US2246940A

US2246940A - Pump control

Info

Publication number: US2246940A
Application number: US263132A
Authority: US
Inventors: Hood John William
Original assignee: Individual
Current assignee: Individual
Priority date: 1939-03-21
Filing date: 1939-03-21
Publication date: 1941-06-24
Anticipated expiration: 1958-06-24

Description

June 24,1941. f b 2,246,940

PUMP CONTROL Filed March 21, 1939 2 Sheets-Sheet 1 lNVENTOR ATTORNEYS June 24,1941. J HOOD 2,246,940

PUMP common Filed March 21', 1939 '2 Sheets-Sheet 2 INVENTOR 13' [ATTORNEYS ii atented June 24, 1941 PUIVIP CONTROL John William Hood, Ridgewood, N. 1., asslgnor to Millard F. Smith, Montclair, N. J.

Application March 21, 1939, Serial No. 263,132

8 Claims.

This invention relates to pump control mechanism and has for its object to provide a control which increases the efllciency and economy of operation.

The invention is especially useful in the pumping of flows of sewage or the like which vary greatly between minimum and maximum limits during the day and during the year.

It has been the practice to provide pumps of large enough capacity to pump at the rate of the maximum inflow, and to employ .pump control apparatus which automatically starts the pump when the fluid accumulated in a well by the inflow rises to a high level and automatically shuts ofif the pump when it falls to a low level. In such systems, whenever the rate of inflow is considerably less than the capacity or pumping rate of the pump, the pump rapidly empties the well and is then shut oil? by the low level cut off. The level then rises again due to the inflow until the high level cut-in starts the pump again. This has heretofore involved the use of pumps of much larger pumping capacity than is required for all rates of inflow except the maximum, with attendant relatively large losses of power due to the use, most of the time, of larger pumping equipment than is required by the flow, and the resulting frequent on and off operation of the pumps.

In accordance with this invention there is provided a control which permits the use of a plurality of pumps of smaller pumping capacity than the maximum flow; and which automatically selects and operates the pump having the capacity more nearly equal to the actual flow at any time, resulting in less frequent on and off operation.

The invention will be more fully understood from the following description and the accompanying drawings of which Fig. 1 is in part a, sectional view along line I--l of Fig. 2 and illustrates a wet well and pumps controlled according to this invention;

Fig. 2 is a vertical view'in section taken at line 2-2 of Fig. 1;

Fig. 3 illustrates control apparatus and circuits for selecting and operating the pumps according to the flow.

The drawings illustrate equipment adapted for pumping an inflow of sewage, received ina well, to a subsequent receptacle. The pump and well arrangement shown in Figs. 1 and 2 comprises a, pit l having a vertical bulkhead H providing a wet well l2 and a dry pit I3. A flume l6 carries the inflow over a weir ll into the wet well l2 from where it flows into a storage tank l which acts as a balancing or storage reservoir for minimizlng changes of the fluid level in the relatively small well.

In the dry pit there are located three pumps l8, l9 and 20 of different pumping capacities, driven by electric motors l8, l9 and 20', re-' spectively. Preferably, the smallest pump it is of sufficient pumping capacity to handle the average minimum rate of flow, the largest pump 20 is of sufllcient capacity to handle the maximum rate of flow, and pump I9 is of intermediate capacity.

The pumps are arranged in multiple, each being adapted to pump from the wet well l2 by suction pipes 2|, 22 and 23 respectively to a force main 24 which is a pipe through which the flow is raised to a tank or other receiving medium from where it may be further dealt with as desired. Preferably, the combined pumping capacities of the two smallest pumps l8 and I 9 should be approximately equal to the capacity of the largest pump 20, for in that case there is present a standby pumping capacity capable of pumping the maximum rate of flow.

For the purpose of energizing the respective pump motors l8, I9 and 20' there are provided switches 16, TI and 18, which when closed connect thleir respective motors with the

power source

38, 39. These motor switches are of the magnetically operated type, having operating magnets 19, and BI, which when energized close their respective switches, and, when deenergized, allow the switches to drop open.

For the purpose of automatically selecting and operating the pumps in accordance with the rate of inflow of fluid and the level of the fluid in the well .there is provided the following control apparatus, including control circuits for energizing the motor switch magnets: v

A small diameter pipe 25 connected into the flume above the weir leads to a vertical pressure pipe'26 at the top of which is attached a receptacle 21, the inside of which is shown in Fig. 3. In this receptacle, and over the opening of the pipe 26 is an air-tight flexible bellows 28 sealed to prevent the leakage of air from the pipe 26 above the fluid level in that pipe, so that an increase in the fluid level in the flume. corresponding to greater flow over the weir, raises the fluid level inpipe 26, compressing the air above it in the pipe and expanding the bellows upward. There is fastened to the top surface of the bellows a rod 29 pivoted at 30 to a lever 3| attached to a fixed pivot 32. On this lever is a standard 32 carrying a metallic member 34 which acts as a wiper arm on a potentiometer resistance 35.

The potentiometer is included in the control circuit of an electric motor 36 receiving its source of power through a transformer 31 from a

power line

38,39. This motor is of a known type having an armature which moves to and stops in a position of equilibrium of its control circuit, so that the position of its armature shaft 40 is changed by moving the potentiometer arm. When the potentiometer arm 34 is in contact with the center of the resistance 35, the shaft 40 is at rest in a central position of angular rotation; 'but when the arm 34 moves either way off center in response to the rise or fall of the bellows, the motor shaft turns one way or the other depending on the direction in which the arm moves, until an electrical balance is again established and the number of degrees of rotation is varied with the amount of movement of arm 34.

On the motor shaft 40 are fastened three cams 4|, 42 and 43 which operate, respectively, the

cam riders

44, 45 and 46. Each cam rider is pivoted on a rod I4, and carries a roller 9 on its free end in contact with the cam surface. Each rider also carries a pair of forked fingers 41 and 48, and each pair of fingers operates a flow responsive control switch, there being three of these switches, 49, 50 and one for the energizing circuit of each motor switch magnet. The switches illustrated are of the well known mercury type operated by tilting. Each switch comprises a glass envelope containing a pair of

switch contacts

52, 53, sealed through the glass at one end and another pair of

switch contacts

54, 55 sealed through the glass at the other end, the

contacts

53 and 55 being connected together externally of the glass tube, as shown. (In switch 50, the contacts are numbered 52', 53', 54' and 55' and in switch 5| they are numbered 52", 53", 54" and 55".) Each switch tube, held approximately horizontally between the fingers 41 and 48, contains sufllcient mercury 56 to cover the two contacts at either end at which the tube is tilted downward. The arrangement is such that when the cam rider rides up on the cam protuberance, it pivots on rod I4 tilting its mercury switch tube backwards to establish the

back contacts

52 and 53, but when the cam rider is of! the cam protuberance, the tube is tilted forward to cause the mercury to cover the

front switch contacts

54 and 55.

The cam 4| is preferably fastened on the shaft so that even when the potentiometer arm position corresponds to zero flow, the cam roller 9 rests on the cam protuberance, and stays there at least until the next cam 42 raises its rider; and cam 42 is adjusted to raise its rider whenever the flow exceeds an amount a little under the capacity of the smallest pump I8, and cam 43 is adjusted to raise its rider whenever the flow exceeds an amount a little under the capactiy of the intermediate pump I9.

There is also provided in each motor control circuit a fluid level responsive switch whose contacts make or break in dependence on the level of liquid in the well I2. These are mercury switches I00, IOI and I02 similar to switches 49, 50 and 5| except that only one pair of contacts is employed, these being 14 and 15 (14' and 15' in switch IOI and 14" and 15" in switch I02) located at one end of the switch tu-be. For operating these switches there is provided a pipe 56, closed at the top and open at the bottom, which extends into the well almost to its bottom. Near the top of the pipe an air tight tube 51 is led from the pipe; and into this tube there are connected

auxiliary tubes

59, 60 and 6|, leading respectively to

receptacles

63, 64 and 65, the bottoms of the receptacles being provided with air tight bellows 66 located over the entering tube so that the bellows are bulged upwardly by air pressure by an amount depending on the level of fluid in the well, in a manner similar to the operation of the previously described bellows 28. Attached to each of these bellows is a rod 81 pivoted to a lever 68 which in turn is attached to a fixed pivot 69. An arm 10 of the lever is fastened to an arm 1| pivoted at 12 and supporting the mercury switch I00 (and IM and I02 in

casings

64 and 65, respectively). The mechanisms holding switches I00, I 0| and I 02 are so adjusted relative to the air pressure in the tubes and the fluid level in the well that the switch controls are closed at a predetermined high .leve in the well and opened at a predetermined low level.

The flow responsive switches and the fluid level responsive switches are interconnected and connected into the energizingcircuits of the magnets of the motor switches in the following manner: Contacts 53" and 54" of flow controlled switch 5| are connected by lead 82 to power wire 39; contact 54" of switch 5| is connected by a lead 83 with the commonly connected

contacts

53 and 55 of switch and contact 54 of switch 50 is connected by a lead 84 with contact 52 of switch 49.

The level controlled switches are connected in circuit with the flow controlled switches and with the motor switches as follows: Contact 52" of switch 5| is connected by a lead 85 with contact 15" of switch I02, and the other contact 14" is connected by lead 86 with the magnet 8| of switch 18, the other side of the magnet being connected with power lead 38 by wire 81. Switch IN is similarly connected in series with contact 52' of flow switch 50 and with magnet 80'of motor switch 11 by

leads

88 and 89. Level switch I00 is likewise connected with the commonly connected contacts 53 and of flow switch 49 by lead 90, and with magnet 19 by lead 9|.

A high level safety cut-in is provided by the mercury switch 13 in receptacle 62, operated in response to the fluid level through tube 58. This switch is connected by leads 94 and 95 in series with power line 39, magnet 92 of magnetic switch as and power line 38. Switch blade 96 of switch I 93 serves, when closed, to energize magnet 19 of motor switch 16 over lead 91, and switch blade 98 simultaneously energizesmagnet of motor switch 11 over the same lead 91, so that when the contacts of switch 13 are closed, pumps I8 and I9 are operated together. An alarm gong 99 connected between power lead 38 and lead operates to sound an alarm whenever switch 62 is closed. The mechanism holding switch 13 is adjusted so that its contacts close at the high emergency level in the well and open at about the low level."

In operation, the level of the liquid in the fiume I6 rises in accordance with the flow over the weir so that the pressure on the air sealed within the top of .pipe 26 increases as the flow increases, thus expanding the bellows 28 accordingly and moving the wiper arm 34 in correspondence. This causes the control motor 36 to rotate, the rotation being in the direction of the arrow when the flow has increased, thus establishing the position of the shaft 40 and its cams.

When the shaft continues to rotate in response to increasing flow, cam

riders

44, 45 and 45 are raised in that order; and when the shaft rotates in the opposite direction in response to decreasing flow, the riders drop accordingly. In the case of a flow somewhere near the minimum flow, the shaft is rotated sufficiently to elevate cam rider 44 but not

riders

45 or 46, so that mercury switch 49 is tilted downwardly at the rear but switches 50 and 5I remain tilted downwardly at the front. Under this condition, the

contacts

52 and 53 of switch 49 are closed by the mercury, the control circuit for the operating magnet 19 of motor switch 16 now being complete from power lead 39, through lead 82, switch contacts 55" and 54" of switch 5|, lead 83, switch contacts 55' and 54' of switch 50, lead 84,

switch contacts

52 and 53 of switch 49 and lead 90 to contact 14 of switch I00.

Upon the level in the well reaching the predetermined high level at which the level switches I00, lol and I02 are adjusted to tilt, the liquid rising in pipe 56 compresses the air sealed in pipe 51 and the attached

air tubes

59, 60 and 6|, distending the bellows in the respective switch receptacles, thereby causing these three level switches to tilt in the direction which causes the mercury to establish their switch contacts.

Since the control circuit has already been established through switch 49, as explained above, the closure of switch I completes this control circuit'through lead 9I and magnet I9, thus energizing the magnet and closing the switch 15 of motor I8, which runs pump I8. Since neither of the other two flow controlled switches 50 and have closed their rear control contacts, their motor controlling circuits are open so that 010- sure of the level controlled

switches

64 and 65 in those circuits has no effect. As pump I8 is now running and has a capacity at least as great as the inflow, the level in the tank will not rise above the high level. Hence, the emergency switch I3 is not closed. If the in-fiow through Weir I8 is substantially equal to the pumping rate of pump I 8, the level in the well will remain substantially constant and pump I8 will keep running. But ordinarily the in-flow will be somewhat less than the pumping rate so that the liquid in the well and storage tank gradually falls. When the low level is reached, the air pressure in the

tubes

59, 50 and 6| falls to the l value required to tilt the switch tubes I00, IM

and I02 to open position, thus de-energizing magnet 19 and causing switch 16 to drop open, which shuts off the pump motor. When the high level" is again reached due to continued inflow without any pumping the tilting of switch I00 again starts the motor I8.

When the flow increases to the point where' cam 42 lifts rider 45, which should preferably occur at practically the capacity of pump I8, flow controlled switch 50 is tilted downward at the rear, opening its front contacts 54' and which opens the control circuit for motor I8; and closes its rear contacts 52' and 53', thus setting up the control circuit for motor I9 through wire 88. Then, if or when the condition of the fluid in the well has closed switch IOI this control circuit is completed through magnet 80 of switch 11, starting motor I9 and pump I9. Pump I9 then stops and starts as the level change between the high and low levels, the operation remaining on this pump so long as rider 45 remains on cam 42 and provided the cam shaft is not turned far enough to lift rider 45.

When the flow itself rises to such a level that rider 48 is lifted, which preferably should occur as. the capacity of pump I9 is neared. the operation is then accordingly transferred to the large pump 20 because wire of its con rol circuit is now energized over rear contacts 52" and 53" of switch 5|, the front contacts 54" and 55" opening to break the other control circuits. Thi large pump then is turned on and off by the level controlled witch I02 as the fluid level changes from high to low.

If the large pump fails to operate, or if for any other reason the level rises to emergency level," the switch 13 is closed, establishing its switch contacts and energizing the circuit through leads 94, and magnet 92, thus closing the arms 96 and 98 of switch 93. This energizes

magnets

19 and 80 of switches I5 and 11, causing pumps I8 and I9 both to run together. At the same time, the gong 99 is energized over switch 13, calling the attendants attention to the fact that the pumps are now operating on the emergency basis.

By the use of this pump control system, it will be appreciated that the use of different size pumps and combinations of pumps may be used in the pumping station and that there is auto matically selected the pump having the rated pumping rate nearest above the rate of inflow at the time. In this way, the fluid is pumped out of the receiving well at nearly the same rate as it flows in, so that the well is not rapidly pumped out in intermittent pumping at close intervals,

but remains at a nearly uniform level, thereby permitting the use of a well of smaller storage capacity than otherwise. This results in substantial power savings and less wear and tear on the pumping equipment because it reduces the frequency of the on and off operation of the pump. It also permits each pump to be run at its designed speed, which yields the maximum eiliciency. It furthermore results in the requirement of less power in pumping the fluid up through the force main, due to the fact that most of the time the smaller size pumps are in operation, with the result that the fluid is not being pumped up through the force'main at the rapid rate at which the maximum capacity pump pumps it. There are greater frictional losses in forcing fluid through a main at a high rate than at a lower rate.

Although the invention has been illustrated with reference to three pumps and their control circuits, it will readily be understood that it may be extended to any number of pum s or combinations of pumps. Furthermore, the apparatus is not limited to the specific types shown, but instead, considerable latitude is permissible in the selection of the individual instrumentalities such as flow measuring and responsive devices, level indicating and responsive devices, and in the particular forms of control switches and motor operating switches employed.

I claim:

1. A control means for a pumping system which pumps from a well supplied by a varying flow, and has a plurality of pumps of different pumping capacities, a driving motor for each of said pumps, a switch for energizing each motor, and a control circuit for closing each of the switches, said control means comprising: a flowcontrolled switch in each control circuit, a fluid level controlled switch in series with the flowcontrolled switches, so that each control circuit is energized to close the corresponding motor switch when its flow-controlled switch and the fluid level controlled switch are both closed, a device responsive to the rate of flow for closing the flow-controlled switch in the control circuit which corresponds to the rate of flow and opening the flow-responsive switches in the other control circuits, and a device responsive to the fluid level in the well for closing the fluid level responsive switches at a high level and opening them at a low level.

2. Apparatus according to claim 1 in which said motor energizing switches are closable by magnets connected into the respective control circuits and energized upon closure 01' the latter.

3. A. control means forv a pumping system which pumps from a well supplied by a varying flow, and has a plurality of pumps of diflerent pumping capacities and a driving motor for each of said pumps, said control means comprising: a control circuit ior operating each motor having in series a flow-controlled switch and a welllevel controlled switch, a selective device operated in response to the rate of flow for closing the flow-controlled. switch in the control circuit which corresponds to the flow and opening the flow-controlled switches of the other circuits, and a well-level operated device for closing the well-level controlled switches of all the control circuits at a high well level and opening them at a low well level.

4. Apparatus according to claim 3 having an auxiliary control circuit for energizing some of the motors and an auxiliary well level operated device for closing said auxiliary circuit at an energizing high level in the well.

5. A control means for a pumping system which 'pumps from a well supplied by a varying flow, and has a conduit through which said well is supplied by the flow, a plurality of pumps of dfierent pumping rates, a driving motor for each of said pumps, and a control circuit for operating each motor, said control means comprising: a pipe leading into said conduit, a device in the conduit for creating variations in pressure in the pipe in response to change of flow in the conduit,,a pressure sensitive device attached to said pipe, a flow-controlled switch in each control circuit closed by said pressure sensitive device during a predetermined range of flow rate, and a control switch in circuit with the closed flow-controlled switch which is closed at a predetermined high fluid level in the well and opened at a predetermined low fluid level.

6. Apparatus according to claim 5 in which said pressure sensitive .device includes a motor controlled'by the pressure to operate the control switches closed thereby.

7. In a pumping system comprising a plurality of pumps for pumping from a well supplied by a varying flow, a driving motor for each of the pumps and a switch for energizing each motor: a control circuit for closing each of the motor-energizing switches, each control circuit containing a flow controlled switch which when closedcloses the corresponding motor switch, a device responsive to the rate of flow for closing the flow controlled switch which corresponds to the rate of flow and opening the flow controlled switches in the other control circuits.

8. A control means for a pumping system which pumps from a well supplied by a varying flow, and has a plurality of pumps 01' different pumping capacities, a driving motor for each of said pumps, and a control circuit ioroperating each motor, said control means comprising: a separate flow-operated switch in the respective control circuits, a well level operated switch arranged to be in series with each flow-operated switch, flow-responsive means for closing the respective flow-operated switches within difierent ranges of flow rates, said means comprising: a selecting device operated in response to the rate of flow for closing the particular flow-operated switch corresponding to that rate of flow and opening the other flow-operated switches, and a well level operated device for closing the well level operated switch which is in series with the closed flow-operated switch at a high well level and opening it at a low well level.

JOHN WILLIAM HOOD.