Abstract:
A probe is mounted on a water submersible pump or other fluid handling device housed within a vault for a transformer, elevator or the like. The probe will extend into any water which accumulates in the bottom of the vault enabling a conductive path to be established through an appropriate electric circuit to the pump motor to permit operation of the pump for pumping water from the vault. Oily fluids, which are immiscible in the water and will normally rise to a level above the water level in the vault, will come in contact with the probe to render the probe nonconductive, thereby inactivating the pump circuit. An alarm is provided to indicate the presence of oil in the vault. In order to prevent false alarms when the probe is nonconductive due to immersion in air, a controller is provided to inhibit operation of the alarm unless a float is raised and the probe is nonconductive.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to submersible pumps, and more particularly to a controller for submersible pumps that can distinguish between fluids such as oil, air and water. By differentiating between different fluids, the pump can be controlled to only pump certain fluids (such as water), and not others (such as oil). Alarms can be generated for fluids that are not to be pumped. False alarms are prevented by distinguishing, for example, between oil and air. 
     Various industrial applications require submersible pumps. For example, electric utilities commonly use water submersible pumps in transformer vaults for dewatering the vaults. If water accumulates in a transformer vault, it may short a power line causing substantial problems delivering electricity to a consumer. Accordingly, water submersible pumps are commonly placed in the transformer vault to pump out accumulated rainwater and the like which may seep into the vault. 
     Electrical transformers are normally filled with an oily fluid for lubricating and cooling the various components of the transformer. This oily fluid has a tendency to leak from the transformer housing into the vault. There is a danger to the environment if the oily fluid is pumped with the water into a waste disposal tank or sewer, as such oily fluids usually contain compounds which are harmful to the environment. Further, if the oil admixes with the water and both are pumped to a treatment disposal facility, suitable separation equipment must be provided to separate the oil from the water so that water can readily be disposed of and the oil recycled, or at least stored in a toxic safe facility. Such separation equipment is an item of considerable expense to a utility. 
     Hydraulic elevators are another application with similar concerns. In particular, the hydraulic oil in the hydraulic shaft tends to leak into the underground vault which houses the elevator piston. This vault may also fill with water during heavy rains due to underground seepage. It is necessary to pump the water out of the vault without pumping the hydraulic oil. 
     U.S. Pat. Nos. 4,715,785 and 4,752,188 disclose oil detection apparatus for use in controlling submersible pumps. In the systems described in these patents, a probe is mounted on a water submersible pump. The probe extends into any water that accumulates in the bottom of a transformer vault, enabling a conductive path to be established that is used to activate the pump. As the water level falls during pumping, oily fluids, which are immiscible in the water and rise to a level above the water, will come into contact with the probe. Since the oil is not electrically conductive, it breaks the conductive path, thereby stopping the pump. 
     It is desirable to generate an alarm in the event that a harmful fluid, such as oil, is detected in an underground vault or the like. Such an alarm can be used to identify a potential problem to a central facility, which can dispatch a technician to investigate further. However, false alarms should be prevented. Such false alarms can occur, for example, if the detection of oil relies on the electrical non-conductivity of the oil, since air (which is also non-conductive) may also set of the alarm. 
     It would be advantageous to provide a method and apparatus to insure that only water is pumped from an industrial vault, without pumping potentially harmful substances such as oil. It would be further advantageous to provide such a method and apparatus in which oil and air are differentiated in order to prevent the occurrence of false alarms. 
     The present invention provides the aforementioned and other advantages. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, control apparatus is provided for a submersible pump, valve or the like. Hereinafter, the term “pump” is not used in a limiting sense, and is intended to cover other fluid handling devices, such as valves. The apparatus includes a conductivity probe and a float. A first switch is responsive to the conductivity probe and the float for activating the submersible pump when the probe detects a conductive liquid (such as water) at a first level and the float is raised to a second level above the first level. A second switch is responsive to at least one of the float and the probe for initiating an alarm condition when the probe does not detect a conductive liquid at the first level and the float is raised to the second level. 
     In an illustrated embodiment, the alarm condition is inhibited whenever the float is below the second level. For example, the first switch can be configured to enable the second switch to operate only when the probe does not detect a conductive liquid at the first level. Alternatively, the second switch can be configured to be directly responsive to both the conductivity probe and the float. 
     In the illustrated embodiments, the first and second switches comprise relays that are responsive to controllers. 
     A method is provided for differentiating fluids in which a submersible pump is submerged. The results are used to control the operation of the pump and an alarm. In accordance with the method, a determination is made as to whether a fluid at a first level above a base of the pump is conductive. A determination is also made as to when the fluid in which the pump is submerged is a liquid which reaches a second level above the first level. A submersible pump is activated when the fluid at the first level is conductive and the liquid reaches the second level. The submersible pump is prevented from running when the fluid at the first level is nonconductive. An alarm condition is initiated when the fluid at the first level is nonconductive and the liquid reaches the second level. The alarm condition is inhibited when the fluid at the first level is nonconductive and no liquid has reached the second level. 
     In the illustrated embodiments, a probe is used in the first determining step to determine the conductivity of the fluid. A float is used in the second determining step to determine when the liquid reaches the second level. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram illustrating a pump and alarm controller in accordance with the present invention; 
     FIG. 2 is a block diagram illustrating an alternate embodiment of the pump and alarm controller of FIG. 1; 
     FIG. 3 is a schematic diagram showing an example implementation of a controller for one of the relays of FIG. 1; and 
     FIG. 4 is a diagram illustrating the operation of a submersible pump in accordance with the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In accordance with the invention, an oil/air/water detection apparatus is provided for use in an industrial vault or the like. During normal operation, when water enters the vault and rises to a first level, the conductivity of the water shorts an electrical probe which closes the contacts in a first switch. As the water continues to rise, it lifts a float which, in combination with the contact shorted by the probe, activates a pump, valve, motor or the like. 
     During abnormal operation, in which a nonconductive fluid such as oil is present, the probe is insulated and does not conduct. As the fluid continues to rise, it lifts the float to the second level which, in conjunction with the nonconductive probe, sets off an alarm. The alarm may be local or remote. For example, a remote alarm may be provided at a central facility from which technicians are dispatched to correct the abnormality that resulted in setting off the alarm. 
     In a situation where there is no oil or water present at the probe, but only air, the probe will not conduct. This could occur, for example, after the initial installation of a vault before any water has entered, in which case the probe will be nonconductive since it is surrounded only by air. Even after water and/or oil has entered the vault above the level at which the probe is mounted, evaporation may take place which causes the level of the fluid to drop below the probe. In this case, the probe is again nonconductive since it is only surrounded by air. If only the conductivity of the probe is used to signal an alarm, false alarms will be generated which will cause needless concern and/or result in the dispatching of a technician for nothing. 
     The present invention avoids the generation of false alarms by monitoring both the conductivity of the probe as well as the level of the float in order to distinguish air from oil. In particular, where nonconductivity of the probe is caused by oil, once the oil rises to the second level where the float is raised, the float will actuate a switch which, in combination with the nonconductivity determined by the probe, can set off an alarm. Where the nonconductivity of the probe is caused by air, the float will not be raised by the air and the float switch will not be actuated. Thus, an alarm will not be triggered. 
     One embodiment of a control system in accordance with the present invention is illustrated schematically in FIG. 1. A first relay generally designated  10  includes a controller  14  which either energizes or de-energizes a relay coil  16  in accordance with predetermined conditions. The controller  14  receives input from a float switch via line  28  and from a probe via line  30 . When the probe is off (i.e., nonconductive), coil  16  is in a condition that will cause switch  18  to couple power from a terminal  12  via line  20  to a second relay unit  40 . When the probe is on (i.e., conductive) due to the presence of water, and the float is also on due to the water having reached a second level above the first level at which the probe is mounted, controller  14  will place coil  16  into a condition that will actuate switch  18  such that the power from terminal  12  is disconnected from second relay  40  and connected instead to a pump (or other fluid handling device)  24  via line  22 . The other end of pump  24  is coupled to neutral  26 . Thus, pump  24  will have the voltage input at terminal  12  across it, and will run in order to pump the water out from the vault in which the pump, float and probe are contained. 
     It will be appreciated by those skilled in the art that the switch  18  can be configured such that it is in the position shown when coil  16  is de-energized. Alternatively, the switch  18  can be configured such that it is in the position shown only when coil  16  is energized. Since the pump will generally only run intermittently, the preferred embodiment is to configure the relay  10  such that switch  18  is in the position shown when coil  16  is de-energized, and will actuate the pump  24  when coil  16  is energized. 
     In order to provide an alarm (which can be local and/or remote), second relay  40  is actuated by the float switch via line  46 . Relay  40  will only be operational if it receives power from relay  10  via line  20 . As indicated above, this will only occur when the probe in nonconductive (i.e., when the probe is immersed in air or oil, and not water). Thus, when relay  40  is energized, and the float has been lifted by a liquid in order to actuate its associated float switch (i.e., the float is “on”), an alarm system  42  will be actuated by switch  44 . On the other hand, if the float has not been raised and its associated float switch is “off”, the alarm system  42  will not be actuated by switch  44 . This situation will occur if the probe is nonconductive (i.e., “off”) due to its immersion in air. In this case, the air will not lift the float, and even though the probe is off, the alarm will not be triggered because there is no liquid in the vault to raise the float. 
     It is noted that although a remote alarm system  42  is illustrated in the figures, a local alarm system can also be provided either instead of or in addition to the remote alarm system. Such a local alarm system would operate in the same manner, and be triggered by switch  44  when the probe is off and the float is on. 
     FIG. 2 illustrates an alternate embodiment in which power to the relay  40  is not obtained from the relay  10 . Instead, relay  40  is coupled to its own power source (not shown). In this embodiment, the controllers of both relays  10  and  40  receive both the probe signal via terminal  30  and the float signal via terminal  28 . The controller  14  of relay  10  turns on the pump when both the probe and float are on. The controller  48  of relay  40  turns on the alarm system  42  via switch  44  only when the float is on but the probe is off. Thus, the alarm will only be triggered when the probe is immersed in oil, and not when it is merely immersed in air. 
     FIG. 3 illustrates one possible embodiment of a relay controller such as the control  14  illustrated in FIGS. 1 and 2. The control used for relay  40  can be identical. 
     In the controller illustrated in FIG. 3, power is supplied through terminals A 1  and A 2 . A transformer T 1  is used to step the line voltage down to, for example, 17.5 volts AC. Diode D 1  and capacitor C 2  are used to rectify and filter the output of transformer T 1 . Capacitor C 1  is used to establish a common for the float switch and probe. The probe is coupled via terminal  30  to a current limiting sensing resistor R 3 . Similarly, the float switch is coupled via terminal  28  to a current limiting sensing resistor R 2 . The output of the probe and float switch pass through respective diodes D 2  and D 3 , respectively, for comparison with respective reference voltages established by Zener diodes DZ 2  and DZ 3 . The result of this comparison and the value of potentiometer R 5  (which provides a sensitivity adjustment) determine the state of transistors Q 1  and Q 2 . The coil  16  of the relay (RLY 1 ) is actuated by transistor Q 1  when the probe and float are both on. 
     It should be appreciated that the circuit of FIG. 3 can be configured to actuate the coil  16  under different conditions, for example, when the float is on without regard for the condition of the probe, as illustrated for relay  40  in FIG.  1 . The output device (e.g., pump or alarm) will be actuated by appropriate terminals  11 ,  13  and/or  15  depending on whether normally closed or normally opened operation is desired. 
     FIG. 4 illustrates the operation of a submersible pump in accordance with the present invention. Pump  50  includes a float  52  which will actuate a float switch  55  when it is raised by a liquid  58  to the level  62 . When liquid is below this level, for example at level  64 , the float will not be raised to a point at which the float switch is actuated. The float switch can comprise, for example, a mercury switch  55  or the like within the float as shown in FIG.  4 . Alternatively, a mechanical switch, Hall effect sensor, reed switch, or the like could be adapted for activation by the float in a well known manner. The pump assembly is submersed within a vault  56  in order to pump liquid from the vault via a pipe  54 . 
     Probe  60  is provided in accordance with the invention to determine whether the liquid  58  is conductive (e.g., water) or nonconductive (e.g., oil). An oil minder control  66  incorporates a relay system as illustrated, for example, in FIG. 1 or FIG. 2, in order to distinguish between air and oil at the level of probe  60  as explained above. 
     In operation, if probe  60  is nonconductive and float  52  has not been raised to the level  62 , no alarm will be generated. This will occur either if the probe  60  is nonconductive due to the presence of air, or if probe  60  is nonconductive due to the presence of oil. On the other hand, if probe  60  is nonconductive and the float  52  has been raised to the level  62 , the float will actuate the alarm due to the nonconductive state of probe  60  and the actuation of float switch  55 . 
     It should now be appreciated that the present invention provides an improved oil detection apparatus for submersible pumps in which an alarm condition is only generated when oil is present. If probe  60  is nonconductive only due to the presence of air, which is a fluid that will not raise the float  52 , an alarm will not be generated. 
     Although the invention has been described in connection with various preferred embodiments, it should be appreciated that numerous adaptations and modifications may be made thereto without departing from the spirit and scope of the invention as set forth in the claims.