Note: Descriptions are shown in the official language in which they were submitted.
~,2:13653
.
ACKGROUND OF THE INVENTION
1. FIELD OF T~i_ INVF~lTION: The present invention relates
in general to an apparatus for monitoring the operation of ~aking
threaded tubular joints and in particular to an apparatus for
counting the number of turns in such ar. operation_
The present invention also relates in general to an apparatus
for monitoring the operation of making threaded tubular joints and
in particular to an apparatus for controlling the speed at which
such joints are made.
2. DESCRIPTION OF THE PRIOR ART. After a bQre hole has
been drilled to an oil or gas deposit, pipe strings are run into
the bore hole for removing the oil or ~as. The pipe strings are
assembled at the well site from pipe sections each having exter-
nal threads at one end and an internally threaded box member at
the other end or external threads at both ends for use with an
internally threaded coupling collar. As the pipe sections are
connected together, they are run into the bore hole. Each pipe
section is assembled to the top of the pipe string utilizing a
power tongs unit which has a rotary jaw member for gripping the
pipe and a motor for rotating the jaw member until the pipe sec-
tion has been tightened to the desired degree. The joint must be
tight enough to prevent leakage and to develop high joint strength
but not so tight so as to damage the threads.
Early prior art techniques involved the determination of the
applied torque to achieve the desired degree of tightness in the
joints. For example, one technique in~olved the adjusting of the
air supply maximum output pressure to a pneumatically driven tong
motor to provide the required maximum torque as dictated by joint
properties and tong power characteristics. Thus, the proper
torque was developed when the tong motor stalled. Another tech-
nique involved the counting of the number of turns ater the
threads had been en~aged at a "hand tight" point.~ These early
technlques were unsatisfactory since torque alone or turns alone
could not guarantee that the threaded ~oint would not leak.
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1 One prior art device which attempted to solve the ~roblem
included means for producing a signal indicating the number of
turns of the pipe section after measurement of a ~iven torque by
the torque measuring means. The device produced a warning of à
5 bad joint upon the measurement of a predetermined_maximum torque
before a measurement of a predetermined minimum ~Dmber of turns
. had occurred or the measurement of the predetermined maximum
number of turns before the measurement of the predetermined
minimum torque had occurred. The device indicated a good joint
upon the measurement of the predetermined minimum torque value
between the measurement of the minimum and maximum number of
turns. Such a device is shown in U.S. Pat. No. 3,368,396 issued
Feb. 13, 1968. Improvements to that device are disclosed in U.S.
Pat. No. 3,606,664 issued Sept. 21, 1971, U~S. Pat. No 3,745,820
issued July 17, 1973, and U.S. Pat. No. 4,091,451 issued May 23,
197~.
U.S. Patent No. 4,176,436 discloses a method and an apparatus
for making threaded joints within a wide range of predetermined
applied torque and turns values. A pipe or a pipe and a coupling
are threaded onto the end of a pipe string. The applied torque
is monitored and, when a reference torque value is exceeded, the
number of turns are counted. When either the actual torque or
the actual turns exceeds a predetermined minimum value for that
parameter and the value of the other parameter exceeds a predeter-
mined minimum value, but is less than a predetermined maximumvalue, a good joint is indicated and the make-up is stopped. A
bad joint is predicted and make-up is stopped whe~ the value of
the actual torque divided by the actual turns fal~s outside a
range of values defined by the slopes of a pair of boundary lines
and predetermined minimum torque and minimum turn values. The
actual turns value is a count which is initiated the first time
12 13~65~3
the actual torque value equals the reference torque value, the
count being incremented when the actual torque value is greater
than the reference torque value and being decremented when the
actual torque value is less than the reference torque value.
s The pri~r art devices typically used turns c~unters which
generated a signal representing one tenth of a re~olution of the
joint member. Such a low resolution is not suitable for making
joints where there may be less than one complete turn between the
reference torque and the maximum torque. Furthermore1 each time
a different pipe diaemter was utilized, the devices had to be
recalibrated to generate the one tenth of a turn signal, For
example, if the rotation of the joint member was sensed by a
wheel engaging the outer surface of the joint member, a different
diameter wheel had to be substituted to maintain the same ratio
of joint member diameter to wheel diameter.
With each of these devices, galling, the tearing or deforming
of the threads on a pipe or coupling, can be a problem. Galling
can be substantially reduced or eliminated by lim~ting the relativ~
speed of rotation between the two members being threaded together. !
The prior art devices typically used turns counters which
generated a signal representing one tenth of a revolution of the
joint member. Such a low resolution is not suitable for making
joints where there may be less than one complete turn between the
reference torque and the maximum torque. Furthermore, the prior
art devices lack the speed control required to effectively prevent
galling.
-
SUMMARY OF THE INVENTION
The present invention concerns an apparatus ~or controllingthe speed of rotation of a joint member during the operation of
making a threaded ~oint and ~ncludes a means or comparing the
rate at which pulses are generated by a turns counter with a de-
sired maximum rate. I the actual turns rate is greater than the
~z~3653
maxi~u~ rate, a signal is generated to slow down the joint making
operation. The signal can be a warning light to indicate to the
operator of a joint making apparatus to slow down the rotation
speed or a control signal to a valve in the hydraulic drive
circuit for the joint making apparatus. The comparision can be
made by accumulating a coun~ total representing the elapsed time
between the actual turns pulses or the number of ~tual turns
pulses occurring during a prede~ermined time interval and by
utilizing minimum elapsed time and maximum number of pulses
reference values respectively.
In the present invention, an idler wheel is biased into
engagement with the outer surface of the joint member being ro-
tated. The idler wheel is coupled to an encoder which generates
'a pulse train having a relatively high number of pulses per
revolution of the idlér wheel. A presettable divide-by-N counter
receives the pulse train and generates an output pulse for each
"N" input pulses. The output pulses are utilized by an apparatus
for controlling the number of turns made and the torque applied
during the operation of making a threaded joint.
The number "N" can be selected to provide pu~ses representing
a predetermined increment of rotation of the join~- member or a
predetermined percentage of a number of turns to be made.
For example, if the encoder generates 10,000 pulses per
revolution of the idler wheel and the joint member outside
" ` -- 1213~53
1 diameter is five times the diameter of the idler wheel, then the
encoder generates 50,000 pulses for each revolution of the joint
member. If "N" is selected to be 500, the divide-by-N counter
will generate output pulses representing l/100 of a revolution of
the joint member. If 0.7 turn is to be made, then "N" is selected
to be 350 and each output pulse represents one pe-~cent of 0.7
t~rn.
Furthermore, the number "N" can be selected to accommodate a
wide range of joint member diameters. If the joint member dia-
meter were changed to be six times the idler wheel diameter, thenumbers 500 and 350 become 600 and 420 respectively to generate
the same number of output pulses. Thus, the idler wheel does not
have to be changed as in the prior art turns counters.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. l is a block diagram of a prior art apparatus for
threading pipe and a control system therefor which can utilize
the turns counter according to the present invention.
Fig. 2a is a plot of torque versus turns illustrating joint
make-up values for typical joints.
Fig. 2b is a plot of torque versus turns illustrating the
turns averaging feature of the prior art apparatus.
Fig. 3 is a block diagram of a high resolution turns counter
according to the present invention.
Fig. 4 is a block diagram of an apparatus for threading pipe
and a control system therefor according to the present invention.
_ Fig. 5 is a flow diagram for the computer in-the apparatus
shown in Fig. 4 for warning the operator when a m~ximum rotation
rate is exceeded.
Figs. 6a and 6b are block diagrams of logic circuits for the
control system shown in Fig. 4 for ~arning the operator w~en a
msximum rotation rate is exceeded.
~Z13~53
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Fig. 1 is a block diagram of a torque and turns controller
which is disclosed in more detail in U.S. Patent No. 4,176,436
issued December 4, 1979. Reference numerals below 200 as
used herein represent the same elements in said p~tent. A power
tongs unit 21 grips and rotates a pipe section 22, the lower end
of which is threaded into a pipe coupling 23 which, in turn, is
threaded into the upper end of a pipe section 24. The pipe
section 24 represents the upper end of a pipe string extending
into the bore hole of a well (not shown). The power tongs unit
21 is well-known in the industry and is not shown in detail.
An upper turns counter 25 senses the rotation of the upper
pipe section 22 and generates a signal representing such rota-
tional movement. Similarly, a lower turns counter 26 senses the
rotation of the pipe coupling 23 and generates a signal represent-
ing the torque applied to the upper pipe section 22 by the power
tongs unit 21. The signals from the counters 25 and 26 and from
the transducer 27 are inputs to a tong remote unit 2~. A computer
29 monitors the counters and transducer signals and compares the
present values of these signals with operator entered values to
provide control signals to the operator. The operator enters
values of low, ~inimum and maximum turns and reference, minimum
and maximum torque through an input device, such as a keyboard,
which can be included in a plurality of input/output devices 31.
Turns counting will be started by the computer 2g when the joint
reaches a reference or "hand tight" torque. When both the torque
and turns criteria have been satisfied, the opera~or will be
signaled by the computer through an output device such as a green
light and a steady audio tone. The computer can signal a bad
joint with a red light and a warbling audio ~one. In addition,
-~ 1 213~6 ~
l the computer can generate a dump signal through the tong remote
unit 28 to the power tongs unit 21 to automatically shut down the
power tongs upon reaching either a good or a bad joint. The
computer 29 can also output signals representing the torque and
turns values to a printer 32 such as a strip char~ recorder or a
digital printer, or a plotter, such as an x-y ploRer.
, Tables are available of ranges of torque and turns values
which will result in a bearing pressure sufficient to form a
pressure seal in a pipe joint. The minimum and m~ximum values
for both torque and turns are read from the tables based upon the
size, connection type, grade and weight for each string of pipe.
These maximum and minimum values define an area 41 for a good
joint and a typical plot of torque versus turns is shown in Fi~.
2a. The counting of the turns begins only after a metal-to-metal
or hand tight make-up has been achieved which is represented as
the reference "REF" dashed line 42. The REF torque value provides
a reference point after which a predetermined number of turns
applied will induce a known stress in the joint provided that the
thread and its materials are within the available specifications.
In practice, however, turns alone cannot be relied upon to achieve
proper stress levels in sealing engagement, since it is i~practica~
to inspect each and every thread property and di~ensions. Nor
does the measurement of torque alone insure proper stress levels
and sealing engagement because dimensional, material and frictiona]
properties vary. Through practical and theoretical analysis, it
has been shown that the make-up of threaded joints simultaneously
_ within certain torque and turns parameters will i~sure joint
integrity.
The computer 29 of Fig. l is responsive to the torque and
turns signals for determining when a good joint has been made.
When either a minimum torque or a minimum turns value has been
` ` ~213653
1 reached, the computer 29 will then look for the minimum value of
the other parameter and signal the operator that a good joint has
been made if that minimu~ value of the uther parameter is reached
before the maximum value for the first parameter is reached.
Thus, during make-up of the joint represented by a circle 43, the
computer senses that the minimum turns value had ~een reached
before the minimum torque value and stopped the make-up of the
joint when the minimum torque value was reached. Conversely,
during the ~ake-up of the joint represented by a circle 44, the
computer sensed the minimum torque value and, therefore, stopped
the make-up of the joint when the minimum turns value was sensed.
A joint represented by a circle 45 reached the maximum torque
value before the minimum turns value was reached indicating a
dirty, rough, damaged, improperly lubricated, or dimensional out
of tolerance thread. A joint represented by a circle 46 reached
the maximum turns value before reaching the minimum torque value,
indicating a worn or out of tolerance thread, a weak or incorrect
thread or coupling material, or perhaps the use of a non-standard
thread lubricant or coating.
It is desirable to avoid making the joints 45 and 46 since
they waste time and, in the case of the joint 45, places more
stress on the pipe string than is required. Therefore, the
apparatus shown in Fig. l automatically predicts such bad joints
and stops the joint making process. A bad joint is predicted
when, after reaching minimum torque, actual torque divided by
actual turns is greater than maximum torque divided by minimum
_ turns. These criteria define a boundary of an in~icating area to
the left of line 47 and above the minimum torque ~ine as shown in
Fig. 2a. A bad joint is also predicted when, after reaching
minimum turns, the actual torque divided by the actual turns is
less than the minimum torque divided by the maximu~ turns. These
" -' ~Z13653
l criteria define the boundaries of an indicating area below line
48 and to the right of the minimum turns line as shown in Fig.
2a. After either the torque or the turns value exceeds a corre-
sponding minimum value, the computer monitors the actual torque
and the actual turns values to prevent movement i~to one o the
indicating areas defined above. When movement in~o either indi-
cating area is detected, the computer 29 of Fig. l turns on a
light indicating that a bad joint is being made. The computer 29
can also generate a dump signal through the tong remote unit 28
to shut off the power tongs unit 21.
The torque and turns values shown in Fig. 2a can also be
utilized to generate other warning signals. For example, when
the actual torque value exceeds the reference torque value REF, a
light can be turned on to indicate to the operator to shift from
a higher speed to a lower speed on the power tongs unit. Such
operation increases the speed with which a joint can be made and
decreases the chances of damaging the threads on either the pipe
sections or the coupling. I~en the make-up line has reached
either the minimum torque or the minimum turns value and ~s
predetermined percentage from the minimum value of the other
parameter, a light can be lighted to indicate to the operator
that he should be ready to shut down the power tongs unit since
the joint is almost finished. Typically, the percentage can be
ninety percent. When the ~ake-up line reaches the minimum torque
value before reaching a LOW turns value, the make-up process can
be stopped because the threads are probably misaligned and con-
_ tinued make-up will damage the threads.
The apparatus shown in Fig. l includes an automatic turns
averaging feature. During the make-up of a pipe, the torque does
not increase linearly with the turns. This is caused by such
factors as wind loading on the pipe and non-concentric pipe.
~~ 121;~653
1 Fig. 2b is a plot of torque versus turns wherein a straight
dashed line represents the average applied torque and the solid,
wavey line represents the actual torque wl~ich is applied. An
area 49 of the actual torque line extends above a reference REF
torque line and can represent one of more turns c~unts before the
. average torque exceeds the reference torque. An ~rea 50 of the
actual toTque line ex~ends below the reference torque line and
can represent one or more turns counts after the average torque
exceeds the reference torque.
In the prior art, the counting of turns was intiated and
continued uninterrupted after the actual torque reached the REF
torque line. Often, conditions such as wind loading on the pipe
or non-concentric pipe would cause the actual torque to reach or
exceed the REF torque line prematurely resulting in false turns
being count~d. These false turns were largely ignored or left up
to the operator to observe and to compensate therefor. Thus, the
false turns became a point for error. The apparatus shown in
Fig. 1 automatically adjusts the turns count for false turns. The
turns are counted by an upldown counter which counts turns when
the actual torque is above the reference torque and subtracts
turns when the actual torque is below the reference torque.
However, when counting, the counter will count down to zero, bu~
never become negative.
In Fig. 3, there is shown a block diagram of a turns counter
and associated circuitry according to the present invention, The
turns counter 25', which may be mounted on the power tongs unit,
_ includes an idler wheel 201 connected to a drive shaft 202. A
spring means 203 is connected to the drive shaft ~02 to bias the
idler wheel 201 against the outside surface of the pipe section
22. As the pipe section 22 is rotated by the power tongs unit 21
(Fig. 1), the idler wheel is rotated by frictional engagement
12136S3
with the pipe section. The drive shaft 202 is coupled to the
¦input of an optical encoder 204 which generates a pulse train
~utput signal on a pair of lines 209 as the idler wheel is rotated.
The encoder 204 is well known, is commercially available and
includes a wheel driven from the shaft 202 and haYing alternate
clear and opaque sections (not shown) positioned ~bout the periph-
ery thereof. A light source is positioned on one side of the
wheel and a photocell on the other side of the wheel. As the
pipe section 22 rotates the idler wheel 201, the wheel in the
encoder is rotated and the photocell detects alternate light and
dark sections of the wheel. The photocell generates a square
wave output signal each cycle of which represents an adjacent
pair of clear and opaque sections and having a frequency propor-
tional to the speed of rotation of the pipe section. The encoder
204 utilizes the photocell output signal to generate a pair of
square wave pulse trains on the lines 209 ninety degrees out of
phase. Thus, during each cycle of the photocell output signal,
two leading and two trailing edges are generated between the pair
of pulse trains. Those skilled in the art will appreciate the
fact that other known types of encoders may be utilized, such as,
mechanical encoders, magnetic encoders, and the like.
Typically, the pulse trains are generated with a large
number of pulses per revolution of the wheel. The two leading
and two trailing edges can be utilized as inputs to a direction
sensor circuit 210 to generate a square wave pulse train output
signal on the line 71. Furthermore, the two pulse trains which
are ninety degrees out of phase can be utilized to generate
a signal representing the direction of rotation on a line 205.
The line 71 is connected to a counting input and the line
205 is connected to an inhibit input of a divide-~y-N circuit
206 The circuit 206 is a presettable divide-by-N counter. The
divide-by-N function may be acco~plished with discrete logic
circuitry or with a programmed microprocessor, An ~ input circuit
- 1213653
1 207 is connected to a preset input of the divide-by-N circuit 206
~or generating a signal representing the number "N". Typically,
the preset input accepts binary signals and the N input circuit
207 includes means, such as switches, for setting "N" in terms of
ones, tens, and hundreds. The circuit 207 converts the decimal
_ input from the switches into a binary signal whic~ is generated
to the circuit 206 to define the number "~1". Of course, any
suitable circuitry can be utilized to generate the "N" signal but
the switches will maintain the nu~ber "N" during any power loss.
The signal on the line 205 prohibits the divide by "N" circuit
from outputting pulses to the computer 29 when the wheel 20l is
rotating in the reverse direction.
A signal is sent on line 212 to the direction sensor 210
fr~m the forward/reverse direction selector circuit 21l. The
circuit 21l allows the forward and reverse direction of the wheel
201 to be selected. Circuit 21l has a two position switch which
is manually positioned by the operator. In one position when the
wheel 201 rotates clockwise this is the forward direction and
counter-clockwise is the reverse direction. When the switch is
placed in the other position, clockwise rotation of the wheel 201
is the reverse direction and counter-clockwise rotation is the .
forward direction.
Each time a pulse is sent from the direction sensor 210 to
the divide-by-N circuit 206 on line 71, when the wheel 201 is
rotating in the forward direction, the number "N" is decremented.
When the number "N" is counted down to zero, a pulse is then
_ output on line 208 to the computer 29. This pulse represents a
predetermined increment of rotation. The nu~ber ''~" is placed
back into the divide-by-N circuit 206 and the process is continued
When the wheel 20l is rotating in the reverse direction the
number "N" is incremented. The divide by-N circuit 206 counter
213~iS3 !
., i
Ii i
1 Iwill count up to a maximum value and then go to zero and then the
jnumber "N" is placed back into the counter and the process is
¦'contined.
I! As previously stated, the direction sensor circuit 210
llplaces a signal on line 205 which prohibits the divide-by-N
circuit 206 from outputting a pulse to the computer 29 when the
wheel 201 is xotating in the reverse direction. Since the turns
licounter 25 may be mounted on the power tongs unit and if the
¦Ipower tongs are allowed to pivot back and forth around the pipe
¦jsection 22, erroneous pulses could be output by the divide-by-N
circuit 206 to the computer 29. The up/down counting ability of
~the divide-by-N circuit 206 compensates for the back and forth
¦pivoting of the power tongs and prevents the outputting of any
l!erroneous pulses.
15 11 If we assume, for the purposes of ~ stration, that the
¦joutside diameter of the pipe section 22 is five times the diameter
¦¦of the idler wheel 201, then the encoder 204 will generate fifty
¦,thousand pulses for each revolution of the pipe section. If "N"
is set at five hundred at the N input circuit 207, the divide-by-
N circuit 206 will generate one hundred pulses for each revolu-
tion of the pipe section on a line 208 and each pulse will repre-
sent one percent of one turn of the pipe section. It can be seen
that the turns counter according to the present invention can be
¦utilized with a wide range of pipe section diameters simply by
¦matching the number "N" to the ratio between the idler wheel dia-
,meter and the pipe section outer diameter to maintain the signal
_ on the line 208 at one hundred pulses per pipe section revolution.
Furthermore, the number "N" can also be selected,to increase or
¦decrease the resolution of one percent per pulse. The turns
3~ llcount r sccording to the present invention hss significantly
-13- j
-` 1~36S3
1 hi~her resolution than the prior art turns counters which generate
a signal each one tenth of a revolution.
The turns counter according to the present invention is
especially useful in the makeup of premium threaded connections.
In such a connection, the number of turns made between the refer-
ence torque position and the minimum torque posit~on (see Fig.
. 2a) is very small, sometimes less than one complete turn. Thus,
a finer resolution than one tenth of a turn is required in order
to make a good joint. In a pre~ium type shouldering connection,
it is desired to have a metal-to-metal seal between the end
surface of the pipe section and a shoulder surface in the pipe
coupling. In the prior art apparatus, it was assumed that such a
seal had been made when a predetermined torque value had been
reached. With the presen~ invention, a number of turns or a
fraction of a turn can be measured when simul~aneously reaching a
particular torque value to more accurately define when the seal
has been made.
For example, assume that the pipe diameter to idler wheel
diameter ratio is five and it is desired to make 0.7 turn. If
the number "N" is set at 350, the divide-by-N counter will generate
one hundred output pulses in 0.7 turn of the pipe section, each
pulse representing one precent of the desired rotation.
In each of the above examples, the number "N" can be found
with a simple formula. If it is desired to generate "P" pulses
per revolution of the member of the joint being rotated, and the
joint member outside diameter is "OD", the idler wheel diameter
_ i5 "WD", and the encoder generates "E" pulses per revolution of
the idler wheel, then the formula for "N" is: _
N= (OD/W~) (E/P)
If it is desired to generate "P" pulses in a predetermined number
of turns "T" of the joint member, then the formula for "N" is:
N~ T(OD/WD) (E/P~
-14-
I lZ136S3
I ~I There is shown in Fig. 4 an apparatus for threading pipe anda control system therefor. The pipe sections 22 and 24, the pipe
~coupling 23, the torque trandsucer 27, the tong remote unit 28
lliand the input/output devices 31 are similar to the like-numbered
¦jelements shown in Fig. 1. The turns counters 25 and 26 can be of
¦Ithe type shown in Fig. 1 or of the type shown in ~ig. 3. A power
. Itongs unit 21 includes tongs 220 for gripping the pipe section
!22 . a tong motor 221 for rotating the tongs 220, and a hydraulic
pump and reservoir 222 for generating hydraulic fluid under
pressure to drive the motor 221. The tongs 220, the motor 221
and the pump and reservoir 222 are well-known in the industry and
lare not shown in detail.
!; A throttle valve 223 is connected between the motor 221 and
I!the pump and reservoir ~ . When the valve 223 is actuated,
!jpressurized 1uid flows from the pump and reservoir 222 through a
isupply line 224, through the valve 223, through a supply line
!225, and to the motor 221. Fluid flows from the motor 221,
~through a return line 226, through the valve 223, through a
l¦return line 227, and back to the pump and reservoir 222. When
Ithe valve 223 is actuated, a bypass port (not shown) is opened
,to connect the lines 224 and 227 and the pressure to the motor
221 is relieved.
In the prior art system shown in Fig. l, the computer 29 can
generate a dump signal through the tong remote unit 28 to the
¦power tongs unit 21 to automatically shut down the power tongs
upon reaching either a good ~oint or a bad ~oint. In the system
_ ¦shown in Fig. 4, the computer 29' can generate th~e dump signal to
actuate the valve, but also can generate a control signal through
ilthe tong remote unit 28 to control the throttle valve 223 as
will be described below. I
- ~Z13~
1 Galling, the tearing or deforming of the threads on a pipe
or coupling, can be substantially reduced or eliminated by limitin
the relative speed of rotation between two members bein~ threaded
together. The system shown in Fig. 4 can be utilized to warn the
operator to slow down the speed of the power tong~ unit 21 or to
aut~matically control the speed utilizing the thr~ttle valve 223.
The computer 29' is similar to the computer 29 of Fig. 1 and
includes a clock which generates a clock signal at a predetermined
frequency. The computer 29' can be programmed, or a standard
counting circuit can be connected thereto, to accumulate clock
pulses and generate an elasped time signal. The elapsed time for
the maximum desired rate can be inputted to the computer 29'
through the input/output devices 31 keyboard and stored. Each
time a turn signal pulse is received from the turns counter 25,
the time elapsed from the last turn signal pulse can be compared
with the stored time to determine if the maximum ro~ation rate
has been exceeded.
There is shown in Fig. 5 a flow diagram of a program for the
computer 29' whereby a warning is generated to the operator of
the apparatus when a maxi~um rotation rate is exceeded. The
program begins at a circle START 230 and enters a decision point
TEST MODE 1 or 2 231. The operator must determine what mode to
operate in for the particular pipe speed that must be tested.
Two modes are required to test a range of rotation speeds from
slow, with pulses every one tenth of a turn, to fast, with as
many as two hundred pulses per revolution. In Mode 1, the fre-
_ quency or pulse rate is measured for the faster speeds. In Mode2, the period or time between pulses is measured ~or the slower
speeds.
If Mode 2 is selected, typically utilizing a switch on the
computer 29', the program branches from the decision point 231 at
-- ~.213653
1 MODE 2 to a program instruction UPDATE CLOCK 248 which updates
the elapsed time by adding the time elapsed since the last time
the clock was updated. The program then enters a TURN SIGNAL
PVLSE ? decision point 232. If no turn signal pulse has been
generated, the program branches at NO to a circle~MAI~ 233 and
returns to the main pro~ram until the next time t~e program
enters at the circle 230. Since the rate at which the computer
branches from the main program to the program shown in Fig. S
exceeds the maximum expected pulse rate for the slower speeds,
the program will loop while waiting for a turn signal pulse. If
a turn signal pulse has been generated, the program branches at
YES to execute a program instruction SAVE CLOCK ET 234 causing
_ the computer to save the value of the elapsed time ET accumulated
between turn signal counter pulses. Then the program executes a
program instruction RESET CLOCK = 0 235 to reset the accumulated
time ET to zero for accumulating a new elapsed time.
The program then enters a decision point TEST ET 236 where
the stored value of the elapsed time ET is tested for a low or a
high value. If the time is lower than a predetermined value, the
turn signal pulses are occuring to rapidly indicating that the
speed of rotation is too high. The program branches at LOW to .
execute a program instruction SET FLASH 237 to generate a signal
to indicate to the operator that he should slow down the speed of
rotation. In response, the operator will slow down the speed of
rotation and the light will be turned off. The program enters
the circle 233 to return to the main program~ If the time is
_ higher than the predetermined value, the turn sig~al pulses are
occuring more slowly indicating that the speed is~below the
warnin~ value. The program branches from the decision point 236
at HIGH to execute a program instruction RESET 238 to reset the
flashing light. The program then enters the circle 233 to return
~` 12~3~S3
1 to the main program. The program instructions 237 and 238 can
also be utilized to directly control the speed of the power tongs
unit.
If Mode l is selected, the program branches from the decision
point 231 at MODE 1 to execute a program instruct~on ADD NEW TURN
SIGNAL PULSES TO COUNTER 239 which adds the TURN SIGNAL PULSES
which have occurred since the last loop through the program of
Fig. 5 to a count total in a counter. Next, the program executes
a program instruction UPDATE CLOCK 240 which updates the elapsed
time by adding the time elapsed since the last ti~e the clock was
updated. The program then enters a decision point TEST CLOCK
TIME 24l to co~pare the elapsed time with a predetermined value
to determine if sufficient time has elapsed to test the numbers
.~ of turn signal pulses. If the elapsed time is too low, the
program branches at NOT TIME to the circle 233 to return to the
main program.
If the test period has elapsed, the program branches from
the decision point 241 at TIME to execute a program instruction
RESET CLOCK = 0 242 to reset the elapsed time to zero. Then the
program executes a program instruction SAVE TURN SIG~NL PULSE
COUNT TOTAL 243 to save the count total in the counter. The .
program then enters a decision point TEST TURN SIGNAL PULSE COUNT
TOTAL 244 to compare the count total with a predetermined value.
If the count total is high, the program branches at HIGH to
execute a program instruction SET FLASH 245 to indicate that the
maximum desired speed has been èxceeded. I the count total is
_ too low, the program branches at LO~ to execute ~program inseruc-
tion RESET FLASH 246 to reset the flashing light.~ The program
instructions 245 and 246 can also ~e utilized to control the
power tongs unit. The program executes a program instruction
RESET TURN SIGNAL PULSE COUNT D 0 247 after either of ehe inseruc-
` 121:~S3
1 tions 245 and 246 to reset the count total to zero. The program
then exits to the main program at the circle 233.
All of the accumulated values in the program of Fi~ 5 can beinitialized at the beginning of the main program. In Mode l, the
count pulse rate is relatively high. Therefore, ~he program
counts the number of pulses occu~ring in a predet~rmined elapsed
. time to determine the speed of rotation. In Mode 2, the count
pulse rate is relatively low. Therefore, the program accumulates
the elapsed time between count pulses to determine the speed of
rotation.
There is shown in Fig. 6a, in block diagram form, a logic
circuit substantially equivalent to the logic of the flow diagram
of Mode 2 of Fig. 5, A number representing a minimum number of
._ turn signal pulses between clock pulses is inputted on a DATA IN
line 250 to a memory 251. This number is loaded into a preset
counter 252 on a line 253 at a preset input. The clock pulses
are an input on a line 254 to an input 255-l of an AND gate 255.
The turn signal pulses from the counter are an input on a line
256 to a set input of the counter 252 and an input 257-l of an
AND gate 257. An output of the counter 252 is connected to an
inverting input 257-2 of the AND gate 257 which has an output
257-3 connected to a SET FLASH line 258. The output of the
counter 252 is also connected to a RESET FLASH line 259 and to an
inverting input 255-2 of the AND 255, The AND 255 has an output
255-3 connected to a count input o$ the counter 252.
When a turn signal pulse occurs, the counter 252 is set to
_ the preset number. The counter is responsive to ~he clock pulses
to count down from the preset number. The counte~ generates a
'`O" output to enable the AND 255, and the AND 257. If the preset
number is reached before the next turn signal pulse occurs, the
countes generates a "l" on the line 259 to reset the flashing
12~3`'55;~
light and disable the ANDs 255 and 257. The next turn signal
pulse again sets the counter to the preset number and the counter
enables the ANDs 255 and 257. If the next urn signal pulse
occurs before the preset number of clock pulses has been counted
down to zero, the AND 257 generates a "1" on the Line 258 to set
the flas~hing li~ht to indicate that the maximum speed of rotation
has been exceeded. The turn signal pulse also sets the counter
252 to restart the counting cycle.
There is shown in Fig. 6b, in block diagram form, a logic
circuit substantially equivalent to the logic of the flow diagram
of Mode 1 of Fig. 5. A number representing a maximum number of
turn signal pulses per twenty clock puises in inputted on a DATA
IN line 260 to a memory 261. This number is loaded into a preset
counter 262 on a line 263 at a preset input. The turn signal
pulses are an input on a line 264 to an input 265-1 of an AND
gate 265. The clock pulses are an input on a line 266 to a
divide-by-twen~y counter 267. An output of the counter 267 is
connected to a set input of the counter 262 and an input of an
~AND gate 268. An output of the counter 262 is connected to an
inverting input 268-2 of the AND 268 which has an output 268-3
connected to a RESET FLASH line 269. The output of the co~nter
262 is also connected to a SET FLASH line 270 and to an inverting
input 265-2 of the AND 265. The AND 265 has an output 265-3
connected to a count input of the counter 262.
After "N" clock pulses twenty clock pulses occur, the counter
267 generates a "l" to set the counter 262 to the preset number.
The counter 262 is responsive to the turn signal pulses to count
down from the presetn number. The counter 262 generates a "O"
output to enable the ANDs 265 and 268. If ~he preset number is
counted down to zerio before "N" more clock pulses twenty occur,
the counter 262 generates a "1" on the line 270 to set the
flashing light and
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~2~
1 disable the ANDs 265 and 268. When the counter 267 generates a
"1", the counter 262 is reset and the ANDs 265 and 268 are enabled
to restart the counting cycle. I~ the counter 267 generates a
"l" before the preset number of turn signal pulses is counted,
the AND 268 generates a "l" on the line 269 to re~et the flashing
light and the counter 262 is reset.
. The SET FLASH instructions 237 and 245 of Fig. 5 or the SET
FLASH signals on the lines 258 and 270 of Figs. 6a and 6b respect-
ively can be utilized to control the valve 223 of Fig. 4. If the
valve 223 is actuated when the set flash in indicated, the valve
223 will be modulated as the speed of rotation is alternately
increased and decreased. The control can be achieved by utilizing
__ conventional pulse ~dth modulated circuitry to match the response
time of the valve and the motor.
In summary, the present invention concerns an increased
resolution turns counter for an apparatus for counting turns when
making threaded joints from a pair of threaded members. The
apparatus includes means for rotating one of the members with
respect to the other member, means for generating a signal repre-
senting actual turns made by the one member. The actual turns
signal generating means comprises means responsive to the rotation
of the one ~ember for generating a first plurality of pulses at a
first frequency proportional to the speed of rotation of the one
member, and means responsive to the first plurality of pulses for
generating a second plurality of pulses at a second frequency
lower than the first frequency, each pulse of the second plu~ality
_ representing a predetermined increment of rotatio~ of the one
member. The means responsive to the rotation of the one member
includes an idler wheel, means for biasing the idler wheel against
an outside surface of the one member, an encoder means, and a
drive shaft coupled between the idler wheel and the encoder
1~13~53
means. The means for generating the second plurality of pulses
lincludes means for dividing the first plurali~y of pulses by a
ipredetermined number N to generate the second plurality of pulses.
IThe means for dividing includes a divide-by-N counter and the
¦means for generating the second plurality of puls~s also includes
means for generating a preset signal representing~he value of
"N" to the counter. The apparatus also includes means for effect-
ing a signal to permit or prohibit the divide-by-N circuit from
'outputting a pulse to the computer when the wheel is rotating in
either forward or reverse directions.
In summary, the present invention also concerns a good control
for an apparatus for making threaded joints from a pair of threaded
members. The apparatus includes means for rotating one of the
Imembers with respect to the other member, means responsive to the
rotation for generating a pulsed signal representing actual turns
made by the one member at a frequency proportional ~o the speed
of rotation of the one member, means for generating a signal
representing the actual torque applied to the one member by the
means for rotating, and mRans responsive to the actual turns
signal for generating an indication to an operator to slow down
the means for rotating one of the members. Utilized in such an
apparatus is means for cont~olling the speed of rotation of the
one member comprising means responsive to the actual turns signal
for generating a signal representing the actual turns signal
pulse xate, means for generating a signal representing a maximum
rate for a desired maximum speed of rotation of the one member,
and means responsive to the actual turns rate signal and the
maximum rate signal for generating an output signal when the
actual turns rate is greater than the maximum rate and wherein
the means for generating an indication is responsive to the
output signal for generating an indication to the~operator ~o
slow down the speed of the means for rotating. ~he actual turns
rate signal can be generated by accumulating a count total re-
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presentin~ the elapsed time between the actual turns pulses or
the number of actual turns pulses occurring during a predetermined
time interval. The means for controlling also includes means
responsive to the output signal for generating a speed control
signal and the means for rotating is responsive to the speed
control signal for determining the speed of rotation of the one
member.
Although the invention has been described in terms of spec-
ified embodiments which are set forth in detail, it should be
understood that this is by illustration only and that the inventio~
~is not necessarily limited thereto, since alternative embodiments
and operating techniques will become apparent to those skilled in
the art in view of the disclosure. Accordingly, modifications
are contemplated which can be made without departing from the
spirit of the described invention.
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