U.S. patent number 3,917,436 [Application Number 05/403,344] was granted by the patent office on 1975-11-04 for dual pump control systems.
This patent grant is currently assigned to Drill-Au-Mation, Inc.. Invention is credited to Ethell J. Dower.
United States Patent |
3,917,436 |
Dower |
November 4, 1975 |
Dual pump control systems
Abstract
Disclosed is a system for regulating and controlling at least
two compounded pumps in a well drilling operation where one pump is
regulated in a fixed relationship relative to the regulation of the
other pump. The functional control of the two pumps can be
interchanged between a manual control location and a remote control
location. Either pump can be selected as the prime control unit.
The functional control parameter for the manual and remote controls
may be compared to one another and regulated relative to one
another to maintain a parity therebetween so that "bumpless"
transfer of the functional controls from one location to another
can be obtained.
Inventors: |
Dower; Ethell J. (Houston,
TX) |
Assignee: |
Drill-Au-Mation, Inc. (Houston,
TX)
|
Family
ID: |
23595438 |
Appl.
No.: |
05/403,344 |
Filed: |
October 4, 1973 |
Current U.S.
Class: |
417/5;
417/34 |
Current CPC
Class: |
F04B
49/007 (20130101); F04B 49/06 (20130101); F04B
49/20 (20130101); E21B 21/08 (20130101) |
Current International
Class: |
E21B
21/00 (20060101); E21B 21/08 (20060101); F04B
49/06 (20060101); F04B 49/20 (20060101); F04B
49/00 (20060101); F04B 049/00 (); F04B
049/02 () |
Field of
Search: |
;175/38,24,25 ;173/3
;417/1-8,34,15,223 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Freeh; William L.
Claims
What is claimed is:
1. A control system for regulating the control of at least two
motive control means relative to one another comprising:
first motive control means including
an electrically controllable source for producing first fluid
control pressure, a manually variable source for producing a second
fluid control pressure, first pressure output means, first pressure
selection means coupled to said first and second fluid control
pressures for selectively supplying one of said first and second
fluid control pressures to said first pressure output means,
second motive control means including
pressure modifier means responsive to an input pressure for
producing a third fluid control pressure at a modified pressure
relative to said input pressure, and another manually variable
source for providing a fourth fluid control pressure, said modifier
means being coupled to said electrically controllable source,
second pressure output means,
second pressure selection means coupled to said third and fourth
control pressures for selectively supplying one of said third and
fourth fluid control pressures to said second output means,
means for also supplying said first fluid control pressure to said
pressure modifier means as said input pressure, and
means for comparing one of said selected ones of said fluid control
pressures with one of said non-selected fluid control
pressures.
2. The apparatus of claim 1 and further including means for
switching said comparing means from the pressures being compared to
the remaining two pressures for purposes of comparison.
3. The apparatus of claim 2 and further including means for
selectively switching said first and second motive control means
relative to said manual controlling means.
4. A control system for regulating the control of two pump means
relative to one another comprising:
first pump means subject to control by pressure,
second pump means subject to control by pressure,
first selection valve means having two inputs and one output,
second selection valve means having two inputs and one output,
an electrically controllable source of control pressure coupled to
an input of each of said first and second selection valve
means,
pressure modifier means for producing an output pressure at a
predetermined modified pressure relative to an input pressure, said
pressure modifier means having an input and an output, said input
being coupled to said electrically controllable source and said
output being coupled to the other of said inputs of each of said
first and second selection valves, the outputs of said selection
valves being respectively coupled to said first and second pump
means, and
said selection valves being operable for coupling said electrically
controllable source of control pressure to one of said pump
means.
5. In a drilling operation employing at least two controllable
pumps,
first pump means and second pump means each responsive to control
by pressure,
first manually operable, control pressure means for first pump
means,
second manually operable, control pressure means for second pump
means,
first means for developing a first control pressure,
second means for developing a second control pressure,
said second pressure developing means being coupled to said first
pressure developing means for providing a said second control
pressure at a fixed relationship relative to the pressure of said
first pressure developing means,
first control valve means for selectively connecting one of said
first manually operable pressure means and said first pressure
developing means to said first pump means,
second control valve means for selectively connecting one of said
second manually operable pressure means and said second pressure
developing means to said second pump means, and
means for reversing the condition of said first and second control
valve means and thereby respectively reversing application of
control pressures to said pump means from said one pressure means
to said other pressure means.
6. A control system for regulating the control of two pump means
relative to one another comprising,
first pump means subject to control by pressure,
a first control valve coupled to said first pump control means,
a first manually variable source of control pressure coupled to
said first control valve,
second pump means subject to control by pressure,
a second control valve coupled to said second pump control
means,
a second manually variable source of control pressure coupled to
said second control valve,
pressure comparison means for sensing the difference in pressure
between a first pressure input and a second pressure input,
one of said first and second manually variable sources being
coupled to one of said pressure inputs,
an electrically controllable source of control pressure coupled to
the other of said pressure inputs and to said first control valve
means,
pressure reducer means for producing an output pressure at a
predetermined ratio of reduced pressure relative to an input
pressure, said pressure reducer means having an input and an
output, said input being coupled to said electrically controllable
source and said output being coupled to said second control
valve.
7. The control system of claim 6, wherein said pressure reducer
means has means for adjusting the predetermined reduction in
pressure.
8. A control system for regulating the control of two pump means
relative to one another comprising,
first pump means subject to control by pressure,
a first control valve coupled to said first pump control means,
a first manually variable source of control pressure coupled to
said first control valve,
second pump means subject to control by pressure,
a second control valve coupled to said second pump control
means,
a second manually variable source of control pressure coupled to
said second control valve,
pressure comparison means for sensing the difference in pressure
between a first pressure input and a second pressure input,
first comparison valve means coupled to said first pressure input
and second comparison valve means coupled to said second pressure
input,
each of said first and second manually variable sources being
coupled to said second comparison valve means, said second
comparison valve means being operable for coupling of one of said
manually variable sources to said second input,
first selection valve means having two inputs and one output,
second selection valve means having two inputs and one output,
an electrically controllable source of hydraulic control pressure
coupled to an input of each of said first and second selection
valve means,
pressure ratio means for producing an output pressure at a pressure
relative to an input pressure, said pressure ratio means having an
input and an output, said input being coupled to said electrically
controllable source and said output being coupled to the other of
said inputs of each of said first and second selection valves, the
outputs of said selection valves being respectively coupled to said
first and second control valves, said selection valves being
operable for coupling said electrically controllable source of
control pressure to one of said control valves and for coupling
said pressure ratio means to the other of said control valves, the
outputs of said selection valves also respectively being coupled to
said first comparison valve means for supplying pressure from one
of said selection valve means to said pressure comparison
means.
9. The control system of claim 8 wherein said pressure reducer
means has means for adjusting the predetermined reduction in
pressure.
10. In a drilling system for controlling the speed of one operating
unit and obtaining a fixed relative control of the speed of a
second operating unit with respect to the speed of said first
operating unit, apparatus comprising:
at least two operating units, each of said units having their speed
of operation controllable by control fluid pressures,
pressure generating means for developing a first control fluid
pressure for one of said units,
means coupled to said pressure generating means for selectively
producing a second control fluid pressure with a ratio relationship
relative to said first control fluid pressure for the other of said
hydraulic units, and
means for varying said first control fluid pressure of said
pressure generating means for varying the second control pressure
to said other unit in a ratio relationship relative to said first
fluid pressure.
11. The drilling system of claim 10, and further including means
for reversing the application of said first and second control
pressures to said units.
12. In a drilling system for obtaining compound control of the
relative speed of at least two operating units, a system
comprising:
first and second speed controllable operating units for providing a
drilling function,
first control means for providing a first control function for the
speed of said first controllable unit,
second control means for providing a second control function for
the speed of said second controllable unit, and
means coupling said second control means to said first control
means and responsive to said first control means to slave the
control function of said second unit to the control function of
said first unit, said coupling means including a selectively
adjustable ratio device for maintaining a predetermined
relationship between the speed control functions of said control
means.
13. A pressure control system for regulating the speed control
function of two pump means relative to one another comprising:
first pump means having a speed control means subject to control by
a pressure function,
second pump means having a speed control means subject to control
by a pressure function,
an electrically controllable source of a control pressure function
coupled to one of said speed control means of said pump means,
pressure modifier means for producing an output pressure function
at a predetermined different pressure relative to an input
pressure, said pressure modifier means having input means and
output means, said input means being coupled to said electrically
controllable source and said output means being coupled to the said
speed control means of said other pump means.
14. The control system of claim 13 wherein said pressure modifier
means includes means for adjusting the amplification of the output
pressure function relative to the input control pressure
function.
15. A control system for regulating the control of at least two
motive control means relative to one another comprising:
first motive control means including
an electrically controllable source for producing first fluid
control pressure, a manually variable source for producing a second
fluid control pressure, first pressure output means, first pressure
selection means coupled to said first and second fluid control
pressures for selectively supplying one of said first and second
fluid control pressures to said first pressure output means,
second motive control means including
pressure modifier means responsive to an input pressure for
producing a third fluid control pressure at a modified pressure
relative to said input pressure, and another manually variable
source for providing a fourth fluid control pressure, said modifier
means being coupled to said electrically controllable source,
second pressure output means,
second pressure selection means coupled to said third and fourth
control pressures for selectively supplying one of said third and
fourth fluid control pressures to said second output means, and
means for also supplying said first fluid control pressure to said
pressure modifier means as said input pressure.
16. In a drilling system for controlling the speed of one operating
unit and obtaining a relative control of the speed of a second
operating unit with respect to the speed of said first operating
unit, apparatus comprising:
a first operating unit having an independent output function and
having a speed control means responsive to a first control pressure
for regulating said output function,
a second operating unit having an independent output function and
having a speed control means responsive to a second control
pressure for regulating said output functions,
means for generating said first control pressure and applying said
first control pressure to said first operating unit,
means responsive to said first control pressure for generating a
second control pressure having a controlled dependent function
relative to said first control pressure, and
means for coupling said second control pressure to said second
operating unit.
Description
BACKGROUND OF THE INVENTION
This invention relates to control systems, and more particularly,
to control systems for controlling the relationship between dual
pumps in a well drilling operation. Specifically, the speed of one
pump is automatically controlled in a predetermined relationship
relative to the speed of another pump.
In a typical rotary drilling operation through earth formations, a
tubular drilling string carries a drilling bit at its lower end and
by rotation of the string and weight on the string, the drilling
bit cuts through earth formation strata and forms a well bore. To
remove the earth cuttings from the path of the bit and to cool the
bit, a system for circulating a fluid (sometimes called mud) into
and out of the well bore is used. The mud circulation system starts
with a surface located pump means which picks up a drilling fluid
or mud from a surface tank and delivers the fluid to the interior
of the tubular drilling pipe or string where it travels to the
drilling bit and exits therefrom in the form of a jet or other type
of fluid course. The fluid then moves upwardly in the annulus
between the outer surface of the drill pipe and well bore and
carries with it cuttings from the earth formations. The return
fluid is delivered or returned from the annulus to the surface tank
for recirculation.
The proper sizing or selection of mud pumps with respect to the
capacity of the pumps for volume and pressure output required is a
major factor in the drilling of a well. This is particularly true
where the output of two or more pumps are combined for the purpose
of increasing the mud circulation rate and decreasing the cost of
drilling. Sometimes, a pump will operate poorly and result in
excessively high maintenance costs if the pump output is increased
for the purpose of increasing the drilling rate. This can be
especially true in instances where the pressure output is
substantially increased. Hence, the pumps should be operated with
care in regard to both efficiency and cost factors.
Increased maintenance costs and decreased life occur when the
capacity of the pump is too small for the operation. On the other
hand, using a pump that has excess capacity is expensive in terms
of high initial cost and the costs of moving it from location to
location. In other words, it is desirable to use a pump or pumps
that are adequate for the task and this means using the pump or
pumps at a top operating efficiency under the most severe
conditions.
Use of two pumps can have advantages. For example, if two pumps are
placed in parallel, the volume output is increased. When two pumps
are so used and they are effectively protected, the compounding of
the pumps has advantages over the use of a single large pump. For
example, if one of two pumps is stopped for one reason or another,
the drilling operation is not seriously hampered because one pump
is still operational. With a single pump, its capacity is affected
by its liner size. Thus, the liner is changed throughout the
drilling operation as the pump capacity requirements change. Where
there are two pumps, they can jointly cover a greater range of
capacity and more days of operation can be obtained without
changing liners.
A pump has a volumetric output which is a function of the RPM
(revolutions per minute) or speed of the prime motor or engine. The
volumetric output of a given RPM results in a defined pressure
which is determined as a function of the circulatory system. It
will therefore be appreciated that the horsepower requirement of
the prime mover is dependent upon speed, volumetric output and
pressure. The horsepower output of the prime mover is typically
regulated by a "throttle" control which regulates its output. In
the use of two or more pumps, their volumetric outputs are combined
to obtain optimized output conditions. Where pump outputs from two
or more pumps are combined, however, it is desirable to have
regulation of the control of the respective pumps for controlling
the total volumetric output requirements under varying
conditions.
SUMMARY OF THE INVENTION
The present invention concerns itself with a system for dual or
simultaneous control of at least two pumps for a well drilling
operation. The control system includes means for manual control at
a rig site and means for remote control from an offsite location.
The manual and remote control means are independent and separate
from one another. In the remote control means, the functional
control for one pump is made dependent upon the functional control
for the other pump in a fixed relationship so that the functional
control of a primary pump exercises a slaved functional control
over a secondary pump. The remote control means are adapted to
permit an exchange of the primary control function between the
pumps and to permit an exchange of control functions between manual
and remote control means. The pumps are controlled by pneumatic
pressure and selectively operative valve means can couple either
the manual pressure control means or remote pressure control means
to a pump. The remote pressure control means for the prime system
provides electrical control signals from a remote location for
operating a current-to-pressure converter at the rig location. The
pneumatic pressure from the converter functionally controls one of
the pumps and is also supplied to a ratio device which reduces or
amplifies the input pneumatic pressure by a fixed ratio to supply a
functional control pressure for the secondary pump. A pressure
comparison system is provided to compare the functional control
pressures for the remote control means to the functional control
pressure in the manual control means so that the two control means
can be regulated or adjusted relative to one another to similar or
equal values, thereby permitting a bumpless transfer of the control
functions from one location to the other location.
The features and advantages of the foregoing system will be more
easily understood from the following detailed description of a
preferred embodiment of the system when taken in conjunction with
the attached drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic illustration of the system embodying the
present invention; and
FIG. 2 is a schematic illustration of component details of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to FIG. 1, an elemental mud circulation system is
illustrated in simplified form for ease of understanding. In FIG. 1
the interior of a tubular casing or pipe string 10 in a well bore
(shown in cross-section) is coupled to a well input line 11. A mud
return annulus 12 is defined between the exterior of pipe string 10
and surface casing for the well bore and is coupled to a mud return
line 13. The mud return line 13 from the casing is coupled to shale
shakers and other reconditioning devices (not shown) for
reconditioning of the mud before it is returned to the mud tank.
The various well-known elements of the reconditioning system are
not shown since they form no part of this invention.
To supply the mud to the well bore, the mud in a mud tank (not
shown) is drawn into an input conduit 13A for the mud pumps
illustrated as 14 and 15. The valves 14A and 15A, respectively, in
the inlets to the mud pumps can be manually operated to cut off the
flow to a pump. The pump 14 outputs a flow of liquid to the well
input line 11 via a valve 16. The pump 15 outputs a flow of liquid
to the well input line 11 via a valve 18.
The mud pumps 14 and 15 (which are conventional) have important
functions in the circulation system which include (1) the promotion
of the ease of drilling by virtue of developing a liquid flow to
provide a jetting action at the bit; (2) the circulation of a
sufficient quantity of mud to keep the bit washed clean; and (3)
the return of solid earth particles or cuttings to the surface,
thereby keeping the hole free of cavings, cuttings and weight
material settlings. The density, viscosity and gel strength of the
mud used has a bearing on the operation of the pumps in that the
pumps are required to maintain a necessary flow velocity to keep
the hole clean.
The mud pumps usually are positive displacement reciprocating types
and the horsepower of a pump is a function of the output volumetric
flow rate and pressure. At its rated speed, a pump will reach its
power rating at the maximum rated pressure for each liner size. To
determine the horsepower needed for a given drilling operation, the
volume of mud necessary to provide sufficient velocity to remove
the cuttings is determined. With the volume of mud determined, the
pressure loss and the pressure drops can be determined to find the
necessary pump pressure. A pressure-volume relationship can be used
then to define the hydraulic horsepower required.
The pump 14 is operated by an engine or motive means 22 while the
pump 15 is operated by an engine or motive means 23. The pump 14
and engine 22 or the pump 15 and engine 23, respectively, are
functionally combined units so that in the description to follow,
the control or operation of a pump or an engine of one unit is
synonymous with operation or control of its associated engine or
pump. The engines 22 and 23 have clutch means (not shown) for
controlling the application of driving power to the pump and
throttle means for controlling the speed of an engine. In FIG. 1,
the present invention will be described in connection with a
control for the throttles, although it will be appreciated that
other regulating means could be controlled. Each of the engine
throttles have manually variable throttle controls 24 and 25, which
are respectively illustrated for each of the engines for pumps 14
and 15. The throttle controls 24 and 25 are manually operable to
adjust a throttle T of an engine by means of a pneumatic pressure
control system. In the pneumatic pressure control system between
the control 24 and engine 22 is three-way valve 26 which can be
independently operated between a position where the pressure
control to the throttle T is exercised by the manual control 24 and
a position where the pressure to the throttle T is from a remote
throttle control 28. Similarly, a three-way valve 27 in the control
system couples the manual throttle control 25 to the throttle T of
engine 23 in one position and in another position couples the
remote throttle control 28 to the throttle T. The remote throttle
control 28 provides an alternate, remote control for the engines
and is responsive to electrical control signals from a remote
location control means 29. When the remote control means 29 is in
command of the remote throttle control 28, the pumps are
synchronized for operation in fixed relationship to one another in
a manner which will be fully described in the discussion to
follow.
Referring now to FIG. 2, the components of the remote throttle
control 28 and the interrelated control devices for the pumps are
illustrated in more detail. For ease of understanding, various
pneumatic control valves are illustrated by circles where the
semi-circular portion which is shaded indicates a closed or blocked
path or condition in a valve and the unshaded semi-circular portion
indicates a flow-through or open condition in a valve.
Beginning at the remote control location 29, a potentiometer 30 is
schematically illustrative of an electrical control means which is
coupled by an electrical path 31 to the remote throttle control 28.
In the remote throttle control 28 is a current-to-pressure
converter 32. The current-to-pressure converter 32 is a
commercially available device, for example, Model 69TA manufactured
and sold by the Foxboro Co. The converter 32 is adapted to respond
to input electrical current signals and provide a proportionate
output pneumatic pressure. The pneumatic pressure output of the
converter 32 is coupled to a pressure-to-pressure amplifier 33
which outputs an amplified pneumatic pressure proportional to the
input pressure. The pressure output of the amplifier 33 is coupled
by output conduits 34A, 35A and 36A, respectively, to a first
selection valve 34, a second selection valve 35 and a pressure
reducer amplifier 36. The valve 35, as shown, is in a position
where the pressure in the conduit 35A is blocked off from the rest
of the system. The pressure in the conduit 34A is coupled by the
position of the valve 34 to couple the pressure in conduit 34A to
the conduits 37A and 37B. The conduit 37A couples to the three-way
valve 26 which, in the position shown, couples pressure to the
throttle control T for the engine 22 for a corresponding control of
the associated pump 14. Thus, it can be appreciated that operation
of the potentiometer 30 in the remote location control 29 produces
an electrical control function which is converted to a pressure
control by the remote throttle control 28 at the drilling location
for control of the engine 22 whenever the valves 34, 26 and 35 are
in the positions shown in the drawings.
The pressure reducer amplifier 36 has output conduits 38A and 38B
which respectively couple the reducer 36 to the valves 34 and 35.
In the position of the valves 34 and 35 shown in FIG. 2, the
conduit 38A is blocked off by the position of the valve 34. The
valve 35, in the position shown, couples the conduit 38B to the
output conduits 39A and 39B of the valve 35. The conduit 39A
couples to the three-way valve 27 which, in the position shown,
conveys pressure to the throttle control T for the engine 23. The
pressure reducer amplifier 36 is a conventional Ratio Control
Station and available from Moore Products. The reducer amplier 36
can be selectively adjusted as schematically illustrated by the
dial 40 to vary the pressure on the output side relative to the
input by a fixed relationship. The device 36 can serve to either
amplify or reduce the pressure as may be desired and produce a
corresponding relative control function. This relationship can be
ratio or percentage. Thus, the pressure control to the engine 23 is
a predetermined function of the pneumatic control to the engine 22
as determined by the setting of the reducer 36.
The valves 34 and 35 are selectively operable. The line and X
designation to these valves schematically illustrates the switching
control means which are coupled to remotely located actuating means
such as a switch 39 at the remote control means 29. When the switch
39 is operated, the positions of both the valves 34 and 35 are
reversed. When the positions of the valves 34 and 35 are reversed,
then the pressure from the amplifier 33 is supplied via the valve
35 and the valve 27 to the engine 23 and the reduced or lesser
pressure from the reducer amplifier 36 is supplied via the valves
34 and 26 to the engine 22. Hence, either pump can be the master
controlled pump from the control means and the other pump can be
the slave controlled pump.
The manual control means 24 is coupled by a conduit 40A to another
input of the valve 26 and, in the position shown, the conduit 40A
is closed or blocked off by valve 26 while the conduit 37A is
coupled to the output conduit of the valve 26. The manual control
means 25 is coupled by a conduit 41A to a second input for the
valve 27 and, in the position shown, the conduit 41A is closed or
blocked off by valve 27 while the conduit 39A is coupled to the
output conduit of valve 27. The valve 26 is adapted for selective
operation by a control means such as a switch 26B at the control
means 29 which is connected to the control device for the valve as
illustrated by the line with the designation Y1. The valve 27 is
adapted for selective operation by a control means such as a switch
27B at the control means 29 which is connected to the control
device for the valve by the line with the designation Y2. Actuation
of the valves 26 and 27 will reverse the pressure control from the
remote control pressure lines 37A and 39A to the control of the
manual control pressure lines 40A and 41A.
The conduit 37B from the valve 34 is coupled to an input of a valve
42. The valve 42, in the position shown, couples the conduit 37B to
one input of a pressure comparison means 43. The conduit 39B from
the valve 35 is coupled to the other input of the valve 42 and is
blocked off or closed by the position of the valve 42. A conduit
40B from the manual control means 24 is coupled to one input of a
valve 44. The valve 44, in the position shown, couples the conduit
40B to the other input of the pressure comparison means 43. The
conduit 41B from the manual control 25 is coupled to the other
input of the valve 44. The valve 44, in the position shown, closes
off the conduit 41B. The input pressures transmitted by valves 42
and 44 to the comparison means 43 are compared and electrical
output signals representative of any pressure difference is
supplied via an electrical conduit 44 to a meter or indicator 45 in
the control means 29. The indicator 45 is arranged to read "null"
signals; i.e., indications when the pressures are equal and, in the
event of inequality, how much difference exists between the
pressures. Since the comparator means 43 detects differences in
pressure, in the described example, it can be determined how much
difference in pressure exists between the operative remotely
controlled pressure controlling the engine 22 and the pressure as
determined by the control setting of the inactive manual control
means 24. By the use of a control device such as an electrical
switch 42B (coupled by lines identified with the character Z) for
the switching control means of the valves 42 and 44, the valve
positions can be reversed. Whenever the positions of the valves 42
and 44 are reversed the relationship of the pressure of the other
manual control 25 to the control pressure for the engine 23 can be
determined.
Relative to the operation of the present system, for a well
drilling operation, the mud properties, hole and pipe configuration
and pump characteristics are considered. Because two pumps have
functionally related characteristics, their operation relative to
one another to optimize their operation can be decided upon so that
they can be operated in a fixed ratio relative to one another. This
predetermined operational ratio is set by the operation of the
selecting dial mechanism 40 of the converter 36.
The valves 26, 34, 27 and 35 may be initially set in the position
shown in FIG. 2 so that the potentiometer 30 in the control means
29 can provide current signals to the current-to-pressure converter
32. The converter 32 provides a pneumatic pressure proportionally
related to the current input. The pressure amplifier 33 serves to
provide an amplified pressure for the system. From the amplifier
33, the pressure output is supplied to the control for the engine
22 via the open valves 34 and 26. The pressure output of the
amplifier 33 is reduced to a ratio value by the pressure reducer
amplifier 40 and is supplied to the control for the engine 23 via
the open valves 35 and 27. As the pressure from the converter 32 is
increased or decreased in response to control signals from the
remote controller 29, the speed of engine 22 (and pump 14) is
correspondingly increased or decreased. At the same time the
control pressure to the engine 23 in proportion to pressure
controlling the engine 22 proportionally increases or decreases the
speed of the engine 23. Hence, in the above illustration, the pump
14 is the prime pump under control, and the pump 15 is the slave
pump which is controlled in fixed relation to pump 14. If the
remote control switch 34B is operated, the valves 34 and 35
respectively change position so that the primary pressure control
from the converter 32 is then supplied to the engine 23. The valves
34 and 35 thus serve as selection valves for selecting the prime
pump and the follower pump to be controlled.
To convert the control operation from the remote control means 29
to the manual control means 24 and 25, the control switch 26B is
operated and the control valves 26 and 27 reverse positions to
couple the manual control means 24 and 25 to the engines 22 and 23,
respectively. At this time the driller can assume manual control
for each of the pumps.
The manual control means 24, and 25 for each of the pumps are
coupled to a comparison valve 44 while the remote control pressures
for each of the engines is coupled to a comparison valve 42. With
this arrangement and the valves 42 and 44 in the position shown in
FIG. 2, the pressure in the manual control means 24 is compared to
the pressure output from valve 34. In this regard the pressure
comparison exists irrespective of the position of control valve
means 26 relative to the engine 22. The pressures supplied to the
pressure comparison means 43 provide a signal output indicative of
the pressure differential to the remote meter 45. Either the
potentiometer 30 or the manual control means 24 can be adjusted to
equalize the pressures between the units. The merit of having equal
pressures in the manual means and remote control means is that the
control of the system can be shifted between these two modes as
described above without changing the effect on the controlled
engine. By operation of valves 42 and 44 the positions of the
valves can be reversed so that both manual controls can be
calibrated in terms of pressure with reference to the pressure
control of the remote control.
While particular embodiments of the present invention have been
shown and described, it is apparent that changes and modifications
may be made without departing from this invention in its broader
aspects; and therefore, the aim in the appended claims is to cover
all such changes and modifications as fall within the true spirit
and scope of this invention.
* * * * *