GB2265690A - Marine vessel air pipe automatic control valve - Google Patents

Abstract

A marine vessel automatic air pipe control valve (10) incorporates a hollow cylindrical housing (1) receiving a hollow cylindrical valve core (3) with a seat (2) for a free ball valve element (5) and a removable access cowling (6) at one axial end of the housing to facilitate inspection, maintenance, repair and replacement of internal valve parts. The cowling (6) is apertured to define an outlet from the valve. Ingress of sea water lifts the ball valve element (5) against the valve seat (2) to close the valve. <IMAGE>

Description

Marine (Vessel) Air Pipe Automatic Control Valve This invention relates marine vessel 'air pipes' and the associated 'air breathing' of enclosures, and is particularly, but not exclusively, concerned with the (valve) control including the autocated closure - of air pipes for tanks fitted to, or installed upon, marine vessels.

The term 'marine' is used herein to embrace in principle any water (or indeed other liquid) borne activity or craft, whether sea, river, inland waterway, lake or reservoir - although the open sea is the environment of particular interest.

The requirements for such air pipe closing devices are prescribed, inter alia, by Regulation 20 of the 1966 Load Line Convention - which addresses safety aspects of marine vessels, including those in relation to loading, buoyancy and freeboard, ie the uppermost continuous deck distance above the water line.

Specifically, among the various requirements are stipulations that ...

The openings in the air pipe heads are to be closed by means of devices of an approved type, which are to be permanently attached to the air pipes in a position ready for use. It is strongly rec3Imended in this respect, that automatic closing appliances be fitted, such as the non-return ball valve type. Automatic closing appliances must be fitted to air pipes situated in way of timber or other deck cargoes which render them in accessible under service conditions.' Moreover ...

'Whenever ball valves are fitted particular attention must be paid to the material and construction of the ball or float.' (Automated) air pipe (valve) closing devices have proved a necessity for a great diversity of marine vessel or ship types in order to maintain the water-tight integrity of vessel hull particularly during large angles of heel, or when the main deck becomes submerged during heavy weather conditions.

The inefficiency or failure of such an air pipe (valve) closing device may result in the uncontrolled ingress of sea water, above and below The normal water line - thereby flooding internal tanks, to potentially beyond the vessel buoyancy and/or stability limits - with the consequent risk of loss of an entire vessel.

It follows that an air pipe (valve) closing device has to be well maintained at all times - as recognised by mandatory thorough internal and external examination, once every 12 months, with a 3 month allowance either side of the anniversary date.

Typically, there will be many such air pipe (valve) closing devices fitted to a vessel - thereby multiplying the inspection burden, particularly when vessels lead an active service life, because of economic utility pressures and remain in port for limited periods, reflecting burdensome port dues and the consequent need for fast turn-around times.

However, hitherto, in practice the design and construction of such air pipe (valve) closing devices has made thorough (internal) inspection impracticable - not least because disassembly or removal for internal inspection of critical component parts, such as the valve element and valve seat, is not provided for in the original design and wholesale removal and replacement of an entire valve is uneconomic or unfeasible in a general port area outside a special repair yard.

Moreover since the valve must remain normally open, in order to preserve tank breathing, conventional valves may be susceptible to the sudden ingress of breaking sea water surges, tending to carry the valve element or member away from its seat - thus preserving its open condition, ie absent any (closing) biassing reaction member.

Failure of such valves to close automatically in such circumstances - ie in the very conditions intended to trigger automatic closing - may lead to the unregulated or uncontrolled intake of sea water directly into below deck enclosed tank regions, typically low in the hull, and which therefore cannot be gravity discharged, for example by provision of a simple overflow pipe.

Thus the term 'air pipe' is used herein in a rather particular specialised marine sense (that is not merely ordinary English language usage) - as generally adopted and recognised by persons skilled in the arts of marine vessel design, construction, inspection and repair and in general maritime operations, including naval architects and surveyors.

Thus, in that regard, the term 'air' embraces the ambient atmosphere and any localised condition of supplementary gases or liquids.

The term 'pipe' embraces any form of duct, conduit or passage of whatever cross-section, orientation or configuration.

Air pipes are associated with a particular category of enclosures, generally 'tanks', such as certain kinds of bulk storage tank, which must 'breathe', or exchange air, continuously with the surroundings, in order to allow pressure equalisation internally and externally of the tank, particularly if used for storage of volatile materials - otherwise tank wall collapse may result.

In that sense, air pipes represent an 'anti-vacuum' facility.

To achieve this, the air pipes generally extend over a vertical path, preferably in a direct line rather than tortuously, from an intended free 'head-space' at the top of a tank, which is generally below deck, to a freeboard region above deck.

The term 'tank' embraces any form of enclosure, confined space or entrained volume for containing material, whether in solid, liquid or indeed gaseous form.

For example, in marine vessels, tanks may be provided for bulk storage and general hull buoyancy or hull weighting ballast tanks.

There may be scme facility for interchangeability of tank functions, for example between cargo storage and fuel oil to be consumed by the vessels engines - in which case the tank breathing may be switched from an air pipe, in the case of a cargo tank, to a vent in the case of a volatile fuel oil tank.

As tanks generally represent large, semi-sealed, below the waterline regions, the uncontrolled ingress of sea water must be inhibited. This risk is greatest when heavy seas break over the deck and impact upon the air pipe upper breathing ends. For this purpose it is knawn to provide a cowling or shield for the air pipe end and moreover an automatic shut-off valve within the cowl, with a valve element able automatically to obstruct the pipe internal passageway.

The term 'valve' employed herein embraces any form of flow control device, whether simply having an on/off function and/or scme intermediate restriction, throttle or regulatory capacity.

Closure of such a valve is triggered automatically by a backpressure, such as encountered with the wash of sea water in a heavy sea swell breaking over the valve.

A distinction is thus drawn, in a recognised marine sense, between air pipes and 'vents'.

In that specialised context, vents are 'natural' breathing passage provisions for those (below-deck) regions which benefit from a free interchange of air, for example cabin, passage, machine room and enclosed deck space - but which in dire emergencies, such as fire or heavy seas, can simply be (manually) shut off or isolated from a source of fresh air for a certain period.

In practice then, venting allows the natural circulation by convection, possibly supplemented by forced air aspiration currents.

A vented space, such as a ship engine, machine or steering gear room, must be provided with adequate internal ('natural'/free ) drainage - for example directly by gravity externally of the vessel.

The number and position of vents and the minimum height of vent apertures in relation to the vessel draught and freeboard are prescribed by regulation.

There is thus no objection to limited casual water ingress through a vent, since it can only pass to a self-draining ccopartment, as opposed to a sealed self-contained tank.

Moreover, a vent can be shut off, without prejudicing an associated ccmpartment in the short term.

In contrast, an air pipe cannot be sealed indefinitely, without prejudicing the integrity (eg by a partial vacuum collapse) of the associated tank - particularly as a liquid in the tank moves around in that same heavy sea, and so needs maximum aspiration.

Nevertheless, occasional shut-off, say upon striking a deck breaking wave in a heavy sea and consequent sea water deck wash can be countenanced, after which the valve can promptly and automatically re-open.

It will thus be appreciated that, reflecting the different character and requirements of air pipes and vents, regulatory constraints preclude the combination of venting and air pipe functions.

In the air pipe case, it is desirable, indeed essential, both to allow the enclosure to 'breathe' - that is benefit from a regular uninterrupted flow - in order to equalise the tank pressure with that of the ambient surroundings.

Otherwise, even minor pressure differentials can cause the collapse of the tank, which is generally relatively thin-walled and unable to withstand such stresses.

Such 'closed air pipe' collapse can prejudice the hull integrity and so the vessel safety.

Conversely, 'open air pipe' flooding of tanks with sea water, prejudices the vessel buoyancy, stability and thus safety.

So critical is the need for (tank) air pipes and the control thereof, that maritime regulations make the aforementioned specific provision therefor.

Similarly, for safety and insurance certification, regular inspection of such valves is prescribed.

However, hitherto the valve construction has not lent itself to ready inspection of critical internal valve operative parts, such as the integrity (eg freedom from structural cracks and surface corrosion) of the valve member and the surface condition and thus contact adequacy of the valve seat.

Dismantling of the structure has not been provided for in the design and construction. For large tanks, a considerable number of such air pipes and control valves must be provided - and thus the problem multiplied.

There now follows a description of a particular embodiment of the invention, by way of example only, with reference to the accoMpanying diagramnatic and schematic drawings, in which: Figure 1 shows a part-sectioned, part cut-away view of an air pipe control valve; Figure 2 shows an end elevation of the air pipe control valve of Figure 1; Figure 3 shows a part-sectioned, part cut-away view of the deck mounting arrangement of the air pipe control valve of Figures 1 and 2; Figure 4 shows a part-sectioned, part cut-away view of a conventional air pipe control valve; Figure 5 shows a part-sectioned, part cut-away view of another conventional air pipe control valve; Figure 6 shows a detail of the conventional valve shown in Figure 5; and Figure 7 shows a part-sectioned, part cut-away view of a marine vessel hull fitted with air pipes in a conventional manner.

Referring to the drawings, and in particular Figure 7, a marine vessel hull 200 is sub-divided fore and aft below the uppermost open main (freeboard or above the water line) deck 230 into a series of enclosures 210 of diverse character by dividing (structural stiffening) walls or bulkheads 211.

Sane of these enclosures 210 are bulk storage tanks - such as a sea water ballast tank 212, a main engine fuel tank 213, a lubricating oil tank 214 and a distilled water tank 215. Each of these tanks 212 through 215 is fitted with an air pipe 219, penetrating the uppermost deck 230 and terminating in an air pipe control valve 220, for example of the conventional kind shown in Figures 3, 4, 5 and 6.

Generally, there is a practical limit upon the size of individual tanks or other water-tight compartments and it is thus commonplace - not least to minimise the potential sea water environmental pollution hazard upon tank penetration, rupturing or other failures - to subdivide tanks.

However, in order to achieve satisfactory aspiration by air pipe operation in a moving hull (and thus moving, eg pitching and rolling, liquid contents) environment, each tank typically requires a minimum of two air pipe access points - one fore and one aft.

Nevertheless, structurally, it is desirable to reduce the number of deck penetrations, whether with air pipes or vents or the like.

Friction effects associated with air flow through a pipe limit the overall length of an air pipe - and thus generally short and straight pipe runs are desirable.

In order to access the ambient atmosphere as soon as possible, an air pipe opening typically need only be as high as the first freeboard (ie above the water line) deck - and can thus penetrate the side of the vessel.

In some vessels (such as an aircraft carrier) the first freeboard deck may also be an open deck.

However, air pipes which open close to the water line are especially vulnerable to sea water intake.

For volatile tank contents, eg with oil storage, air pipes typically extend to the uppermost continuous deck.

In contrast, a vent must typically go to an open deck for uninhibited access to a source of fresh air - but may even be omitted altogether in air-conditioned vessels with forced air circulation.

With the vessel static, eg unloading and loading in port, certain basic air pipe constraints prevail.

Thus, when emptying a (liquid) storage tank, there is a tendency for the tank head space above the liquid to evacuate -and thus air intake is required to equalise the tank pressure with the ambient atmospheric pressure.

Conversely, upon liquid fill, there is a need to evacuate gases from the head space - in order to avoid over-pressurising the tank.

Dynamically, additional functional constraints are imposed.

Thus, once a vessel is under way, should the vessel take a heel and an air pipe, particularly such as one mounted upon the side of a vessel, go below the water line, unless the air pipe is automatically and instantly closed upon such sea water bulk contact, there will arise a continuous intake of sea water through the open valve into the air pipe and associated tank, while the vessel is still under way - and in effect a vessel can lose critical buoyancy and be 'driven', suddenly and uncontrollably, under propulsion and gravity below the water until it eventually impacts the sea bed.

As described in more detail later, air pipe control valves are required by regulation to have an automatic safety operation to shut-off the ingress of sea water into tanks from which it cannot drain.

To this end the air pipe valve control construction typically incorporates a free-floating ball valve element - which normally rests under gravity away from an internal valve seat, but which, if operated as intended, is floated and driven against the valve seat, to close the valve and the air pipe, by the impact of an onrush of sea water.

The present invention is concerned with an improved air pipe and in particular an automatic air pipe shut-off/closing valve construction.

Other enclosure, designated 'compartments' in marine tenninology, such as a pump room 216, main engine room 217, steering gear rocm 218, and even below deck cabin living accatrnndation, are provided with ventilator shafts 239, to provide uncumbered natural air breathing for human occupants and operating machinery.

Thus these ventilator shafts 239 terminate in normally open ends 240, for example with mushroam or trumpet heads to discourage casual sea water spray entry, but which may incorporate emergency shut-off valves for use in say heavy (storm) seas or fire, when the safety of the vessel is at stake.

A further specialised enclosure category is a volatile liquid tank, such as a crude oil cargo tank 219, which is fitted with a inert gas line 211 to provide an inert gas blanket 214 in the head space above the liquid bulk in the tank.

A changeover valve 212 enables the inert gas line 211 to be switched to air pipe operation and thus the tank use to change over to, say, a supplementary engine fuel tank.

Referring to Figure 4, a knawn automatic air pipe control (ie shut-off) valve 40 construction comprises a hollow upright cylindrical housing 42 with a top mounting plate 44 incorporating an aperture 47 communicating with a goose-necked top of an air pipe 45 of the function described with reference to Figure 7.

A free 'floating' ball valve element 41, typically a hollow metal construction, is located within a valve chamber 49 within the housing 42 and normally rests, under gravity, upon a safety gauze flame trap panel 39 upon a detachable bottom plate 48.

An aperture 37 in the bottom plate 48 is too small for the valve ball 41 to pass through, but allows the passage of air and other gases and for the ingress of sea water to float the ball 41 upwards within the valve chamber 49, until it abuts firmly against a valve seat 43 around the upper aperture 47.

A more refined and elaborate air pipe control valve assembly 50 is shown in Figures 5 and 6, in which an outer housing 52 comprises a hollow, open-ended, cylinder, mounted with its axis generally horizontal.

An inner cylindrical valve core or body 54 incorporates a generally part-spherical valve seat 53, co-operating with a hollow ball valve element 51, which is free to run between the axial ends of the core 54 until it abuts end plates 61, 62.

The end plates 61, 62 close the opposite ends of the housing 51, but do not seal, as they incorporate venting apertures allowing as indicated by bi-directional (flow) arrows 66 - the passage of air and gases and the ingress of sea water to float the ball valve element upwards against the seat 53.

The entire housing 51 and internal assembly are mounted upon the end of a vertical air pipe 55 through a mounting flange 56.

This is typically a fully-welded construction, and so makes no provision for access or disassembly.

Moreover, the ball valve 51 is only too readily driven to - and held at - one end or other upon impact with sea water flowing through the valve fram one end to another - thus preventing the valve fran closing as required.

It is with improvements of the Figures 5 and 6 type of air pipe automatic closure valve that the present embodiment of the invention is particularly concerned, and as depicted in Figures 1, 2 and 3.

Referring to Figures 1 through 3, an - air pipe automatic closure valve 10 comprises a cylindrical outer housing 1 mounted with its axis general horizontal.

The housing 1 is closed at one end 21 but is partially open at the other end 22.

An inner cylindrical valve core or body 3 is located co-axially within the housing 1 and incorporates a part-spherical valve seat 2 let into a cylindrical radially-depending boss.

This provides a geometrically more conforming seat profile and thus a more effective seal in practice than say with a hole simply drilled into the wall of the core 3.

At one (open) end of the core 3 is an annular outer peripheral mounting flange 11, secured through a heat resistant gasket 9 to an annular inwardly depending flange 31 at the corresponding end of the housing 1.

The valve core or body 3 is closed at one axial end 23, but is generally or partially open at the opposite end 24 to the outside atmosphere, albeit through a gauze flame trap 7, clamped over a breathing aperture in the cover 6, between flanges 11 and 12 at the corresponding partially open end of the housing 1.

The volume of the chamber 34 between the housing 1 and valve core 3 and the volume of the valve chamber 33 is such as to preserve the through flow capacity of the valve 10, so that, in its open condition, it does not represent a flow restriction to an associated air pipe 25.

A removable part-cylindrical outer cover or shroud 6 is supported from the flange 12 and carries an end baffle or shield plate 28, which allows the passage of air, but deflects the casual ingress of sea water spray.

Nevertheless a heavy sea breaking over a vessel deck on which the valve 10 is mounted may rush into the valve chamber. In such an eventuality, the ball valve element 5 is buoyant - enabling it to float - and is carried by the water upwards in the valve chamber until it fills and the ball 5 is pressed against the seat 2 thus effectively closing the valve, by separating the valve chamber 33 from the peripheral annular region 34 between the housing 1 and the core 3 in communication with the air pipe 25.

me ball valve element 5 is free to run within the core 3 between its ends 23, 24, but can float upwardly upon the ingress of sea water through the entry port end 24.

The relative disposition of the ball 5, its associated valve seat 2 and the valve body 3 in the 'rest or static position of the ball 5 - that is with the valve effectively open - can also be appreciated from Figure 2, which shows the end cover 6 removed.

The entire housing 1 and its contents are mounted upon the air pipe 25 through a mounting flange 26, with the axis of the housing 1 either aligned with the longitudinal (ie fore and aft) axis of the vessel hull, or transversely thereto.

In order to facilitate access for periodic inspection, maintenance, repair and replacement, the operative parts of the valve can be exposed by simply removing the end cover 6, as demonstrated in Figure 2.

Such denouncing of the cover 6, is simply effected by unthreading the lock nuts 8 fran a series of circumferentially-spaced studs 29, to release or unclamp the support flange 12 for the cover 6 from the annular end flange 31 of the housing 1.

The ball 5 can then be removed fran the valve core 3 for inspection itself - and unobstructed inspection of the valve seat 2.

Indeed the entire valve core 3 itself, being also carried on the same studs 29 through its outward annular flange 11, can also be removed and replaced in its entirety.

The correct relative orientation of the core 3 and housing 1 are preserved by a locating stud 4 in the flange 31 and a corresponding notch in the flange 11. In this way there is no risk of inadvertently remounting the valve core 3 with the valve seat 2 in any other position than uppermost in the housing 2 otherwise valve function would be impaired.

Generally, embodiments of the invention, such as that described and illustrated, may be fabricated from standard section piping and plate suitable for welding.

For simplicity and reliability the valve comprises essentially only four principal parts, secured together by a simple bolting operation and thus readily dismantled with ordinary tools, enabling quick routine inspection, overhaul, repair or part replacement, by non-specialised technical personnel, such as are available at ports.

Figure 3 shows an automatic air pipe closing (valve) device or appliance, 19, such as described with reference to Figures 1 and 2, fitted upon the deck of a ship.

Mare specifically, and merely by way of example, a vertically disposed air pipe 18 penetrates the main continuous uppermost freeboard deck 16 and ccmmunicates at its upper end through the automatic closing valve 19 with the ambient atmosphere and at its lower end with an enclosed upper ballast tank 13. This may reflect the arrangement of, say, a bulk carrier vessel.

The valve 19 is shielded by a bulwark 17 and the tank 13 is constructed within an external structure 15 and a hopper 14.

Claims (1)

1. Claims

   I.

   An automatic valve control and closing device (10) for an air pipe on a marine vessel tank, comprising an outer housing (1) mountable upon an air pipe (25) and open at one end (24), a valve body (3) removably mounted within the housing and a combined access and part-closure plate (6), incorporating a breathing aperture (27), mountable over said one end.

   II.

   An automatic air pipe closing valve as claimed in Claim 1, comprising a cylindrical outer housing incorporating a cylindrical inner core with a valve seat formed in an aperture in its upper surface, and a buoyant ball valve member loosely fitted into said core and movable on to said valve seat upon the ingress of sea water, whereby to close the valve and inhibit the intake of sea water into the air pipe.

   III.

   An automatic air pipe closing valve, as claimed in Claim 1, incorporating an end cowl closure plate for both the valve body and inner valve core and mounted at one axially open end thereof.

   IV.

   An automatic air pipe closing valve, as claimed in any of the preceding claims, wherein the valve seat is formed on a cylindrical radially inward extension of the valve core.

   V.

   An automatic air pipe closing valve substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

   VI.

   An air pipe for a marine vessel incorporating an automatic closing valve as claimed in any of the preceding claims.

   VII.

   A marine vessel incorporating an air pipe and automatic air pipe closing valve as claimed in any of the preceding claims.

   VIII.

   A (marine) tank/enclosure air pipe (regulator/control) valve comprising a valve chamber housing a valve element movable within the housing and locatable upon a valve seat at the periphery of a flow control port the housing incorporating a demountabl e/dismantl able access portion, to facilitate internal inspection of the valve mechanism, including the valve element and valve seat.

   IX.

   A marine tank air pipe control valve assembly comprising a housing (mountable upon a tank vent (air) pipe a valve chamber suspended/carried within the housing leaving an internal control volume therebetween a valve seat in the valve chamber a flow control port communicating with the valve seat a movable valve element upon the valve seat a removable access portion in the housing allowing inspection, removal and maintenance of the valve chamber, seat and housing.