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Description  |
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TECHNICAL FIELD
This invention relates to a multi-tank/multi-pump water pressure system,
particulary the application of the pump control mechanism.
BACKGROUND ART
The prior art researched has clearly shown a number of techniques used to
provide water through various booster systems. These techniques offer a
number of options with various levels of success, in providing controlled
water booster systems.
U.S. Pat. No. 4,344,741 (TOMOHIKO TAKI) shows an automatic supply system
with a single tank having a controlled air charge, preventing the release
of water from the pneumatic tank from a single pump supply to maintain a
constant source of water.
U.S. Pat. No. 4,290,735 (SULKO) shows a plurality of pumps each being of a
capacity to provide high head and volume disposed into a common manifold
to provide pressure boosted water in a highrise building using a
pressurestatic switch as means of control consisting of various control
switches and relays, with an auxiliary pump having an accumulator tank.
U.S. Pat. No. 3,775,025 (MAHER & MAHER) shows a constant pressure pumping
system unit consisting of two pumps, one being of variable speed providing
a constant pressure, whereas the second pump provides constant speed with
control switches providing the perimeters of the system.
U.S. Pat. No. 3,746,471 (GRAY & ANDERSON) shows a water pressure booster
system using auxiliary pump to super charge pressurized reservoir, with a
plurality of pumps controlled by various relays and sensing switches.
U.S. Pat. No. 3,744,932 (PREVETT) shows an automatic sequence control
system for pump motors. This system provides automatic controlling of a
plurality of pumps using various control switches, flow meters, relays
along with logic gates thus providing a complex control system.
U.S. Pat. No. 3,639,081 (GRAY & ANDERSON) shows a liquid pressure booster
system with cutoff for minimum flow levels consisting of a plurality of
constant speed pumps and pressure-regulating valves along with time delay
relays and a single pressurized tank with various other complex electrical
controls.
To the contrary, none of the references show a "MULTI-TANK/MULTI-PUMP WATER
PRESSURE BOOSTER SYSTEM" presented by the inventor.
BACKGROUND AND SUMMARY
The present invention relates to tank type water pressure booster systems
employing constant speed pumps, and more specifically it relates to water
pressure booster systems employing hydropneumatic bladder or diaphragm
type tanks and constant speed electrically driven pumps automatically
sequenced to operate to satisfy water system flow demand requirements
throughout the full system multi-pump capacity without the utilization of
control or timing relays or solid state electrical/electronic
timing/controlling devices or flow actuated devices to provide water
throughout the full system design range at a specified increase of
pressure and maintained within acceptable tolerances of a specified design
pressure to suit domestic water system service requirements. The term
constant pressure is purposely avoided as it is in reality a misnomer in
the pumping industry and is both highly impractical and virtually
unobtainable in economical domestic water pressure booster systems. Actual
system pressure variation of plus five percent, minus ten percent in low
pressure (up to 150 PSI design pressure) booster applications is not only
acceptable, but quite common and frequently utilized in establishing
design parameters of control. In high pressure applications a lesser
percentage of pressure variation usually will be found, although a
pressure variation of plus 10 PSI, minus 20 PSI on a 250 PSI system is
not uncommon. Multipump water booster systems of both tank and tankless
types are supplied with inlet pressure either from a conduit or reservoir
source of supply at a pressure that is usually lower than is required to
meet the domestic water service requirements of the facility being
supplied. The pumps are parallel connected and fitted with appropriate
isolation and discharge check valves to permit individual operation or
simultaneous operation while pumping from a common source into a common
conduit, and providing a specified increase in pressure. When required or
desired, these pumping systems may be furnished with pressure reducing
valves connected either one on the discharge of each pump before entering
the common high pressure conduit, or in any desired arrangement of
parallel connected pressure reducing valves installed between the common
high pressure conduit and the service to the facility. The systems are
designed to sequence the pumps as required to satisfy the flow demand of
the facility being supplied; automatically selecting the pump or any
combination of pumps best suited to satisfy system flow demand at any
given time, and (when furnished with auto shut off feature) to turn all
pumps off under conditions of no demand. When a system is designed having
two or more equally sized pumps, a means of automatic or manual
alternation or sequencing selection is usually provided in order to
equalize wear and operating time.
Systems furnished with the design features as described above have been
found to be highly energy efficient and economical of operation since they
have the ability to select the smallest energy consuming combination of
pumps required to be in operation to suit the system demand at any given
time and (when so equipped) to shut off with zero demand. The application
of a hydropneumatic tank (usually an optional item) to such systems
further enhances the energy conservation aspect of these systems, since it
enables the reservoir capacity of the tank to supply low volume usage to
the facility while allowing the system pressure to be reduced from the
maximum high value when the pump shuts off at zero demand (+.ident.to +
PSI) to an acceptable low value for system operation (generally -10 to
-.degree.PSI). Thus a volume of water can be furnished to the facility
without starting a pump. The disadvantages found in most of the above
described systems are that the tank and zero or low demand shut off
feature is provided only as extra cost options, there are some systems
lacking in the ability of the controls to perform a claimed function, and
in virtually all systems the method to attain the functions is by means of
costly control and timing relay circuitry or solid state electronic
control devices coupled with also costly flow sensing devices. Flow and
current sensing devices are the most commonly used items for sequencing
control of present day state of the art multi-pump automated pump control
systems. Both have the common disadvantage of working in combination with
timing relays which function to start the next pump of the system
instantaneously when the signal from the flow or current sensing device is
received, and to maintain the pump in operation for a predetermined period
of time. During this transition, the prior operating pump is usually
sequenced off.
Brief surge demands are extremely common in many types of buildings, such
as hotels, schools, office buildings, apartments, hospitals, entertainment
centers, etc. With each occurence, a larger pump may be sequenced on for
the predetermined time setting of the timing device while a smaller pump
is sequenced off. In extreme cases continuous back and forth cycling
between a small pump and a larger pump in a system may continue without
cessation throughout the greater part of a day. This is not only hard on
the equipment but also wasteful of energy. It is not uncommon to employ
time clock control to prevent such cycling from occuring.
Most equipment users desire and specify a type of pump failure feature that
will provide an alarm indication and start an alternate pump in the event
of failure to a pump while in the operational sequence. This feature is a
standard extra cost option for failure of the lead (number one) pump in
most designed pumping systems, however most manufacturers do not offer a
feature to protect from failure to a main pump except on a custom
engineered basis. Another occasionally requested feature by system users
is the high suction pressure shut off. With this feature, the pumps are
programmed to shut off and remain off if the inlet pressure to the system
reaches a predetermined high level sufficient to supply the facility
without the boost in pressure provided by the pumps. This too is usually
offered as an extra cost option, it is highly desireable for installations
wherein the input pressure has wide variation since it automatically
prevents the pumps from running unnecessarily.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 shows the basic piping arrangement of the water booster system
constructed in accordance with an embodiment of the inventor;
FIG. 2 is a combined circuit and systematic diagram of the control system
according to the present invention;
FIG. 3 is as FIG. 1, showing pressure reducing values added to the system;
FIGS. 4 and 5 show the controls for adding additional pumps to the system
with the means of tank three;
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 is a diagramatic form of the present invention. Inlet source 15
provides water to suction manifold connected to pumps indicated
respectively as 1, 2, 3, which are connected for parallel operation when
energized. The output of pump number 1 flows through check valve 36 and
through gate valve 39, into service line 6; pump 2 flows through check
valve 37 and through gate valve 40 into line 6; pump 3 flows through check
valve number 38 and through gate valve 41 into line 6. Primary tank 4 is
connected to line 6 by line 30 with a service valve 42 adjacent to line 6
and an orifice check valve 11 between tank 4 and service valve 42 with
sensing point 51 directly adjacent to discharge of primary tank 4.
Secondary tank 5 is connected to line 6 by line 32 which flows through
solenoid valve 13 and intersects line 31 and flows into line 30 between
orifice check valve 11 and servicing valve 42, and into line 6. Line
number 32 has a sensing point 52 adjacent to secondary tank 5 and a bypass
line 33 with check valve 12 around solenoid valve 13 returning into line
32. Pressure sensing switch two 8, pressure sensing switch three 9 and
pressure sensing switch four 10 are all connected to sensing point 52 by
line 34. Pressure switch one and the high pressure side of pressure
differential switch 14 are connected to the sensing point 51 by line 35.
The low pressure side of pressure differential switch 14 is connected to
sensing point 53 by line 79.
FIG. 2 is an electrical schematic which is verbally defined in the SEQUENCE
OF OPERATION describing the function of each component in operating
detail.
FIG. 3 is a diagramatic form of the present invention as described in FIG.
1 with the addition of the following: pressure reducing valves 47, 48, 49
and 50 which are placed in lines 70, 73, 71 and 72 respectively.
FIGS. 4 and 5 is an electrical and piping schematic which is verbally
defined in the sequence of operation describing the function of each
component in operating detail.
SEQUENCE OF OPERATION
For explanatory purposes, let it be assumed that electrical power is being
provided to the system, the system is properly connected hydraulically to
inlet and outlet plumbing, water is being supplied to the inlet by a
regulated source of supply, and the system is set up for automatic
operation. Present system demand is zero, both primary and secondary tanks
are fully charged and all pumps are idle due to the zero demand condition.
This can be referred to as static or standby service condition. Referring
to the drawings, FIGS. 1 and 2, the sequence which will occur when demand
is placed on the system will be as follows: Water will be drawn from the
primary tank FIG. 1, (4) to service needs, FIG. 1, (6) until the pressure
in the primary tank is reduced to the set point of pressure switch PSI,
FIG. 1, (7) this is usually 10 to 20 PSI below the pressure at which PSI,
FIG. 1, (7) opens to stop the number one pump, FIG. 1, (1). When pressure
switch one closes its contacts (refer now to FIG. 2, (7) it completes an
electrical circuit through the normally closed auxiliary starter contacts
FIG. 2, (16 and 17) of motor starters M2 and M3 FIG. 2, (18 and 19) and
through the closed contacts of hand off auto selector switch FIG. 2, (21)
to energize motor starter one FIG. 2, (18) and its running indicator lamp
FIG. 2, (24). Simultaneously energized by pressure switch one is the
secondary tank solenoid valve FIG. 1, (13) and FIG. 2, (13). Pump number
one is started in the conventional manner by closure of the motor starter
contacts, supplying power to the motor windings (as will be pumps 2 and 3
FIG. 1, in later descriptions).
Water will now be supplied to the service both from the number one pump and
from the secondary tank through the now opened normally closed solenoid
valve FIGS. 1 and 2, (13). The primary tank FIG. 1, (4) places no
appreciable draw on the system because the fill rate is restricted to a
small volume by the orificing through the seat of the check valve FIG. 1,
(11). If the demand is small, the pressure in the secondary tank FIG. 1,
(5) will be reduced only slightly, and the number one pump will continue
in operation to supply service demands and recharge the primary tank FIG.
1, (4). When demand is increased beyond the capacity of the number one
pump the secondary tank pressure will quickly be reduced by the discharge
of water to service needs through the open solenoid valve FIGS. 1 and 2,
(13). When pressure is reduced to the set point of pressure switch two
FIGS. 1 and 2, (8) the contacts close to complete a circuit through the
closed contacts of the electric alternator FIG. 2, (28) and through the
closed contacts of the auto section of the number two pump hand off auto
selector switch FIG. 2, (22) to the coil FIG. 2, (19) of the number two
pump magnetic motor starter, placing number two pump FIG. 1, (2) into
operation and energizing the number two pump running indicator lamp FIG.
2, (25). Simultaneously with closure of pressure switch two contacts, the
coil of the electric alternator FIG. 2, (27) will become energized.
Simultaneous with actuation of magnetic motor starter number two the
auxiliary starter contact M2 FIG. 2, (16) opens to break the operating
circuit to pump number one. Pump number one stops and service demand is
now supplied by the output of pump number two through the 20 to 40 percent
system design capacity range.
Both primary and secondary tanks accept recharge pressure when service
pressure is greater than tank pressure, through the orifice check valve
FIG. 1, (11) to the primary tank and through the small bypass line FIG. 1,
(33) and check valve, FIG. 1, (12) to the secondary tank. Conversely with
increasing service demands and reducing pressure, both the primary and
secondary tanks will supply water as available to service needs; the
primary tank through the unrestricted direction of flow through the
orifice check valve FIG. 1, (11) and the secondary tank through the open
solenoid valve FIG. 1, (13). With increased demand and further reduction
in pressure to the set point of pressure switch three FIGS. 1 and 2, (9)
the contacts close to complete an operating circuit to the number three
magnetic motor starter FIG. 2, (20) and to the number three pump running
indicator lamp FIG. 2, (26). Pressure switch three also completes a
redundant operating circuit to pump number two, through the upper set of
contacts FIG. 2, (9) which has no effect since pump two is already in
operation. Likewise the normally closed M3 auxiliary contact FIG. 2, (17)
opens but performs no function because the required function (stopping the
number one pump) was previously performed by the M2 auxiliary contact FIG.
2, (16). The number three pump is started by the magnetic starter in the
conventional manner and the number two and three pumps operate in parallel
to provide service requirements through the 40 to 80 percent range of
system design capacity. While in this mode of operation, both primary and
secondary tanks continue to function as previously described to charge and
discharge to stabilize system output pressure and assist the pumps in
meeting service demands. As additional demand is placed upon the system,
the pressure will be further reduced to the set point of pressure switch
four FIGS. 1 and 2, (10) upon closing its contacts, pressure switch four
completes a second operating circuit to the motor starter number one FIG.
2, (18) bypassing the initial start circuit and the cut-out circuit of the
M2, M3 FIG. 2, (16) and (17) normally closed auxiliary starter contacts.
Starter number one operates, placing number one pump into operation and
number one pump running lamp FIG. 2, (24) will be simultaneously lighted.
The system is now operating at full design capacity to meet service
damands of 80 to 100 percent of full system design capacity and will
continue in this mode of operation until service demand is reduced.
When flow demand is reduced, system pressure in both the primary and
secondary tanks will increase. Pressure switches PS4, PS3 and PS2 FIG. 2,
(7) (8) (9) will be opened in reverse order from that in which they
closed. As each switch opens the pump that was being controlled by the
respective switch will be stopped. When pressure switch two opens FIG. 2,
(8) it will also deenergize the coil of the alternator FIG. 2, (27). When
the coil deenergizes the alternator contacts FIG. 2, (28) shift to the
opposite position, thereby selecting the number three pump to be the first
sequence main pump for the next cycle of operation. When the number two
magnetic starter FIG. 2, (19) is deenergized its normally closed auxiliary
contact M2 FIG. 2, (16) which completes the restart circuit to number one
pump through the previously closed (when pump three was stopped) M3
auxiliary motor starter contact FIG. 2, (17). Pump number one restarts to
provide low system demand and recharge the primary and secondary tanks.
When the primary tank pressure is increased to the actuation point of
switch one FIGS. 1 and 2, (7) the switch opens to stop the pump and return
the system to the static service condition where it will remain until such
time as demand is placed upon it to begin a new cycle of operation.
STAGING ADDITIONAL PUMPS AS IN FIGS. 4 AND 5 WITH SEQUENCE OF OPERATION
The invention is readily adaptable to controlling additional pumps within a
common system without extensive modifications. FIGS. 4 and 5 are provided
as an example for field addition of two pumps to the previously described
three pump system. To facilitate control, a third tank FIG. 5, (67) of
equal or slightly less capacity than the secondary tank is piped in
parallel to the secondary tank FIG. 1, (5) and is provided with similar
flow control devices consisting of normally closed solenoid valve FIG. 5,
(65) and bypass check valve FIG. 5, (55). The check valve and the tank
combination are selected to provide a slightly faster rate of recharge
than the secondary tank. With the arrangement shown, the added pumps will
be controlled by magnetic motor starters M4 and M5 FIG. 4, (56 and 57) and
will be entered into the systems operational sequence after the second
sequence main pump of the three pump system is started. Control power for
the two pumps being added is from the common source supplying the basic
three pump system FIGS. 2 and 4, (58 and 59). The only electrical
components required to be added to the basic triplex control panel are the
auxiliary motor starter contacts M2A and M3A FIG. 4, (60 and 61). Magnetic
motor starters M4 and M5 FIG. 4, (56 and 57) with the associated hand off
auto control switches FIG. 4, (62 and 63) and the alternator FIG. 4, (64)
are used for controlling the pumps being added and can be provided in a
separate duplex pump control panel.
When the second sequence main pump of the basic three pump system is
started, auxiliary motor starter contacts M2A and M3A FIg. 4, (60 and 61)
will both be in the closed position. Power is then applied to the normally
closed solenoid valve FIG. 4, (65) on the discharge line FIG. 5, (66) of
tank three FIG. 5, (67). Water from tank three is now discharged to
augment the output of pumps two and three, FIG. 1, (2 and 3). When
pressure drops to the set point of pressure switch PS5 FIGS. 4 and 5, (68)
its contacts will close, the alternator coil FIG. 4, (64) will become
energized, and power will be applied through the closed contacts FIG. 4,
(69) of the alternator and through the closed contacts of the hand off
auto selector switch FIG. 4, (62) set in the auto position to the coil of
magnetic motor starter M4 FIG. 4, (56). When the main contacts of M4
close, pump number four will be placed into operation to supply additional
water to the service. With additional service demand the pressure in tank
three FIG. 5, (67) will be reduced further. When it reaches the set point
of pressure switch PS6 FIGS. 4 and 5, (77) its contacts will be closed to
energize magnetic motor starter M5 FIG. 4, (57) through the closed
contacts of hand off auto selector switch FIG. 4, (63). Pumps two, three,
four and five now operate simultaneously to supply system demands. If
pressure continues to be reduced, pressure switch PS4 FIG. 2, (10) of the
basic system will close its contacts at the set point and restart pump
number one FIG. 1, (1) of the basic system. Pumps one through five will
now operate simultaneously to supply maximum system design capacity to
service needs, and will remain in operation until service demand is
reduced. When service demand is reduced, the pressure in the secondary
tank FIG. 1, (5) and in tank number three FIG. 5, (67) will be increased.
Pressure switches PS4, FIG. 2, (10) PS5 FIG. 4, (68) and PS6 FIG. 4, (77)
will reopen in reverse order from that in which they closed and stop the
respectively controlled pump. When pressure switch PS5 FIG. 4, (68) opens
its contacts, the alternator FIG. 4, (64) will become deenergized and
shift the contacts FIG. 4, (69) to the opposite position to select pump
number five for the first sequence of operation when the next operational
cycle requiring pump four or five is required.
GENERAL COMMENTS ON SYSTEM OPERATION
When pump number one is started in the first sequence, the primary tank
charge is depleted by approximately 90 percent, and the system pressure is
at its lowest operating value. At the instant of pump number one starting,
pressure in the system begins to increase, not only from the pump output,
but also from the charge in the secondary tank. System control is
transferred from the static mode of the primary tank to the dynamic mode
of the secondary tank. Thus, the ability to combine the advantage of the
large reservoir capacity of the primary tank, and the ability to
accurately sequence and provide timing control to the pumps, while
operating without overloading, and at the system design pressure, is
achieved. More simply stated, the secondary tank controls pump sequencing
at system design pressure, while the primary tank controls the static
system pressure which is allowed to vary through the optimum differential
range of the primary tank. The dual tank feature enables dual pressure
sensing to suit the mode of operation, and provides dual range control.
The ability of the two hydropneumatic tanks to augment pump output during
dynamic operation provides a high degree of stability and efficiency to
the system. Under conditions of varying flow demand, the tanks continually
charge or discharge water to assist the pumps in meeting system
requirements. Brief surge demands can be supplied by the tank output
without switching to a larger pump or starting an additional pump (as
occurs with flow activated switching devices). Minimum run periods for the
pumps are established by the differential band of the pressure switches
employed, and the time period required to increase the pressure in the
secondary tank through the range of pressure switch differential. This
eliminates the possibility of the pump short cycling (and also eliminates
the need for electrical or electronic minimum run timers). In effect, the
secondary tank becomes a dampened switching chamber, protected from the
effects of surge demands (which can be supplied by the tanks reservoir
capacity), is not at all effected by pressure spikes, and provides as the
end result a highly stable, accurate and simple means to sequence pumps in
automated multipump systems.
The degree of accuracy in switching/sequencing the pumps is limited
primarily by the quality and design of the pressure switches and the size
of the secondary tank. By sizing the lead pump for a slightly higher
pressure than the main pumps, the tanks can be charged to a pressure of 5
to 10 PSI above system design requirements, which then permits sequencing
to the first main pump at system design pressure, starting the second main
pump slightly (2 to 5 PSI) below system design pressure, and the restart
of the lead pump at 5 to 10 PSI below system design pressure. Thus a very
narrow band for switching control can be established, and is limited only
by the degree of sophistication of the switching devices and the size of
the secondary tank.
PUMP FAILURE MODE OF OPERATION
With competitive systems this feature is usually offered as an extra cost
option and consists of a relay logic circuit actuated by a pressure
switch. The logic is such that should the pressure at any time be reduced
to the set point of the pressure switch, conclusion is drawn that the pump
that should be operating has failed; usually the conclusion is also drawn
that the pump that should have been in operation at the particular time of
the occurence was the number one or lead pump. Therefore the title "lead
pump failure" is commonly applied to this optional feature. The relay
logic applied functions to start the first sequence main pump and lock it
into continuous operation until such time as a manual reset button is
pressed. An audible or visual alarm is also actuated on this condition.
The relay logic may function to remove the failed lead pump from service
but does not in all cases do so.
Pump failure feature of the invention is an inherent design characteristic.
Because the dynamic control of this system is exercised by means of a
pressure being maintained within the secondary tank, the system will
simply bypass any pumps in the operating sequence which fail to provide
proper output, and select the pump in the next sequence position of
operation to meet service requirements. In selecting this alternate pump
to provide service demand, it will not be sequenced into continuous
operation until manually reset, but will be placed into operation only for
so long as is required to meet service demands. The pump will then be shut
off in the normal manner and the system will automatically be reverted
into the static service condition. The only observable effect will be that
if the number one pump was the failed unit, the primary and secondary
tanks will not be recharged to the full pressure normally attained when
the system sequences into the static service condition. The total system
capacity will of course be reduced by the capacity of the failed pump.
HIGH SUCTION PRESSURE SHUT OFF
This is an energy saving feature which is normally offered as an extra cost
option on competitive systems. It functions to prevent the pumps from
operating at any time that the system inlet (supply) pressure is high
enough to supply service needs without requiring a pressure boost. This is
a standard design characteristic of the invention and is furnished on all
systems. Function is quite simple and is performed by pressure with PSI
FIGS. 1 and 2, (7). Since the inlet pressure will pass directly through
all pumps and into the primary tank FIG. 1 (4) at any time that the inlet
pressure is higher than the set point of pressure switch PSI FIGS. 1 and
2, (7) PSI will remain in the open position and the pumps will not be
started. Service demands will be provided by the inlet pressure.
CONTROL OF SYSTEM HAVING VARIABLE INLET (SUCTION) PRESSURE AND NOT
FURNISHED WITH PRESSURE REDUCING VALVES
When a water booster system must operate under conditions of having a
variable inlet pressure, the minimum inlet pressure must be utilized as
the base value in determining the set points for all of the pressure
switches used for starting and sequencing the pumps. This is essential to
prevent the pumps from failing to shut off under conditions of minimum
inlet pressure. For installations wherein the inlet pressure fluctuates
through a wide range of variation, efficiency of such systems can be
improved by the addition of a differential pressure switch FIGS. 1 and 2,
(14). The differential pressure switch functions to prevent the pumps from
shutting off as a result of an increase in the inlet pressure. It
maintains the number one pump in operation until such time as the primary
tank pressure FIG. 1, (4) equals the combined pressure of the inlet
pressure plus the set pressure of the differential pressure switch. In
this manner, both the primary tank, FIG. 1, (4) and the secondary tank,
FIG. 1, (5) will be charged to the maximum pressure attainable at the time
at which the differential pressure switch opens to stop the number one
pump and place the system into static mode of operation. Hydraulic
connections of the differential pressure switch are to the suction
manifold FIG. 1, (15) for the low pressure side and to the pressure
sensing point of the primary tank FIG. 1, (51) for the high pressure side.
The electrical power for the maintaining circuit to the number one pump is
through the closed contacts of the differential pressure switch, FIG. 2,
(14), through the closed M1 auxiliary starter contact, FIG. 2, (29) and
then through the normal operating circuit for motor starter number one
FIG. 2, (18) as previously described.
EXPANSION CAPABILITY
The operational description provided for staging additional pumps as in
FIGS. 4 and 5 illustrates; The basic operational simplicity with which
additional pumps may be controlled by applying the same principle of
operation as the basic invention employs. This method of staging and
controlling with a specific design pressure range, a virtually unlimited
number of pumps without requiring complex relay or electronic circuitry is
a unique advantage of the invention. The basic features derived by this
means of control are retained throughout the full operational range of the
system. Heretofore a five pump automated pump control system providing the
standard design features of this system could only be undertaken by
employing the highest state of the art technology utilizing costly and
complex relay and electronic controlling devices. The cost of such control
systems can far exceed the cost of the pumps. This is not a forseeable
occurence with this method of control. There are varied methods in which
additional pumps can be staged and sequenced into the system. Depending
upon system design tolerances it is conceivable that as many as four or
more pumps could be controlled by a single dynamic control tank. The
method of alteration/sequencing the pumps to equalize operating hours is
totally flexible. Any type of multi-pump sequencing device could be
employed. In undertaking the design of this system, basic simplicity of
control combined with highest reliability and minimum cost has been a
foremost objective.
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