Description

The ADS-10D Automated Drawworks System (ADS) is used for hoisting the traveling equipment
of a drilling rig to remove and insert tubulars into the well bore.
The ADS is a gear-driven drawworks with VFD-controlled AC motors and multi-plate friction
brakes.
Optional resistive (regenerative) braking via the main motors can be applied to augment the
friction brakes.
The drawworks components are mounted on a unitized skid.
The driller, at an operator control station, uses a dedicated joystick and switches to remotely
operate the ADS through a Varco Integrated Control Instrument System (V-ICIS).
Wire Rope Drum
The wire rope drum is supported by two bearing carries mounted to a structural steel skid.
The drum is fitted with Lebus grooving for 1 5/8-inch wire rope.
A crown saver toggle valve is located above the drum.
The valve is located where it can be activated by the wire rope, just short of the point at which a
crown collision would occur.
When the valve is activated it sends a signal to a crown saver pressure switch which alerts the
control system to stop the drum.
Gearboxes
The 1500 HP, single-speed, double-reduction gearboxes transfer power between the AC motors
and the wire rope drum. Mounted on the clutch shaft is a pneumatically released, spring-
operated, multi-disc clutch that transmits torque between the first and second gear reduction. The
clutch must be engaged for all velocity control by the motors during hoisting and lowering.
Lubricating oil for the gears and bearings is supplied by an external electrical pump system with a
frame-mounted reservoir.
Clutch
The clutch provides the opportunity to disengage the drive motors from the drumshaft.
This is used in ESD situations to reduce the (motor) inertia that the plate disc brakes must retard.
It is also used when electrical repairs or maintenance is being performed, and it is necessary to
tune the VFDs by running motors, or change motors.
AC Motors
The ADS uses 1150 HP (continuous rating), variable speed AC motors to drive the wire rope
drum through the gearboxes.
The motors are coupled to the gearboxes with double spherical gear drive couplings.
The wide range of motor speed allows the ADS to achieve a broard range of hoisting speeds.
Using multiple motors increases hoisting capability.
Motor Blowers
The motor blowers provide open loop, forced-air cooling to the AC motors.
Friction Brakes
The brake is a combination spring and air-operated, multi-plate disc brake.
It applies braking to the drum during operations as well as parking braking.
Two braking methods are available to the operator:
Dynamic breaking using the friction brakes and regenerative braking through the AC motors.
One brake is mounted at each end of the drum-shaft.
The rotating brake discs are spline-coupled to the drum-shaft, and the brake housing is attached
to the skid.
Each brake has three water-cooled discs for dynamic braking control and a single, air-cooled
brake disc for added static parking and emergency stopping capacity.

1
Rotary Encoders
Rotary encoders provide speed and block position information. Encoders are direct-coupled to
each motor and are coupled to the clutch shaft by a drive belt.

Sensing and Feedback Devices

Sensing devices are used to monitor equipment functions. Sensor device outputs are sent to the
control system where they are processed to provide feedback for closed-loop control and to
display status information to the driller. Several types of sensing devices are used. The various
sensing and feedback devices and their locations are illustrated in Chapter 4, Troubleshooting,
Electrical Components Diagram.

ADS Control System

The ADS control system processes all data from the operator controls to the drawworks, and all
feedback from the drawworks to the operator. The processed data is used to control all
drawworks functions and inform the operator of drawworks operations and status. The control
system also provides these safety features:
􀂉Drill line protection

􀂉Collision protection

􀂉Equipment protection

Friction Brakes
The brake is a combination spring and air-operated, multi-plate disc brake. It applies braking to
the drum during operations as well as parking braking.
Two braking methods are available to the operator: dynamic breaking using the friction brakes,
and regenerative braking through the AC motors.
One brake is mounted at each end of the drum-shaft.
The rotating brake discs are spline-coupled to the drum-shaft, and the brake housing is attached
to the skid. Each brake has three water-cooled discs for dynamic braking control and a single, air-
cooled brake disc for added static parking and emergency stopping capacity.
Rotary Encoders
Rotary encoders provide speed and block position information.
Encoders are direct-coupled to each motor and are coupled to the clutch shaft by a drive belt.

Sensing and Feedback Devices

Sensing devices are used to monitor equipment functions. Sensor device outputs are sent to the
control system where they are processed to provide feedback for closed-loop control and to
display status information to the driller.
Several types of sensing devices are used.
The various sensing and feedback devices and their locations are illustrated in Chapter 4,
Troubleshooting, Electrical Components Diagram.

ADS Control System

The ADS control system processes all data from the operator controls to the drawworks, and all
feedback from the drawworks to the operator.
The processed data is used to control all drawworks functions and inform the operator of
drawworks operations and status.
The control system also provides these safety features:
􀂉Drill line protection

􀂉Collision protection

􀂉Equipment protection

2
 Operation Overview
The ADS is operated semi-automatically, meaning the operator is in constant control of the ADS
through use of a joystick and switches whose outputs are fed to the Drawworks through the
control system.
Modes of operation are selected during initial setup and configuration of the equipment.
This is done through the V-ICIS operator control screen. (Refer to the V-ICIS User’s Manual for
more details.)

The joystick is spring-loaded so it returns to center position when released, which is the off
position for safety.

The joystick is used as a velocity control where the speed of hoisting or lowering the traveling
equipment is proportional to the displacement of the joystick handle. The operational positions of
the joystick are listed below.

Desired Joystick Position ADS Response

Operation

Lowering with motors or Forward from center Angle of joystick position determines the command
dynamic brakes position .speed of the traveling assembly
Back from center Angle of joystick position determines the command
Hoisting with motors
position .speed of the traveling assembly
Actual speed is determined by the hook weight and
position of travelling assembly, limited by angle of
.joystick from center position

ADS control switches are located on the V-ICIS control panel. They are described below.

Control/Indicator Function
Turns parking brake on/off and selects operation in automatic mode
ADS PARKING BRAKE switch
.using the OFF/AUTO and ON switch positions
OVERRIDE indicator .Illuminates when system interlocks have been overridden
EMERGENCY STOP Used in an emergency situation. When pressed, the following events
pushbutton switch :occur
)located on the right control panel( .Shuts off power to the ADS .1
.Spring-applied brake actuator vented (brakes applied) .2
.Motor VFDs off .3
.Clutch remains engaged .4

3
Operating Modes
Normal Mode
This mode is used for most operations. When the system is in the Normal Mode, joystick control
is scaled to the driller-defined maximum speeds. All position-based travel limits are active.
Slow Mode
This mode is used for fine position control. When the system is in Slow Mode, joystick control is
scaled for 10 % of the maximum settings. All position-based travel limits are active.
Slip and Cut Mode
The Slip and Cut Mode is used when replacing worn wire rope. When the system is in Slip and
Cut Mode, operating speed is limited to a maximum fast-line speed of 60 ft/min, and all position-
based travel limits and safety interlocks are disabled. A warning is displayed on the drillers screen
when the Slip and Cut Mode is active. All braking functions remain normal.
Block Position Calibration Mode
The driller enters this mode by selecting it on V-ICIS. When the system is in Block Position
Calibration Mode, all position-based travel limits and safety interlocks are disabled and the driller
is notified of this condition. The lower travel limit and upper travel limit are disabled until the block
position calibration is completed.
Electronic Driller Modes
The driller enters this auto-drilling mode by selecting it on V-ICIS.
There are four auto-drilling modes. These modes can be activated individually or in combination
to optimize drilling control. The system uses motor dynamic braking as required for the following
operations (mechanical braking is used to perform control in the ROP Mode).
􀂉Rate of Penetration (ROP) Mode - controls the rate of decent of the traveling equipment while
drilling to a preset rate of penetration. This mode is useful when setting the bit on the bottom, or
when drilling soft formations where controlling the penetration rate is important in drilling a
consistent hole. ROP Mode takes precedence over other modes.
􀂉Weight on Bit (WOB) Mode - controls the rate of decent of the traveling equipment to maintain a
preset weight on the drill bit.
􀂉Torque Mode - controls the rate of decent to maintain a preset torque limit of the top drive. This
mode is useful for increasing the life of the drill bits, and can also be used to reduce the possibility
and effects of slip-stick.
􀂉Delta P Mode - controls the rate of decent of the traveling equipment to maintain a preset
pressure in the standpipe. This mode is only used with down-hole motors.
The delta standpipe pressure is an indication of the drill bits reaction torque into the formation.

Operation Overview
Electronic Driller Modes
Examples of using a combination of modes are as follows. In either example, torque can be
added to reduce the occurrence of slip-stick:
􀂉The combination of ROP and WOB modes are used to smoothly control the movement of the
drill string and maintain constant WOB.
􀂉The combination of ROP and Delta P modes are used when drilling with constant torque on
down-hole motors while limiting the maximum rate of penetration.

4
Braking Modes

Parking Brake Mode

This mode is used by the driller to support the load using the Varco friction brake for long periods
of time, or when the driller is not present at the drillers operator station.
The control system enters the Park Brake Mode when the driller activates the parking brake
switch, or automatically, due to a period of inactivity at zero speed command (joystick is left at
center-position).
If the driller activates the parking brake switch while the block is moving, the block will be
decelerated at maximum rate according to the velocity profile by the motors. When the drum is
stopped, the friction brake will set. Once the friction brake is supporting the load, the torque limit
to the VFD is zeroed.
If the parking brake was applied due to inactivity time-out, or by the Park Brake switch, the
operator must toggle the Park Brake switch to the OFF position to disengage the Park Brake
Mode. When the Park Brake Mode is disengaged, the load is transferred from the friction brake to
the AC motors (refer to Torque Transfer Sequence).

Brake Mode
This mode is used by the driller to support the load using the Varco friction brake for short periods
of time when the driller does not want to support the load using the AC motors, such as when the
rig crew is working below the block.
To enter the Brake Mode the driller moves the joystick to the Brake position (detent to right). To
disengage and release the brake, the driller moves the joystick back to the zero
speed (center) position. At this time the load is transferred back to the AC motors. (refer to
Torque Transfer Sequence).

Stopped Mode
The driller must release the park brakes before moving the block in any direction.
Releasing the park brakes causes the load to be transferred from the brakes to the AC motors.
Once the motors are holding the load, the system is considered to be in the Stopped Mode. All
normal operations of hoisting and lowering begins and ends with the system in Stopped Mode
and the load being held by the AC motors. If the block is left in the Stopped Mode without any
movement for three minutes the system will automatically transition from stopped to park. (Note
that the three minute Stopped Mode time is site configurable.)

Principles of Operation
The control system controls acceleration, velocity, and deceleration of the traveling assembly in
both the hoisting and lowering directions while maintaining safe and reliable operation.
By following a velocity profile, the control system optimizes the driller’s ability to maximize the
speed of trips between positions in the mast/derrick (between the travel limits).
Travel of the block assembly following the full velocity profile (from upper travel limit to the lower
travel limit and back again) is described in the paragraphs below, for operation under normal
conditions.

5
Definitions
Lower Deceleration Point
When lowering, the lower deceleration point is the lowest position at which regenerative braking
can be utilized to safely stop the block assembly without passing the lower travel limit.
The lower deceleration point is calculated by adding the calculated stopping distance for
downward travel to the lower travel limit position.
Stopping distance is calculated based on available braking torque (from brakes and motors),
system inertia, lines strung, hookload, and block position.
Lower Travel Limit
The lower travel limit is the driller defined position of lower most travel.
The control system will not allow the lower travel limit position to be set below the known position
of the drill floor.
The control system, as part of the Zone Management System (ZMS), will automatically adjust the
lower travel limit based on the information regarding the position of other equipment that can
enter the zone in which the block travels.

It is the responsibility of the driller to ensure the lower travel limit setting is adequate to
prevent equipment hanging below the blocks and from striking other equipment or the drill
floor.

Hoisting Deceleration Point

When hoisting, the hoisting deceleration point is the uppermost position at which the block will
begin deceleration to safely stop the blocks without passing the upper travel limit and keep
tension in the drill line. The hoisting deceleration point is calculated by subtracting the stopping
distance from the upper travel limit. Stopping distance is calculated based on available braking
torque (from brakes and motors) and system inertia, lines strung, hookload, and block position.

Definitions
Upper Travel Limit
The upper travel limit is the driller-defined position of uppermost travel. Just as the control system
will assist the driller in preventing floor collisions, it will also assist in preventing crown collisions
by not allowing an upper travel limit to be set above what is known by the control system to be the
maximum height before striking the crown block.
Regenerative Braking
Regenerative braking is the use of the motors, in generator mode, to provide the braking function.
When regenerative braking is in use the power generated is returned to the DC bus. If this results
in an increase in voltage on the bus, because there is insufficient load on the bus to absorb
power, chopper circuits will feed power from the DC bus to a resistor bank. In the case of a
chopper or resistor failure, the control system will reduce the available braking power figure
accordingly and will use the reduced power to calculate maximum lowering velocity and stopping
distance.
Velocity Control
The VFD system works as a velocity control system. The information on the position of the
joystick is sent to the VFD as a maximum desired motor speed, as limited by the velocity profile.
The center position of the joystick represents zero velocity (stationary drum). The difference
between the desired velocity and the actual velocity is an error signal used by the control system.

6
Lowering the Block - Tripping
Reaching Lowering Velocity
When the driller commands downward travel of the block from a stopped condition (where the
brakes support the load), the control system will perform a torque transfer sequence and begin to
accelerate the drum using the motors. The control system calculates the maximum safe
downward acceleration to prevent birdnesting the drill line on the drum. Based on the calculated
acceleration, the control system provides the appropriate speed and torque limit commands to the
VFD system. The velocity command is ramped as calculated by the control system until either the
velocity indicated by the position of the joystick or a maximum velocity, as limited by the
equipment, is achieved.
Maintaining Maximum Velocity
The maximum velocity is determined from the position and inertia of the load, and the available
braking capacity of the motors and the friction brake. Once the block has been accelerated to its
maximum lowering velocity, that velocity is maintained, and overspeed is prevented, by using the
velocity control of the VFD system (regenerative braking) and the friction brake.

Principles of Operation
Lowering the Block - Tripping
Stopping
As the driller continues to command lowering, the block assembly will continue to travel down at
maximum velocity until reaching the lower travel limit. The driller can stop the block assembly
before it reaches the lower travel limit by returning the joystick to center position, thereby
commanding zero velocity. The block assembly will decelerate to zero velocity according to the
velocity profile. Sufficient motor torque is applied to hold the load in place.
Lowering the Block - Drilling
After the proper parameters have been entered the drilling ahead task, the operator raises the
string off the slips by moving the joystick back. The VFDs are activated and the AC motors begin
to ramp up torque. Dynamic pads are engaged as the torque builds and the static brake released.
Once the torque value needed to hold the drill string has been achieved the brakes are released
and the string rises. After the slips are disengaged, the driller moves the joystick back to neutral,
and the motors hold the string stationary. The driller engages the electronic driller, releases the
joystick and the ADS takes over the drilling control.
After the stand is drilled down, the parking brakes are engaged (static), and slips are set. The
connection is broken out, the driller pulls back on the joystick to hoist up the Top Drive System
(TDS). Once at the TDS is at its upper limit, a new stand of pipe is inserted and TDS spins in and
makes up both connections.

Lowering the Block - During Power Failure

When a total power outage occurs you can lower the traveling block by manual operation
of the brake release control valve as follows:

Actuating the hand lever on the brake release control valve will release the brake. This
control is for emergency use only.

1. At both pneumatic panels, verify the pressure gages indicate zero pressure.
2. At both pneumatic panels and both brake control boxes, rotate the handle on the 3-way ball
valves to the MANUAL position for local control.
3. At the LH pneumatic panel, slowly move handle on the brake release control valve to lower the
load. Release the handle to stop lowering.
4. Return control to automatic mode (remote operation) by rotating the handle on all
3-way ball valves back to the AUTO position.

7
Hoisting the Block
Releasing Brakes
When the driller commands upward travel of the block from a stopped condition (where the
brakes support the load), the control system will perform a torque transfer sequence and begin to
accelerate the drum using the motors. The velocity command is ramped as calculated by the
control system until either the velocity indicated by the position of the joystick or a maximum
velocity, as limited by the hookload and available power is achieved.
Maintaining Maximum Velocity
The maximum velocity is determined from the position and inertia of the load, and the available
braking capacity of the motors. Once the block has been accelerated to the maximum hoisting
velocity, that velocity is maintained, and over speed is prevented, by using the velocity control of
the VFD system.
Deceleration and Stopping
When the block reaches the hoisting deceleration point the velocity command is ramped to zero
and regenerative braking torque, if required, is applied to decelerate the load safely to the upper
travel limit, as calculated to prevent fouling or bird nesting the drill line.
When the velocity drops to zero, sufficient motor torque is applied to hold the load in place.
Torque Transfer Sequence
The torque (or load) transfer sequence is a method of smoothly transitioning from a friction brake-
held load to a load supported by the AC motors. The transition is accomplished by sending a
small hoisting speed command (about five RPM at the motor) and a torque limit to the VFD
system. This calculated torque limit is based on hookload, number of lines and number of motors,
and is of a magnitude large enough to support the load (excessive torque could cause damage to
the ADS and related equipment).
Once the feedback torque from the motors equals the calculated torque limit, the friction brake is
ramped to zero over a short period of time.
As the brakes are being released and as soon as the system detects movement in the hoist
direction, the speed command is ramped to zero and the torque limit is ramped to maximum.
Ramping of the torque limit in this manner, as opposed to instantaneous changes, prevents
transients that could cause unnecessary and undesirable gearbox vibration should the drum
begin to rotate in the lowering direction, the brakes are reset and the torque transfer torque limit is
increased before trying again.
The torque transfer sequence is repeated three times before an alarm is generated.

Protection Features
Although the drillers experience and skill provides the primary safety functions, the controls
system provides the secondary functions described below.
Drill Line Protection

The driller is ultimately responsible for accelerating and decelerating in a manner that
does not damage the drill line.

This protection is designed to give maximum life to the drill line. Drum acceleration when lowering
is limited, based on hookload and the number of lines strung, to a value that will keep tension on
the drill line. Deceleration is also limited when hoisting to keep a similar tension on the drill line.
Drill Line Pull Limit Protection
This protection prevents excessive tension on the drill line.
The control system monitors the measured hookload against the driller-entered hookload value.
The driller-entered value is used to determine the maximum torque limits for each motor. These
values limit the acceleration of the system and prevent over-pull on stuck pipe.

8
Collision Protection
The driller is ultimately responsible for operating the ADS in a manner that avoids
collisions with the crown, drill floor, or other drilling equipment.

This protection is designed to avoid collisions with the crown block, drill floor, or other drilling
equipment. Deceleration limits when lowering are calculated based on the hookload, number of
motors assigned, and number of lines strung. Deceleration limits when hoisting are based on the
acceleration required to keep tension on the drill line.
From these deceleration limits, and known system time delays, stopping distances are calculated.
The Zone Management System (ZMS) and driller-entered travel limits define the allowable zones
of travel for the traveling assembly. The combination of the deceleration limits, calculated
stopping distances, and driller-entered limits define the velocity profile, or safe operating
envelope. The control system uses this information to control the movement of the traveling
assembly and allow operating the system at the highest acceptable speeds while keeping the
systems within the operating limits of the associated equipment.

Equipment Protection
Various parameters are monitored to ensure that the equipment is operating properly and will not
be damaged by loss of utilities. Major parameters being monitored include:
􀂉Lube oil pressure

􀂉Brake air pressure

􀂉Rig supply air pressure

􀂉Brake cooling water temperatures

􀂉VFD and AC motor parameters

Loss of these services or components, or operation outside the recommended limits of these
components, may cause the control system to enter a fault mode and stop the ADS until the
problem is corrected. For some faults, a driller-initiated override is available to allow the block to
move at maximum speed if the driller determines that the overall safety of the rig is best served
by continuing to operate the ADS, or associated equipment.

Protection Features
Emergency Stop (E-stop)
The control system can initiate two types of emergency stops:
1. Stopping the ADS by immediate removal of power, as in an uncontrolled stop.
When this type of E-stop is generated the system will simultaneously dump all air from the spring-
applied brakes and send all VFDs to coast. Conditions that lead to this type of E-stop include:
􀂉Activation of driller’s E-stop pushbutton switch

􀂉ADS Control System failure

􀂉Activation of the crown saver switch

􀂉Loss of communications with remote I/O block controlling brake bypass solenoid valves

2. A controlled stop with power available to the ADS to achieve the stop, then removal of power
when the stop is achieved. When this type of E-stop is generated the system will set the velocity
set point to zero and set the system for maximum deceleration. After zero speed is accomplished
the system will dump all air from the spring-applied brakes and send all VFDs to coast.
Conditions that lead to this type of E-stop include:
􀂉VFD PLC fault

􀂉Block speed mismatch (command vs achieved)

􀂉Failed torque transfer sequence (motor/brake)

􀂉Low air pressure

􀂉Block movement while stopped (creep)

􀂉Loss of communication to the VFDs

9
The driller can override the control system by pressing an override pushbutton on the
operators control station. When the ADS is in override mode, all position safeties are
inactive and the drawworks is allowed to operate at a maximum speed of 50 ft/min only.

Reference Material
Vendor documents are provided for additional information on the ADS and its components, and
ADS operation.

Specifications
Physical Specifications
:Size Height (max.) .in 101

Width (max.) .in 120

Length (max.) .in 296

Weight .lb max 100,000

Component Specifications
:AC motor Power rating (max.) HP (Intermittent) 1,150 HP (Continuous) 1,400

Speed (max) RPM 3,000

SCFM air 3,000
Cooling (each motor)

:Gearbox Type Single-speed, double-reduction, parallel shaft

overall (Dry Sump) 10.71:1

:Ratios first stage (input) 2.90:1

second stage 3.69:1

Torque rating ft lb (input shaft) 11,000

Weight lb 13,000

:Brake
Brake size plate, 36-inch diameter-4
:Dynamic braking system Type
disc, water-cooled, pressure-applied brake-3

:Emergency & Parking brake Type Spring-applied, air-cooled, pneumatically-

released multi-disc brake (engages three
dynamic discs (noted above) and the single air-
cooled disc)
Minimum rig air pressure psi 135
required
ft lb 149,000
Maximum dynamic braking
torque at 120 psi

:Air quality (per ISA Standard S7.3-1981) Max. particle size: 5 micron

Dew point: 10º C below minimum ambient temperature, and not to exceed 2º C in
any case

Flow rate to each brake -water 195 GPM

:Brake cooling

10
 Component Specifications
M BTU/hr (total continuous) system 6.0
Brake: (cont) Brake cooling heat dissipation capacity required
hp each (150º F max. outlet water 1950
Power rating
temperature and 50º F max. temperature
(continuous)
.rise) Water inlet pressure 40 psi max
Wire rope drum: Wire rope diameter inch-5/8 1
Drum core diameter inches 36
Drum length inches 71
Grooving Lebus for 1 5/8-inch diameter rope
:Wire rope Size and Type inch diameter 6 X 19 Extra Improved-5/8 1
Plow Steel (EIPS)
Specification API Specification 9A, Specification for Wire Rope

Power Requirements
Electrical
Control system VAC, 60 Hz, 15A 120

Pneumatic

Pressure psi (min) 135

11