JPH0239920Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an anti-corrosion static eliminator for cargo tanks in ships such as tankers.

Heating tubes are arranged inside a cargo tank, such as a chemical tanker or a product tanker, and are electrically connected to the tank wall by means of supporting supports. In addition, stainless steel, copper alloy steel, and the like are used for the heating tube from the viewpoint of durability against heat and cargo. On the other hand, the walls of the tank are coated with a special coating such as epoxy resin paint, which protects the tank wall from corrosion. At the hole, the steel that makes up the tank wall will be exposed inside the tank. There is a unique electrode potential difference, that is, a difference in ionization tendency, between the steel of the tank wall and the stainless steel of the heating tube, and because they are electrically connected, seawater ballast is used in the tank during ballast voyages. When a tank is installed, an electrical circuit is formed and current flows, causing electrolytic corrosion (electrolytic corrosion) in the steel of the tank wall, which has a high tendency to ionize. At this time, since the heating tubes are spread over a wide area in the tank and the pinholes in the paint are localized, corrosion concentrates at the pinholes, resulting in corrosion holes. To prevent electrolytic corrosion of steel, materials such as aluminum and zinc, which have a greater tendency to ionize, are normally used, but in the case of tankers such as those mentioned above, it is impossible to use these materials due to the cargo. The above can be achieved by electrically insulating the required parts of the heating pipe from other parts of the heating pipe and the tank wall using an insulating material such as Teflon (tetrafluoroethylene resin), which has high durability against heat and cargo. Since a circuit like this is not formed, current will not flow,
No electrolytic corrosion occurs. However, in this case,
When cleaning the tank, the high-speed water jetted into the empty tank from the cleaning machine can rub against the heating pipe, especially when the load is half-loaded (sloshing), which generates splashes that can rub against the heating pipe at high speed or inside the tank. When heating, steam flowing at high speed inside the heating tube rubs against the inner wall of the heating tube, and static electricity is generated and accumulated in the electrically insulated parts of the heating tube.
There is a risk of explosion. To prevent an explosion, the static electricity generated in the heating tube can be released to the ship's hull through bonding to prevent static electricity from accumulating in the heating tube, but with normal bonding, the heating tube and the tank wall are at the same potential. As a result, the electrolytic corrosion prevention effect is lost. In this way, prevention of electrolytic corrosion (corrosion protection) and prevention of static electricity accumulation (static charge elimination) require electrical insulation and bonding, which are originally contradictory and opposite measures, and it has been impossible to achieve both at the same time.

The purpose of this invention is to provide a corrosion-preventing static eliminator for cargo tanks that can achieve corrosion protection and static neutralization at the same time.

The anti-corrosion static eliminator according to this invention is installed in a cargo tank of a ship that has a heating tube inside, where a required part of the heating tube is electrically insulated from other parts, and the insulated part of the heating tube is connected to a resistor. It is therefore electrically connected only to the wall of the tank and is characterized in that the resistor is embedded in a corrosion-resistant insulating material contained within the container.

According to this invention, with the above-mentioned simple device, it is possible to simultaneously achieve corrosion protection and static neutralization of a cargo tank as follows. In other words, when a seawater ballast is installed in a tank, a circuit like the one described above is formed between the heating tube and the wall of the tank, and current flows, but if the heating tube and the wall of the tank are electrically connected, By appropriately setting the resistance values of the resistors, the current flowing between them can be made so small that almost no electrolytic corrosion occurs in the steel of the tank wall. In addition, static electricity generated in the insulated portion of the heating tube escapes to the hull through the resistor and does not accumulate in this portion, which has the effect of eliminating static electricity. Furthermore, since the resistor is embedded in a corrosion-resistant insulating material placed inside the container, there is no risk of it becoming energized by contact with seawater ballast, etc. There is no risk of corrosion.

Embodiments of this invention will be described below with reference to the drawings.

Figure 1 shows a stainless steel heating tube 2 and anti-corrosion static eliminator placed in the central cargo tank 1 of a tanker, and the bottom wall 3, side wall 4 and top wall 5 of the tank 1 are coated with epoxy resin paint. is applied. Note that, in order to simplify the drawing, the aggregate and the like in the tank 1 are omitted.

The heating tube 2 is divided into a heating coil portion 6 arranged in a meandering manner slightly above the tank bottom wall 3, and two vertical tube portions 7 connected to both ends of the heating coil portion 6 in a watertight manner. Both ends of the coil section 6 are bent vertically upward, and as shown in FIG. 2, stainless steel flanges 8 and 9 are fixed to both ends of the coil section 6 and the lower ends of the two vertical tube sections 7, respectively. ing. The flange 8 at one end of the coil part 6 and the flange 9 of one vertical pipe part 7 are connected by stainless steel bolts 10 and nuts 11 to a Teflon annular PETSKIN 12, Teflon washers 13 and 14, and Teflon washers 13 and 14. They are connected to each other via an insulating cylinder 15. The same applies to the flange 8 at the other end of the coil part 6 and the flange 9 of the other vertical pipe part 7.
The coil section 6 is electrically insulated from the two vertical tube sections 7. In addition, as shown in FIG. 3, a plurality of coil part supporting members 17 are firmly fixed to the aggregate 16 provided on the tank bottom wall 3 in a horizontally protruding manner, and the coil parts 6 are made of stainless steel at a plurality of locations. The coil part 6 is fixed to the upper surface of these supporting members 17 via a Teflon sheet-like packing 20, a Teflon washer 21, and a Teflon insulating tube 22 by U-bolts 18 and nuts 19 made of electrically isolated from the

Two vertical pipe support members 23 are fixed to the tank side wall 4 in a horizontally protruding manner, and as shown in FIG. and Natsuto 25,
These support members 23 are fixed to their respective distal end surfaces.

The part of the coil part 6 near the vertical pipe part 7 and the flange 9 of this vertical pipe part 7 are connected to the resistor 2 placed in a stainless steel container 26 as follows.
7 (for example, a resistance value of about 10 ⁶ Ω). The container 26 serves to connect the flange 8 of the coil part 6 and the flange 9 of the vertical pipe part 7, and has a cylindrical shape with an open top, and a screw shaft 28 is integrally formed on the lower end surface of the container 26. . This screw shaft 28 is passed through the flange 9 of the vertical pipe section 7, the packing 12, and the flange 8 of the coil section 6 from above through a Teflon insulating cylinder 29, and the screw shaft 28 is fitted with a Teflon washer. A stainless steel nut 31 is screwed through 30. The container 26 contacts and is electrically connected to the flange 9 of the vertical pipe section 7, but there is a packing 12 between the container 26 and the flange 8 of the coil section 6.
It is electrically insulated by an insulating cylinder 29 and a washer 30. The threaded shaft 28 of the container 26 has a hole 32 that passes through it vertically.
The inside and the hole 32 are filled with a corrosion-resistant insulating material 33 made of synthetic resin. The resistor 27 is embedded in an insulating material 33 within the container 26, and has lead wires 3 coated with Teflon tubes at both ends.
4 and 35 are connected to each other. Coil part 6
A terminal 36 is provided on the outer surface of the circumferential wall near the vertical tube portion 7 , and the first lead wire 34 of the resistor 27 is connected to this terminal 36 through the hole 32 of the screw shaft 28 . Also, the second lead wire 3 of the resistor 27
5 is connected to the inner surface of the peripheral wall of the container 26. The coil portion 6 is constructed by the first lead wire 34, the resistor 27, the second lead wire 35, the container 26, the flange 9 of the vertical tube portion 7, the vertical tube portion 7, and the vertical tube support member 23. It is electrically connected to the tank side wall 4. Further, the portion of the coil portion 6 closer to the other vertical tube portion 7 and the flange 9 of this vertical tube portion 7 are electrically connected by the resistor 27 in the same manner as described above, and the coil portion 6 has two parts. It is electrically connected to the tank side wall 4, ie, the hull 37, only through the resistor 27.

In the above, it is unavoidable that pinholes exist in the coating on the walls 3, 4, and 5 of the tank 1, and when the seawater ballast is installed in the tank 1, the gap between the heating coil part 6 and the wall of the tank 1 A circuit as described above is formed, and current flows through each resistor 27. However, since the resistance value of each resistor 27 is large, the current value flowing through it is very small, and the steel forming the wall of the tank 1 hardly causes electrolytic corrosion. Furthermore, static electricity is generated in the coil section 6 due to tank cleaning, agitation of cargo, high-speed flow of steam within the coil section 6, and the like. If it is assumed that the coil portion 6 is completely electrically insulated from the vertical pipe portion 7 and the wall of the tank 1 as described above, the coil portion 6 may be damaged due to the generation of static electricity.
becomes a high potential instantaneously, and it takes a very long time for the static electricity to spontaneously discharge, and the static electricity remains accumulated in the coil portion 6, so the coil portion 6 is maintained at a high potential, creating a danger of explosion. However, in the case of the above embodiment, even if static electricity is generated in the coil section 6 and the potential starts to rise, the static electricity escapes from the coil section 6 to the hull through the resistor 27 and does not accumulate in the coil section 6. Therefore, the potential of the coil portion 6 decreases. Therefore, the risk of explosion due to the accumulation of static electricity is reduced. In addition, the coil part 6
The potential change curve when static electricity is generated changes depending on the resistance value of the resistor 27. Also,
Since the resistor 27 is embedded in the corrosion-resistant insulating material 33 filled in the container 26, there is no fear that it will come into contact with seawater ballast or the like and become energized. There is no risk of corrosion. Further, since the container 26 also serves as a connection between the coil portion 6 and the vertical tube portion 7 of the heating tube 2, it is possible to downsize the device and reduce costs.

Although not shown in the drawings, a heating pipe and a corrosion-preventing static eliminator are also disposed within the side cargo tank 38 in the same manner as described above.

FIG. 4 shows an embodiment different from the above, in which the upper end of a cylindrical container 39 with an open top is fixed to the lower surface of the flange 8 of the coil portion 6 of the heating tube 2 in a watertight manner, and the container 39 is filled with water. A resistor 27 is embedded in the corrosion-resistant insulating material 33. The first lead wire 34 of the resistor 27 is connected to the inner surface of the container 39, and the second lead wire 35 is connected to the flange 9 of the vertical tube part 7 through a hole 40 made in the flange 8 of the coil part 6. has been done. The flange 8 of the coil portion 6 is connected to the container 39 and the first lead wire 3.
4, electrically connected to the flange 9 of the vertical tube section 7 by a resistor 27 and a second lead wire 35; The rest is the same as in the above embodiment, and the same parts are given the same reference numerals.

[Brief explanation of the drawing]

Figures 1 to 3 show one embodiment of this invention,
Figure 1 is a cross-sectional view of a tanker equipped with a device based on this invention, Figure 2 is an enlarged partially cutaway view of the main part of Figure 1, and Figure 3 is an enlarged view of the support part of the heating coil against the tank bottom wall. FIG. 4 is a vertical sectional view of the container attachment portion showing another embodiment of this invention. 1... Cargo tank, 2... Heating pipe, 3... Tank bottom wall, 4... Tank side wall, 5... Tank top wall,
6...Heating coil section, 7...Vertical pipe section, 26,3
9... Container, 27... Resistor, 33... Insulating material.

Claims (1)

[Scope of utility model registration request] In a cargo tank 1 of a ship in which a heating tube 2 is disposed, a required portion of the heating tube 2 is electrically insulated from other portions, and the insulated portion of the heating tube 2 is isolated only by a resistor 27. Walls 3, 4 of tank 1,
5 and a resistor 27 is electrically connected to the container 26,
An anti-corrosion static eliminator for a cargo tank, characterized in that it is embedded in a corrosion-resistant insulating material (33) contained within a tank (39).