Download - 7 Drilling Brake
-
8/11/2019 7 Drilling Brake
1/16
Davorin Matanovi
Drilling
BRAKE
-
8/11/2019 7 Drilling Brake
2/16
Mechanical brake
Mechanical brake is the essential part of thederrick.
Its purpose is to slow down and stop the downwardsmovement of the drill string.
It also serves to control the load on the bit.
The frictional brake consists basically of flexiblesteel bands that fit around the drum flanges, eachhaving one end anchored and the other free.. When the free end is pulled (by means of a brake lever,
the whole band tightens around the drum flange andslows or stops it by friction.
-
8/11/2019 7 Drilling Brake
3/16
Band frictional
brake
Construction
Drum flanges have wearresistant rims bolted to them.
They are gripped by the brakebands as they tighten.
The brake bands have a lining
of brake blocks. The blocks are composed of
asbestos fiber compoundedwith a bonding agentinterwoven with cooper wire.
The blocks are bolted to thebrake bands with brass boltscountersunk on the inside ofthe band circle.
One end (the dead end) of
each brake band is anchored;and the other end (the liveend) is attached to the manualbrake lever by means of acamshaft.
-
8/11/2019 7 Drilling Brake
4/16
Blocks bolting
API standard defines friction blocks
with four or six bores
-
8/11/2019 7 Drilling Brake
5/16
Blocks with six
bores Blocks with four
bores
API
No.A (mm) B (mm) C (mm)
1 152,4 31,8 88,9
2 177,8 38,1 101,6
3 203,2 44,5 114,3
4 228,6 50,8 127
5 254 57,2 139,7
6 279,4 63,5 152,4
7 304,8 69,9 165,1
The thickness of theblock is not defined, but
it is possible to use
several block thickness:
t*
(mm)15,9 19 22,2 25,4 28,6 31,8
(inch) 5/8 3/4 7/8 11
1/81 1/4
API
No.D (mm) E (mm) F (mm)
10 152,4 31,8 88,9
11 177,8 38,1 101,6
12 203,2 38,1 12713 228,6 38,1 152,4
14 254 38,1 177,8
t*(mm) 15,9 19 22,2 25,4(inch) 5/8 3/4 7/8 1
-
8/11/2019 7 Drilling Brake
6/16
Screw diameter
for blockfastening is 9,525mm (3/8") with
the flat -countersunk headwith angle of 120
and thread;16UNC-2A.
o
120
-
8/11/2019 7 Drilling Brake
7/16
Several factors affect breaking capacity: The first is the ratio between the diameter of
the brake flange and the diameter of the drumspool.
Another is a band width.
That is according tofriction area.
Third one is the angle of wrap, that means thedistance that the brake band wraps around
the flange. It can be from 270 to 330.
-
8/11/2019 7 Drilling Brake
8/16
330 wrapping 270 wrapping
-
8/11/2019 7 Drilling Brake
9/16
Equalizer
At the front of the hoist, the brake bands arefastened with heavy-duty pins or bolts to a dead
anchor firmly fastened to the draw works frame atthe center of the drum. This dead anchor is in the form of a yoke and acts as
an equalizer to ensure that each brake band will
receive an equal amount of tension. The equalizer also switches the full load to one band if
the other fails.
The brakes must be adjusted properly to make sure thelong lasting work. Some draw works have automaticequalizing devices.
-
8/11/2019 7 Drilling Brake
10/16
Cooling The brakes are cooled with clean fresh water
circulated through the drum shaft to the brakeflanges.
Cooling is necessary to help dissipate the heat that isgenerated by the friction of brake lining on flanges.
It is important for water to be fresh to prevent mineraldeposition that would affect the cooling system.
The water is pumped by the system that hasindependent power.
The great amount of generated heat must be
removed quickly to prevent poor braking actionand excessive wear on blocks and flanges.
-
8/11/2019 7 Drilling Brake
11/16
Frictional brake actsas it is shown on
picture.
The force on thelever that driller
must apply is
defined as:
( ) ( ) N
elRbM
lebQ
lbtF
ookkv
kbr
k
kbr
k
pk 490
1122 ..
=
==
-
8/11/2019 7 Drilling Brake
12/16
Where:
Fk the force the driller must apply on the lever, Ntp force in the free end of band, N
bk length of the short lever, m
lk length of the long lever, m
Qbr.
braking force on the flange, N
e natural logarithm base (2,718)
- coefficient of friction (0,5)
o wrap angle (from 270 to 330)
Rkv brake flange radius, m
Mbr. breaking moment that must be achieved,Nm
rkon final drum diameter, m
b drum efficiency (0,95)
Kbr.
factor due the dynamic forces (from 1,2 to2,5)
Dkv braking flange diameter, m (1,8 to 2,8)DbDb drum diameter, m
F force in the wire rope, N
kv
brbr
R
MQ
=2
..
.. brbkonbr KrFM =
( )
2
8,28,1
2
bkvkv
DtoDR
==
-
8/11/2019 7 Drilling Brake
13/16
Auxiliary brakes Auxiliary brakes are used in the hoisting
system to slow the rate of descent of the
traveling block with a heavy load. They ensure that a heavy load comes down slowly
and smoothly.
Care must be taken, to prevent the blocks fromfalling faster than they could be stopped by thefriction brake alone.
Auxiliary brake should be hydrodynamic
brake or electrodynamic brake.
-
8/11/2019 7 Drilling Brake
14/16
Hydrodynamic brake
Hydrodynamic brakeis often called as the
water-brake,
because it works bythe action of fluid;
normally water.
-
8/11/2019 7 Drilling Brake
15/16
The fluid is circulated by a moving rotor,and mechanical energy is converted intoheat within the fluid itself.
The amount of mechanical energy that canbe absorbed depends upon the quantity
and velocity of the fluid in the workingchamber.
It will be increased with revolving speed ofthe rotor.
To control the operating level, driller simplyopens or closes the valve that controls thelevel of the water in the brake.
So the main control should be in thecirculating system.
Maximum allowable brake outlettemperature must never exceed 77 C (180F).
-
8/11/2019 7 Drilling Brake
16/16
Electrodynamicbrake
An electrodynamic brakeconsists basically of a largesteel armature drum thatrotates in a magnetic fieldproduced by electromagnetsaround the drum. The combination of drum motion
(rotation) and magnetic fieldscauses electric currents (eddycurrents) to flow in the drum.
They react with the stationarymagnetic fields to resist the drummotion and produce a retardingor breaking action.
The amount of breaking action iscontrolled by adjusting thestrength of magnetic fields, bythe amount of direct current.
ROTOR
WATER
INLET
WATER OUTLET
ELECTRO
MAGNETS