Rotary kinetic fluid motors or pumps – With control means responsive to non-cyclic condition... – Plural diverse condition responsive
Reexamination Certificate
1999-11-09
2001-06-26
Ryznic, John E. (Department: 3745)
Rotary kinetic fluid motors or pumps
With control means responsive to non-cyclic condition...
Plural diverse condition responsive
C415S112000
Reexamination Certificate
active
06250876
ABSTRACT:
TECHNICAL FIELD
The invention relates to a centrifugal pump, in particular a hygienic centrifugal pump, provided with a primary and a secondary shaft seal at the rear wall of the pump chamber and in which cooling flushing and barrier fluid (hereinafter referred to as flushing fluid) is passed to and from the compartment between said seals, optionally in a flushing fluid circuit.
BACKGROUND ART
It is known to arrange thermo sensors in the flow path of the flushing fluid from the technical field of centrifugal pumps with dual shaft seal and in which the compartment between the primary seal and the secondary seal is flushed with cooling flushing fluid However, this arrangement does not function quite satisfactorily, if for instance the pump fluid is the same or substantially the same temperature as the flushing fluid. The monitoring thus becomes less reliable.
BRIEF DESCRIPTION OF THE INVENTION
The object of the invention is to provide a centrifugal pump of the above type which is more sensitive to leaking pump fluid through the primary seal than known pumps such that the pump itself activates an alarm (or optionally shuts down), if the leakage becomes too extensive.
The centrifugal pump according to the invention is characterised in that a sensor means is provided in or at a discharge pipe from the compartment between the primary seal and the secondary seal, said means being adapted to measure at least the turbidity, electrical conductivity and temperature of the flushing fluid for activation of an alarm in case of leaking pump fluid through the primary seal. As a result the pump operates in a particularly reliable manner due to the early detection of any leakage at the primary seal. Another reason for the reliability is that an alarm is activated, if the pump fluid leaks through the primary seal, even when a clear pump fluid with the same temperature as the flushing fluid is used. In the instance the electrical conductivity thus causes the sensor means to render a signal. In other situations the sensor means reacts to the changed transparency (turbidity) of the flushing fluid or a change in temperature thereof. In many cases all of the parameters: turbidity, temperature, electrical conductivity are changed at the same time. When an alarm signal is rendered, the motor of the centrifugal pump may be turned off automatically to stop the pump.
According to the invention the sensor means may comprise at least three sensor members, viz a sensor member for measuring the turbidity of the flushing fluid, a sensor member for measuring the electrical conductivity and a sensor member in form of an electric temperature sensor for measuring the temperature of the flushing fluid, said sensor members, which are adapted to render electric signals, are parallel coupled and connected to an electric alarm system such as an alarm circuit, e.g. on a chip. As a result the pump is particularly sensitive, as it reacts at practically any pump fluid leakage through the primary seal.
Furthermore according to the invention the sensor member for measuring the turbidity may be a photo cell provided with a light-emitting diode. This embodiment has proved particularly reliable.
Moreover according to the invention the sensor member for measuring electric electrical conductivity may be formed of two mutually interspaced electrodes in form of steel legs, whereby the centrifugal pump is highly sensitive to leakage through the primary seal.
According to the invention the sensor member for measuring the temperature may be formed of a thermometer indicating the temperature digitally, whereby the centrifugal pump becomes particularly reliable.
Furthermore according to the invention the sensor means may be built-in in the compartment between the primary seal and the secondary seal close to the location at which the flushing fluid is discharged from the compartment, whereby the reliability is enhanced, as the sensor means is well-protected,
According to the invention the signals from the sensor members may be standardised before they are processed in the alarm device to obtain easy comparison and processing of the signals.
Moreover according to the invention the processing of the signals in the alarm device may be performed in a logical OR-circuit, which has proved particularly advantageous.
According to the invention the signals from the three sensor members may be transferred to a neural network for recognition of signal patterns which have proved to be characteristic of the operation modes to be monitored. This renders a particularly reliable detection.
According to the invention the alarm device may be adapted to monitor the change of the signals as time goes by resulting in enhanced detection sensitivity.
Furthermore according to the invention each of the sensor members may be adjusted to a specific threshold value which must be exceeded, before the alarm device accepts the signal from the sensor member in question, whereby the number of false alarms is reduced.
Finally according to the invention the threshold values may be adjusted to obtain the most advantageous relation between the probability of detecting an undesired event (leakage) and the probability of a false alarm. The probability of detecting an undesired event (the leakage) is thus improved at the same time as the probability of a false alarm is kept to a minimum.
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patent: 3741679 (1973-06-01), Johnston
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patent: 5263825 (1993-11-01), Doolin
patent: 5605436 (1997-02-01), Pederson
APV Fluid Handling Horsens A/S
McDermott & Will & Emery
Ryznic John E.
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