Constant Pressure Pumping Unit

Abstract

A pumping unit is disclosed for use with water delivery systems where the demand is variable. The unit has first and second pumps with the drive of the first pump variable and operable to provide a constant pressure at any speed while the drive of the second pump provides a constant speed therefor. The drive of the first pump is responsive to the pressure established by it in the system so that its speed varies with the demand as measured by said pressure. A control for the drives includes control circuitry having a switch responsive to pressure in the system established by the unit and having high and low pressure limits and placing the second pump in service only when a predetermined high pressure cannot be maintained by the first pump.

Description

BACKGROUND OF THE INVENTION

In fluid delivery systems, particularly water systems for relatively tall buildings, the maintenance of a predetermined pressure has presented problems because widely fluctuating demands make control by a single pump impractical.

Multi-pump arrangements have been employed with constant speed drives but these have failed to provide sufficient flexibility to enable economical and satisfactory operations throughout the range of expected demands to be effected.

THE PRESENT INVENTION

The objective of the present invention is to provide a pumping unit that meets, with minimum power requirements, the full range of demands placed on a water delivery system of which those of tall buildings are examples.

This objective is attained by providing a pumping unit including first and second pumps. The drive of the first pump is variable and provides for a constant pressure at any speed and is responsive to the pressure in the system as a measure of the demand thereon while the drive for the second pump provides for a constant pump speed. The unit includes control cotrol having control circuitry for both pumps and includes a switch responsive to the pressure in the system and having high and low pressure limits and providing for the operation of the second pump at the low pressure limit and the discontinuance of its operation when a predetermined high pressure in the system is established.

In operations, where a high pressure demand exists, the second pump comes into service and control means are provided to permit both pumps to remain in operation but with the first pump throttled back as the pressure builds up thus ensuring economy in operation and maintenance of adequate pressure in the system with extremely limited variations in the pressure in the delivery system.

THE PREFERRED EMBODIMENT OF THE INVENTION

In the accompanying drawings, the preferred embodiment of the invention is shown of which

FIG. 1 is a plan view of the pumps, their connections, and their control valves;

FIG. 2 is a side view thereof; and

FIG. 3 is a schematic view of the control circuitry.

A pumping unit includes a frame 5 on which pumps 6 and 7 are mounted. These may be, in the disclosed embodiment, vertical turbine or horizontal centrifugal pumps having one, two, or three variable speed or constant speed pumps or combinations thereof.

The pump 6 is coupled to an adjustable speed drive, generally indicated at 8 and including a constant speed motor 9 capable of producing full motor torque from full input motor speed to zero R.P.M. A satisfactory drive, of the hydro-viscous wet clutch type and utilizing a hydraulic control, is manufactured by Borg-Warner Corporation of Tulsa, Oklahoma, and sold under its trademark "Infi-Drive." The details of the device are not shown herein but are disclosed in a copyrighted print published by the manufacturer. The pump 7 has, for its drive, a constant speed motor 10.

The water supply system 11 has oppositely opening check valves 12 and 13 between which there is a T 14 connected to the manifold 15 with which the intakes of the pumps 6 and 7 are in communication when their valves 16 and 17, respectively, are open. The check valve 12 prevents flow from the manifold 15 to the supply system 11. The manifold 18, to which the outlets of the pumps 6 and 7 are connected by valves 19 and 20, respectively, is connected by a T 21 to the water delivery system 22 which is provided with a discharge conduit generally indicated at 23.

The discharge conduit 23 has a hydraulic line 24 connected to the variable orifice controller of the drive 9 to transmit the pressure existing in the delivery system 22 thereto thereby causing the speed of its motor 9 to be automatically varied to maintain the wanted pressure in the delivery system. The discharge conduit 23 also is provided with a hydraulic line 25 in communication with a pressure responsive switch generally indicated at 26, see FIG. 3, in a lead 27 and operable to connect it to a lead 27A when a predetermined high pressure exists in the delivery system 22 and to connect the lead 27B to the lead 27 when that pressure is not maintained.

In accordance with the invention, the pump 6, due to the fact that it is operative to maintain a constant pressure throughout the speed range of its drive 8, is able to meet a substantial range of demands on the delivery system 22. If the demand exceeds the capacity of the pump 6, the pressure responsive switch 26 closes the circuit 27B and the pump 7 is brought into service and operates at its full capacity. The added capacity of the pump 7 is reflected in a lowered demand on the pump 6 and its drive 8 is accordingly throttled back as the pressure in the delivery system 22 increases. Should the demand drop enabling the switch 26 to again connect the leads 27 and 27A, the pump 7 drops out of service.

The operation of a pumping unit in accordance with the invention is more fully detailed in connection with the discussion of the circuitry schematically shown in FIG. 3 which also includes a vacuum pump, employed when a suction lift is needed. The vacuum pump is not shown but the motor by which it is driven is generally indicated at 29 in FIG. 3.

In FIG. 3, a generally indicated circuit 30 includes the circuit 31 for the pump motor 9, the circuit 32 for the pump motor 10, the circuit 33 for the vacuum pump motor 29, and the primary of a transformer 34. The circuit 31 has parallel leads 31A and 31B and the circuit 32 also has parallel leads 32A and 32B. The leads 31B and 32B are reduced voltage leads.

The secondary of the transformer 34 includes a control circuit, generally indicated at 35 under the control of a switch 36 and provided with parallel leads 37, 38, 39, 40, 41, 42, 27, 43, 44, 45, and 46. The lead 37 is provided with a lamp 47 indicating that the power is "on" while a normally closed temperature responsive, safety switch 48 controls the other leads.

The leads 38 and 39, which comprise the first section of the circuit, control the operation of the motor 9 and are under the control of a common switch 50 having three positions, an "off" position, a first position in which the control of the operation of the motor 9 is manual and a second position providing for the automatic control thereof. For that reason, the leads 38 and 39 are interconnected at 51 with the lead 38 having a relay 52 and parallel leads 38A and 38B connected to the lead 39 which then joins the lead 38. The lead 38A has a timer 53 while the lead 38B has a lamp 54 to show that the motor 9 is energized and the pump 6 in service which results when the relay 52 is energized as it then closes its switches 52A in the starter leads 31B of the motor circuit 31.

The lead 39 has, between the switch 50 and the connection 51, the normally open switch 55A of the relay 55 located in the parallel lead 127B of the lead 27B, a normally open switch 52B of the relay 52 in parallel with the switch 55A, and the normally closed switch 56A opened by the timer 56 after a predetermined interval, fifteen minutes by way of example. The timer 56 is located in the parallel lead 44A of the lead 44. While the other timing means may be and desirably are relays, the timer 56 is motor driven and self-resetting, such a model No. HP518A6, made available by Eagle Signal, a division of Gulf & Western Industries, Inc., Davenport Iowa.

The lead 39 has a normally open switch 53A closed after a brief delay, 10 seconds by way of example, when the timer 53 is energized, and the relay 57, which, when energized, closes the normally open switches 57A of the starter leads 31A of the motor circuit 31.

It will thus be apparent that when the switch 50 is set in its first or manually position to utilize the entire lead 38, as when the system is to be filled, the starter leads 31B are first closed and, after a brief delay, the starter leads 31A are also closed.

The leads 40, 41, and 42, which comprise the second section of the circuit, control the operation of the motor 10 of the pump and are under the control of a manually operable switch 58 that, like the switch 50, has three positions, an "off" position, a first position in which the operation of the motor 10 is manually controlled and a second position in which the operation thereof is automatic.

The lead 40 includes a relay 59 and parallel leads 40A and 40B connected to the lead 41 which then joins the lead 40. The lead 40A has a timer 60 and the lead 40B has a light 61 to indicate when the motor 10 and, accordingly, the pump 7 is in service. The relay 59 is operable, when energized, to close the normally open switch 59A of the starter leads 32B of the motor circuit 32.

Between the switch 58 and the relay 59 and the parallel leads 40A and 40B, there is a connection 62 placing the normally open timer switch 60A and a relay 63 in the lead 41 in parallel with the relay 59 and said parallel leads. The relay 63, when energized, as it is after a short, say ten second, dwell once the timer 60 is energized, is operative to close the normally open switches 63A of the leads 32A of the circuit 32.

Thus, when the switch 58 is set for manual control to utilize the entire lead 40, as when the delivery system is being filled, the starter leads 32B are closed in advance of the starter leads 32A.

The lead 41 has, ahead of the switch 58 a pair of normally open switches, the switch 64A closed when the relay 64 in the lead 42 is energized and the switch 57B closed when the relay 57 is energized. A connection 65 between the leads 41 and 42 is located between the switches 64A and 57B of the lead 41 and between a normally open switch 66A and a normally closed switch 67A in the lead 42.

The switch 66A is closed for a short predetermined interval, say 30 seconds, when the timer 66 in the lead 27B is energized and the switch 67A is opened after a short delay, say 15 seconds, after the timer 67 in its lead 27A is energized.

The leads 27, 43, 44, 45, and 46 comprise a third section and the lead 43 has the normally closed switches 63B and 68A and a relay 69. The switch 63B is closed when the pump 7 is not in service and the switch 68A is closed when the speed of the drive 8 is zero. To this end, the lead 46 is provided with a relay 68 including a pressure responsive switch 68B held open by oil pressure delivered through the hydraulic line 68C from the variable orifice controller of the drive 8. The lead 44 includes the normally closed switch 55B which is open when the relay 55 is deenergized, the normally open switch 69A of the relay 69 and the timer 56 which is a self-setting type and operating on a 15 minute cycle, for example.

The lead 45 includes a vacuum operated switch 70 and a relay 71 which when energized closes the switches 71A in the motor circuit 33.

Assuming that the switches 50 and 58 have been set to provide for automatic control of the operation of the pumps, i.e., the switch 50 connecting the lead 38 to the lead 39 and the switch 58 connecting the lead 41 to the lead 42 and assuming the pressure in the system is at the predetermined high pressure level, the switch 26 in the lead 27 connects the lead 27A thereto and the timer 67 is then enegized, opening the switch 67A in the lead 42 thereby deenergizing the relay 64. Under these conditions the motor 10 for the pump 7 is deenergized as the switch 66A is now open.

Assuming that the speed of the drive 8 is then zero, the relay 69 is energized closing its switch 69A in the lead 44 so that the timer 56 is energized and at the end of the predetermined period, say 15 minutes, the normally closed switch 56A in the lead 39 is opened thereby deenergizing the relay 52 and the timer 53. It should be noted, however, that if the demand increased during the 15 minute period, the switch 56A would close and the timer 56 be reset.

Assuming that the pressure drops below the predetermined high level, the leads 27B and 127B become both connected to the lead 27 by the switch 26. As a consequence the relay 55 is energized closing the relay switch 55A to maintain the pump 6 in operation with the consequent closing of the switch 52B and the starting of the timer 66 which for a short period, say 30 seconds, closes the lead 42 starting the motor 10 in operation since the relay switch 57B is now closed.

As before stated once the pressure reaches the high level the lead 27A is again connected to the lead 27 and the timer 67 started which will in a few moments open the lead 42 to the relay 64.

It will thus be seen that, in automatic operation, the pump 6 stays alone in service until the demand is such that it is unable to maintain the pressure in the delivery system at the required high level. For the reasons before stated, the motor 10 then is started and the added capacity of the pump 7 enables the demand to be met with the speed of the pump 6 dropping back and with the motor 9 remaining in service until the speed of the drive 8 drops to zero.

Claims

We claim:

1. A pumping unit for a water delivery system where the demand is variable, said unit comprising first and second pumps, a drive for each pump, the drive for the first pump including a constant speed motor and pressure responsive means operable to vary the drive speed to provide a constant pressure throughout a wide range of system demands, the drive for the second pump including a constant speed motor, a delivery conduit section with which the outlets of both pumps and the pressure responsive means of the first pump drive are in communication, a control circuit for said drives including a pressure responsive switch having low and high pressure positions and said conduit section includes means in communication with said pressure responsive means of said first pump drive and with said switch utilizing the pressure in said section as a measure of the demand on said system, said control including circuitry in control of both motors and operable to place said second pump in service only when a predetermined high pressure cannot be maintained by the operation of said first pump and means responsive to a zero speed of the variable drive to de-energize it for a predetermined interval.

2. The pumping unit of claim 1 and means operable to terminate the operation of the second pump after a predetermined time interval when the switch is brought into its high pressure position to ensure that the predetermined high pressure is re-established and not the result of a surge.

3. The pumping unit of claim 1 and a vacuum pump connected to the delivery system at the intake side of said pump, and said third section includes an additional lead including a normally open switch, a connection with the intake side of said system operable to close said switch in response to suction, and a relay in said additional lead operable to place the vacuum pump in operation.

4. A pumping unit for a water delivery system where the demand is variable, said unit comprising first and second pumps, a drive for each pump, the drive for the first pump including a constant speed motor and pressure responsive means operable to vary the drive speed to provide a constant pressure throughout a wide range of system demands, the drive for the second pump including a constant speed motor, a delivery conduit section with which the outlets of both pumps and the pressure responsive means of the first pump drive are in communication, and circuitry including a first section including the motor (9) of the first pump, a second section including a pressure responsive switch (26) having a low-pressure, high-demand position and a high-pressure low-demand position, and means (24) in control of said switch effective to operate it to be responsive to the pressure in said system as a measure of the demand on said system, said third section including means (68, 68A, 68B, 68C, 69, 69A, 56) responsive to a zero demand and operable to open the first section relative to its motor, a relay (67) included in the third section in the high-pressure, low-demand position of said switch and operable to open the second section relative to its motor and means (66) and (55) in the low-pressure, high-demand position thereof operable to close the first and second sections of the circuit relative to their motors.

5. The pumping unit of claim 4 in which the first section includes a lead (39) provided with a normally open switch (55A), the second section includes a lead (42) provided with the normally open switch (66A) and a normally closed switch (67A), the means included in the third section of said low-pressure, high-demand position include first and second parallel elements (55, 66), the first element (55) operable when energized to close the normally open switch (55A) of the first section and the second element (66) operable when energized to close the normally open switch (66A) of the second section, and the means (67) included in the third section in said high-pressure, low-demand position operable when energized to open the normally closed switch (67A) of the second section.

6. The pumping unit of claim 4 in which said second section includes a second lead (41) provided with a normally open switch (57B) and the first section includes a relay (57) operable to close said normally open switch (57B) when the first section is closed relative to its motor.

7. The pumping unit of claim 6 in which the first lead (42) of the second section includes a relay (64), the second lead (41) of the second section includes a normally open switch (64A) closed when the last mentioned relay is energized, and a connection (65) between said first and second leads between the two switches of each of them to provide a holding circuit for said first lead relay whereby, in said high-pressure, low-demand position, the second circuit is opened relative to its motor by the relay (67) then placed in the circuit by said pressure responsive switch (26), said last named relay being of a time delay type.

8. The pumping unit of claim 4 in which the means responsive to the zero demand includes a normally closed switch (56A) in the first section, and a self-setting timer (56) operable to effect a cycle for said switch whenever a zero speed exists in which said switch (56A) is opened and then closed after a predetermined interval and to repeat said cycle as long as said zero demand exists.

9. The pumping unit of claim 8 in which the means responsive to the zero demand includes a switch (63B) and the second switch includes a relay (63) operable to open said switch (63B) whenever said second section is closed relative to its motor.

10. The pumping unit of claim 8 in which the means responsive to the zero demand includes a normally closed switch (55B) with which the timer (56) is in series and the first section includes a relay (55) operable to open said switch whenever the first circuit section is closed relative to its motor.

11. The pumping unit of claim 4 in which the third section includes a first lead (46) provided with a relay (68) and closed by said means at said zero demand, a second lead (43) including first and second normally closed switches (63B and 68A) and a relay (69), and a third lead (44) including a normally closed switch (55B), a normally open switch (69A), and a self-setting timer (56) operable to open said first section relative to its motor for a predetermined time interval, means controlled by said switch (26) in its high-pressure, low-demand position to open said third lead (44) and means controlled by said second section to open said second lead (43) whenever said section is closed relative to its motor.

12. The pumping unit of claim 4 in which both motors include circuits having a series of pairs of parallel leads each having a normally open switch, one lead of each pair effecting a voltage reduction, and each of the first two sections includes a first relay operable to close the normally open switch of the reduced voltage leads of the appropriate one of the motor circuits, a parallel time delay relay and a parallel normally open switch closed by the time delay relay and a third relay operable to close the normally open switch of the other lead of each pair of the appropriate motor circuits.

13. The pumping unit of claim 12 in which each of the first two sections includes a manually operable switch having two operating positions in the first of which it is subject to control by the third section and in the second of which it is independent thereof.