Patent Publication Number: US-2011077875-A1

Title: Sump monitoring method and apparatus

Description:
This invention relates to a method of monitoring the operation of one or more sumps in order to predict an overflow condition and to apparatus for carrying out such a method. This invention also relates to a method and apparatus for monitoring the condition of a pump and to a method of prioritising sump maintenance visits. Although the present invention will be described herein with particular reference to the operation of electrically controlled pumps in a pumping station it is not to be construed as being limited thereto. 
     A typical pumping station comprises a plurality of wells or sumps, each said well or sump having an inlet to admit liquid thereinto and an outlet to remove liquid therefrom. Each outlet is associated with one or more pumps which, in use, transfer the liquid from the well or sump to the outlet for further processing. 
     Sumps are commonly used in pumping stations for pumping sewage to sewage treatment works. Inlet and outlet lines carry the sewage to and from the pumping station. Each channel may be closed or open and may be arranged to carry flood or rain water at peak flow times in order to prevent or reduce flooding of land and property. 
     According to a first aspect of the invention there is provided a method of monitoring one or more sumps in order to predict an overflow condition comprising:
         pumping, using at least one pump, liquid from the or each sump;   monitoring the liquid level in the or each sump using a level monitoring means and to output liquid level data;   monitoring at least one operating condition of the or each pump and outputting pump condition data; and   processing the liquid level and pump condition data, using processing means, to predict whether the sump will overflow within a predetermined future period.       

     Conveniently, the prediction as to whether the sump will overflow is either performed at a location remote from the sump or is transmitted to a location remote from the pump. Such an arrangement is convenient as it allows remote monitoring of the or each sump. 
     Monitoring of the liquid level and/or of the pump condition or both may be performed substantially continuously or may be performed from time to time, and perhaps periodically. 
     The pump condition data and the liquid level data may be used to determine the pump operating condition. If it is determined that the pump is not operating efficiently an indication may be made at the remote location that the pump may be faulty and requires attention. 
     Processing means may be provided at or near the sump or at the remote location or both. The processing means may process information from the liquid level monitoring means each time a measurement is made thereby. The processing means may calculate a rate of change of liquid level and use the rate of change to predict whether the sump may overflow within a predetermined future period. The future period may be one hour but other periods may be used and the predetermined period may be adjusted. 
     An alarm signal may be transmitted or generated if an overflow is predicted within the predetermined period. Alternatively processing means at the remote location may generate an alarm signal. 
     Preferably the processing means combines information from the liquid level monitoring means and the pump condition monitoring means. A high priority alarm signal may be generated at the remote location if an overflow is predicted within the predetermined future period. Engineers may be directed to the sump in response to the high priority alarm signal. 
     Accordingly an indication is provided if the pump is at fault or if a flood is predicted or if an overflow is predicted and the pump is faulty. 
     This is particularly advantageous where water companies are subject to fines if flooding occurs as a result of a fault with the or each pumps in a sump. 
     The liquid level monitoring means may be conventional. Preferably the liquid level is monitored every second. Data from the liquid level monitoring means may be output to the transmission means and transmitted to a processing means at the remote location or may be output to a local processing means. 
     The liquid level monitoring means or the processing means may be provided with a maximum rate of flow into the sump. Further, the liquid level monitoring means or the processing means may be provided with a maximum rate of flow out of the sump. A signal may be transmitted from the liquid level monitoring means in event of the rate of change of liquid level in the sump being greater than the predetermined maximum rate of change. 
     A rapid outflow resulting in a rapid decrease in liquid level may indicate a burst in an outflow pipe and an, appropriate signal may be generated. 
     An increase in liquid level in the absence of flow into the sump may indicate a blockage in the outflow pipe and an appropriate signal may be generated. 
     The pump monitoring means monitors at least one operating condition of the pump. More than one operating condition may be monitored. Data relating to the pump condition is transmitted to the processing means. The processing means may be local or remote or both. 
     The operating condition monitored may be selected from one or more of the following: temperature of the pump, current drawn by the pump, or the like. 
     The pump may be provided with a restart mechanism since in many cases the pump does not operate continuously but may allow the sump to fill before pumping the liquid out. Such a mode of operation may reduce total energy consumed and so can reduce energy costs to the pump operator. The restart mechanism may be automatically initiated at a certain liquid level. The pump monitoring means may generate a pump failure signal if the restart mechanism fails to restart the pump on a predetermined number of consecutive occasions. Typically a pump failure signal may be generated if the pump fails to start on three consecutive occasions. 
     Alternatively, or in addition, the pump monitoring means may monitor a current load to the pump. If this increases it may indicate that the pump load is increasing. Combined with for example an increase in the liquid level this might indicate a blockage in the outlet and an appropriate signal may be transmitted to the remote location. 
     A thermal sensor provided in thermal connection with the pump may similarly provide data indicative of a load on the pump. 
     A flow switch may be provided on the pump operable to measure a flow rate of liquid through the pump. A reduced flow rate through the pump may indicate a blockage within the pump especially when associated with rising liquid levels within the sump. 
     Means of measuring the efficiency of the pump may also be provided. This may be based for example on a volume of liquid pumped in relation to the pumping time (ie the time for which the pump is operated). For example, if the volume of liquid pumped in a predetermined time does not align with the pump characteristics then it might be inferred that the something is not operating as it should; the pump might have a problem, there might be a blockage on the outlet, etc. 
     Such early warning indications may be transmitted to the remote location. 
     It is envisaged that the remote location may have means arranged to rank the indicators and signals in terms of those with immediate problems and those needing inspection combined with those sumps in which there is an imminent risk of flooding. 
     According to a second aspect of the invention there is provided a method of prioritising maintenance of a series of pumps provided at remote locations whereby each pump is located in a sump;
         monitoring the liquid level in the or each sump using a level monitoring means and outputting liquid level data;   monitoring at least one operating condition of the or each pump and outputting pump condition data;   processing the liquid level and the pump condition data, using processing circuitry, and prioritising pump maintenance visits according to the processing.       

     Processing means may be provided at the pump location arranged to process data from the liquid level monitoring means and pump condition means. The processing means may compare the data to reference data and may generate an appropriate indicator signal if input data does not fall within predetermined reference data ranges. Alternatively, or additionally, the processing means may be provided remote of the pump location. 
     The indicator signal may be transmitted from a local processing means at the pump location to the remote location. Alternatively processing means may be provided at the remote location and liquid level data and/or pump condition data may be transmitted to the processing means at the remote location. 
     The liquid level may be monitored substantially continuously or from time to time, and perhaps periodically. Preferably liquid level and pump condition are monitored at predetermined intervals. Suitable intervals may be every 1 sec, 5 sec, 10 sec, 30 sec, 1 min, 5 min or any other suitable interval. Preferably at least one of the liquid level monitoring means and the processing means is arranged to calculate a rate of change of liquid level. Advantageously the rate of change of liquid level may be used to predict whether the sump might over flow within a predetermined period. The predetermined period is advantageously one hour but may be different. 
     According to a third aspect of the invention there is provided apparatus for monitoring a condition of one or more remote sumps from a remote location comprising a pump located in the or each sump
         pump monitoring means arranged to monitor at least one operating condition of the or each pump and output pump condition data;   sump water level monitoring means arranged to monitor a water level in the sump and output water level data;   processing means arranged to input pump condition data and water level data and output status indication data;   wherein an output indicative of the pump condition is generated from the status indication data.       

     A transmission means may be provided and arranged to transmit data from the apparatus to a remote location. 
     Preferably the output is arranged to indicate if any one or more of the pump conditions monitored deviate from a normal predetermined range for that condition. In a most preferred embodiment the output at the remote location indicates if the pump is not operating within a normal set of conditions and also if there is a risk of overflow of the sump. It is advantageous if the output indicates whether the sump may overflow within a predetermined period or the output may provide an estimate of an interval before an overflow condition of the sump is reached. 
    
    
     
       The invention will now be further described by way of example only with reference to the accompanying drawings in which: 
         FIG. 1  is a schematic arrangement of a number of remotely located sumps and a remote location; 
         FIG. 2  is a schematic illustration of a typical sump, and 
         FIG. 3  is a schematic indication of steps taken in processing information. 
     
    
    
     As is illustrated schematically in  FIG. 1  a typical installation comprises a remote monitoring location  1  connected by transmission means  2  to each of a number of sumps  4 . Each sump is located in a liquid flow line  6 . The or each sump may be in the same liquid flow line  6  or may be located in different liquid flow lines. 
     Typically the liquid flow lines are transmitting sewage waste water from domestic and commercial premises to a sewage treatment unit. Liquid flow lines are arranged to flow by gravity wherever possible but it is often necessary to provide one or more pumping stations in the line. Each pumping station may have one or more sumps, from which liquid is pumped along the liquid flow line  6 . The invention may equally be applied to other pumps and flow lines and is not limited to the pumping of sewage. 
     Each sump comprises a reservoir  8  having an inlet  10  and an outlet  12 . A pump  14  is provided in the sump and is arranged to pump liquid from the sump into the outlet. More than one pump may be provided in some sumps. 
     A pump condition monitoring means  16  is provided connected to the pump and to the transmission means  2 . 
     The pump condition monitoring means is arranged to monitor at least one condition indicative of pump condition. The condition may be one or more of an operating temperature of the pump, a flow indicator, an efficiency of the pump, a current load drawn by the pump, but would typically be the current load and/or operating temperature. These conditions may indicate that the pump is not operating effectively even if it has not failed. The conditions may deviate from a normal predetermined range of values if a problem is occurring and maintenance at this stage may prevent failure of the pump. 
     The pump is also provided with a restart mechanism (not shown) whereby the pump is automatically started when a water level in the sump reaches a first level  18 . The restart mechanism is arranged to start the pump. In an event where the pump fails to start the mechanism will retry starting after an interval. In a preferred embodiment if the pump fails to start after three consecutive attempts a signal is output. The signal may be output to the transmission means  2  and transmitted to a remote processing unit  20  at the remote location  1 . 
     Alternatively a local processing unit  22  may be provided at each sump  4  and an output of a processing means  22  may be transmitted by suitable mans such as a radio transmitter, phone lines, cable, cellular phones, other suitable equipment which may yet to be developed, to the remote location. Remote processing means  20  may be provided at the remote processing unit in addition to the local processing unit  22 . At the remote location a pump condition display will indicate a pump failure indication or signal in respect of the pump which has not started. If the pump has not failed but the pump condition monitoring means indicates that the pump is not operating efficiently and within a range of predetermined normal parameters an appropriate warning signal is output at the remote location. 
     The sump is also provided with a liquid level monitoring means  24 . The location is schematically indicated in  FIG. 2  but the liquid level monitoring means may be located elsewhere in the sump depending on the type of liquid level monitoring means utilised. The water level monitoring means may be conventional and well known such as ultrasonic level sensors. The liquid level is measured from time to time and perhaps periodically. The interval may be 1 sec, 2 sec, 3 sec, 4 sec, 5 sec, 30 sec, 1 min, 5 min or any other interval as desired. Substantially continuous monitoring may be used. 
     A minimum liquid level  26  occurs when pumping is complete. When the liquid level reaches a first level  18  a signal is sent to the or each pump in the sump to begin pumping. The liquid level should begin to drop if the pump output is as great as the liquid flow into the sump. 
     If the liquid inflow is greater than the pump output then the liquid level continues to rise. When the liquid level reaches a high point  28  an alarm output may be output to the transmitting means. In a preferred embodiment the liquid level monitoring means or one of the local or remote processing means is arranged to calculate a predicted rate of liquid level increase and generate an alarm signal at the remote location if an overflow condition  30  may be reached within a predetermined period, typically an hour. 
     The alarm signal generated at the remote location may indicate that an overflow condition is imminent and also whether the pump is working normally, is operating outside some predetermined parameters or whether the pump has failed. 
     The remote processing means is arranged to receive data inputs from each sump and to output appropriate condition signals. The remote processing means is also arranged to prioritise proposed maintenance visits to each sump. 
     Liquid flow lines to sewage treatment units typically are arranged to transport sewage water only and do not in normal conditions receive rain water. However, in high precipitation conditions rainwater may enter sewage flow lines causing unusually high flow rates and possible cross contamination. The high flow rates into the sump may lead to an overflow condition. 
     If the overflow condition results from the high flow rate into the sump and the pump can be shown to be operating normally this overflow is attributed to as inevitable and a company responsible for the liquid flow line is not held to be at fault. However, if the pump is shown to be not working or to be at fault then the company is held responsible for appropriate maintenance of the pumps and may be fined for an overflow occurring as a result of inadequate maintenance. 
     Consequently it is desirable to prioritise maintenance visits to sumps. Those close to overflow and in which the pump has failed have highest priority. Sumps which may overflow but in which the pump is operating normally have low priority since no penalty is incurred in respect of these sumps. 
     Additional advantages may accrue from the remote monitoring of pump conditions and sump liquid level. Flow meters  30  and  32  may be provided in the inlet and outlets respectively. Information from one or both of these may be output to the transmission means or local processing means. If the liquid level rises and the pump is operating normally in a period of normal precipitation this scenario may indicate a blockage in the outflow. This may be confirmed by inlet flow meter results being within a predetermined normal range in combination with a rise in liquid level. Unusual condition results from a pump in combination with a low outlet flow meter reading may be associated with a blockage in the pump. A leak in the outlet line may be indicated by unusually high rate of change of level. 
     Outputs at the remote location may be visual, audible, or printed. It will be understood that processing of data for an individual sump including diagnosis of faults may occur at the local processing means. Alternatively raw data may be transmitted to the remote location and processed there. Prioritisation of maintenance visits is carried out at the remote location where information from all the sumps is received.