Draw Works

7/15/2019 Draw Works

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CONTENT

CONTENT...............................................................................................1

Cap 1 Function........................................................................................2

Cap 2 Types and characteristics............................................................3Cap 3 Main systems................................................................................8

a) Main drum.........................................................................9

b) Catheads..........................................................................10

c) Stationary brake (main brake).....................................12

d) Auxiliary brake...............................................................17

Cap 4 Power calculation.......................................................................23

Cap 5 Inspection....................................................................................24

Cap 6 Drawworks brake band.............................................................25

REFERENCES......................................................................................36 APPENDIX 1



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Drawworks

1 FUNCTION

- Drawworks Functions

The Drawworks is one of most important equipment on drilling rig. Theunit supplies the hoisting power, the drawworks spools the drilling line as pipeis run into and pulled out from the well. The drilling line spools out under gravity and is reeled in by an electrical or diesel engine.

Figure 1.1 Schematic Draw



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1. MAST & SUBSTRUCTURE2. CROWN BLOCK3. TRAVELLING BLOCK4. TOP DRIVE5. ROTARY TABLE6. DRAWWORKS7. DRILLING LINE8. DEADLINE ANCHOR

2 TYPES AND CHARACTERISTICS

Depending on the engines on the rig, the drawworks can be either:- MECHANICAL

- ELECTRICAL

- MECHANICAL

Diesel engines are directly connected (compounded) to the drawworkby chain. This system is still in use for small Drilling Rigs (under 1500 HP),but is no longer used on medium-Hi powered rigs( 1500 & 3000 HP).



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Figure 2.1 Schematic draw



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- ELECTRICAL

Electrical system are normally used today on land rigs and is the onlysystem in use on offshore rigs. The drawworks are generally connected to1000 HP D.C. engines, although A.C. engines are now being used as well.

Figure 2.2 Schematic draw



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- Connection Drawworks-Engines

The connection between the drawworks and the engines can beeither:- CHAIN DRIVEN- GEAR DRIVEN

Electric type(chain driven)

Figure 2.3 Chain driven



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ELECTRIC TYPE (Gear-Driven)

Figure 2.4



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3 MAIN SYSTEMS

a - Main Drumb - Catheadsc - Stationary Brake (Main brake)d - Auxiliary brake

Figure 3.1 Drawworks main systems



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a - Main Drum

- Main Drum Diameter - The diameter of the main drum is a function of thediameter of the drilling line being used. It is preferable to have the drum aslarge as possible to reduce the number of wraps and the bending of thecable.

- Drum Length - The length of the drum is a function of the distance _ between Crown block and Drawworks.

- Fleet Angle - To reduce the wear on the drilling line, it is good practice tokeep the angle alpha under degrees. (see pictures)

Figure 3.2 Fleet angle



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b - Catheads

- Spinning line and Breakout Cathead

Catheads are winches with pneumatic clutch and are mounted on theextremity of the secondary drum of the drawworks. The make up cathead islocated beside the driller's console and the break-out cathead is located onthe opposite side of the driller's console. The catheads apply the pullingforce on the hand tongs connections.- Model 16 Spinning line Cathead- Model 16 Breakout Cathead

Figure 3.3 Cathead



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- Employment scheme

For safety reasons and convenience their employment comessupplanted from the dedicated equipments.

Figure 3.4



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c - Stationary Brake

- Band Brake- Disk Brake- Regenerative Brake System

Figure 3.5 Band brake



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- Band Brake

- Description (parts)- BRAKE HANDLE- LEFT BAND- RIGHT BAND- BALANCE BAR

- Braking action

Braking action is activated by pushing the _ Brake handle downtowards the floor. Through a strength multiplier system, the braking force istransmitted onthe _ balance bar, then to the brake bands, and finally to the two drums on

either side of main drum. Heat produced by the braking action is dissipatedthrough the circulating water cooling system.

- Disk B rake

Depending of the size the drawworks, there are 2 to 4 hydraulically-actuated calipers. In addition to these main calipers, each disc brakesystem has 2 dedicated calipers (normally closed) that are used as theemergency and parking brake.These calipers are actuated by an independent hydraulic system. Diskbrakes can be mounted on Drawworks that was originally equipped withband brake.



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Figure 3.6 Disk brake

- Advantages

The advantages are:- Greater braking capability- Emergency braking system- Possibility of Remote control

- Significant noise reduction during drilling

- Use

Disk Brake is a development of the band brake, due to the necessity tohandle heavier loads



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Figure 3.7 Disk brake



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- Performance Comparison diagram of 3 brake combinations

Figure 3.8 Performance diagram



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- Regenerative Brake System

- New generation of drawworks: The newest generation of drawworks(4000-5000 HP), mounted on ultradeep offshore rigs, have a direct drivetransmission system, permanently connecting the drawworks to the motors.When the travelling block descends in the derrick, the motors turns in theopposite direction, producing an opposite current and hence a brakingaction.

- NOTE: This braking system, is not able to hold, when the motors are rest,hence the need for emergency and parking the disk brake system.

Figure 3.9 Regenerative Brake System

d - Auxiliary brake / dynamic brake

The function of the auxiliary brake is to assist the main brakingsystem during rapid descent of the blocks with heavy string weights. Theauxiliary brake prevents the overheating and premature wear of mainbrakes.



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Types:- Hydrodynamic Brake- Elettromagnetic Brake

- Hydrodynamic Brake

That system is still in use on small drawworks. However, on medium-Hi powered drawworks, this system has been replaced by theElectromagnetic brake.

Figure 3.10 Hydrodinamic brake

- Description

The Hydrodynamic brake consisting of two box with a rotor pressed

onto the main drive shaft and two stators. When the main shaft rotates therotor drags water against the two stators, producing a braking action.Braking capability can be regulated by increasing or decreasing the water levels in the "Hydraulic Brake box".



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Figure 3.11 Hydrodinamic brake schematic



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- Electromagnetic brake.

The electromagnetic brake consists of a stator with coil, two magneticpoles and a rotor pressed onto the main drive shaft. When the driller activates the brake control, a magnetic field is produced by 4electromagnetic coils mounted concentrically inside the drum. By varyingthe amount of current to these stationery coils, the driller can control theamount of braking torque applied to the rotating drum.

Figure 3.12 Electromagnetic brake schematic



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- "Baylor" brakes

The use of electromagnetic brake began with diesel-electric rigs. Almost all drawworks today a equipped with "Baylor" brakes. Baylor Brakesare manufactured in 5 standard sizes for nominal drilling depths up to30.000feet.

Figure 3.13 Baylor brakes



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- Braking force

The diagram shows the values of braking force as a function of rpmof the drawworks shaft. Notice how the electromagnetic brake is alsoeffective at low speeds.

Figure 3.14 Braking Force Diagram



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4 POWER CALCULATION

WORK = Force x StepPOWER= Force x Pooh velocity

Figure 4.1 Power calculation

- Hook Power

Ph = Hook Power (HP)Ve = Pooh velocity (m/s)P = Weight on Hook (kg)

- Drawwork Power



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F = Pull to Fast line equal to:P (Weigh on Hook) / N (Number of lines)Vf = fast line velocity equal to:Ve * = 2 R n (rpm drawwork shaft)E= Efficiency of sheaves. This value (empiric)provided by API in function of number of lines.

5 INSPECTIONS

- Periodic inspections

The API applicable references are: API RP 7L and API RP 54 (chapt.

9.4 and 9.5). and the Manufacturer's recommendations.ENI policy requires the API Category IV inspection (as per API RP

7L) every 5 years.

Figure 5.1 Drawwork Inspection



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6 DRAWWORKS BRAKE BAND

• The drawworks brake system uses coolant from the brake water coolingtank to cool the brakes.• As shown in Figure 6.1, the coolant enters the water union on the end of the drumshaft, passes through both brake rims The coolant then returns tothe drumshaft.• The heated coolant will then flow back to the coolant reservoir where it isallowed to cool again.• Use the protection of antifreeze, Inhibitor and water to best meet the unit‟srequirements for its ambient operating temperature.• The use of inhibitor will help prevent corrosion of the system pipework and

brake rims.• Do not use 100% Inhibitor (Nalcool or equivalent) as this will increase theconcentration of antifreeze in the cooling system which will then increasethe concentration of dissolved solids and non-dissolved chemical inhibitors.

Figure 6.1 Brake Cooling Schematic

• Support roller and jack screws (item # “2” in Figure 6.2), located behindthe brake bands assist in the rolling action of the brake bands when bandlift-off occurs.• When the brake handle is in the applied position, clearance between therollers, jack screws, and bands should be approximately ¼” (6 mm).



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Brake Adjustment;

• Adjust the brake handle (item # „1” in Figure 6.4) height using the mainbrake anchor eyebolts located at the front of the brake bands (item # “1” inFigure 6.2)• Ensure an even gap is maintained between the stopping blocks and thebrake equalizer beam (item # “11” in Figure 6.2) to enable even break bandapplication.• Adjust the main brake anchor eyebolts with the brake handle in the upposition.• Gauging of the gap between the stopper blocks and the equalizer beammust be done with the brake handle down and the brake applied.• Ensure the centerline of the keyway on the brake linkage shaft is 30° fromthe horizontal when the brakes are engaged.

• Rollers should be adjusted to give proper band clearance. The proper clearance is 1/8” between the roller and with the band brakes engaged.

Figure 6.2



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Figure 6.2 Band Brake Assembly



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Table 6.1



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Table 6.2

Brake Band Maintenance

Replace brake flanges when they are worn to the extent displayed inFigure 6.3.



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Figure 6.3 Brake Band Flanges Worn-out



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Figure 6.4



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Figure 6.4 Remote Brake Linkage Assembly



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Table 6.3



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Figure 6.5 Band brake components



REFERENCES

1. Wheatherford mechanic - Drawworks

2. Drilling engeneering manual

3. IADC - Drilling manual

4. Saipem 23533775-RIG-BOOK

5. API specification 7K 《Drilling equipment criterion》

6. API recommended practice 7L《Procedures for Inspection, Maintenance,

Repair, and Remanufacture of Drilling Equipment》

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