Pump washout diagnostic system

Abstract

A hydraulic pump system includes a hydraulic pump with reciprocating pistons. A rotational encoder is provided to sense values representative of a rotational velocity in a rotating drivetrain member. The values are analyzed to indicate a washout condition affecting the displacement of at least one piston. The hydraulic pump is scheduled for maintenance and repaired based upon the outcome of this analysis.

We claim: 
     
         1 . A hydraulic pump, comprising:
 a plurality of reciprocating pistons each mounted in co-axial alignment with a corresponding one of a plurality of cylinders;
 each of the cylinders being in fluidic communication with a corresponding intake opening and a corresponding discharge opening; 
   at least one prime mover;   a drive linkage coupling each of the plurality of reciprocating pistons with the at least one prime mover,   the drive linkage being operable for rotational motion that at different times produces
 a first axial shifting motion such that each of the plurality of reciprocating pistons respectively within each corresponding one of the cylinders moves in a first direction to perform an intake stroke capable of drawing fluid through the intake opening and into the corresponding one of the cylinders, and thereafter produces 
 a second axial shifting motion such that each of the plurality of reciprocating pistons within each of the cylinders moves in a second direction opposite the first direction to perform a discharge stroke capable of expelling the fluid from the cylinder through the corresponding one of the discharge openings; 
   and as to each cylinder
 a suction valve mounted proximate the corresponding intake opening for the cylinder, 
 structure mounting the suction valve for movement between a closed intake position and an open intake position,
 the closed intake position being normally operable for sealing of the intake opening during the discharge stroke, 
 the open intake position being normally operable for permitting passage of the fluid into the cylinder during the intake stroke, 
 the intake valve and the structure mounting the intake valve being subject to wear such that the intake valve ceases to be normally operable for sealing of the intake opening during the discharge stroke; 
 
 a discharge valve mounted proximate the corresponding discharge opening for the cylinder, 
 structure mounting the discharge valve for movement between a closed discharge position and an open discharge position,
 the closed discharge position being normally operable for sealing of the intake opening during the intake stroke, 
 the open discharge position being normally operable for expelling the fluid from the cylinder during the discharge stroke, 
 
 the discharge valve and the structure mounting the discharge valve being subject to wear such that the valve ceases to be normally operable for sealing of the discharge opening during the discharge stroke; 
   a rotational member of the drive linkage is constructed and arranged to vary in rotational position over time concomitant with the first axial shifting motion and the second axial shifting motions,   means for assessing a rotational speed of the rotational member during the rotational motion and for producing signals that contain information representative of the position of a detector object over time; and   a controller configured with program language to receive the information and process the same for frequency analysis to identify a problem in hydraulic sealing by at least one of the intake valve and the discharge valve.   
     
     
         2 . The hydraulic pump of  claim 1 , wherein the hydraulic pump is operable for hydraulic fracturing operations in the nature of well stimulation. 
     
     
         3 . The hydraulic pump of  claim 2 , wherein the hydraulic pump is a triplex pump. 
     
     
         4 . The hydraulic pump of  claim 2 , wherein the hydraulic pump is a quintuplex pump. 
     
     
         5 . The hydraulic pump of  claim 2 , wherein the hydraulic pump is an octuplex pump. 
     
     
         6 . The hydraulic pump of  claim 1 , wherein the means for assessing includes a plurality of optical targets mounted on the rotational member and an optical detector configured to produce the signals as a result of sensing the optical targets. 
     
     
         7 . The hydraulic pump of  claim 1 , wherein the means for assessing includes a plurality of magnets mounted on the rotational member and a magnetic pickup configured to produce the signals as a result of sensing the magnets. 
     
     
         8 . The hydraulic pump of  claim 1 , wherein the means for assessing includes a manifold downstream of the discharge openings, the manifold being equipped with a pressure sensor configured to produce the signals as a result of sensing pressure variations associated with at least one of the first shifting motions and the second shifting motions associated with each of the plurality of cylinders. 
     
     
         9 . The hydraulic pump of  claim 8 , wherein the frequency analysis includes a Fourier transform-based frequency analysis to isolate a frequency indicative of the washout condition. 
     
     
         10 . The hydraulic pump of  claim 8 , wherein the program language utilizes a time domain of the frequency analysis to associate the frequency indicative of the washout condition with a particular one of the plurality of cylinders. 
     
     
         11 . The hydraulic pump of  claim 1 , wherein the frequency analysis includes a Fourier transform-based frequency analysis to isolate a frequency indicative of the washout condition. 
     
     
         12 . The hydraulic pump of  claim 1 , wherein the program language utilizes a time domain of the frequency analysis to associate the frequency indicative of the washout condition with a particular one of the plurality of cylinders. 
     
     
         13 . The hydraulic pump of  claim 1 , wherein the prime mover is an internal combustion engine. 
     
     
         14 . The hydraulic pump of  claim 13 , wherein the internal combustion engine is a diesel engine. 
     
     
         15 . The hydraulic pump of  claim 13 , wherein the internal combustion engine is a reciprocating gas engine. 
     
     
         16 . The hydraulic pump of  claim 1 , wherein the prime mover is an electric motor. 
     
     
         17 . A method comprising;
 placing a wellhead in fluidic communication with a plurality of hydraulic pumps respectively as set forth in  claim 1 ;   supplying a frac fluid material to the plurality of pumps;   actuating each of the plurality of pumps to perform respective first axial shifting motion and the second axial shifting motion to pump the frac fluid through the wellhead for purposes of hydraulically stimulating a well,   identifying the washout condition to select a pump in need of maintenance among the plurality of hydraulic pumps, and thereafter,   performing maintenance on the pump in need of maintenance to repair the washout condition.