JPS613889A - Device for preventing spark erosion in ship - Google Patents

Abstract

PURPOSE:To provide a titled device which prevents efficiently spark erosion by the constitution in which a propeller shaft and diesel engine crank shaft are electrically insulated and that the propeller shaft and hull are connected to the earth via a variable resistor interposed therebetween. CONSTITUTION:The propeller shaft 4 and crank shaft 5 of a ship in which a diesel engine 2 is used as a main propulsive engine are connected via an electrical insulation joint 6 to block the current to be passed from the shaft 4 to the shaft 5 by the potential difference between the shaft 4 and the hull 1 and to prevent the spark erosion in the shaft 5. A shaft earth device is interposed between the shaft 4 and the hull 1 and the variable resistor 20 is provided between the brush of the device 8 in contact with the shaft 4 and the hull 1 to conduct the current from the shaft 4 to the hull 1 thereby blocking the stary current and preventing the corrosion of the shaft 4. The wear of the brush and the consumption of a sacrificial electrode 7 are prevented by regulating adequately the earth current.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a spark erosion prevention device for a ship, and more specifically, for a ship using a diesel engine as the main propulsion engine, to prevent the occurrence of spark erosion due to the potential difference between the propeller shaft, which is the propulsion shaft, and the ship body. Spark erosion refers to the cloudy marks that occur on the main diesel engine's crankshaft, especially on the sliding surface with the main bearing (also refers to the roughness of the white metal surface), and this phenomenon occurs when the crankshaft is equipped with a shaft grounding device. The fact that it is rarely seen on ships, that the white turbidity corresponds to the crank angle at which the thickness of the oil film on the main bearing is the thinnest, and as a result of microscopic observation, there was something that appeared to be molten sputum due to electrical discharge on the white metal surface. From what was discovered, etc., the hull (
It has been determined that spark erosion is caused by a potential difference between the main bearing) and the propeller shaft (crankshaft).

In other words, the electrical potential difference between the hull and the propeller causes a current to pass through the seawater to the propeller, and when the oil film is thinning while the crankshaft is rotating, it is discharged from the crank journal to the white metal of the main bearing, creating a spark. Conceivable.

By the way, this spark erosion was introduced in Japan in 1933.
Although it was discovered in bits and pieces from around 2013, the impact was not large enough to be considered a problem at first, but recent developments include higher output and longer strokes for main engines, higher performance hull paints, and larger diameter propellers. The spark erosion phenomenon caused by lubricating oil additives, etc. has become more severe, and countermeasures have been required.

According to the research results, the hull is -600m
V, the propeller is -200mV, spark erosion is due to a potential difference of 400mV, and in ships equipped with shaft earthing devices up to now, if the propeller shaft-hull potential is 80mV or less, spark erosion will occur. It has been reported that erosion does not occur, and it is currently desired to maintain the potential difference below 50 mV by means of a shaft grounding device.

The conventional shaft grounding device described above forms a closed circuit that grounds the propeller shaft and the ship's hull, and uses zinc as a sacrificial anode on the ship's hull side. Specifically, it connects a brush to the rotating crankshaft to ground it. In order to reduce contact resistance and reduce contact resistance, we use silver carbon for the brushes and a silver band for the sliding ring fitted to the propeller shaft, so the contact sliding surfaces must be cleaned at least twice a day. In order to maintain performance, labor-intensive maintenance is required. This is because spark erosion has recently been noted in ships equipped with the above-mentioned shaft grounding device, and unstable fluctuations are also observed in the actual measurement results of contact resistance, confirming the need for frequent maintenance. has been done.

On the other hand, as long as the contact resistance is small, the potential difference between the propeller shaft and the hull is kept low, but this causes a large current to flow and the consumption of the zinc increases more than necessary, so the amount of zinc must be significantly increased. No.

Therefore, there is a contradiction in that while the contact resistance is low, the zinc is rapidly consumed, and if maintenance is neglected, spark erosion will occur due to an increase in the contact resistance.

In view of this, the present invention can prevent the occurrence of spark erosion without requiring extensive maintenance.
Moreover, the purpose of the present invention is to provide a new spark erosion and lotion prevention device that can reduce zinc consumption even in a low contact resistance range.

In order to achieve the above object, the present invention connects a propeller shaft and a diesel engine crankshaft via an electrically insulating joint in a ship using a diesel engine as a main propulsion engine, and also connects the propeller shaft and the ship's hull. A shaft grounding device is interposed therebetween, and a variable resistance is provided between the brush that contacts the propeller shaft of this grounding device and the hull.

An embodiment of the present invention will be described below with reference to the drawings.

In the schematic diagram shown in FIG. 1, 1 is a ship body equipped with a main diesel engine 2, 3 is a propeller, and a propeller shaft 4 and a crankshaft 5 are connected via an electrically insulating joint 6, which will be described later. Further, 7 is a sacrificial anode (zinc), and 8 is a shaft grounding device that connects the propeller shaft 4 and the hull 1 in front of the electrically insulating joint 6'.

The electrical insulation joint 6 has a cross-sectional configuration shown in FIG. 2, and includes a flange plate portion 9 shaped at the shaft end of the propeller shaft 4;
The flange plate portion 10 formed at the shaft end of the crankshaft 5 is butted against the insulating spacer 11 made of FRP-epoxy resin, etc., and a plurality of circumferential portions of the single stroke plate portion 9.10 are insulated 12, They are connected by fastening members consisting of insulating washers 13, 14 and nuts 15. This insulating port 12 has a threaded portion 12a" at its tip as shown in FIG.
An insulating coating layer 16 made of polyphenylene sulfide resin, fluororesin, etc. is formed on the circumferential surface except for the flange plate parts 9 and 10, and even though it is inserted into the insertion holes of both the flange plate parts 9 and 10, the layer 16 prevents both plate parts 9. Electrical conduction across the IO is prevented. In addition, the insulating washers 13 and 14 are made of FRP-
When screwing Nara) 15 onto Porto 12 using an insulating material such as epoxy resin and tightening both flange plates fiB9 and 10,
Electrical insulation is provided between the bolt head 12b and the flange plate portion 9, and between the nut 15 and the flange plate portion lO. Thus, the propeller shaft 4 and the crankshaft 5 are electrically insulated at the joint portion by the insulating spacer 11, the insulating port 12, and the insulating washer 13, 14.

As shown in FIG. 4, the shaft grounding device 8 has a sliding ring (silver band) 16 tied to the propeller shaft 4 and a holder 18 for a brush 17 in contact with the sliding ring (silver band). A wire 19 is connected, and a variable resistor 20 is installed in the middle of the ground wire 19.
The resistance value of o is varied according to the contact resistance between the sliding ring 16 and the brush 17. For example, when the contact resistance increases, the resistance value of the variable resistor 20 is lowered and the resistance value is changed to the shaft grounding device 8 side. Constructed to improve the flow of anti-corrosion current.

In the prevention device configured in this manner, the electric potential difference between the propeller shaft 4 and the hull l causes the propeller shaft 4 to be moved from the crankshaft 5.
The current that attempts to flow is blocked by the insulating joint 6,
Therefore, spark erosion on the crankshaft 5 is prevented. By the way, if the insulation is insulated by the insulating joint 6, the current may stray and electrolytic corrosion may occur at a new location. However, since there is a shaft grounding device 8, the current flows through the propeller shaft 4 pass sliding ring 16 → derailleur 17 → ground wire 19 to the hull l, which prevents the current from straying. In addition, if the contact resistance increases at the contact area between the sliding ring 16 and the brush 17, the earth current on the hull L side will naturally be suppressed, and as mentioned at the beginning, wear and tear on the members 16 and 17 will occur. arise. However, as mentioned above, the variable resistor 2 connected to the ground wire 19
If you lower the resistance value of 0, contrary to the increase in contact resistance,
The overall resistance value remains the same or decreases, allowing the earth current to flow smoothly, so that the component 16.1
7 has little wear and tear, and even if the maintenance effort required to replace this member is greatly reduced, no trouble will occur. Furthermore, due to the presence of the variable resistor 20, there is no need to reduce the contact resistance between the sliding ring 16 and the brush 17 more than necessary, so that the consumption of zinc as a sacrificial electrode can be prevented.

As understood from the above explanation, according to the present invention,
Since the propeller shaft and crankshaft are electrically insulated at their joint, the current that would otherwise flow between them based on the potential difference between the propeller shaft and the hull is cut at the joint and flows toward the crankshaft. Therefore, there is no discharge from the crank journal to the white metal of the main bearing, or spark erosion. Moreover, since the current that strays due to the electrical insulation is guided to the shaft grounding device and flows to the hull, electrolytic corrosion does not occur in new locations, and the variable resistor inserted between the brush hull Since the anti-corrosion current can be controlled by following fluctuations in contact resistance, the amount of zinc used as a sacrificial electrode can be reduced, unnecessary wear and damage caused by excessive corrosion protection can be prevented, and the labor required for maintenance can be reduced. This can be significantly reduced.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, in which Fig. 1 is a schematic diagram of a ship equipped with a spark erosion prevention device, Fig. 2 is a partially cutaway side view of an electrically insulating joint, and Fig. 3 is an insulating bolt. FIG. 4 is a schematic diagram of the shaft grounding device. l...Hull 2...Diesel engine 4...Propeller shaft 5...Crankshaft 6...Electrical insulation joint 8...Shaft grounding device 17...Brush 20...Variable resistor patent Applicant: Nippon Pillar Industries Co., Ltd. Agent: Patent Attorney Suzu 7 ■ Takashi - Figure 1 Figure 2 Figure 3 ゛#t

Claims (1)

[Claims] (1) In a ship using a diesel engine as the main propulsion engine, the propeller shaft and the diesel engine crankshaft are connected via an electrically insulated joint, and a shaft grounding device is interposed between the propeller shaft and the hull. A spark erosion prevention device for ships, which includes a variable resistance between the brush that contacts the propeller shaft of a grounding device and the ship's hull.