FORM 2

THE PATENTS ACT, 1970 (39 of 1970)
As amended by the Patents (Amendment) Act, 2005
& The Patents Rules, 2003 As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
Pump Performance Analyzer for a Centrifugal pump
APPLICANTS
Samundra Institute of Maritime Studies, 518, 5th floor, Sai Commercial Building, Govandi Station road, Govandi, Mumbai-400088,
INVENTORS
Mr. Maneesh Jha of A - 602, Belle Vista, Plot No.46-48, Sector -15, Belapur, Navi Mumbai 400 614., Ms. Ambika Poojari T-10, Room No - 206, Pratiksha Nagar, Sion (E), Mumbai 400 022 and Mr. Ravindra Sawant of Takshila, 9B Flat No 34, Mahakali Caves Road, Andheri (E), Mumbai-93, all Indian Nationals.
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed.

FIELD OF THE INVENTION
The present invention relates to a pump performance analyzer for a centrifugal pump. More specifically, the present invention relates to generating user-friendly information for optimizing performance and troubleshooting of the centrifugal pump.
BACKGROUND OF THE INVENTION
Centrifugal pumps are widely used in shipping and other industries. The manufacturer's data supplied along with the pumps, describe the performance of the pump with respect to flow rate and head of the pump it is operating at. In practical applications, an average operator of the pump does not have the knowledge to understand and practically interpret the manufacturer supplied information on head, quantity, efficiency, power and net positive suction head of the pump.
The specific gravity of the operating liquid of the pump may be different from that of the liquid specified by the manufacturer. Also, locations of pressure sensing instruments may be different from those mentioned by the manufacturer. Moreover, the pump may have deviated away in service from the original anticipated behavior due to wear and tear of internal parts. Therefore, corrections are required to be made in the manufacturer's data for accurate practical interpretations.
Further, cavitation has been a silent killer for many centrifugal pumps. An average operator has no idea about how to find out whether a pump is cavitating. The damage becomes evident at much later stage and usually results in huge expenses due to loss of operations and damage to the pump. In order to check whether the pump is cavitating, the operator has to dismantle the pump, which is a time consuming and cumbersome task.
It is also not possible for the operator to find out whether the centrifugal pump is operating at a best combination of head and flow rate at which the energy consumption of the pump is minimum and the efficiency is maximum. Operating the pump at any other head and flow rate combination causes more energy consumption, leading to wastage of energy. It also

damages the pump, as extra energy not utilized for useful work causes vibration, heat, undue stresses, thereby reducing the working life of the pump.
In light of the foregoing, there exists a need for a tool/apparatus that can solve the above-mentioned problems and provide user friendly information for the pumps in operation so that the operator can optimise the pump performance and also use it as diagnostic tool in case of troubles. An average operator without having any sound knowledge of centrifugal pump operations and troubleshooting should be able to use the tool/apparatus effectively.
SUMMARY OF THE INVENTION
Various embodiments of the present invention provide a pump performance analyzer for a centrifugal pump. The pump performance analyzer comprises pressure transducers disposed at pre-determined locations of the centrifugal pump for measuring suction and discharge pressures thereof; a flow rate indicator for indicating a flow rate corresponding to a pump operating head computed based on a specific gravity of an operating fluid of the centrifugal pump and a difference of the suction and discharge pressures; a cavitation indicator for computing a Net Positive Suction Head available (NPSHA) based on a difference of a fluid vapour pressure and the suction pressure and generating a cavitation alert when the NPSHA is less than a Net Positive Suction Head required (NPSHR) at the indicated flow rate; and a pump wear-out indicator for computing a pump operating head and a power at closed discharge valve operation and generating an alert when the head and power deviate from pre-determined head and power at a zero flow rate condition.
Preferably, the pump performance analyzer comprises a power alert generator for generating an alert when a power drawn by the centrifugal pump is greater than a predetermined power at the indicated flow rate; and an efficiency indicator for indicating an efficiency of the centrifugal pump at the indicated flow rate and generating an alert when difference between the efficiency and a maximum efficiency exceeds a pre-set value.

Preferably, one or more discharge valves of the centrifugal pump are modulated automatically for operating the centrifugal pump at an efficiency substantially equal to a maximum efficiency of the centrifugal pump.
Preferably, the pump wear-out indicator generates a casing ring wear out alert when the head is significantly less than the pre-determined head at the zero flow rate condition and the power is significantly higher than the pre-determined power at the zero flow rate condition.
Preferably, the pump performance analyzer comprises a shore line characteristic indicator for indicating characteristics of a shore pipe line connected to a discharge side of the centrifugal pump by plotting values of discharge side head against corresponding flow rate.
Various embodiments of the present invention provide a method of analyzing performance of a centrifugal pump. The method comprises measuring suction and discharge pressures through pressure transducers disposed at pre-determined locations of the centrifugal pump; indicating a flow rate corresponding to a pump operating head computed based on a specific gravity of an operating fluid of the centrifugal pump and a difference of the suction and discharge pressures; generating a cavitation alert when a Net Positive Suction Head available (NPSHA) is less than a Net Positive Suction Head required (NPSHR) at the indicated flow rate, the NPSHA being computed based on a difference of a fluid vapour pressure and the suction pressure; and computing a pump operating head and power at a closed discharge valve operation and generating an alert when the head and power deviate from pre-determined head and power at a zero flow rate condition.
DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION
The aspects, features and advantages of the invention will be better understood with reference to the following detailed description, accompanying drawings and appended claims, in which, Fig.l is a block diagram illustrating various components of a pump performance analyzer of a centrifugal pump, in accordance with an embodiment of the present invention;

Fig.2 is a graph illustrating relationship between various parameters of a centrifugal pump, in accordance with an embodiment of the present invention.
Fig.3 is a graph illustrating a shore characteristic curve of the pump performance analyzer, in accordance with an embodiment of the present invention; and
Fig.4 is a flowchart illustrating a method of analyzing performance of a centrifugal pump, in accordance with an embodiment of the present invention.
Referring now to figures, and more particularly to Fig. 1, wherein various embodiments of the invention can be practiced. The pump performance analyzer 100 analyses the performance of a centrifugal pump 102, and comprises pressure transducers 104, a control panel 106 and a processing and output module 108.
The centrifugal pump 102 is a well known roto-dynamic pump that uses a rotating impeller to create flow by addition of energy to a fluid.
The pressure transducers 104 comprise a suction transducer 110 and a discharge transducer 112 disposed at pre-determined locations of the centrifugal pump 102 for measuring suction and discharge pressures respectively. In an embodiment of the present invention, the suction transducer 110 is connected to suction side of the centrifugal pump 102, and discharge transducer 112 is connected to discharge side of the centrifugal pump 102.
The control panel 106 may be fitted on a side wall of the centrifugal pump 102 and includes a dual starter for operating the pump 102. The control panel 106 comprises an energy meter 114 for measuring and recording actual power consumption of the centrifugal pump 102.
The processing and output module 108 is configured to analyze pump performance based on pump operating parameters such as suction pressure, discharge pressure and pump power received from the pressure transducers 104 and the control panel 106 and generate user-friendly information for optimizing performance and troubleshooting of the centrifugal pump 102.

The processing and output module 108 comprises a flow rate indicator 116, a cavitation indicator 118, a power alert generator 120, a pump wear-out indicator 122 an efficiency indicator 124, and a shore characteristics indicator 126.
The flow rate indicator 116 is configured to indicate a flow rate of the pump 102 based on a pump operating head computed based on a specific gravity of an operating fluid of the centrifugal pump 102 and a difference of the suction and discharge pressures. When the pump 102 is operational, the flow rate indicator 116 may calculate the pump operating head H using the following equation:

where, pressure(bar) is the difference of discharge and suction pressures with correction of the locations of pressure sensing points and SPG is specific gravity of the operating fluid. The specific gravity of one or more operating fluids may already be inputted into the processing and output module 108 by the user.
Once the pump operating head is computed, the flow rate indicator 116 interprets the flow rate Q from an H-Q curve (curve A illustrated in Fig.2 as per pump's characteristic data) already inputted by the user in the processing and output module 108.
It may be noted that the flow rate indicator 116 indicates the flow rate of the pump 102 without using a flow meter. When verified using a flow meter under various operation conditions of the pump 102, the display accuracy of the flow rate indicator 116 was found to be within ±3%.
Further, a drop in pressure from a suction flange of the pump 102 to the lowest pressure point inside the pump 102 varies according to the flow rate. This drop in pressure can cause the operating fluid to vapourise inside the pump 102 and subsequent implosion can cause damage to pump parts. The cavitation indicator 118 is configured to generate an alert when the drop in pressure from a suction flange to the lowest pressure inside the pump 102 causes the pump 102 to cavitate.

The cavitation indicator 118 determines the vapor pressure of the operating fluid from the vapor pressure tables of different operating fluids already fed into the processing and output module 108. The cavitation indicator 118 determines the vapor pressure corresponding to a temperature either inputted by the user or sensed by a temperature sensor. Thereafter, the cavitation indicator 118 converts the difference of the vapor pressure and the suction pressure to 'a Net Positive Suction Head available (NPSHA)' in meters using equation (1).
The cavitation indicator 118 then compares the NPSHA with the Net Positive Suction Head required (NPSHR) as per the pump's characteristic data (curve B illustrated in Fig.2) for the flow rate indicated by the flow rate indicator 116. When the value of NPSHR is greater than NPSHA, it means that the pump 102 may cavitate.
In such a condition, the cavitation indicator 118 generates an alert for the user immediately using audio and visual alarms. The user may take a remedial action by reducing the flow rate, increasing the suction head or reducing the fluid temperature.
The power alert generator 120 is configured to generate an alert when a power drawn by the centrifugal pump 102 is greater than a pre-determined power at the indicated flow rate. A significantly higher power drawn is an indication of higher than normal pump resistance due to issues in power transmission or problems with pump parts. The power alert generator 120 is also configured to continuously display the power drawn by the centrifugal pump 102 and the pre-determined power at the indicated flow rate.
The pre-determined power at the indicated flow rate is obtained from the power vs flow rate curve (curve C illustrated in Fig.2 as per pump's characteristic data) already inputted into the processing and output module 108 by the user. Also, details regarding specific gravity of various fluids are inputted into the processing and output module 108. Based on the specific gravity of the operating fluid, the processing and output module 108 may modify the power and flow rate curve i.e., curve C.

The pump wear-out indicator 122 is configured to compute a pump operating head and a power at a closed discharge valve operation and generate an alert when the head and power deviate from pre-determined head and power at a zero flow rate condition. In the closed discharge valve operation, the discharge valve of the pump 102 is closed ensuring that the pump 102 is full of the operating fluid.
Preferably, the pump wear-out indicator 122 generates a casing ring wear out alert when the head is significantly less than the pre-determined head at the zero flow rate condition and the power is significantly higher than the pre-determined power at the zero flow rate condition. The pre-determined power and head are deduced from power-flow rate curve (Curve C of Fig.2) and head-flow rate curve (Curve A of Fig.2) already inputted into the processing and output module 108 by the user.
During the closed discharge valve operation, the flow rate should be ideally zero and the head should be high, as the flow rate and head are inversely proportional to each other. When the head is significantly less than the expected head, the flow rate is greater than zero. During the closed discharge valve operation, a flow rate greater than zero is the amount leaking through the wear ring, thus indicating that the wear ring is worn out.
The 'casing ring' wear out is one of the most common reasons for the poor performance of centrifugal pumps. Thus, the pump wear-out indicator 122 facilitates checking the condition of casing ring without dismantling the pump 102.
In accordance with an embodiment of the present invention, a decrease in total head for zero flow rate conditions and decrease in power required may also suggest clogging of pump vanes, etc, as in this case the pump 102 will not be able to develop the rated head and the power consumption will also be low.
During the operation of the pump 102, there is always a best combination of head and flow rate at which the energy consumption of the pump 102 is minimum and the efficiency is maximum. The point of best combination of head and flow rate is known as Best Efficiency Point (BEP) or operating point of the pump 102. It is desirable to operate the pump 102 close to the BEP for good discharge rate and longer pump life.

The efficiency indicator 124 is configured to determine and display the efficiency of the pump 102 for the flow rate indicated by the flow rate indicator 116. The efficiency indicator 124 is further configured to compare the efficiency of the pump 102 with the maximum efficiency and generate an audio or visual alert when difference between the efficiency and the maximum efficiency exceeds a pre-set value. In an embodiment of the present invention, this pre-set value may be set by the user. The efficiency indicator 124 is further configured to continuously display the percentage deviation of efficiency from the maximum efficiency.
The shore line characteristic indicator 126 is configured to indicate characteristics of a shore pipe line connected to a discharge side of the centrifugal pump 102 through a shore characteristics curve (as illustrated in Fig.3). The shore characteristics curve is obtained by plotting values of discharge side head against corresponding flow rate. The operating point of the pump 102 depends on the characteristic of the shore pipe line.
In an embodiment of the present invention, the centrifugal pump 102 may comprise one or more pumps, and the shore line characteristic indicator 126 may plot individual shore curves for each pump or plot a single shore curve for a combined flow rate of the pumps. The shore characteristic curve illustrated in Fig.3 comprises curves for three different combinations of the pumps.
The characteristic of shore pipe line comprises of two components 'static' and 'dynamic1. Static characteristic depends on the height of the discharge point in the shore pipe line from center line of the centrifugal pump 102. Higher static head alters the operating point and reduces the flow rate of the pump 102. Dynamic head of the shore pipe line depends on the length of the discharge line, number of bends, internal roughness of pipe line valve and fittings in the pipe line etc. Higher values of these elements compound in increasing the resistance of the pipe line, thus increasing the discharge head and reducing the flow rate of the pump 102.
Therefore, from the shore characteristic curve, the shore line characteristic indicator 126 can indicate whether the shore line resistance is high or low. This information is of

significant commercial importance especially when centrifugal pump 102 is used with the discharge cargoes. When the cargo discharge rate is found to be low, the vessel can come out clean with the strong technical evidence suggesting problems in the shore pipe line.
During multi-pump operation, the shore line characteristic indicator 126 may take the flow rates of all combinations into consideration, compare each flow rate with the 'best efficiency' flow rate and recommend the combination of parallel pumps, which operate close to the BEP. The shore line characteristic indicator 126 may also display the key pump parameters of all the pumps.
The processing and output module 108 may be implemented using a simulated signal board and pump performance software. The simulated signal board is designed for simulation of the various signals, such as suction pressure, discharge pressure, power consumption, and shore characteristics (static as well as dynamic). The simulated signal board may include a power supply, PLC system, various connectors for communication of the signals to control panel and pump performance software, add on Digital I/O & Analog modules for interfacing the simulation signals with the pump performance software, and digital panel meters for displaying different pump parameters.
The pump performance software analyzes the pump performance by calculating necessary parameters, such as operating head, NPSH, Power consumption, and so forth. It also derives necessary parameters such as flow rate, power consumption, efficiency, NPSH from pump characteristics data already inputted by the user.
The centrifugal pump 102 may comprises one or more discharge valves, which are modulated automatically for operating the centrifugal pump 102 at an efficiency substantially equal to the maximum efficiency This modulation is aimed towards operating the pump 102 either close to BEP or to avoid cavitation. In the processing and output module 108, the user sets a BEP flow rate. A deviation of indicated flow rate from the BEP flow rate is measured and an electric signal is generated, strength of which is dependent on the deviation value. The electrical signal is converted into an equivalent pneumatic signal for operating pneumatic valve(s) fitted in the discharge line of the pump 102.

Fig.4 is a flowchart illustrating a method of analyzing performance of a centrifugal pump, in accordance with an embodiment of the present invention.
At step 402, the suction transducer 110 is connected to a suction side of the pump 102 for measuring suction pressure and the discharge transducer 112 is connected to discharge side of the pump 102 for measuring discharge pressure. The vertical distances of the suction and discharge transducers 110 and 112 from the pump center line are measured and offsets for the pressure sensing locations with respect to pumps center line are corrected for increasing the accuracy. The pump's characteristic data provided by a manufacturer and parameters such as vapor pressure and specific gravity of various operating fluids are fed into the processing and output module 108.
Then at step 404, a flow rate of the pump 102 is indicated. The flow rate is determined from a flow-head curve (as per pump's characteristic data) for a pump operating head, where the pump operating head is computed using equation (1) based on a specific gravity of the operating fluid of the centrifugal pump 102 and a difference of the suction and discharge pressures. In addition to the flow rate, other pump parameters that may be indicated include efficiency as percentage of the maximum efficiency and the head.
At step 406, a Net Positive Suction Head available. (NPSHA) is computed and a cavitation alert is generated when the NPSHA is less than a Net Positive Suction Head required (NPSHR) at the indicated flow rate. The NPSHA is computed using equation (1) based on a difference of a fluid vapor pressure, the suction pressure and the specific gravity of the operating fluid. The NPSHR is obtained from pump's characteristics data already fed into the processing and output module 108.
Further, at step 408, a discharge valve of the pump 102 is closed ensuring that the pump 102 is full of operating fluid. Then, the head and power are computed at the closed discharge valve condition. A casing ring wear out alert is generated when the head is significantly less than the pre-determined head at the zero flow rate condition and the power is significantly higher than the pre-determined power at the zero flow rate condition. The pre-

determined power and head are obtained from pump's characteristics data already fed into the processing and output module 108. During the closed discharge valve operation, a flow rate greater than zero is the amount leaking through the wear ring, thus indicating that the wear ring is worn out.
Although the invention has been described with reference to a specific embodiment, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiment, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the scope of the invention as defined in the appended claims.

We claim:
1. A pump performance analyzer for a centrifugal pump, the pump performance analyzer
comprising:
pressure transducers disposed at pre-determined locations of the centrifugal pump for measuring suction and discharge pressures thereof;
a flow rate indicator for indicating a flow rate corresponding to a pump operating head computed based on a specific gravity of an operating fluid of the centrifugal pump and a difference of the suction and discharge pressures;
a cavitation indicator for computing a Net Positive Suction Head available (NPSHA) based on a difference of a fluid vapour pressure and the suction pressure and generating a cavitation alert when the NPSHA is less than a Net Positive Suction Head required (NPSHR) at the indicated flow rate; and
a pump wear-out indicator for computing a pump operating head and a power at closed discharge valve operation and generating an alert when the head and power deviate from pre-determined head and power at a zero flow rate condition.
2. The pump performance analyzer as claimed in claim 1, which comprises:
a power alert generator for generating an alert when a power drawn by the centrifugal pump is greater than a pre-determined power at the indicated flow rate; and
an efficiency indicator for indicating an efficiency of the centrifugal pump at the indicated flow rate and generating an alert when difference between the efficiency and a maximum efficiency exceeds a pre-set value.
3. The pump performance analyzer as claimed in claim 2, wherein one or more discharge valves
of the centrifugal pump are modulated automatically for operating the centrifugal pump at an
efficiency substantially equal to a maximum efficiency of the centrifugal pump.

4. The pump performance analyzer as claimed in claim 1, wherein the pump wear-out indicator
generates a casing ring wear out alert when the head is significantly less than the pre-determined
head at the zero flow rate condition and the power is significantly higher than the pre-determined
power at the zero flow rate condition.
5. The pump performance analyzer as claimed in claim 1, which further comprises a shore
line characteristic indicator for indicating characteristics of a shore pipe line connected to a
discharge side of the centrifugal pump by plotting values of discharge side head against
corresponding flow rate.
6. A method of analyzing performance of a centrifugal pump, the method comprising:
measuring suction and discharge pressures through pressure transducers disposed at pre-determined locations of the centrifugal pump;
indicating a flow rate corresponding to a pump operating head computed based on a specific gravity of an operating fluid of the centrifugal pump and a difference of the suction and discharge pressures;
generating a cavitation alert when a Net Positive Suction Head available (NPSHA) is less than a Net Positive Suction Head required (NPSHR) at the indicated flow rate, the NPSHA being computed based on a difference of a fluid vapour pressure and the suction pressure; and
computing a pump operating head and power at a closed discharge valve operation and generating an alert when the head and power deviate from predetermined head and power at a zero flow rate condition.
7. The method as claimed in claim 6, which comprises:
generating an alert when a power drawn by the centrifugal pump is greater than a pre-determined power at the indicated flow rate; and

indicating an efficiency of the centrifugal pump at the indicated flow rate and generating an alert when a difference between said efficiency and a maximum efficiency exceeds a pre-set value.
8. The method as claimed in claim 7 wherein one or more discharge valves of the centrifugal pump are modulated automatically for operating the centrifugal pump at an efficiency substantially equal to a maximum efficiency of the centrifugal pump.
9. The method as claimed in claim 6, which comprises generating a casing ring wear-out alert when the head is significantly less than the pre-determined head at the zero flow rate condition and the power is significantly higher than the pre-determined power at zero flow rate condition.
10. The method as claimed in claim 6, which comprises indicating characteristics of a shore
pipe line connected to a discharge side of the centrifugal pump by plotting values of discharge
side head against corresponding flow rate.