Drawworks Brakes and Drum Designs

Transcription

By John L’Espoir
Drawworks Brakes and Drum Designs
What is a fleet angle and what is a self-energized brake design?
Why use a hydromatic brake if it cannot stop a drum?
Drum Design
When starting with the design of a
drum, the engineer must make a lot of
decisions before the pencil ever hits the
paper—or, these days, before the hand
hits the mouse.
The design depends on:
●
●
●
●
●
●
●
●
●
●
●
Single line pull and wire line size
required
How many feet must be spooled up
How long the barrel can be without
making the drawworks too wide
A width that meets fleet angle
requirements
Brake flanges large enough to hold
the load
Cooling for the flanges: either by
forced air, water splash, or water
circulation
Whether a grooving jacket is used
Choice of a wire line anchor and
what side will it be on
Choice of a floating drum mounted
on bearings or one keyed to the shaft
Choice of a long shaft through the
center, or two stubshafts bolted to the
drum body
Whether a retarder is used.
We discussed the clutch capacity,
single-line pulls, and even the clutchmounting location last month (Water
John L’Espoir has enjoyed a 40-year career in
portable drilling equipment design. He holds
a bachelor of science degree in mechanical
engineering and was formerly the director of
engineering for the George E. Failing Co. in
Enid, Oklahoma. John was born in the Netherlands and moved to Enid in 1969. He is the
founder, owner, and president of Enid Drill
Systems Inc. He received the 2003 NGWA
Technology Award.
50/ November 2009 Water Well Journal
Figure 1. The drawworks on a Failing Strat 100 had an SLP of 18,000 pounds,
eight line reeving required about six layers. EDSI replaced this drawworks to get
25,000 pounds SLP. Note the old LEBUS held on top of the new LEBUS. The rig
capacity increased from 4500 feet to 7500 feet for gas field work. Only three
layers required for eight lines.
Well Journal, October 2009). A drum
barrel should be long enough to spool
up all wire required to pull the kelly out
of the table and up into the mast retract,
if so designed. It is preferable to use a
maximum of three layers of rope on the
drum to avoid excessive loss of singleline pulling power.
Designing a drum on bearings has
the advantage that a block will be lowered much easier in the mast, especially
with light loads such as a single sheave
snatchblock with no load. On the other
hand, bearings must be lubed, and this
lube will at some time find its way into
the clutch. The drum barrel would be
used to contain a small amount of gear
oil or be hand-packed around the bearings with grease. A more effective
design will install self-lubed, sealed
bearings plus a simple shaft seal with
grease packed behind it to keep dirt and
sand away from the bearings.
Designing a drum that is keyed to the
shaft brings its own problems, such as
pressing the shaft into the drum bores.
Stepped diameter bores and keys in only
one flange makes this process easier.
Then the drum must be locked for axial
movement. The length of the barrel
determines the fleet angle. The distance
TRANSFER OF TECHNOLOGY/continues on page 52
NGWA.org
Figure 2. The length of a LEBUS jacket may not be altered. Fitting to the drum
must be done by wearplates or machining on the drum. An altered jacket is worse
than a flat, smooth barrel. A negative fleet angle will spool up all the wire line
on one side, which is extremely dangerous. It will stack and then jump, causing
shockloads and destroying the line. Wire line rollers or guide sheaves must be
installed to correct the problems. Drum flange-mounted kicker bars usually do
more harm than good.
TRANSFER OF TECHNOLOGY/from page 50
from drum to crown sheave must be
known. The wire line in the middle of
the drum to the sheave should be 90 degrees, or perpendicular to the centerline
of the drum shaft. Offset drums to one
side or the other can still meet this
requirement by simply tilting the drum
slightly. Fleet angles between ¼ degree
and 1¼ degree are considered ideal.
The engineer must determine what
type of drilling the drawworks will be
used for. Are one, two, or even three
drums required? Should the two main
drums be side-by-side on a common
shaft? Or should there be a stacked design, whereby each drum has its own
shaft? Will the wire line feed off on the
rotary side (underslung) or come off the
top? This is extremely important when
designing the brakes.
Brake Drums
No matter what steel is used, all
drums wear out. Rolled-ring-style, mildsteel, welded-on drums are frequently
used. It becomes a major job to repair
those in the field. Bolt-on-style brake
drums are better. Material may be selected from cast iron, forged alloy steel,
or fabricated mild steel. A band brake
Figure 3. Our Ewbank Model M-100
three drum stacked design drawworks
has dual, equalized, self-energized
brakes on the two main (front) drums
while the sand reel (back) has a single
band brake.
must be self-energized. This means that
the band must be pulling on the anchor
pin. If the wire line is wound up backwards, you will not be able to hold even
10 percent of the load.
Internal brakes in winches are for
one direction only. When lifting a drillcollar, if the winch doesn’t hold, simply
unspool the line and hold the lever in
the same position until it starts spooling
up again. Now try your brake to hold
the load. If it doesn’t, you have internal
brake problems.
It still baffles my engineering mind
that the width of the band does not enter
into the equation to hold the load. A 1inch-wide band will hold as much as a
6-inch-wide band. Width will determine
only the life of a band. The wider the
band, the longer service life it will have.
The following is a report on friction
materials and a calculation made by
Jim Schmitz of Scan-Pac for the Ewbank
Model M-60 main drum brake:
Due to tight controls concerning the
health hazards of asbestos in the environment, along with potential liability
problems, virtually no woven asbestos
brake lining is currently being produced
in this country. As an alternative, synNGWA.org
thetic yarns are being used to manufacture non-asbestos woven products as
an asbestos alternative. The current
asbestos-free product exhibits a slightly
higher friction coefficient, generally in
the range of 5 to 10 percent over the
former asbestos products, while maintaining similar high-temperature characteristics. An additional benefit for the
non-asbestos products is a substantial
reduction in moisture absorption, because of both immersion and high humidity. During the last 15 or more years,
since the introduction of non-asbestos
woven lining, we have found substantial
acceptance by manufacturers as well as
in the aftermarket for this product. With
regard to the friction-coefficient rating
system, the standard test procedure
uses a cast iron drum and is run at 150
pounds per square inch and 1200 feet
per minute. Experience has indicated
that the friction level is reduced by 5 to
8 percent when a steel drum is used.
Speed and pressure variations also result
in performance variations, which are indeterminate dependent on the specific
formulation being used.
Figure 4. The larger Ewbank drawworks use bolt-on, alloy steel, flame-hardened,
forged-brake drums.
Figure 5. Formulas and lesson on brake design copied from the Machinery’s Handbook (courtesy of Industrial Press Inc.).
M-60 brake design specifications:
SLP 20,000 pounds
● Radius 311⁄16 inches
● Band wrap 320 degrees =
5.58 radians = ϴ
● Brake load at 22-inch rim is 6700
pounds = P
● Apply coefficient of friction µ = .48
● Total leverage to driller 27.42
Formula T = P (1/(еµθ–1))
еµθ = е.48 ⳯ 5.58 = 14.6
T = 6700 (1/(14.6–1)) = 493 pounds
Allow 25 percent for safety and this
load becomes 1.25⳯493 = 615 pounds.
With a ratio of 27.42:1, the force by the
driller’s hand must be 615/27.42 = 22.4
pounds.
●
Disc Brakes
Text and pictures courtesy of
Don Harmon Co.
There are several projects in process
on disc brakes right now, but those that
apply to water well drilling are probably
sufficient for our purposes. On horsepower greater than 500, we are using
water-cooled disc brakes, both Wichita
and KOBELT.
NGWA.org
Water Well Journal November 2009 53/
Figure 6. Always keep friction material dry and very clean. Moisture and any kind
of lube will drastically lower the coefficient of friction. Keep linkage pins clean
and lubed. For maximum efficiency, adjust them so that the final link attached to
the band is pointing to the center of the drum.
Figure 7. Russian coredrill Model EUF-650A unit is located approximately 50
miles southwest of Cairo in the Oasis of Kom-Aushim in the Sahara Desert.
The double brake bands have a dual purpose. The one on the left is used to lock
the internal planetary, which will cause the drum to turn when the brake is set.
In other words, the left brake is actually the drum clutch, while the right brake
is the drum brake. See schematic (Figure 8).
Figure 8. Note: The author cannot translate the Arabic notes. I hope it is safe?
Retarder (dynamic) brakes have been
used on well-servicing rigs for several
years. One of the first applications was
done in the Permian Basin, where a
large KOBELT disc was used to replace
the old Parmac brake. Since then, we
have learned many things, but overall
performance is greatly enhanced with
air-operated discs and calipers. This
gives the rig operators better control
from top to bottom. In many cases, the
brakes are used to bring the blocks to a
complete stop; this is not possible with
water brakes. The prime consideration is
horsepower dissipation. I don’t have to
tell you the limits on air-cooled discs
and that they may easily be abused; the
operation is so simple that rig operators
can ask more than a disc can deliver.
Education is primary, but after a few
brake pad failures, they soon learn limits and still get improved performance.
There is no magic in the application:
hook loads/drop speeds/distance add up
to horsepower per trip.
We now have a few rigs in service
with “total disc braking”; the drum
flanges were replaced with discs. On
these, we use a caliper that has a failsafe “maxi-brake pod,” air-controlled
but spring-applied in the event of air
failure or the need for parking. Springapplied calipers are not easily controlled
for dynamic braking; therefore, there is
a need for air-applied with spring-override for safety. On pure retarder braking,
air-applied is sufficient; the drum flange
brakes are used as backup.
The accompanying photo (Figure 9)
was made showing the 5026CM
caliper—air-applied with the spring set
function included—no flange brakes are
on this Taylor rig, only discs. Controls
for “total disc” braking had been the
concern. Other engineers tried to do this
with “over-engineered” control circuits,
computers, hydraulics, WABCO controls, you name it. I insist on KOBELT
control valves, and ask that the original
equipment manufacturer comply strictly
with KOBELT recommendations. This
includes a lever control valve and a
pilot-operated relay valve installed in
each caliper. The pilot air sends the signal to the relay valve; the relay valve
sends air quickly to the caliper (it is a
NGWA.org
Figure 9. This rig, under construction, features a 4-inch-wide by 48-inch-diameter
disc brake for the drum. This is the only brake system for the drum.
⁄4-inch capacity valve). Unless this is
done, delays in brake response cause
lack of control. Understand, however,
that this applies only to those rigs with
total-disc braking. Retarder (dynamic)
braking can be accomplished with simple precision regulators and three-way
on/off control valves. The relay valve is
an option and, in my opinion, worth the
cost.
On the Wichita applications, the
Kopper-Kool design has proven to be
a real asset. W-N Apache has several
water well rigs in service with the
Wichita brake mounted directly to the
drum shaft. Although some are “spring
applied,” they claim that with their own
3
Figure 10. The rotating parts inside a Parmac double 15 series. Note the sharp edges. These knives will slice (shear) the water
due to close tolerances and high speeds. The water gets hot. This is kinetic energy turned into thermal energy.
NGWA.org
Figure 11. Note the double-drive speed-increase ratio. When the brake is needed,
a jawclutch is engaged. The one-way clutch allows the block to go up without
retardation. Shown is the Parmac 15-inch double rotor. Note the very large brake
bands.
Figure 12. One-way clutch (courtesy of
Warner Electric Formsprag).
1
2
4
3
5
6
8
9
7
computer control and feedback for drill
pressure, it is a superior system. I cannot question this success, as there have
been only a few rigs delivered, and I
have not had the pleasure of seeing one
on location.
So in summation: Calipers are available in air-applied, spring-applied, and
dual-air-applied with a spring set failsafe function. Discs are available in a
wide range of sizes, up to and including
72-inch-diameter water-cooled. Wichita
has their Kopper-Kool brake available
in horsepower sizes from 25 through
3300 hp continuous! Disc brake installations are increasing in numbers.
Retarders
Water or electromagnetic retarders
are all based on turning kinetic energy
into heat, which is then cooled by the
air. The most common brand in the
NGWA.org
water well industry is Parmac LLC,
which produces the Parmac Hydromatic® or Hydrotarder® brake. Because
these are water brakes, they are often
referred to as hydromatic brakes or
hydrotarders.
A large selection of sizes fit rigs with
hookloads from 60,000 to 1,000,000
pounds. A customer must decide the
maximum lowering speed of the drill
string. On water well rigs with short
masts, about 180 feet per minute is maximum, requiring only 10 seconds for 30foot joints. In the calculation to size the
brake, the following are needed:
●
●
●
●
●
Brake drum diameter
Number of lines to the block
Maximum string load (usually hook
load of mast)
Maximum lowering speed
Increase ratio of drive
General Description of
a Hydromatic Brake
(Courtesy of Parmac LLC)
The Hydromatic Brake is a hydrodynamic device that absorbs power by
converting mechanical energy into heat
in the working fluid, which is normally
water. Resistance is created exclusively
by fluid friction and agitation of the
fluid being circulated between the vaned
pockets of the rotor and the facing
vaned pockets of the stator. The amount
of mechanical energy that can be absorbed in this manner is dependent on
the quantity and velocity of the fluid in
the working chamber. The velocity of
any specific quantity of fluid in the
working chamber will be increased with
the increased rotary speed of the rotor
Figure 13. Horsepower chart (courtesy of Parmac).
Figure 14. Parmac on Ewbank Model M-100 with air-clutch drive. When space
is available on a wide frame such as pictured, a large-size air clutch can be used,
using pneumatic logics and interlocks to allow the brake to be operated automatically when needed. This system releases the brake when hoisting the block in the
mast. A Parmac’s brake holdback capacity can be controlled by the amount of
water flowing into the brake. This may never be cut off 100%; steam could form
instantly, blowing out the seals. The inlet valve must be easily reachable by the
driller to adjust, as the string gets heavier.
up to the maximum operating speed of
the brake.
Hydromatic brakes and hydrotarders
are versatile pieces of equipment. Originally developed for use on heavy-duty
rotary drilling rigs, uses have spread to
other areas such as cranes, hoists, ski
lifts, on- and off-road highway vehicles,
gravity conveyers, and dynamometers.
Any equipment that generates a surplus
of energy on descent can profit for the
smooth, fluid action, “power absorbing”
efficiency of the hydromatic brake or
hydrotarder.
The hydromatic brake has been used
primarily on oil drilling rigs to retard
the descent of the drill pipe into the
well. It is a speed-retarding device only
and cannot completely stop the load
being controlled. The hydromatic brake
is used to control the descent of the
hook load to a speed the drawworks
friction brake can stop safely.
A large water-cooling system is
needed to supply cool water to the
brake. Water is heavy, sometimes hard
to get, and it will freeze. Some rigs use
a closed loop system whereby water
and antifreeze is mixed and contained
on the rig. Let us look at some horsepower calculations.
Hook hp = (weight ⳯ speed)/33,000.
To lift a 60,000-pound load at 180
feet/minute would be (60,000 ⳯ 180)/
33,000 = 327 hp.
When lowering this load at that
speed, it generates 327 hp, which is
equal to 243 kilowatts. If we could capture this energy and use it, a four-hour
brake operation could supply electricity
for my home for one month. The brake
usage is only when tripping back into a
deep hole with a heavy string.
Refer to Figure 11. Once the string
weight gets to approximately 20,000
pounds, the jawclutch (3) will be engaged manually. (Some manufacturers
elect to shift this with air.) The driver
sprocket (2) is now locked to the shaft,
which is keyed to the drum. Driven
sprocket (5) is on bearings and is bolted
to the one-way overriding clutch (4) to
allow freewheeling when the block is
hoisted up. When fully releasing the
band brakes (1), the clutch (4) will drive
crossover shaft (6), which will turn
sprockets (7) and (8) and drive the brake
(9). At this point, the drill string is on a
controlled descent with the band brake
held free. Final stopping will be when
applying these band brakes (1). In simple words, the Parmac is a brake band/
drum saver. Even a small brake can absorb enormous amounts of energy; 100
hp per hour is equal to 74.5 killowatts
per hour.
The author does not recommend a
valve in the discharge line from the
brake. Caution must be taken to never
exceed a pressure of 25 pounds per
square inch in the brake nor let the discharge water temperature get above
180ºF.
Eddy Current Retarders
In the early 1980s, the author
selected a series of electromagnetic
retarders for use on a drilling rig with
NGWA.org
Figure 15. Electromagnetic retarder installed on a Failing 2500 CF operating currently in Australia. Drilling depth is 4000
feet and we quote “the braking system works like a dream.” Picture courtesy of Daly Bros. Drilling in Australia, taken March 5,
2002. Note that the brake is heavily guarded while in operation to protect against rotating parts and extreme heat transfer.
Figure 16. Text and pictures courtesy of Mustang Dynamometer Co.
the help of Don Ganzhorn Sr. The unit is
air-cooled and lightweight. Variable
holdback can be controlled through a
10-turn 12 VDC-30 amp potentiometer,
built into the control panel. A jawclutch
is still recommended, along with an
overriding clutch as used on the Parmac.
The medium series C-160 was used
which will hold back as much as 180
hp.
Principles of Electromagnetic
Absorbers
These power absorbers are simple
devices, low in cost, used for testing
such items as engines, engine components, transmissions, gear boxes, tires,
and belts. Because of the power absorber’s inherent design and operation,
it is ideally suited for test standard operations. However, it also has many uses
in both portable and mobile applications. Although specified primarily for
new test stand installations, the power
absorber is practical as an “add-on” unit
for upgrading existing absorption equipment that has become too small for the
application. The fast-responding power
absorber is electrically controlled, aircooled, and requires minimum maintenance. The power absorber has no
frictional wearing surfaces and is completely free of all air, water, hydraulic,
and associated servitudes. Operating on
the eddy current principle, the power
absorber establishes a magnetic field by
energizing the stationary field coils with
direct-current (DC) power. Rotation of
the iron rotors in the magnetic field generates eddy currents in the rotors that
produce a counterforce to the direction
of the rotary motion. Power absorption
is dependent on the amount of DC
power applied to the field coils and
input revolutions per minute of the rotors. The absorbed energy is converted
into heat in the two rotors, which are
located external of the coils. The rotors
are designed with curvilinear cooling
fins for fast heat dissipation into the
atmosphere. This design provides the
smallest physical size for air-cooled
eddy current design absorbers.
Lubrication
Drum bearings, pillowblock bearings, shaft cross journals, Parmac pinion
bearings, jawclutches, and one-way
sprocket bushings all need a goodquality gun grease. A one-way clutch
needs to be half full with oil. Do not use
EP lube or oil with slick additives.
Mobil Jet Oil II, which is preferred, is a
synthetic lubricant. Also approved are
Shell Turbine Oil 500 and Exxon Turbo
Oil 2389. Quantity should be approximately 7 ounces or 207 cc.
NGWA.org
Service and Operations
●
●
●
●
●
●
●
Inspect drawworks brakes.
Inspect drawworks brake linkages.
Adjust and lube as necessary.
Inspect oil in one-way clutch.
Check shaft endplay on the Parmac.
Check plumbing and valve. Note the
intake valve should have a 1⁄2-inch
hole drilled through to allow water to
get to the Parmac.
Check system for proper drainage in
freezing weather.
Inspect that the correct size of wire
line is used to match grooving and
wire line sheaves.
Brakes and Drawworks Drums
In the May issue, we discussed
briefly how to calculate the length of a
wire line that can be stored on a drum.
I’ve had a number of people call and ask
to explain this formula. Well, I always
use my own formula (Figure 1). It
seems to work well and ends up showing about 2% less in capacity.
Let us plug in some dimensions:
D = 22 inches
B = 8 inches
D – B/2 = A = 7 inches
C = 12 inches
D average = D + B/2 = 15 inches
or A + B = 15 inches
Use ¾-inch wire line
To get the number of wraps (W)
around the full length of the barrel,
divide C by the wire line diameter. So
12 inches/¾ inch = 16 = W. If this is a
fraction, always delete the fraction and
only use the whole number.
Now let’s find the number of layers
(L) of wire line if they are stacked one
right on top of the other one. Let us take
A and divide it by the wire line diameter.
So you have 7 inches/¾ inch = 9.333
= L. As before, we delete the decimals
so that L = 9.
One circumference on DAVE (the
average diameter) will be calculated in
feet as follows: DAVE × π /12 = ___
NGWA.org
Resolutions to Make Today
1. Write an inspection report for the
following items:
a. Brake drums and bands
b. Linkage and pins
c. Disc brake disc and calipers
d. Retarder and drive assembly.
2. Determine what maintenance tools
should be on the rig.
3. Record any applicable model numbers of items, such as the Parmac, retarder, one-way clutch, or disc brake.
4. Obtain parts and service manuals for
these from the manufacturer who
built the rig.
5. Establish a personal contact with
engineering and parts supply staff.
Coming next month. Drawworks: The
rest of the story. What are catheads or
catworks? How do we choose from
bevel gears, spiral bevel gears, or
hypoid gears? Are chains dry, brush
lubed, or oil bath?
Interested in the book Transfer of Technology? It is available in the NGWA
Bookstore. The member rate is $75; the
nonmember rate is $87.50. Call NGWA
at (800) 551-7379 to order your copy
today.
Figure 1. Formula for calculating the length of wire line that can be stored in
drum.
feet. The drum capacity multiplies this
length by W (number of wraps) and by
L (number of layers). The formula becomes now: DAVE × π/12 × W × L =
___ feet. In our example, it becomes:
15 × π/12 × 16 × 9 = 565 feet. If your
calculator doesn’t have the π button,
use 3.14 or plug in 22/7.
Please make the effort and measure
one of your drums and go through this
exercise. This system has worked for me
for 40 years and we have built a lot of
drums. And yes, the wire line fits on the
drums.
Brake Linkages
As the equipment gets older, we find
worn-out brass and steel bushings in the
Figure 2. Standard shaftings fit the Fafnir VCJ 17⁄16-inch
pillow blocks.
remote brake linkage to clutches and
brakes. The result is a hard to control
drawworks. Brake levers have to be
lifted way up to release and then they
release all at once, requiring swift action
to catch the load.
The contractor operating this 3000foot rig did away with expensive factory
bushings and used standard, cold-rolled
117⁄16-inch shaftings that fit the Fafnir
VCJ 117⁄16-inch pillow blocks (Figure 2).
A little grease will go a long, long time
and provide a smooth rotation. If the
rod yokes or pins are worn out, replace
them. If the shaft arms are worn out,
replace them or drill them out for
an oversize yoke pin. Operation of a
mechanical drawworks becomes a lot
easier on the arms and brains of the
operator.
The Parkersburg Brake
Shown is the older model double 15inch brake (Figure 3). It has been modified to get absolute free-wheeling from
the clutch while the block goes up. The
shaft has been drilled for passage of air
via a rotor seal to the dual element size
11.5VC500. The internal drum is
mounted directly to the shaft that is supported by the two pillow blocks shown.
The chain moves whenever the drum
moves. The pneumatic system is
designed in such a way that when the
brake is needed, one valve is flipped on
Figure 3. The Parkersburg brake.
for the duration and the clutch kicks in
and out automatically. Owner-operator
Scott is very pleased when handling
80,000 pounds hook load with the band
brakes completely free from his brake
drums. A plate-style clutch tends to
backspin the Parkersburg when the
traveling block goes up due to internal
clutch friction.
The newer series of Parkersburg such
as the model 122 (12 inches, two plate)
requires a double ratio chain drive to get
the high operating rpm’s required.
WWJ
Dedication
This series is dedicated to the education of John L’Espoir’s two grandsons,
Ethan Daniel Atwood and Elliott John
Atwood (right), who are each destined
to become a drilling rig engineer.
Opposing points of view or questions?
Contact us at Enid Drill Systems
(580) 234-5971, fax (580) 234-5980,
[email protected].
Waiver: The views expressed in this
article are the author’s opinion and are
based on the engineering education,
skills, and experience gained in a lifelong industry commitment. No part of
this article is intended to replace or
supersede any information supplied by
others. The contents of this article may
not be used in any type of legal action.
NGWA.org

Drawworks Brakes and Drum Designs

Transcription

Similar documents

Parts List Power Lock™ Series

Information material for Van-Mark brakes

compact wheel loaders

Apehanger Install

Compliments of - Main Street Magazines

Bending Brakes FAQ - Van Mark Products

/ View - the toughest mining vehicles available

£10 £10

68-73 Datsun 510 Rear Disc Brake Conversion

Forum Presentation