PAULSEN TRULS H (NO)
PATENT ABSTRACTS OF JAPAN, Vol. 10, No. 81, (M-465); & JP 60222389 A (ISHIKAWAJIMA HARIMA JUKOGYO K.K.) 6 November 1985.
| 1. | 1. A method for protection of a submersible ballast pump (4) of the type comprising a pump head (5), a riser pipe (7) projecting upwards therefrom having a pump drive shaft, and a top piece (6) with a motor, arranged in conjunction with the pump drive shaft, against freezing when not in operation, c h a r a c t e r i z e d i n that air is caused to circulate in a circulation cycle (12,14,15,13) that includes the riser pipe (7). *& 2. |
| 2. | A submersible ballast pump (4) apparatus of the type comprising a pump head (5), a riser pipe (7) projecting upwards therefrom having a pump drive shaft, and a top piece (6) with a motor, arranged in conjunction with the pump drive shaft, c h a r a c t e r i z e d i n that the submersible ballast pump riser pipe (7) is coupled into a forced circulation cycle (12,14,15,13) for air.*& 3. |
| 3. | The apparatus according to claim 2, c h a r a c t e r i z e d i n that the circulation cycle (12,14,15,13,7) comprises a fan (14) for circulation of the air in the circulation cycle.*& 4. |
| 4. | The apparatus according to one of the claims 23, c h a r a c t e r i z e d i n that the circulation cycle comprises a vertical pipe (15) from a pressure line (20) from the pump and to the lower section of the riser pipe, optionally to an inlet tank (8) for the pump provided at the lower end of the riser pipe.*& 5. |
| 5. | The apparatus according to claim 4, c h a r a c t e r i z e d by a plurality of transverse pipes (21) disposed between said vertical pipe (15) and the riser pipe (7). |
The invention also relates to a submersible ballast pump apparatus of the type comprising a pump head, a riser pipe projecting upwards therefrom having a pump drive shaft, and a top piece with a motor, arranged in conjunction with the pump drive shaft.
The invention has evolved particularly in connection with commercial tank ship operation in Arctic regions, currently an area of potential that shipbuilding yards and shipping companies in the northern regions have been making concrete efforts to develop.
The environmental challenges in these regions are great and, in particular, the low possible ambient temperature of about-40 is significant, creating problems that require their own special solutions.
In connection with submersible ballast pumps of the type comprising a pump head in the ballast tank, a top piece with a motor arranged on deck, and a riser pipe with a pump drive shaft disposed between the top piece/motor and the pump head, one may expect to confront difficulties in cold areas, especially Arctic regions. Ballast pumps operate using sea water, and during periods of inactivity these pumps will be vulnerable to freezing due to the fact that they are located in chambers having a temperature below the freezing point, and the water remains in the pumps can freeze up. Vertical submersible pumps of the type dealt with here are often of a structural height equal to the height of the tank (18-20 m) and have product-lubricated--i. e, water lubricated--bearings.
Although the pumps are constructed to be self-draining when not in operation, the formation of water film in the narrow clearances within the pump head and in the bearings is unavoidable. If these water films should freeze into ice, tests and calculations have shown that substantial forces will be necessary to free the pump rotor, and this means that the operation of the ballast pump will be impeded.
One possible solution is, of course, to bring the inner components of the pump up to a temperature that prevents them from freezing solid.
The purpose of the present invention is to make it possible to prevent this type of freezing in a simple and reliable manner, while complying with safety requirements.
The inventive concept is based on the utilization of air or another suitable gas to bring the inner components of the pump up to a temperature that will prevent them from freezing solid. Air is a medium that is safe, it penetrates into narrow openings everywhere, and it is inexpensive for the construction of such a system.
According to the invention, therefore, a method is proposed for the protection of a submersible ballast tank as mentioned in the introduction, which method is characterized in that air is caused to circulate in a circulation cycle that includes the riser pipe.
The forced air circulation is distinguished by the feature that the circulation air will penetrate everywhere in narrow clearances and bearings and prevent them from freezing, or alternatively it will thaw out any ice that has frozen onto the pump components. The air circulation is forced, meaning that the air is constantly being supplied with energy from an exterior source, which contributes to the warming of the circulation air.
The invention also relates to a submersible ballast pump apparatus as introduced above, which apparatus is characterized in that the submersible ballast pump riser pipe is coupled into a forced circulation cycle for air.
An especially practical and simple embodiment form of an apparatus according to the invention is one where the circulation cycle comprises a fan for circulating the air in the circulation cycle. The effect of the fan will transfer into heat, and the circulation air will therefore theoretically become hotter and hotter. There will, of course, be some leakage of heat to the surroundings, not only within the pump, and there will not be any danger of overheating. The temperature of the air will be determined by the effect of the fan, the operating time, and the leakage of heat to the surroundings.
The invention provides for a favorable combination of air circulation and utilization of the heat that is stored in the air due to the effect of the fan. This permits almost the simplest possible structural design for the heating system for the pump. An explosion-
proof embodiment is obtained in a simple manner by the utilization of a standard explosion-proof fan motor.
The circulation system optionally may have built-in auxiliary heat provided through electrical heating or through heat exchange using steam or hot water.
It is conceivable that the air circulation system would have to be provided with insulation in order to limit the heat loss to the surroundings.
The invention will now be explained in more detail with reference to the drawings, wherein: Figures 1,2 and 3 show a transverse sectional view of typical ballast tanks under various loading conditions, Figure 4 is a transverse sectional view of a tank arrangement, Figure 5 is a view of a so-called multi-suction arrangement, i. e., an arrangement wherein a pump provides suction from a plurality of ballast tanks, Figure 6 is a strictly schematic illustration of a possible system according to the invention, and Figure 7 is a strictly schematic illustration of yet another possible system in accordance with the invention.
Figure 1 is a transverse sectional view of a tank ship 1 having a cargo hold 2 and a ballast tank 3. In the state illustrted in Figure 1, cargo hold 2 is fully loaded and ballast tank 3 is empty.
Inside the ballast tank is provided a submersible ballast pump 4. This pump comprises primarily a pump head 5, a top piece 6 with a motor, and a riser pipe 7 having a drive shaft (not shown) running between the motor (also not shown) and the pump head. The pump head is disposed in an inlet tank 8.
In Figure 2 the same transverse section is shown with the cargo tank 2 unloaded and with sluicing to ballast tank 3 in progress.
Figure 3 shows the situation where the cargo tank is empty and ballast pumping is in effect.
The significant point of these Figures 1-3 is that they show various operative conditions wherein freezing in pump 4 could occur.
Figure 4 is a side view of a tank ship having ballast tanks 2. Figure 5 is a sectional illustration of how a ballast pump 4 can serve a plurality of ballast tanks 2', 2", 2"', where the inlet tank 8 is coupled to adjacent tanks 2", 2"'with the aid of pipes 9,10.
Figure 6 is a strictly schematic illustration of how the invention can be realized. There we find the submersible ballast pump 4, having a top piece 6 mounted on deck, a riser pipe 7 in the ballast tank 2, and a pump head 5 in an inlet tank 8. The ballast water surface in ballast tank 2 is indicated here by line 11. Hence, in the illustrated situation ballast pump 4 is more or less empty of water, and pump 4 is at a standstill.
From ballast pump 4 there run two branch lines 12,13, one above deck, taken from top piece 6, and a branch line lower down in the area where liquid surface 11 is located when the ballast tank is empty and the pump is inactive. These branch lines 12 and 13 are joined to a fan unit 14 with the aid of a pipe 15. Branch line 13 may, for example, be taken directly from riser pipe 7 or from inlet tank 8, which is in communication with the riser pipe.
In the circulation cycle formed by branch line 12, fan unit 14, pipe 15 and branch line 13, and pump 4, there will be air which is circulated with the aid of fan 14. This is basically a closed air circulation system; and when the fan is in operation, the effect of the fan will be transferred into heat and will warm up the circulation air. In pump 4, primarily in riser pipe 7, the air will penetrate into all of the narrow openings and, in particular, in the pump medium-lubricated bearings (not shown) in the riser pipe for the drift shaft. By this means, the parts are prevented from freezing. Any ice that may have frozen on the pump components will be thawed out. Fan 14 is put into operation when the pump is partially filled or empty of water and is inactive. In the circulation cycle there are provided two valves 16 and 17. These valves 16,17 in the air circulation system are designed as valves for water pressure, as they will be a part of the entire ballast system and will be subjected to full pump pressure when ballast pumping takes place. Fan 14 and circulation pipe 15 will be used only when ballast tank 2 is empty or nearly empty and the water system consequently is almost devoid of pressure.
The indicated conduits 18,19 are suction lines connected to inlet tank 8. The line 20 above deck from pump 4 is a pressure line for ballast water from the pump.
Figure 7 shows a modified system according to the invention. The general construction is the same as in Figure 5, except that here more branch lines 21 have been inserted between riser pipe 7 and circulation pipe 15. These branch lines or interconnecting pipes 21 are evenly spaced so that air is permitted to circulate into riser pipe 7 at the places where the water surface does not block the supply of air.
The motor bearings and the pump's journal bearings situated in the deck-mounted top piece 6 are oil-lubricated and need not be included in the tempering system.