Method and system for detection and localization of a fluid related to a piston machine

1. A method for detecting and localizing a valve leak in a piston machine having a shaft, comprising:

attaching one or more vibration sensors to a valve block of the piston machine;

measuring vibrations from at least one of the vibration sensors;

attaching a sensor to the piston machine where the sensor is configured to produce, directly or indirectly, an angular shaft position signal for the shaft;

determining, directly or indirectly, an angular shaft position signal for the shaft;

transforming vibration signals from the one or more vibration sensors into one envelope signal representing an instant vibration level;

using the angular position signal for constructing window functions that pick the envelope signal in selected angular shaft sectors;

using the window functions to find sector based averages of the vibration level, and

comparing said averages with a critical ambient vibration level to detect and localize leaks in one or two valves.

2. The method of claim 1 , further comprising:

letting the window functions represent 2p non-overlapping sectors, where p is the number of pistons in the piston machine;

setting a leak alarm if a group of p or more adjacent sectors have a vibration level exceeding the critical level; and

determining, if the leak alarm is a set, leaky valves as those valves having closing sectors that match either the first p sectors or the last p sectors of said group.

3. The method of claim 1 , further comprising:

determining the center angle of the envelope vibration signal by Fourier analysis;

using said center angle to construct two wide and complementary window functions representing shaft sectors for highest and lowest vibration level;

using these window functions and the envelope function to find the average signal level in said sectors; and

setting a leak alarm if the highest vibration level exceeds the critical value; and

determining, if the leak alarm is set, a leaky valve as the valve having its closing sector nearest to the window sector of highest vibration level.

4. The method of claim 1 , further comprising setting the critical vibration level that triggers a leak alarm equal to a multiplicative factor times a minimum value of sector based vibration levels.

5. The method of claim 1 , further comprising setting the critical vibration level that triggers a leak alarm to a value that is either calculated from an empirical formula as a function of pump speed and discharge pressure, or picked from a look-up table, and where in both cases past measurements of normal ambient vibrations are incorporated.

6. The method of claim 1 , further comprising presenting an actual leaking valve or valves for a human.

7. The method of claim 1 , further comprising:

attaching a sensor to the piston machine where the sensor is designed to produce a digital timer signal with one pulse per revolution;

determining all timer events when the timing signal turns from a low value to a high value or from high value to low value;

finding corresponding revolution periods from a difference between successive timer events;

finding corresponding average pump speeds and center times;

applying a suitable 1D interpolation/extrapolation method to find angular pump speed for all time samples;

time integrating said speed to obtain an accumulated pump shaft angle;

calculating a difference between said accumulated angle and real angular shaft position at a first timer event; and

finding pump shaft position as the accumulated pump angle minus said difference.

8. A system, comprising:

a piston machine, comprising:

a plurality of cylinders, a piston disposed in each of the cylinders;

a suction valve and a discharge valve coupled to each of the cylinders via a valve block;

a vibration sensor attached to the valve block;

a crankshaft coupled to the pistons; and

a rotary angle transmitter configured to provide one pulse per revolution of the crankshaft; and

a computer communicatively coupled to the vibration sensor and the rotary angle transmitter, the computer configured to:

generate an angular position signal for the crankshaft;

transform a vibration signal from the vibration sensor into an envelope signal representing an instant vibration level;

construct, using the angular position signal, window functions that pick the envelope signal in selected angular shaft sectors;

find sector based averages of the vibration level using the window functions, and

compare the averages with a predetermined ambient vibration level to detect and localize leaks in up to two of the valves.

9. The system of claim 8 , wherein the computer is configured to:

generate the window functions to represent 2p non-overlapping sectors, where p is a total number of pistons in the piston machine;

set a leak alarm based on a group of p or more adjacent sectors having a vibration level that exceeds a predetermined level; and

determine leaky valves to be those valves having closing sectors that match either a first p sectors or a last p sectors of said group.

10. The system of claim 8 , wherein the computer is configured to:

determine a center angle of the envelope vibration signal by Fourier analysis;

use the center angle to construct two complementary window functions representing shaft sectors for highest and lowest values of the vibration level;

use the complementary window functions and the envelope signal to find the average signal level in the sectors;

set a leak alarm based on the highest vibration level exceeding a predetermined value; and

determine a leaky valve to be the valve having its closing sector nearest to the window sector of highest vibration level.

11. The system of claim 8 , wherein the computer is configured to set a predetermined vibration level that triggers a leak alarm equal to a multiplicative factor times a minimum value of sector based vibration levels.

12. The system of claim 8 , wherein the computer is configured to set a predetermined vibration level that triggers a leak alarm based on past measurements of normal ambient vibrations wherein the predetermined vibration level is either calculated from an empirical formula as a function of pump speed and discharge pressure, or selected from a look-up table.

13. The system of claim 8 , wherein the computer is configured to provide a display identifying a leaking valve.

14. The system of claim 8 , wherein the computer is configured to:

determine all timer events based on one edge of the pulse;

determine revolution period of the crankshaft based on a time difference between successive instances of the pulse;

determine corresponding average pump speeds and center times;

apply at least one of interpolation and extrapolation to find the angular pump speed for all time samples;

time integrate pump speed to obtain an accumulated pump shaft angle;

calculate a difference between the accumulated angle and actual angular shaft position at a given pulse; and

find the pump shaft position as the accumulated pump angle minus said difference.

15. A non-transitory computer-readable medium encoded with instructions that when executed cause a computer to:

receive one pulse per revolution of a crankshaft from a rotary angle transmitter attached to a piston machine;

receive vibration signals from a vibration sensor attached to valve block of the piston machine;

generate an angular position signal for the crankshaft based on the one pulse per revolution;

transform the vibration signals into an envelope signal representing an instant vibration level;

construct, using the angular position signal, window functions that pick the envelope signal in selected angular shaft sectors;

find sector based averages of the vibration level using the window functions, and

compare the averages with a predetermined ambient vibration level to detect and localize leaks in up to two valves of the piston machine.

16. The computer-readable medium of claim 15 encoded with instructions that when executed cause a computer to:

generate the window functions to represent 2p non-overlapping sectors, where p is a number of pistons in the piston machine;

set a leak alarm based on a group of p or more adjacent sectors having a vibration level that exceeds the predetermined level; and

determine leaky valves to be those valves having closing sectors that match either the first p sectors or the last p sectors of said group.

17. The computer-readable medium of claim 15 encoded with instructions that when executed cause a computer to:

determine a center angle of the envelope vibration signal by Fourier analysis;

use the center angle to construct two complementary window functions representing shaft sectors for highest and lowest values of the vibration level;

use the complementary window functions and the envelope signal to find average signal level in the sectors;

set a leak alarm based on the highest vibration level exceeding a predetermined value; and

determine a leaky valve to be the valve having its closing sector nearest to the window sector of highest vibration level.

18. The computer-readable medium of claim 15 encoded with instructions that when executed cause a computer to set the predetermined vibration level that triggers a leak alarm equal to a multiplicative factor times a minimum value of sector based vibration levels.

19. The computer-readable medium of claim 15 encoded with instructions that when executed cause a computer to set the predetermined vibration level that triggers a leak alarm based on past measurements of normal ambient vibrations wherein the predetermined vibration level is either calculated from an empirical formula as a function of pump speed and discharge pressure, or selected from a look-up table.

20. The computer-readable medium of claim 15 encoded with instructions that when executed cause a computer to provide a display identifying a leaking valve.