (25) project into the hold means (4)
for a cleaning operation and are retractable therefrom when the hold means (4) are
to be loaded with solids material cargo, deck level mounted valve means (91) in said
suction inlet line (92), (90, 94) in said header means, (16a) in said fluid supply
lines (16), (18a) in said second branch lines (18),and (21a) in said fluid discharge
lines (20) for controlling the flow of water therethrough, and characterized in that
the nozzle means (40) of each jet pump (9), is disposed in and extends transversely
of an open-topped chamber (55) and across which the said entrainment jet (57) flows
and which is defined by a housing (39), and means for guiding the washing water entrained
solids material passing through the aperture (27) into the entrainment jet (57) is
constituted by a hopper or funnel (56) having an upper wider open end provided with
an outwardly projecting rim (63) which is inset in the aperture (27), which, rests
on, and is removably fixed to an annular supporting lip (64) which is rigid with the
tank top ceiling (6) and which projects beneath the aperture 27, said hopper (56)
having a lower narrower end which is removably fixed to said housing (39) and said
hopper (56) being in communication with said entrainment jet (57) through the open
top of the chamber (55).