K.C.LTD

Overview

The world best system for Corrosion Protection

A turning propeller shaft on a ship becomes electrically insulated from the hull by the lubricating oil film in the bearings and by the use of non-metallic bearing materials in the tail shaft. When the shaft is insulated in this way an electrical potential can be measured between the shaft and the hull and this can accelerate corrosion in the ship. If the ship has a system of cathodic protection, whether it is sacrificial anode or an impressed current system, the shaft insulation will prevent the propeller and the boss from receiving protection.

The electrical potential between the shaft and the hull can also cause a heavy current to flow in bearings when the oil film breaks down or is contaminated with seawater. This current can cause deep pitting of the bearing surface. Excessive wear on the shaft bearings can often be traced to this cause.

Now in addition it’s necessary to reduce the spark erosion causing the excessive wear on main engine metal bearings and this shaft earthing is the most appropriate method. All the troubles can be avoided and cathodic protection can be extended to the propeller if the shaft is properly earthed with a propeller shaft slip ring. The effectiveness of the shaft earthing system should ensure a maximum contact resistance of no greater than 0.001 ohms for a water filled bearing and 0.01 ohms for an oil filled bearing on millivolt meter.

Our own tests indicate that high silver content brushes running on a silver track have repeatable low conductivity that can maintain these limits and ensure a low resistance contact is maintained even under dirty conditions. The shaft earthing assembly comprises a pair of high silver content / graphite compound brushes mounted in balanced brush holder, running on a copper slip ring with solid silver inlay track. Each brush holder has a adjustable spring tensioner which is supplied preset to the minimum, and results in a pressure of 225g/cm2. With this arrangment our high quality brush is in excess of one year life.

Brushes for shaft earthing device get worn down by mechanic friction on slip ring for the drain of spark inside main engine and high elctric potential from stern bearing/propeller. The readings of earthing are checked through mV meter which should be maintained below a level.

K.C. LTD. pproduce high quality silver graphite brush and good earthing silver slip rings for longer life. Our slip ring and brush on silver meterial are always strong enough to endure any tough conditions.

Components

Analog mV Meter

Overview

- Easy reading of shaft potential
- Earthing condition is well identified by different color as below (Analog)
- Green color (below 80 mV) : Normal.
- Red color (above 80mV) : To be checked and cleaned.
- Alarm signal can be connected to ship’s alarm monitoring system (Digital)
- 4~20mA data signal can be provided (Digital)

FISHING LINE
TYPE	READINGS	SIZE(W x D x H)	RANGE
Analog	Gauge	150 x 100 x 200	0 ~ 150mV
Digital	Digital meter	200 x 130 x 00	0 ~ 250mV

Digital mV Meter

Overview

Specification

- Automatic / Manual Mode
- 4.3” TFT LCD Display
- Very easy and convenient operating and access by simple finger touch on screen
- Easy to see all data parametric readings on the screen by RS485 communication Program easily connected with
ship's automation monitoring system

FISHING LINE
TYPE	READINGS	SIZE(W x D x H)	RANGE
Analog	Gauge	150 x 100 x 200	0 ~ 150mV
Digital	Digital meter	200 x 130 x 00	0 ~ 250mV

Slip Ring
X
Slip Ring
Overview
- Made of silver for high conductance and low resistance.
- 20 year design life under normal operation.
- Supplied together with SUS bands and Pressure tapes for installation.
- Proper Length will be provided according to Shaft out diameter.
Brush Holder
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Brush Holder
Overview
- Helps the brushes get in touch with center of slipring tightly
- 225g/cm² kept by spring tension
- Single Brush holder is for monitoring
- Double Brush holder is for grounding
- Supplied together with connection bars for installation(See our installation manual for the details)
Silver Graphite Brush

X

Silver Graphite Brush

Overview
- Made of high density low resistant silver graphite (80% silver and 20% graphite)
- Min. 1 year Design life time
- Excellent grounding efficiency
- One set (3pcs) per shaft is provided for the most efficient grounding i.e. 1 pc of brush is for potential monitoring/reading and 2 pcs of brushes are for proper grounding.

Overview

Components

Analog mV Meter

Digital mV Meter

Slip Ring

Brush Holder

Silver Graphite Brush