Pumps – Condition responsive control of pump drive motor – Responsive to accumulation of pumped liquid in receiver
Reexamination Certificate
1999-10-29
2001-03-20
Freay, Charles G. (Department: 3746)
Pumps
Condition responsive control of pump drive motor
Responsive to accumulation of pumped liquid in receiver
C417S044100
Reexamination Certificate
active
06203281
ABSTRACT:
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.
REFERENCES:
patent: 4466777 (1984-08-01), Kimberlin
patent: 4595341 (1986-06-01), Castell-Evans
patent: 4678403 (1987-07-01), Rudy et al.
patent: 4715785 (1987-12-01), Gurega
patent: 4752188 (1988-06-01), Gurega
patent: 4804936 (1989-02-01), Sale
patent: 5049037 (1991-09-01), Carson et al.
patent: 5324170 (1994-06-01), Anastos et al.
patent: 5856783 (1999-01-01), Gibb
Freay Charles G.
Lipsitz Barry R.
McAllister Douglas M.
Richal Corporation
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