OCIMF_Mooring_Equipment_Guidelines_(Second_Edition)

brake application, but has disadvantages such as senslllv,ty to changes in friction, dependency of
sett.ing force on rope force and sensitivity [0 reel.ing direction.

The main factors which affect tbe actual holding capacity of the band brake are discussed below:

75.2.1 Torque applied

Figure 7.3 shows the results of a series of brake holding load tests on a VLCC when the torque
app!.iedis varied. It can be seen that tbc holding load will drop appreciably when the torque applied
is lower t.han the recommended value. It is, therefore, C$scntial that tbe operator apply the brake
properly.

20

15

w

~~

...Jo~

:§~. 10

zo(!)

<t:~~

::Zo:

Il. <t:

5

10

(gel

/ """"

20

(196)

/

~

./

30

(294)

40

(392)

./ v "

50

(490)

60

(588)

BRAKE HOLDING POWER -METRIC TONS (kN)

This Diagram Illustrates The Reduction In Brake Holding Power

Which Occurs When The Applied Torque Is Insufficient.

Desired

Holding

Power

70

(686)

FIGURE 7.3: EFFECT OF APPLIED TORQUE ON BRAKE HOLDING POWER

Shipboard inspections have shown that winch brakes are very often not torqucd 10 their design level;

and, in some tests two men were requjred to apply tile required torque. Hence, sever~l VLCC

operators are now installing hydraulicaUy actuated brakes on new VLCCs and are retrofitting them

on older VLCCs to ensure proper brake balding load. Obviously, il is essential tbat the winch brakes

be operated properly to achieve desired holding loads.

Also, it has been found that some winch act.uators and controls are poorly positioned. As a result,

the operator is unable to see what is happening on deck. Proper design is essent.ial to ensure proper

operation.

7.5.2.2 Condition of the Winch

The physical condition of [he .... 'inch gearing and brake shoe linjngs have a significant effect on brake

bolding load capacity. Oil, moisture or heavy rust on the brake linings or brake drum can reduce

brake holding load capaciry by up 10 7S'l1Jo. Many operators run Ihe winch with the bTake set slightly

to bum off or wear off the oil or moisture. (Care, howeveT, must. be taken to ensure that excess

wear is no! caused by this practice when using composite brake linings.) Excessive winch speed can

also reduce brake balding capacity by the build-up of heat in the composite brake lining_

7.5.2_3 Winch in Gear

The bolding load capacity of a brake can be increased by lc~ving tbe winch ill gc.aT with tbe steam

on_ However, resort to this practice should be regarded as only an emergency measure with limited