FIELD AND BACKGROUND OF THE INVENTION

The invention relates to an air pipe head for venting a tank of a vessel, such as a ballast tank, an oil tank, a fresh water tank or a sewage tank.

When a tank of a vessel is filled with a liquid, it needs to be vented to allow air to escape from the tank as the tank is filled. Also, in many cases, one or more vents that are provided for this purpose also need to be capable to operate as overflow passages, to allow liquid to escape when a tank is filled to its full capacity, to protect the pumps and the tank from damage. Conversely, when liquid is discharged from a tank, the vent provides for a passage that allows air to enter the tank to fill up the volume left by the discharged liquid. Furthermore, the vents allow air to flow in and out of the tank to equalize pressure difference due to variations in temperature.

For vents having an outer opening at a deck of a vessel or that are otherwise exposed to waves, it has to be ensured that no or no significant volumes of splash water or water running over the deck can enter the vent even when the air vent is exposed to heavy weather, i.e. strong wind and large amounts of water.

In many applications, another important characteristic of such air pipe heads is a high flow rate of air into the tank, so that the tank can be emptied quickly, and a high flow rate of liquid out of the tank so that no damage occurs even when the tanks is filled at a high flow rate until it flows over via the vents. A further desired characteristic, in principle conflicting with the previous characteristic is compactness. An air pipe head is often mounted on a weather deck where it constitutes an obstacle occupying space on the deck.

From GB 8618, GB 9292, GB 184 395, GB 266 257 and DE 1 119 705, air pipe heads are known having a housing bounding a venting channel having a central venting channel portion extending to an upper end and bounded by a venting channel wall and an outer venting channel portion contiguous with the central venting channel portion and extending downwardly outside of the venting channel wall to one or more venting channel end ports opening downwards into the environment. The end ports are located in an annular end port zone extending around the venting channel wall. An annular floater extends around the venting channel wall and is guided for guided movement between an uppermost position closing off the end port or end ports and a lowermost position spaced below the end port or end ports. The housing further bounds an annular cavity extending around the venting channel wall in which the annular floater is arranged.

The housings shield the floaters, in particular from being blocked by items contacting the floater, such as cables, chains or ropes. The housings also shield the end ports from ingress of splash and water running over the deck. However, such air pipe heads are relatively bulky.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a simple, compact and robust air pipe head that allows a high flow rate of ambient air into the tank and a high flow rate of air and/or water out of the tank, while reliably closing if exposed to splash water or water running over the deck.

According to the invention, this object is achieved by providing an air pipe head according to claim 1.

Because water can enter the annular cavity through the relatively large lower openings very quickly, if an amount of splash water that would be sufficient to cause entry of water through the end ports reaches the air pipe head, the floater moves quickly up from its lowermost position to its uppermost position and reliably closes off the end ports before significant amounts of water can enter the ventilation channel. Moreover, air can escape quickly via the relatively small upper venting opening while air flowing out via these relatively small opening at a high speed effectively reduces water ingress into the annular cavity and in particular to such an extent that no significant amounts of water reach the end ports. The quick escape of air via the relatively small upper opening is also advantageous for a quick response of the floater, which reliably ensures closing of the end port or end ports in response to water reaching the air pipe head. Because of the quick response, extended shielding of the end port or end ports and/or a particularly long upward venting channel extending upwardly from the end port or end ports is not required, so a compact housing can be achieved.

According to a further aspect of the invention, an air pipe head according to claim 14 is provided. Because the heating member and the conductor ends connected of the defrosting heater are hermetically enclosed by the cable gland and the sleeve, there is no need for a seal between the heating member and the heater cavity that needs to meet particular requirements for the air pipe head to be certified as explosion proof. Accordingly it can be ensured that the air pipe head is safe for use in environments where an explosion hazard exists in a more reliable and simple manner.

Particular embodiments of the invention are set forth in the dependent claims.

Further objects, features, effects and details of the invention are described below with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a perspective view of a first example of an air pipe head according to the invention;

Fig. 2 is a side view of the air pipe head according to Fig. 1;

Fig. 3 is a side view in cross-section along a plane obliquely to the drawing plane of Fig. 2 intersecting a central axis of the air pipe head; Fig. 4 is a side view of a second example of an air pipe head according to the invention; and

Fig. 5 is a side view in cross-section along a plane V-V in Fig. 4.

DETAILED DESCRIPTION

The invention is first described with reference to the example shown in Figs. 1-3. The air pipe head according to the example shown has a housing 1 including a lower housing part 17 and an upper housing part 18. The housing parts 17, 18 may for instance be casted from an aluminium alloy. The housing 1 bounds a venting channel 2 and has a flange 32 that may for instance be bolted to a flange 33 of a venting pipe 34 of a tank. The venting channel 2 has a central venting channel portion 3 extending to an upper end 4 covered by the upper housing part 18 and an outer venting channel portion 6. The central venting channel portion 3 is bounded by a venting channel wall 5. The outer venting channel portion 6 is a continuation of the central venting channel portion 3 and extends outwardly of the central venting channel portion 3 and of the venting channel wall 5 to venting channel end ports 8, where the venting channel 2 opens downwardly into an annular end port zone 7 below the end ports 8 and extending around the venting channel wall 5. In this example, the venting channel 3 ends at a plurality of end ports 8 that are distributed in circumferential sense and each occupy a circle segment. The distribution of the end ports 8 in circumferential sense is preferably evenly. It is however also possible to provide a single end port extending over a major portion or the entire circumference of the annular ring zone. If the single end port extends over the entire circumference of the annular ring zone, portions of the upper housing part outside and inside of the end port are preferably connected via support members such as fins or posts interconnecting portions of the upper housing part outside and inside of the end ports. An annular floater ring 9 extends around the venting channel wall 5 and is guided for guided movement between an uppermost position 9' closing off the end ports 8 and a lowermost position 9 spaced below the end ports 8.

The floater ring 9 has a sealing member 35 on top of a main body of the floater ring 9. The sealing member 35 is of a more flexible and/or soft material than the body of the floater ring 9. This allows the body of the floater ring 9 to be of light, rigid material with a low coefficient of friction relative to metal, such as Polyethylene or Polyamide, so that free vertical movabihty of the floater ring 9 is ensured with little risk of sticking due to tilting of the floater ring, while a reliable sealing of the end ports 8 is ensured by the flexible and/or soft sealing member.

Reliable sealing of the end ports 8, even if the floater ring 9 is urged into its uppermost position 9' with relatively little force is achieved, because, seen in cross-section, the body of the floater 9 tapers towards its to end and the sealing member 35 is in the form of a flat ring mounted to the top end of the body of the floater ring 9 and having inner and outer portions freely projecting radially inwardly and outwardly of a top end portion the body of the floater ring 9. By flexing when pressed against a top end surface of the annular cavity 10, the flat, ring shaped sealing member 35 can easily accommodate to the shape of the top end surface of the annular cavity 10 around the end ports 8 in a sealing manner.

The housing 1 further bounds an annular cavity 10 extending around the venting channel wall 5. The annular floater ring 9 is arranged in the annular cavity 10. The annular cavity 10 is bounded on its outside by an annular cavity wall 11 extending around the outside of the floater ring 9 over a full circumference of the floater ring 9.

The annular cavity 10 communicates with an environment of the air pipe head via upper openings 19 and lower openings 14. The end ports 8 are located higher than the floater ring 9. The upper openings 19 are vertically spaced from the lower openings 14 and the upper openings have a smaller total open surface area than the lower openings 14. Preferably, the total open surface area of the upper openings 19 is at most 25% and more preferably at most 15% of the total (summed up) open surface area of the lower openings 14.

The lower openings 14 are positioned, shaped and dimensioned for allowing water to flow into and out of the annular cavity 10, for driving the floater 9 up from its lowermost position 9 to its uppermost position 9' in response to water flowing into the annular cavity 10 and for allowing the floater 9 to descend from its uppermost position 9' to its lowermost position 9 in response to water flowing out of the annular cavity 10.

If an amount of splash water that would be sufficient to cause entry of water through the end ports 8 reaches the air pipe head, splash water quickly enters the annular cavity 10 from below through the relatively large lower openings 14, so the floater ring 9 moves up quickly from its lowermost position to its uppermost position and reliably closes off the end ports 8 before

significant amounts of water can enter the ventilation channel 2. Quick entry of water from below into the annular cavity 10 is further enhanced, because, air can escape quickly via the relatively small upper venting openings 19.

Moreover, air flowing out via these relatively small openings 19 at a high speed effectively reduces water ingress into the annular cavity 10 and in particular to such an extent that no significant amounts of water reach the end ports 8. Because of the quick response of the floater 9, extended shielding of the end ports and/or a long upward outer venting channel portion extending upwardly from the end port or end ports is not necessary, so a compact housing- can be achieved.

The end ports 8 are located at a level higher than a level range at which the floater 9 and the annular cavity wall 11 are located. This is also

advantageous for allowing high flow rates through a compact construction, because the venting channel opens into the environment closely to its upper end along a path passing above the floater 9, the annular cavity 10 and the annular cavity wall 11. The floater is effectively shielded against damage and against being blocked by items in the vicinity of the air pipe head, such as ropes or chains, since the annular cavity wall 11 extends around the outside of the floater 9 over a full circumference of the floater 9.

The upper openings 19 are located above the floater ring 9 in its lowermost position so water can rise into the annular cavity over the entire height of the floater ring 9. The lower openings 14 are located below the floater ring in its uppermost position which is favourable for enhancing upward thrust of water entering the annular cavity 10 onto the floater ring 9 moving upward.

Because the lower openings are at a level substantially equal to a lower end of the floater ring 9 in its lowermost position, the floater ring 9 is completely shielded and thereby protected against damage by objects hitting the air pipe head, while splash water is can flow into the annular cavity 10 easily.

The lower openings 14 are open in a downward direction. This allows spray water to enter the annular cavity 10 from underneath the annular floater 9, thereby driving the floater 9 upwards particularly quickly.

The upper openings 19 are open in an upward direction. This is advantageous for a quick outflow of air when water enters the annular cavity 10 from below. Furthermore, if air flows into the ventilation channel 2 quickly during discharging of a tank connected to the ventilation channel, air flowing in through the upper opening 19 flows towards the floater ring 9 in a downward direction and counteracts upward movement of the floater ring 9 due to the air flow through the annular cavity 10 towards the end ports 8.

Such upward movement of the floater ring 9 caused by an airflow from the environment of the air pipe head into the end ports 8 could cause the end ports 8 to be closed by the floater ring 9, resulting in a too high vacuum in the tank.

The radial clearances between an inner or outer one of vertical wall surfaces 12, 13 of the annular cavity 10 and the floater ring 9 is preferably less than 3 mm and more preferably less than 2 mm. This is advantageous for a compact construction and for avoiding tilting of the floater ring 9.

The upper openings 19 are located radially outside of the floater ring 9 and in the annular cavity 10 a spacing 20 between the floater ring 9 and the annular cavity wall 11 is left forming a vertical passage from the upper openings 19 to the lower openings 14. Via this vertical passage, water

(including any water that enters the annular cavity via the upper openings 19 can evacuate quickly from the annular cavity 10 and during filling and discharging of liquid from the tank communicating with the ventilation channel 2, ventilation of a large portion of air from the ventilation channel 2 to the environment of the air pipe head and vice versa can pass through this vertical passage.

To ensure a particularly quick entry of spray water into the cavity 10 from under the floater ring 9, the lower openings 14 preferably have a total surface area of at least 80% and more preferably at least 90% of a cross- sectional surface area of the annular cavity 10 in a horizontal plane

perpendicular to the vertical air pipe head axis 30.

For achieving quick closing of the end ports 8 and for avoiding increased friction or even blocking of vertical movement of the floater ring 9, it is furthermore advantageous if the floater ring 9 is of a relatively large height.

To this end, the ring profile of the floater 9, seen in cross-section along a plane through the central axis 30 thereof, preferably has a height that is at least 125 % of its width.

The housing 1 has an upper housing part 18 including the outer annular cavity wall 11 and a lower housing part 17 including the venting channel wall 5 and projections 31 located radially outwardly from the venting channel wall 5. The floater ring 9 in its lowermost position rests on these projections 31.

This allows the housing 1 to be manufactured efficiently from casted housing parts 17, 18. For efficient manufacturing of the casted upper housing part 18, it is moreover advantageous if, as in the present example, the upper housing part 18 is fully open in downward direction inwardly of the outer annular cavity wall 11.

In this example, the openings 14, 19 via which the annular cavity communicates with the environment of the air pipe head are distributed in circumferential sense and each occupy a circle segment. The distribution of these openings 14, 19 in circumferential sense is preferably evenly. It is however also possible to provide a single upper and/or lower opening extending in circumferential sense over a major portion or the entire annular cavity. If the single opening extends over the entire all of the annular cavity, portions of the housing outside and inside of the opening are preferably connected via support members such as fins or posts interconnecting portions of the housing outside and inside of the opening.

In Figs. 4 and 5 another example of an air pipe head according to the invention is shown. This air pipe head is adapted for use in cold conditions and in conditions where explosive gasses may be present and it is therefore mandatory that equipment is certified to be explosion proof in the sense that potentially explosion igniting phenomena occurring therein are hermetically shielded from the environment. For use in cold conditions, the air pipe head is equipped with electric defrosting heaters 121 for heating the housing 101, so that sticking of the floater 9 due to freezing up of water (e.g. rain or spray water) or the formation of white frost is avoided.

In the housing 101 heater cavities 122 are provided in which the defrosting heaters 121 are mounted.

The defrosting heaters 121 each have a power supply cable 123 with conductors 124, 125 in an insulating sheath 126, a heating member 127 coupled to the conductors 124, 125 for converting electrical power received via the conductors 124, 125 into heat, a cable gland 128 engaging an end of the power supply cable 123 and a sleeve 129 mounted in the heater cavity 122. The cable gland 128 and the sleeve 129 hermetically enclose the heating member 127 and conductor ends connected thereto. Thus, the heaters 127 and ends of the conductors 124, 125 connected thereto are hermetically shielded from the environment, regardless of any seal between the heater 121 and the heater cavity 122 or the housing 101. Thus, it is ensured that the heaters 121 are explosion proof without requiring proof that the sealing between the heater 121 and the heater cavity 122 or the housing 101, if any, is explosion proof. Accordingly, it can be ensured reliably and at relatively low costs, the heated air pipe head meets the requirements for being explosion proof. Also, because the seahng is between components of the heater itself, it can be ensured more reliably, that explosion proof properties are not compromised by corrosion. If the gland 128 and the sleeve 129 are of metal, these parts are preferably of the same metal and more preferably of the same metal alloy.

For achieving an effective heat transfer from the heaters 121 to the housing 101 and avoiding local high exterior surface temperatures of the heaters 121, the heaters 121 are each provided with a heat transfer member 130 extending in the sleeve 129. Each heat transfer member 130 is a body of heat conductive material, such as aluminium or copper and effectively distributes heat within the heater 121, before it is transferred out of the heater via an outer surface of the heater 121. Effective heat distribution through the housing is ensured by providing that the housing 101 is made of heat conductive material, such as a cast sea water resistant aluminium alloy.

To avoid that the explosion proof properties of the heaters 121 suffer from tampering with the heaters 121 or other disassembly by persons lacking the required expertise, the cable gland 128 and the sleeve 129 are

permanently connected to each other.

Several features have been described as part of the same or separate embodiments. However, it will be appreciated that the scope of the invention also includes embodiments having combinations of all or some of these features other than the specific combinations of features embodied in the examples.